tht ieee ALARA " rs % Li x 5 t t ; eS Th) Wi i a \ i \ t Ly bir eae. ‘ ati p i wits ate ut Scott : es i BML A Sr at es i prey ai ita b hired Ay * ure ; 3 i : ty ay sf , i f : ps : ; if TCU ebay etre ditay Gini a tes f i ; ; ily i Os a . ‘ ; i x un \ x vt as Nah eae pet . . " re : nit + i rt) ps E i Gt ; : , \ ait) i . ets } The encyclopaedia of municipal and sanit The Encyclopzdia of Municipal and Sanitary Engineering The Encyclopedia of Municipal and Sanitary Engineering A HANDY WORKING GUIDE IN ‘ALL MATTERS CONNECTED WITH MUNICIPAL AND SANITARY ENGINEERING AND Administration EDITED BY W. H. MAXWELL A.M.Inst.C.E. Borough and Waterworks Engineer, Tunbridge Wells; Past President of the Institute of Sanitary Engineers, &c. ; AND Heme ie BROWN M.R.San. Inst. Editor of ‘‘ The Sanitary Record” NEW YORK D. VAN NOSTRAND COMPANY 23 MURRAY AND 27 WARREN STREETS 1910 VY, PREFACE In the present day the constant addition to the duties and responsibilities of local authorities imposes upon them many new departments of work, and at the same time intensifies existing powers and obligations in all matters of municipal and sanitary engineering. It has thus become well-nigh impossible for those interested in local administration to keep themselves informed, even in general outline, on the many and varied subjects to which attention is now demanded by the State. The requisite information can only be gained by the expenditure of time, labour, and money in searching through a mass of literature mainly in the form of papers and reports. For the first time such information is presented in dictionary form, convenient for immediate reference. To further facilitate this, the longer articles are divided into sections, the order of which, as well as the pith and scope of the article, being shown by a brief index at the head. Acts of Parliament affecting the various subjects dealt with are quoted when necessary, and a careful system of cross-referencing has been followed in order that the reader may rapidly acquire information on the cognate aspects of a subject. The work has been prepared by many leading experts, whose experience in the matters with which they deal is well known; but the information has been gathered from all parts of the world, and the Editors tender cordial thanks to all those engineers and local authorities who have so readily placed the results of practical experience at their disposal. The Editors desire to record the assistance they have received from Mr. G. Cadogan Rothery and Mr. C. F. Tweney in planning and editing “ The Encyclopedia.” LIST OF CONTRIBUTORS ADAMS, Professor Henry, M.Inst.C.E., M.I.Mech.E., F.S.L, F.R.San.I. Apy, C. E., M.J.1. AncEL, R. J., M.Inst.C.E., A.R.I.B.A., Borough Engineer and Surveyor, Bermondsey. Boyp, R. A., M.S.A. Burne, E. Lancaster, A.M. Inst.C.E., A.M.I.Mech.E., Consulting Engineer. CHAMBERS, SipnEY H., Surveyor Hampton Urban District Council. Derriss, Wotr, B.A. (Lond.), M.I.Mech.E. Dizpin, W. J., F.L.C., F.C.8., formerly Chemist and Superintending Gas Engineer, London County Council. Firtu, Lieut.-Col. R. H., R.A.M.C. Fow.er, Dr. GILBERT J., F.I.C., Consulting Chemist to the Manchester Corporation Rivers Comuittee. FREEMAN, ALBERT C., M.S.A. FREEMAN, W. MarsHALL, of the Middle Temple, Barrister-at-Law. FRETWELL, W. E., Lecturer on Plumbing and Sanitary Science, L.C.C. School of Building. GARFIELD, JoSEPH, A.M. Inst.C.E., Sewerage Engineer, Bradford. Hosart, H. M., M.Inst.C.E., M.LE.E., &. Hotmes, Basit, Secretary Metropolitan Public Gardens Association. JENNINGS, ARTHUR SEYMOUR, Editor of The Decorator. JENSEN, GERARD J. G., C.E., Consulting Engineer. Kenwoop, H. R., M.B., B.S., D.P.H., Professor of Hygiene and Public Health, University College, London. LatHam, FRANK, Borough Engineer and Surveyor, Penzance. Marriort, W., Assistant Secretary Royal Meteoro- logical Society. Martin, ArtHur J., Engineer. MaxweE LL, W. H., Assoc.M.Inst.C.E., Borough and Waterworks Engineer, Tunbridge Wells. Moor, C. G., M.A., F.LC., F.C.S., Public Analyst for the County of Dorset and the Borough of Poole. Owens, Dr. Joun S., A.M.Inst.C.E., M.R.San.I. PARTRIDGE, W., F.I.C. M.Inst.C.E., Consulting PorpacE, A., Firemaster, City of Edinburgh. RipEt, 8., D.Sc.(Lond.), F.1.C., F.R.San.I. RoTHery, G. Capocan, of The Sanitary Record and The Electrical Engineer. Suenton, H. OC. H., M.8.E., Consulting Engineer. SOMMERVILLE, Davin, B.A., M.D., D.P.H., Lecturer on Public Medicine, King’s College, London. THompson, Gisson, Editor of The Surveyor. THompson, Alderman WILLIAM. THRESH, JoHN C., M.D., D.Sc., Medical Officer of Health for the County of Essex. TurNER, SYDNEY G., Assoc.M.Inst.C.E., Barrister- at-Law. Wauus, G. WuiTE, F.S.8., Secretary and Director, Royal Sanitary Institute, London. Watson, JouN JD)., M.Inst.C.E., Engineer to the Birmingham, Tame and Rea District Drainage Board. WessER, W. H. Y., C.E., Consulting Engineer. Winstow, C. E. A., Massachusetts Institute of Technology, Boston, U.S.A. THE ENCYCLOPAIDIA MUNICIPAL AND SANITARY ENGINEERING. Abattoirs.—Acts of Parliament—Site— Accommodation — Lairs and Pens — Slaughter- houses — Tripe-Dressing Department — Pig Department—Refuse Removal—Water Purifica- tion—Inspection Lairs—Hospital for Diseased Animals—Entrance Lodge—Cost. Acts oF Parniament.—The following are the Acts of Parliament relating to slaughter- houses : Markets and Fairs Clauses Act, 1847; Towns Improvement Clauses Act, 1847; Public Health Act, 1875; Public Health (London) Act, 1891 ; Public Health Act, 1908. The clause in the Public Health Act, 1875, reads as follows :— ‘Any urban authority may, if they think fit, provide slaughter-houses, and they shall make bye-laws with respect to the manage- ment and charges for the use of any slaughter- houses so provided.” “For the purposes of enabling any urban authority to regulate slaughter-houses within their district, the provisions of the Towns Improvement Clauses Act, 1847, with respect to slaughter-houses, shall be incorporated with this Act.” ‘‘ Nothing in this section shall prejudice or affect any rights, powers, or privileges of any persons incorporated by any local Act passed before the passing of the Public Health Act, 1848, for the purpose of making and maintaining slaughter-houses.” (38 & 39 Vict. c. 55, s. 160.) Sirz is the foremost consideration, and the place selected should be near the cattle market, or in conjunction with it, so as to prevent the long journey through the town for the cattle, to inconvenience them as M.8.E. little as possible, and to prevent the loss of weight which an animal suffers on a long journey. The site should also be either near or alongside a railway siding or waterway wharf, for precisely similar reasons. For the easy and cheap conveyance of the dead meat to the butchers’ shops and cold storage, it will be necessary to have the slaughter-house in as central a position as possible. The approach roads to the site should be as wide as possible, allowing the cattle an easy passage to the lairs. The laying out or planning of the site is a very important point, and care must be exercised to group the whole accom- modation for each class of cattle. There appears to be little doubt that the large slaughter-house is much the better idea; the system of having a number of small slaughter- houses, each to be used by one butcher, having many disadvantages and lending itself to serious objections, owing to the inability to properly inspect the meat before it is removed. The planning and construction of the two types are practically similar; and we will confine ourselves to the single large slaughter-house and the necessary buildings adjoining. Accommopation.—In designing a _ public slaughter-house, it is usual to provide for the following accommodation : (1) Lairs for cattle ; (2) pens for sheep ; (3) slaughter-house; (4) tripe - dressing department; (5) pig - killing department, consisting of sties, covered yard, scalding-house, tripe-dressing department, and a meat-dressing department ; (6) cold stor- age (sometimes); (7) refuse receptacle and B ABA destructor ; (8) water purification plant; (9) inspection lairs for cattle before being slaughtered; (10) hospital for cattle under observation, with slaughter-house attached ; (11) porter’s or superintendent’s lodge and administration block, including office and weighing machine. ° It will be seen that a well-appointed abattoir contains many departments; and it will therefore be impossible in the present article to go fully into the details of each department. It is proposed, however, to bring out the general principles in planning, and state the requirements necessary in this class of building. We will now deal briefly with each portion of the accommodation, proceeding in the order set out above. 1. Larrs ror Cartiu.—The places where the animals are rested previous to being killed. They should be placed as close as possible to the slaughter-house, but should not enter directly into it, but into a passage or corridor leading into the slaughter-house. It is usual to make the lairs of sufficient size to accommodate three days’ meat supply. The paving should be of hard impervious materials, e.g., asphalte; but in the corridor granite setts are best, as the beast struggles when he “smells blood’; and asphalte is rather too slippery. The walls for six feet from the floor should be lined with hard smooth material, e.g., iron. The lairs must be well ventilated, lighted, and drained. The upper part may be used for storage purposes. In the lair, water and hay troughs should be fitted for feeding purposes. 2. Pens ror Suerp.—These should be con- structed and arranged in an exactly similar manner as the lairs for cattle. 3. THe SiavcHTER-HoUSE.—There are two systems upon which this may be designed: (a) A number of small complete slaughter- houses; (b) one large hall. The latter form ensures much more cleanliness and more efficient supervision of the meat, and for these reasons alone it is to be recommended. The hall should be large enough to allow for killing three days’ meat supply in one working ENCYCLOPAIDIA OF ABA day. All cattle, large and small, may be killed in this large hall—also sheep. The hall should, where possible, face the north, be in close connection with and easy of access to the cold storage, tripe-dressing, and the cattle lairs and sheep folds. Light and ventilation must be plentiful; and protection from the heat of the sun is very necessary. Floors should be of hard, impervious material, and walls should be of light colour. It is usual to line the walls for a height of six feet with white glazed bricks, this allowing great facilities for cleansing. Drainage must be carefully considered, no gullies or gratings being per- missible in the slaughter-house. The floor should have a good fall towards the large doors through which the dead meat will be carted. Along the side wall an open channel should be constructed, delivering on to gullies outside the building, with gratings over, to prevent solids entering the drain. This drain should be carried to the water-purification plant, and the contents purified before being turned into the town sewer. The necessary killing rings must be placed in convenient positions in the floor. Doors should be made sliding, not folding. Water should be laid on in plentiful supplies, stand-posts being erected to each “killing bay.’’ The walls must be strong enough to carry the girders which support the winches and necessary hoisting and travelling gear. The necessary lavatory accommodation for the users of the slaughter-house must be provided near by. 4. Tripz-pressing Departmenr. — This should be provided close to, and opening out of, the slaughter-house, and fitted with basins with running water, scalding coppers, dressing and scrubbing tables, and hot and cold water basins. Steam willbe plentiful, and ventilation must be effective to carry this off. Light must also be plentiful. The floor and walls must be hard and washable, and similar to those of the slaughter-house. 5. Pia Kinuinc Deparrment.—This depart- ment is quite separate from the other portion of the abattoir, and consists of :—(a) Pig-sties for each butcher capable of holding three days’ ABA supply of pork, adjoining which, and separated by a gangway, are the (0) Killing and bleeding pens, which are covered over. (c) Scalding house, which is close to the killing yard, and must be provided with scalding coppers fed by hot water. Hoisting gear on travelling trolleys should be provided, by which the dead pig may be hoisted over the copper, plunged in, and then run on to the dressing house which adjoins. (d) Dressing house. This should be provided with plenty of suspension hooks on which to hang the meat. It should adjoin, or be close by, the cold storage, so that the meat may be transferred to this part for storage after being dressed. (e¢) The tripe- dressing department, adjoining the dressing house should be fitted up in a similar manner to that described for cattle. Store room for tools, dressing rooms for butchers, and lavatory accommodation should also be provided. 6. Comp Storace.—This is essentially an advantage for the private butcher. It must be in close proximity to the cattle and pig slaughter-houses, and comprise cold-producing machinery room, coal stores, boiler-house, and annexes or antechambers. It should be capable of holding three days’ supply of meat, open direct on to the yard, with large sliding doors, and be so lighted that light is obtained and heat excluded. It should be placed, if possible, on the north-eastern side of the site with the south and west sides adjoining the slaughter-house, or some part of the buildings. Overhead pulleys travelling on rails must be provided for the conveyance of meat. All the inside faces of the walls should be lined with glazed bricks or tiles for the full height. 7. Reruse Disposau.—Ample means must be provided for the disposal of the refuse, and the most effective way appears to be the Pohlwil apparatus—a German invention. This system has been fitted up in duplicate at the City of London abattoir, Islington. The process is as follows:—The machinery consists of a steam-tight cylinder made of boiler plates, and fitted with hopper inlet and outlet with screw-down cover, steam connections, pressure MUNICIPAL AND SANITARY ENGINEERING. ABA gauge and safety valve, and provided inside with steel rollers. All the diseased carcases (which must be cut up), including skin, bones, and all offal, is inserted into the cylinder through the hoppers. The cover is then screwed down and steam injected under pressure. After a certain time, the cylinder is made to revolve and the inside cylinders also revolve, thus crushing up the whole of the contents into a fine brown powder. The cylinder is stopped, the cover removed, and the apparatus started again slowly, when the powder falls into a pit below. The great advantage of this system is that all the refuse of whatever description may be shot into the cylinder. The powder may be sold as a manure and is rich in fertilising qualities. In many abattoirs the refuse is disposed of either by burning or carting away in wagons. In any case the building used must be isolated, but in a central position, closed and well ventilated, and lighted by a top light. Near this may be placed the tripe-washing troughs. 8. Water Porirtcation Pxranr. — Before turning the contents of the drains into the main sewer or river (if one adjoins or is near the building), it should be put through a purification process. 9. Inspection Larrs.—Near the entrance to the abattoir should be placed inspection lairs for the cattle and pigs, so that they may be inspected by the veterinary surgeon previous to transit to the “killing lairs.” Suspected cattle and pigs should then be passed on to special detention lairs, and diseased ones on to the slaughter-house and premises for such. 10. Hosprraz ror Diszasep Animaus.—This should be entirely isolated from the other building, and consist of lairs and slaughter- house, with meat store attached, so that carcasses which are discovered to be diseased may also be stored in it. 11. Entrance Lopegz.— A small house should be provided for the superintendent of the abattoir, to which may be attached a weigh office, office for medical officer or veterinary surgeon, meter-house for gas or electric light, and store room for tools, &c., B 2 ABC and near, or adjoining the offices, should be placed the w.c. and urinal accommodation, and, in some cases, waiting rooms for drovers and cattle dealers. Cost.—This, naturally, varies for different towns. Some have small abattoirs, which supply the needs, whereas others, ¢.g., Birken- head, have one on a very extensive scale. On referring to the returns collected from different towns, the cost appears as follows :— Preston costs about 11d. per head of population Birkenhead ,, 2/6 4 ” ” Carlisle » 8/6 4 3 ” Leeds » 1/2sd. ,, ‘3 ” Paisley » L1/64d. ,, ss i we A. B. C. Process (Sewage Treatment). —The precipitants used in this process are alum, blood, clay and charcoal. The blood is now omitted and it is probable equal results would be obtained by the alum alone. The process is used at Aylesbury and Kingston-on- Thames. A ‘native guano” is made from sewage by this method at Aylesbury, but there is considerable difference of opinion as to the commercial value of the product. The effluent is reported very pure, and the process appears to be carried on without nuisance. The quantity of sludge produced is considerable, and at Kingston this is disposed of by the Native Guano Company. : Absolute-rest precipitation tanks.— This type of tank is not used to any very large extent owing to the amount of fall and tank accommodation required. The “continuous- flow’ tank is more generally employed. After settlement in the absolute-rest tank, the top water is gradually drawn off by floating arms down to the level of the precipitated sludge, the latter being let off through a sludge- penstock. With quiescent sedimentation, two or three hours’ settlement is usually sufficient to yield a fairly satisfactory tank liquor. The tanks should be used in parallel, and the sludge should be frequently removed. ENCYCLOPADIA OF ABY Abyssinian tube wells.—These consist of iron tubes from 1} in. to 4 in. diameter driven into the ground until the subsoil water is reached for the purpose of quickly obtaining, by means of a pump fixed at the top, a temporary supply of water. Wells of this description were first extensively used during the Abyssinian cam- paign, hence the name by which they are now popularly known. These wells are also known sometimes as Norton’s tube wells, and American tube wells. The iron tubes are driven into the ground in lengths by means of a ‘“monkey ’’ — the first tube having a hard steel nozzle, the lower 2 feet of the sides of the tube being perforated. Successive lengths of tube are screwed on and driven until the necessary depth is reached. Such tubes have been satis- factorily put down to as much as 150 feet depth, but the usual limit is about 50 feet. The most suitable strata for obtaining water by this means are the chalk, gravel, and coarse sand where well satu- rated. The system is not suitable in fine sand, clay or marl, and the tubes cannot, of course, be driven through hard rock beds. After the tubes have been driven and water has been reached a hand-pump is attached and the yield of the well and quality of the water tested. Should the results prove un- satisfactory the well may be driven deeper, or the tubes withdrawn and redriven at another likely site. Abyssinian tubes are sometimes advantageously driven at the bottom of ordinary sunk wells for the purpose of in- creasing the yield. Where favourable condi- tions exist, a driven tube well affords a cheap, ready and safe means of securing temporary supplies. The quantity of water obtainable Abyssinian Tube Well. ACC will vary greatly according to the conditions of the site, nature of the strata, depth of well, and capacity of the pump, but if favourably placed a 1} in. diameter well may be expected to yield from 150 to 600 gallons per hour, a 2in. diameter from 800 to 1,500 gallons, and a 3in. diameter from 500 to 2,500 gallons. The cost of tube wells also varies according to the circumstances to be dealt with, but under ordinary conditions in gravelly ground a 1}in. by 30 ft. well may be expected to cost about £10, or 7s. per foot of depth, including all expenses of labour, materials and cartage. A 2in. by 30 ft. well would cost under similar circumstances about £15, or 10s. per foot of depth. W. H. M. Access Pipe.—A pipe having an air-tight, removable lid or a manhole giving access to the interior of the pipe and thence to the drain, soil, or waste pipe upon which it is fixed. Such pipes are most usefully provided at bends and junctions to provide means for clearing obstructions and for cleaning pur- poses. (See also CLEANING EvE.) Accumulator (hydraulic).—An appli- ance for storing water under pressure, whereby very heavy work may be accom- plished in a short time. It consists of a long vertical cylinder fitted with a weighted ram, which works, water-tight, through a stuffing box and gland at the top. By pumping water into the bottom of the cylinder the ram with its weight is raised, and the pressure due to the same may be utilised for driving hydraulic cranes, lifts, riveting or other machines, where the work is of an intermittent nature. The water supply to the cylinder is auto- matically regulated by causing the weight to strike levers, so arranged that when the cylinder is full and the ram at the top of its stroke, the forcing pumps are stopped; when approaching emptiness through the use of the water, the pumps are started again by the descent of the ram. The pressure per square inch will be equal to the total weight in lbs., including that of MUNICIPAL AND SANITARY ENGINEERING. 5 ACE the ram and the connections that move with it, divided by the cross-sectional area of the ram in square inches. The work stored in the accumulator is equivalent to the total weight in Ibs. multiplied by the height in feet through which it is raised; less a slight fractional loss in each case. The usual work- ing pressure for cranes and lifts is about 750 lbs., for machine tools. 1,500 lbs. and upwards per square inch. E. L. B. Acetylene.—Acetylene is a colourless gas, having a sweet ethereal smell. As ordinarily made it has a peculiar penetrating odour like that of garlic, due to the impurities which it contains. Chemically, it is an unsaturated hydro-carbon, having the formula C,H», and containing by weight 12 parts of carbon to 1 of hydrogen. Its specific gravity is 0°9, that of air being taken as unity. At 62° F. 1 cub. ft. = 0°0685 lbs. and 1 lb. = 14°6 cub. ft. Jt is slightly soluble in water, 10 volumes of which at 62° F. dissolve 11 volumes of acetylene. If, however, the water is saturated with salt, 20 volumes of it dissolve only 1 of the gas. Acetylene may be prepared in various ways, but for practical purposes it is obtained from calcium carbide, a hard greyish substance, generally of a fine crystalline texture, which is made by reducing quicklime with coke in the electric arc. The reaction is as follows :— Ca0 + 8C = CaCg + CO Baa Calcium Carbonic Quicklime. Carbon. Carbide. Oxide Gas. The specific gravity of calcium carbide is 2°22, and it contains five parts of calcium to three of carbon. When calcium carbide is brought into con- tact with water, the following double decom- position takes place :— Cal, + HO = CaO + GH, cae Water. Quicklime. Acetylene. The quicklime at once combines with the excess of water to form siaked lime, Ca[HO}. Theoretically, the quantity of water required ACE is under half a pint per pound of carbide, but in practice a pint must be supplied. Theoreti- cally also 1 lb. of pure carbide should give 5°93 cub. ft. of acetylene. In practice 5 cub. ft. is a good output; but yields up to 5°22 cub. ft. are claimed. Acetylene burns with a brilliant and steady flame, and during the past ten years has come into extensive use for small lighting installa- tions. In this country alone some 800 forms of generator have been patented, of which about one-tenth have been placed on the market. A good generator should work at a low tempera- ture and a low pressure, and should effect a complete decomposition of the carbide, so as to give a maximum yield of gas. The latter may be generated either by allowing the water to drip on to the carbide, or by dropping the carbide in small pieces into the water, the latter method possessing several important advantages. Two or three horizontal screens or gratings should be placed in the water to catch the carbide, and prevent it from drop- ping into the lime sludge which settles at the bottom. Generators are either ‘‘ automatic” or “non-automatic,” the former making the gas only as required for use, and the latter con- tinuously. With non-automatic generators holders must be provided to store the gas whenever the demand falls short of the supply. This form of generator is to be preferred. Commercial calcium carbide is never pure, and the resulting gas likewise contains traces of other substances ; the chief impurities being phosphuretted and sulphuretted hydrogen and ammonia. The gas should, therefore, be passed through a purifier before use. Acetylene has a high calorific value, namely, 1,504 B. T. U. per cubic foot, exclusive of the heat latent in the water vapour due to com- bustion. A cubic foot of the gas requires for complete combustion about 12 cub. ft. of air, the products being carbonic acid gas, water, and nitrogen. A mixture of avetylene and air is explosive when the proportion of the former is anywhere between 3 per cent. and ENCYCLOPADIA OF ADA 82 per cent. of the whole. The gas alone will explode when subjected to sudden com- pression. Composition tubing should never be used to carry acetylene, and the pipes should be of the best iron barrel, not less than 2 in. in dia- meter. The pipes may be somewhat smaller than for coal gas. When acetylene is burnt in ordinary gas- burners the flame smokes, and large quantities of soot are deposited. The best results are obtained from special burners with steatite tips, so formed that the gas is shielded from the hot nipple by a layer of air. The flame is small, white, and intensely bright, and owes its luminosity to the incandescent par- ticles of carbon which it contains. The amount of light obtained from acetylene varies with the make and size of the burner, ranging from 24 candles per cubic foot with burners consuming 4 cub. ft. per hour to 40 or 48 candles with 1 cub. fb. burners. The larger burners are, therefore, the more economical. For equal volumes acetylene gives many times as much light as coal gas burnt in a flat flame burner, and from 14 to 24 times as much as coal gas used with a good incandescent mantle. Light for light it consumes more oxygen, and evolves more CO, and heat than an incan- descent gas-burner, but very much less of each than the old flat flame burner with coal gas. With calcium carbide at its present price acetylene cannot compete with coal gas used with Welsbach mantles ; but its brilliancy and convenience will ensure its adoption in many situations where coal gas is not obtainable. A. J. M. Adams’ Sewage Lift.—This is an appa- ratus in which high-level sewage is applied to the work of raising low-level sewage to an intermediate, or middle level, intercept- ing sewer. High-level sewage enters the “flush tank,” which discharges its contents through a siphon, followed by a drop-pipe, into the ‘“air-cylinder”’ shown below, thus displacing the air contained in the latter, and ADA foreing it through an “air pipe,” which con- veys it to the “‘ forcing cylinder” or “ejector” situated some distance away in the low-level district. This air is there utilised to drive out the liquid contents of the “forcing cylinder ” through the rising main shown in the figure. After having been thus lifted the sewage gravitates to the nearest middle-level intercepting sewer. The “air cylinder,” after having been charged with the liquid contents from the “flush tank,” is emptied by means Cy TKKG G AMG WSS WOE \S LA JIE TTITi yy = ry Bare gh NEES 7 S Y yt Van 2 Se ST a /| pst ese Dr LULA Ree ea ee te ied” eed am Pence AIR CHAMBER OR POWER STATION SITUATED IN HIGH LEVEL DISTRICT. 4 MUNICIPAL AND SANITARY ENGINEERING. SAF INTERCEPTING SEWER SITUATED in MIOOLE LEVEL : DISTRIC -AER the height of the lift, &c., from 60 per cent, up to’ 500 per cent., or more for high lifts. The system is also applicable to raising sewage of underground conveniences, base- ments situated below sewer level, and such like. It is in operation at Douglas, Ilkley, Bowness, Crayford, and other places. Aérating Tiles (for Bacterial Bed Floors).—Aérating floors are most satis- factorily formed by constructing a floor of MANHOLE On INTERCEPTING SEWER errr rT Bar ] V Y Y Y y L Ze je ONE FORCING CHLINDER- oR EJECTOR SEWAGE EJECTING oR FORCING CHAMBER SITUATED in LOW LEVEL DISTRICT. Adams’ Sewage Lift. of a siphon shown in the illustration, and thus prepared ready for the next charge from the “flush tank.” The liquid delivered by the siphon from the ‘air cylinder” and the sewage from the rising main off the ejector are both delivered by gravitation to the middle- level intercepting sewer. Where high-level sewage is not available the town water supply is sometimes used to give the necessary head for creating the requisite pressure of air, but this obviously adds to the working cost of the system. The quantity of liquid used to raise a given volume of sewage varies according to local conditions, concrete 6 in. or 9 in. thick, according to the nature of the foundation, and then overlaying the same with a false or hollow floor of aérating tiles. Such a floor affords the best opportunities Fic. 1.—Ames’ Aérating Tile for Bacteria Beds. AER for the thorough and uniform aération of the superincumbent filtering medium, which is now recognised to be an essential feature in the efficient working of bacterial methods of purification. The tiles now used in this con- nection are of great variety of design, but all have a similar object in providing a strong open flooring so as to admit of the free circulation of air and at the same time afford adequate support for the superin- cumbent filtering materials. The three tiles illustrated are respectively of Ames’, Mans- field’s, and Stiff’s pattern, but there are many other varieties. They are usually made of stone- ware or hard burnt Staffordshire clays, and, though they need to be of ample strength, should not be heavier than absolutely neces- sary, otherwise the cost of carriage will render Fic. 2.—Mansfield Aérating Tile. Fig. 3.—Stiff’s Aération Drainage Channels. the flooring expensive. The ‘“ Mansfield”’ tile is simple and efficient, and, in the writer’s experience, costs from 2s. 6d. to 2s. 9d. per square yard laid complete. Aérobic and Anaérobic (Treatment of Sewage).—These terms, which are applied to two different classes of bacteria, simply mean “living with air”? and “ living without air.” In 1861 Pasteur discovered that many bacteria could live, and even set up active fer- mentation, in the absence of oxygen, and he, therefore, gave these organisms the name of anaérobes. His statements, being soon cor- roborated, resulted in the classification of bacteria into two groups—the «érobes and the ENCYCLOPADIA OF AER anacrobes. To the aérobes are due the con- version of urea into ammonia, and ammonia into nitrate. To the anaérobes is attributed the decomposition of cellulose and allied substances with evolution of marsh gas, the removal of oxygen from nitrates with simul- taneous oxidation of organic matter, and the decomposition of complex organic matter, with production of ammonia, hydrogen, and other substances. In sewage purification the work of the anaérobic bacteria is mostly done in the sewers and in the septic tank, whilst that of the aérobic class is confined mainly to the percolating beds. In contact beds both aérobic and anaérobic conditions obtain according to the alternating periods of rest and work. Fischer in “ Structure and Functions of Bacteria’ states that in the aérobic bacteria the process of respiration is the same as in all ordinary organisms. They absorb oxygen and with it break up non-nitrogenous bodies, such as glycerine or sugar, into carbonic acid and water. They are also able, like plants and animals, to assimilate nitrogenous substances, such as peptones and amido compounds, although with less gain of energy and less easily than they can carbonaceous bodies. Many of the aérobic bacteria are totally unable to live without oxygen, and when deprived of it die, as would a mouse in pure hydrogen. They are exclusive, or obligatory aérobes. Contrasted with the obligatory aérobic bacteria we have the obligatory anaérobic forms, which thrive only in the absence of oxygen, small traces of this gas being sufficient to inhibit growth. Between these extremes there is a great host of bacteria representing every gradation between the two modes of life. These are the facultative anaérobes, which, while growing best with a plentiful supply of oxygen, are nevertheless able to exist with a very small amount, and even with none at all, although in this case their vitality is often much impaired. Anaérobic bacteria, both obligatory and facultative, are found every- where in Nature where the air cannot penetrate, or where it is replaced by other gases in the AFT deeper layers of the soil; for instance, in the mud of rivers and standing waters, or the ooze of the sea bottom, and in manure. In all such places anaérobic bacteria are the prin- cipal, and often the only, forms of life, and by the fermentative and putrefactive processes they set up they effect the disintegration and removal of dead animals and plants. W. H. M. After-flush.—A small quantity of flush- ing water discharged into a closet basin after fhe main flush from the cistern has been expended. Its object is to ensure that the closet trap is fully charged. Air Compressor.—When air is required at a very moderate pressure a steam engine can be made to serve the purpose of a com- pressor, in which case the air is drawn in through the “exhaust”? port and delivered through the “ inlet” ports—the valve setting being modified to suit the circumstances. any pressure over about 20 lbs. per square inch, the cylinder, and especially its ends, must be water-jacketed in order that the heat due to the compression of the air may be carried off. Slide valves are unsuitable in this case, and their place is usually taken by disc valves automatically lifted from their seat- ings by the suction and discharge of the air, like those ofa pump. The suction valves are made as light as possible and of comparatively large diameter, and are fitted with very light springs, so that they may open readily and not ‘“ wire-draw’”’ the incoming air, and also close with a minimum of shock. To ensure a full cylinder and to diminish resistance the valves are, in some cases, opened “ positively ”’ by means of cams in the same manner as those of gas or oilengines. Equally important is the reduction of clearance spaces to the lowest practicable degree, as any compressed air remaining in the cylinder or valve passages, after the piston has completed its stroke, repre- sents wasted work. MUNICIPAL AND SANITARY ENGINEERING. For. AIR The chief source of loss in an air compressor is due to the fact that the heat is removed after instead of during compression, with the result that much of the work has been use- lessly spent in producing heat which is after- wards dissipated. This loss may be greatly reduced by dividing the work into stages, in which case the air is compressed to a certain point in one cylinder, then cooled by passing through pipes surrounded by water and after- wards further compressed in another cylinder. Two or more stages, with intermediate cool- ing, are adopted according to the range of pressures. Air may also be compressed by the direct action of falling water; this method is in use at several of the large waterfalls in America and Canada. (See ‘‘Comprussep ArR.’’) E. L. B. Air, Atmospheric, Purity of.—Air is a mixture, composed approximately of oxygen, 21%; nitrogen, 78°06 %; and argon, 0°94 % by volume. Traces of hydrogen, carbon dioxide, ammonia, and ozone, as well as of the rare elements krypton, neon, coronium, and others, are normally present in the atmosphere, with a variable amount of aqueous vapour and dust. The most impor- tant impurities are as follows :— Micro-oRGANISMS AND Dust.—These are by far the most dangerous impurities to be dealt with. Air free from dust probably exists only as a laboratory product. Dust is partly organic and partly mineral; itincludes particles of soil, vegetable matter, animal substances, micro-organisms, particles of sea salt, volcanic and meteoric dust, soot and other matters discharged from chimneys, pollen of grasses and flowers in the country. According to Aitken, there are 300 to 3,000 dust particles in a cubic centimetre of country air, from Argyllshire ; whereas that of London contains 48,000 to 150,000 per cubic centimetre. Mineral dust is found in all parts of the atmosphere ; organic only in the lower strata. . Micro-organisms are usually absent from the air at an altitude of over 6,500 feet and over AIR the ocean beyond 120 miles from land. The air of cities is rich in micro-organisms. The importance of dust as an impurity lies in its power of disseminating disease, and its effect in the production of rain and fog. Without dust in the air it appears certain that we could have neither rain nor fog, as a nucleus is required for each drop of water. Carson Droxripe exists in normal air to the extent of about 8 parts in 10,000, not 4 parts as is often stated. It results from the oxida- tion of organic matter, as in respiration and combustion. It has now been shown to be inert and non-poisonous, and acts only by displacing oxygen. Its presence is, however, used as an indicator of pollution from other causes, and 6 or 7 parts per 10,000is considered the permissible limit. Carzon Monoxipre.—This is a colourless and odourless gas, very poisonous, and having the same density as nitrogen. It is found usually as the result of imperfect combustion, or a coal-gas leakage; 1 part in 400 of air causes poisoning, and 1 % is rapidly fatal. Sewer Gas.—When present in the air in large quantities, sewer gas is known to have the effect of lowering the power of resistance of the human system to disease, and is moreover objected to on account of its characteristically unpleasant smell. Aqueous Vapour.—This is a very impor- tant constituent of the air, but can hardly be called an impurity. In the form of fog in smoky cities it is very injurious to health, although the evils arising from such fogs depend on the sulphur acids and solid matter held by the water rather than on the water itself. When the atmosphere is very damp, or approaching its saturation point, evapora- tion is impeded, the effects of heat and cold are more felt, and depression and other unpleasant sensations are experienced. The degree of saturation is called the “relative humidity,” it is usually 60 to Te Other impurities may result from special ENCYCLOPADIA OF AIR trade processes, and under particular con- ditions, asin mines; but the above are those of most importance under ordinary circum- stances in civilised countries. J. 8. O. Air-Lift—A method of raising water, petroleum, &c., from tube wells, by means of 4 lo lo jo lo lo b lo lo peora age. lop wr NOS ey nea LES © BPM EICE d Rabat cr I S19 = 5 i = ~ 25] EA Ie =~ a Hee ST BAe Se oe Saf eddy qe Ss cll Jo ao oe oe be = 2a = ¢ o a Qe yyy 4 Lh, 1 al wget 1 Oy bag oa Weak ( oO , ‘ a ' wt \re C z 1 compressed air. The apparatus is extremely simple and usually consists of two pipes 10 AIR lowered into the borehole—one for conveying compressed air, the other for carrying the water to the surface; both pipes are sub- merged to a certain depth in the liquid 0 b> raised. Referring to Fig. 1, A. P. AP Ba be RT RM. oe y= of 25 LEN LN WEES WT. a To £0.90. oe. e = Ole? Be BS 77223 GRAN ss fc — ‘i = sme FCS > OH —so a] o> = = = = =e Er a =- <. eo s> =. [~ — _—- Stich ea = ay sent Tem ae a) Ste] Sof +| -_ == Be ‘ NG oo e oe » ae a ase = e pl Po zeZie ee = Fie. 2. represents the air pipe, R. M. the water pipe or rising main, and W. T. the well tube. In some cases the air pipe is placed concentrically within the rising main (Fig. 2). When the well tube is of sufficient depth and suitable area, it may itself serve as a rising main. The working principle is as follows :—Air is MUNICIPAL AND SANITARY ENGINEERING. 11 AIR forced down the pipe A. P. and allowed to escape, at the bottom, into the water con- tained in the rising main R. M. This aérates and, therefore, reduces the specific gravity of the contents of R. M., with the result that the liquid is pressed or floated upwards by the superior weight of the column of non- aérated liquid outside it; as this leads to a constant replenishment of the rising main the liquid rises in a continuous stream. The drawings show the form of nozzle used by Dr. Pohlé, the reintroducer of the system. Since that time various improvements have been made in details; most of them consist in discharging the air through a narrow slit in order that it may more thoroughly mix with the liquid and avoid the formation of large bubbles which are apt to slip through the water without doing their share of work and also cause a pul- sating delivery. A recent improvement is to employ a tapered rising main (Price’s Patent) which allows the air to expand later- ally and permits the velocity of the water to be more uniform. The air acts entirely by volume as it has only to impart buoy- ancy to the water, but in order to escape into the rising main it must be supplied at a pressure just sufficient to overcome that due to the column of water above the nozzle. As this pressure diminishes as the top of the pipe is approached the bubbies of air expand (isothermally) as they rise and escape, at atmospheric pressure, at the outlet. It the water, after being raised, has to be taken in a lateral direction it should be allowed to flow there by gravity from an open tank, into which the rising main discharges, other- wise there will be a difficulty in getting rid oftheair. The ‘‘ submergence” or depth that the nozzle has to be immersed in the water contained in the borehole is governed by the height of the lift, in other words, the distance from the working level of the water in the well, to the height to which it is to be raised. In practice this varies from one and one-third to about twice the lift. Generally speaking, the deeper the submergence the greater is the AIR economy, as less air is wasted; on the other hand the borehole must be correspondingly deepened and the air pressure increased in proportion. Although the efficiency is low, seldom reaching 40% under the best conditions, its great simplicity and conveni- ence, coupled with the fact that more water can be raised by this system, from a given sized borehole, than by any other means, give it an important place amongst water- raising appliances. The system is in use for public water supply purposes at the Birken- head and Tunbridge Wells Corporation Water- works. (See ‘‘Compressep Arr,” ‘AIR Compressors,” ‘“‘ Hyprosraric Hrap.”’) E. L. B. Air Vessel.—(See ‘“‘ Pumps ann Pumpine Macuinery.”) Algz, Growth in Water Supplies.— Numerous low forms of vegetable life may occur in potable waters, and many of these it is impossible to classify or to identify. During their life history some assume several different forms, and frequently free swimming cells are found which may belong to the animal kingdom or may simply be the spore form of an alge, or of a fungus. Practically all the extremely small organisms which contain chlorophyll are alge, and Cooke’s definition of these may be accepted as most useful for all practical purposes. ‘“ Algals, or Alge,” he says, are “ cellular flowerless plants, for the most part without any proper roots, or mycelium, living, with rare excep- tions, entirelyin water, andimbibing nutriment by their whole surface, from the medium in which they grow.” Just as the colouring matter of leaves varies from the darkest green to the brightest red, so the colouring matter in the alge varies, but the great majority contain chlorophyll of some shade of green. In the absence of sunlight they cease to grow, light being essential for the formation of ENCYCLOPADIA OF 12 ALG chlorophyll. Warmth encourages growth, cold retards it, and probably there is a range of temperature for each organism within which it can live but beyond which it will speedily perish. There is doubtless also an “optimum” temperature at which growth is most rapid. Many of these low forms of plant life produce spores, and these are far ° more resistent to adverse influences than the organisms which produced them, hence after all growth has apparently disappeared from the water spores may be lying dormant, capable of producing an abundant crop as soon as the environment is once more favour- able. Whilst many are capable of growing in the purest of natural waters, there is no doubt that rapid proliferation is only possible where the water contains traces of impurity in solution. In large reservoirs algoid growths rarely prove troublesome, but occasionally for some unexplained reason some species will multiply with such enormous rapidity as to discolour the whole of the water, and on occasions impart to it an odour and taste. Usually the latter do not develop until the stage of rapid development is passed, then the nutriment in the water being exhausted or the conditions having become unfavourable, the organism dies, and in decomposing produces the compounds which impart the odour and taste. Apart from the trouble which may be caused by the development of any odour, these organisms when in unusual abundance rapidly choke sand filters, and cause grave incon- venience. Often when a water has been cleared from one class of organism others will, at a later date, appear. Thus in the Staines reservoir of the Metropolitan Water Board an enormous growth of Oscillatoria appeared in the autumn of 1907. By the use of copper sulphate these were removed, but in the spring of the following year Asterionella, Synedra and Cyclotella appeared and seriously impeded the process of filtration. Alge are more prone to appear in uncovered small reservoirs, especially if fed by spring water. Covering so as to exclude light is the only effectual remedy. For further information ALL on this important subject consult Cooke’s “Fresh Water Alge ’ and Thresh’s “ Examina- tion of Water and Water Supplies.” Valuable information bearing upon the removal of alge by copper sulphate will be found in a paper by Dr. Kemna in Vol. XI. of the “ Transac- tions of the Association of Water Engineers.” (Vide also section on ‘‘ MicRo-oRGANISMS IN Water.’’) J.C. T. Alloys.—(Scee “ Merats.”’) Alumina and Lime (treatment of sewage).—The sewage of the eastern dis- trict of the city of Glasgow is treated with the precipitants alumina and lime in the proportion of two of the former to one of the latter. The sludge, after the admixture of hot lime, is pressed into cake by means of sludge presses, and when mixed with street-sweepings and ashes is disposed of for manurial purposes. The cost of the treat- ment per million gallons of sewage is put at £3 8s. Alumino-Ferric (Spence’s) is a com- mercial sulphate of alumina containing a small proportion of sulphate of iron, used as a sewage precipitant with the after addition of lime. It should be free from much excess of acid, as this wastes the lime. The gela- tinous alumina removes the suspended and some of the dissolved organic matter, and the iron removes sulphide. After sedimentation, a clear and colourless liquid can generally be run off, leaving a voluminous sludge. (See ‘‘ PRECIPITANTS FOR SEWAGE.’’) Ambulances.—Acts of Parliament—Site— Accommodation — Accessories —- Ambulances — Stretchers—Litters. Acts oF ParniamMENt.—Public Health Act, 1875; Isolation Hospitals Act, 1898. Sr1rz.—Ambulance stations are generally in conjunction with or near the police or fire station, the horses being then available for both purposes. 13 MUNICIPAL AND SANITARY ENGINEERING. AMB Accommopation.—Provision must be made for the housing of one or more horse ambu- lance vans, one or more hand stretchers, attendants’ house, work room, harness room, stables for horses with store rooms and hay loft. Accessories. — This article deals more particularly with the necessary appliances needed for street ambulance work rather than ambulance stations, and these consist of ambulance carriages and wagons, stretchers, and litters. Hach apparatus will be briefly dealt with, including the materials used in its construction. AMBULANCE CARRIAGES AND Wacons.—lt is a difficult matter to lay down hard and fast rules for the construction of these, as many points have to be taken into consideration, e.g., the amount available for the supply of horses, the nature of the roads, &c. The horse ambulance is the one recommended by the St. John’s Ambulance Association. “It is capable of carrying three patients on stretchers and one attendant inside. The stretcher and its mountings on the off side of the carriage can be removed, folded up, and attached to the roof, the cushion which was resting on the brackets designed for the pur- pose being removed. The upper stretcher on the near side is mounted on an elevator which can be lowered much on the principle of parallel rulers. This elevator can be removed, and, if made to fold up, can, with the stretcher, be attached to the roof. The lower stretcher and its mountings are also made detachable, and when removed, an omnibus remains, while, if desired, the whole of the fittings restore the vehicle to an ambulance for three stretcher cases. The dimensions of the body of the carriage are: height, 6 ft.; width, 4 ft. 6 in.; length, 6 ft. 4 in.: the well extending approximately 4 ft. 6 in. from the rear. A cupboard is available for surgical appliances when the off side stretcher is not in position, but this has to be removed when this stretcher is used.” (‘‘ Municipal Engineer’s Specification,” 1905, p. 83.) The doors at the back of the carriage are hung folding and AMB should leave the whole of the back clear, to give easy access and facilities for getting the stretchers in and out. Ventilation is obtained by having some of the small lights on the side made to open. The materials used in the construction are ash for the framework with mahogany panels, the well being made with birch sides and deal floor, the roof of pine covered with canvas and painted. Cushions should be stuffed with hair and covered with leather or waterproof canvas. The ‘‘ Municipal Engineer’s Specification,” 1905, p. 83, gives the following different varieties of horse ambulances : 1. Van-shaped without a well. 2. Van-shaped similar to No. 1 but provided with a short well, room being left for the turn- ing of the front wheels under that part of the body. 3. A similar vehicle with a long well, and a fore-carriage under which the front wheels turn. 4. Brougham shaped. 5. A light four-wheeled conveyance. SrrercHers.—These consist of a bed on which the patient reclines, poles and tra- verse bars and also feet, carrying straps, and straps for securing the patient, and a hood or covering of canvas. A stretcher generally weighs from 20 lbs. to 30 lbs. , Brp.—This is generally about 6 ft. long and 22 in. wide. The bed is generally made of canvas, sail-cloth, woven wire, cane, or other suitable materials. It is advisable not to have the width more than 22 in., or transport by railway will be impossible. The bed must be firmly fixed to the poles, though easily capable of being detached when necessary. Pillows or cushions may be provided. Poizs.—These may.be of ash or pine, steel tubing, or wood and iron combined, and extend about 12 in. beyond the bed at each end. The upper side should be rounded to afford protection for the canvas. The handles may with great advantage be telescopic. Traverse Bars.—These are used to keep the poles apart and complete the framework on 14 ENCYCLOPADIA OF AMI which the bed is fixed and kept tight. They are generally hinged to allow of the stretcher being folded up when notin use. The material is the same as the poles. Frrr.—tThese are generally of wood or iron and fitted with castors, to allow of the stretcher being pushed about. They should raise it about 6 in. from the ground. Srraps.—The carrying straps are made of either web or leather, and have adjustable loops for regulating the length for bearers of different heights. The straps for securing the patient are of the same material, and two or three in number, and for police purposes wrist straps are provided. Lirrers.—The following is a specification of litters by the St. John’s Ambulance Association appearing in the “ Municipal Engineer’s Speci- fication,” No. 1, 1905, p. 88, and if followed will give all the necessary requirements for this class of ambulance:—‘‘ Litters. The Ashford litter undercarriage is provided with two wheels 836 in. in height, usually with indiarubber tyres. It has a cranked axle to enable the stretcher- bearers to pass between the wheels instead of lifting the stretcher over them. It is fitted with four arms, capable of being used as legs or handles, which can be locked in either a horizontal or vertical position. A hood and apron are usually supplied as part of the litter.” R. H. B. American Tube Wells.—(See ‘ Anys- SINIAN WELLS.”’) Amines Process (sewage treatment). —tThis is a chemical precipitation process, which, it is claimed, sterilizes the sewage. The precipitants used are lime and herring-brine, in the proportion of 224 grains per gallon of lime and 4 grains of the brine. Lime alone in large quantities inhibits putrefaction and nitrification. In 1891 the system was tried at Salford, on the continuous flow principle. The wet sludge amounted to about 26 tons per million gallons. ANE Anemometer.—The direction of the wind can be ascertained from the indication of a well-balanced vane or weathercock ; or when this is not available by observing the drift of smoke. The velocity and pressure of the wind are recorded by means of anemometers. The instrument most generally used is the Robin- soncup anemometer. In this instrument four hemispherical cups, fixed at the extremities of cross arms attached to a vertical axis, are caused to rotate by the force of the wind. By means of an endless screw the revolutions of the vertical axis are communicated to a series of wheels, which indicate on dials the number of miles of wind. The graduations have been calculated on the supposition that the velocity of the wind is three times that of the motion of revolution of the cups. Later experiments, however, have shown that this value is too high, and differs also with the size of the instrument. For anemometers with 9-in. cups and 2-ft. arms. the factor is 2°2, and for anemometers with 5-in. cups and 1-ft. arms the factor is 2°8. The difference between consecutive readings of the dials gives the number of miles of wind which have passed the cups since the last reading. It is cus- tomary to express the rate of the travel of the wind in miles per hour. The instrument can be constructed to give a continuous record of the velocity of the wind. (For other forms of anemometers, see ‘“‘ Winp Forcs.”’) W. M. Anaérobic bacteria Gin sewage treat- ment).—(See ‘“‘ A#inopic AND ANAHROBIC.’’) Anti -Siphonage Pipes. — (See PHONAGE.”’ “Sr- Antiseptics are agents which retard or prevent putrefaction or decay. The difference between them and disinfectants is mainly one of purpose; the latter being directed to the destruction of the organisms of disease, and the former to the prevention of injury by microbial life to food or other commercial MUNICIPAL AND SANITARY ENGINEERING. 15 ANT products. Nearly all concentrated chemical solutions hinder the growth of organisms, but many of them in weak dilution actually pro- mote the development; instances are, salt, sugar, and acetate of potash. Disinfectants require to be antibacterial in a much weaker state. Another difference is that antiseptics as used in food must obviously be non-toxic. Since organisms only grow actively within certain limits of temperature and require water for their development, heat and cold outside those limits, or drying, act as natural antiseptics. Tinned goods are usually heated to boiling point or a little higher, but a temperature of 65-70° C., maintained for twenty minutes, kills nearly all bacteria though not their spores, and is sufficient to preserve milk for a reasonable time.t As to the effect of cold, flesh is preserved in commerce either as chilled, near freezing point, from 1 to 2° C., or for a longer time as hard frozen, from 9 to 18°C.; butter at temperatures down to 15° C., milk is frozen at 0°5° C., while fruits keep better just above freezing. Even at 10° C. bacterial multipli- cation is checked. Many organisms, how- ever, survive even when cooled to — 252° C. (Macfadyen & Rowland), therefore decay can recommence when the temperature is raised. Chemical antiseptics are numerous, and not al) innocuous. Ordinary “smoking” dries the surface and also impregnates it with acetic acid, formaldehyde and creosote. In salting the antisepsis is subordinate to a pro- cess of diffusion whereby the salt, with some- times nitre and sugar—neither of them strong antiseptics—pass inwards and displace the juices containing putrescible albuminoids: these pass out into the brine and leave the food drier and less susceptible to change, but, deprived of about one-third of its nutritive value, apt to cause scurvy when used too exclusively as a diet, and also less digestible. Small quantities of certain stronger anti- septics enable the original qualities to be in great part retained, and prevent decay for a 1 The International Congress of Hygiene, 1908, agreed on a minimum of 85° C. for ‘‘ Pasteurization,” but this had main reference to tubercle bacilli. ANT; considerable period with less influence on digestion than the old curing processes. Meat has been preserved with moderate success in an atmosphere of carbonic acid. Joints are often injected in the cavities with preservative solutions, usually boric acid, to wash out serous liquid and leave a small quantity of the antiseptic. Most acids are more or less inimical to bacteria and therefore inhibit putrefaction ; the value of acetic acid for this purpose is familiar, and formic acid, which has about three times the power, could prob- ably replace acetic in most of its uses. Sulphurous acid for foods is not satisfactory, but is much used for preventing decay in casks, for finings, and by butchers. Salicylic acid has been frequently employed in fruit preparations, but is prohibited in many countries. Sodiwm benzoate in 0:1 °/, strength is probably safer. Fluorine compounds in about the same proportion are sometimes used on the Continent in brewing. But the most popular antiseptics are boric acid for cream, butter, bacon, fish and milk, and formaldehyde, chiefly for the latter. The writer has shown that 1 in 2,000 of boric acid, or 1 in 50,000 of formaldehyde, is capable of keeping milk sweet for twenty-four hours even in warm weather, and neither is injurious in these proportions. Many aromatic bodies are antiseptic, but are not admissible in food on account of their taste or other properties. Total prohibition of chemical preservatives as sometimes advo- cated is illogical in view of the fact that salt, nitre, and vinegar, which can all be poisonous and are not the most effective antiseptics, are used in such quantities without question. An English Departmental Committee published their investigation of the subject in 1901, and recommended that formaldehyde be prohibited, that no preservative whatever should be allowed in milk, that the only preservative lawful in cream be boric acid in amount not exceeding 0°25 °/, and in butter and margarine an amount not exceeding 0°5 °/,; that as to salicylic acid not more may be used in foods than 1 grain per pint of liquid, or per pound of ENCYCLOPAIDIA OF 16 ART solid, its presence in all cases to be declared ; finally that in dietetic preparations for infants and invalids all chemical preservatives be prohibited (special supply for this purpose is in many cases practised at present). They concluded that preserving agents were needed, that the nature and amount should be declared on the label, and that a Court of Reference should be appointed to prescribe standards and for questions arising; but the subjects are still awaiting legislation. Another important application of antiseptics is to wood and cordage, in suppressing destruc- tive fungi and insects. The simple tarring sufficient for cordage does not penetrate the interior of wood, so that in the latter case a preservative liquid is made by pressure to enter the vessels. Copper sulphate (Kyanizing) was the earliest agent used, and is still found effective. Creosote oils are now commonly employed, but have the disadvantage of increasing the inflammability. S. R. Aqueducts.—Artificial water-ways con- structed for the conveyance of water through long distances, mostly for purposes of public supply. (See “ Water Suprry.”) Artizans’ Dwellings.—The term “ Arti- zans dwellings” is generally restricted to dwellings constructed for the accommodation of the working classes by a public company or association, or by a local authority or other public body, or a philanthropist, or group of philanthropists. They form but a small pro- portion of working class dwellings, for whereas there were in 1901 about eight million inhabited houses in the United Kingdom occupied hy about nine million families, of which it may be assumed seven million were of the working class, the total number of families accommodated in artizans’ dwellings coming within the foregoing definition is less than a quarter of a million. Until recently it was the common practice to construct most of these dwellings on the flat system in blocks, but there has latterly been a reversion to the ART cottage and other types of small houses. The dwellings erected are now of five types :— 1. Common lodging-houses, with either bunks or cubicles, and large common rooms. 2. Block dwellings, four or five storeys high. 3. Tenement houses of three storeys. 4. Cottage flats in two-storey self-contained dwellings. 5. Cottages of various sizes, self-contained, with gardens. Among the principal agencies for the erec- tion of lodging-houses may be included Rowton Houses, Limited, a society which has built six “ hotels for working men,” providing 5,162 cubicles, and having in each house a dining-room, reading-room, and sundry work- shops and offices for common use, at an inclusive cost of £400,000 and an inclusive rent of 7d. per day which has enabled a gross profit of £15,000 per annum to be made, sufficient to pay over 5 % on the capital. The artizans’ dwellings societies or com- panies in London have built dwellings, mostly in blocks, for 125,000 persons, and throughout the country 420 co-operative societies have built 48,000 houses, mostly cottages, at a cost of £10,000,000. Co-partnership housing societies, which are growling very rapidly, have for their basis four main principles: first, that the tenants should hold shares in a society which owns the houses; second, that they should share in all profits made by the estate ; third, that land should be bought in bulk and developed with open spaces and a limited number of houses per acre; fourth, that the spirit of fellowship and community should be fostered by the formation of societies of various kinds, and the provision of rooms and institutions for common use. They have a capital of over £1,000,000 and have developed estates at Birmingham, Ealing, Hampstead, Letchworth Garden City, Sevenoaks, Manchester and elsewhere. Municipalities have been entrusted with important powers and duties with respect to the supervision, improvement and provision M.S.E. MUNICIPAL AND SANITARY ENGINEERING. 17 ART of artizans’ dwellings by means of no less than 28 Acts of Parliament, of which the chief are :— (1) The Public Health Act, 1875 (sanitary clauses), together with the amending. or corresponding measures, the Public Health Acts (Amendment) Acts, 1890 and 1907, the Public Health (London) Act, 1891, and the Public Health (Scotland) Act, 1897; and bye-laws made under the provisions of the same ; (2) The Housing of the Working-Classes Act, 1890, with amending Acts of 1893, 1894, 1896, 1900 and 1908, which consolidate a number of previous enactments, known as Artizans’ Dwellings Acts ; (3) The Small Dwellings Acquisition Act, 1899 ; (4) The Municipal Corporations Act, 1882 (Sect. 111), and the Working Classes’ Dwell- ings Act, 1890; (5) The Labourers’ (Ireland) Acts, 1885 to 1906 ; (6) The Standing Orders of Parliament for Local Improvement and Public Companies Bills. So far as the provision of houses is con- cerned, the most important of these are the Housing of the Working Classes Acts, 1890- 1903. Part I. of the Act of 1890 enables urban authorities to condemn, clear and re-plan insanitary areas and to construct dwellings to re-house the working classes displaced. Over £8,000,000 has been spent under this and preceding Acts on clearance schemes, at a cost of £50 to £70 for each person displaced, in addition to an outlay, partly or wholly re- munerative, of £50 to £70 per head for dwellings in which to re-house the dispossessed. The principal schemes have been in London, Glasgow, Liverpool, Manchester, Leeds and Birmingham, but there have been schemes at Bath, Birkenhead, Bolton, Bradford, Brighton, Coventry, Devonport, Dublin, Leigh, Plymouth, Prescot, Portsmouth, Salford, Sheffield, South- ampton, Stretford, Sunderland and Wigan. Part II. of the Act provides for (1) the closing c ART and demolition by urban and rural local authorities of houses unfit for human habita- tion; (2) the removal of buildings which obstruct light and air; (3) the clearance and reconstruction of small unhealthy areas. It is estimated that there are over 700,000 houses which ought to be dealt with by these pro- visions, but the average number dealt with annually under all three heads is less than’ 10,000, and the amount spent on schemes for clearing small areas from 1890 to 1907 was only about £150,000. Part IIT. as amended by subsequent Acts enables local authorities to acquire land, borrow money, and purchase, or build and let artizans’ dwellings furnished or unfurnished of any kind. It also enables them to lease land to companies and private individuals for the construction of such dwellings. It was an ‘adoptive’ Act, but the new Act of 1909 makes it compulsory everywhere. Land may be compulsorily acquired at its ‘“‘fair market value’”’ which in default of agreement has to be determined by a single arbitrator appointed by the Local Government Board. Money may be borrowed by local authorities either in the ordinary way by mortgage or by the issue of stock, or it may be obtained at rates varying with the movements of the money market from 3 to 4 per cent. from the Public Works Loan Commissioners. It has to be repaid within periods not exceeding 80 years for the land, and 60 years for the buildings. The total amount borrowed under Part III. amounts to about £2,750,000 of which over £2,000,000 is in respect of pro- vincial towns. Part IIT. has been ‘adopted ”’ by the London County Council, 12 metro- politan borough councils, 30 county boroughs, 45 town councils, 50 urban district councils, and 12 rural district councils, or a total of 149 councils. Altogether the municipalities in Great Britain have built about 22,000 dwellings with 60,000 rooms. These include 80 model lodging houses in Glasgow, London, Belfast, Aberdeen, Manchester, Salford, Southampton, Blackburn, Bury, Paisley, and Perth, constructed at a cost of from £40 to ENCYCLOPADIA OF ART £60 per inmate, or an average of £65 per head for building and furnishing, and let at charges of from 4d. to 7d. or an average of 6d. per night inclusive. Municipal block dwell- ings to the number of 12,500 with over 30,000 rooms have been constructed in London, Dublin, Edinburgh, Glasgow, Douglas, Liver- pool, Manchester, Nottingham and Sheffield. The cost of building varies from £70 to £140 per room, but in most cases is between £85 and £100 per room; the rents per room average in London (per room) 3s. ld. per week, Scotland and the provinces 2s. 3d. per week. Most of the dwellings consist of two or three rooms. Municipal tenement houses to the number of 2,800 with 6,800 rooms have been built in Liverpool, Manchester, Sheffield, Plymouth and Devonport. The cost of building averages £70 per room; rents average 1s. 10d. per room per week. Most of the dwellings are of two or three rooms. Municipal cottage flats to the number of about 2,200 with 6,000 rooms have been built in Battersea, Dublin, East Ham, and West Ham. The cost of building varies from £40 to £80 and averages £70 per room; the rent averages 2s. 3d. per room per week, and the dwellings are about evenly divided between two, three, and four rooms. Municipal cottages to the number of 4,500 with 20,000 rooms have been built in 75 towns and villages, among which the most interesting schemes are those at Sheffield, Richmond, Merthyr Tydfil, Sevenoaks, Hornsey, and the cheapest are in Altrincham, Bangor, Exeter, Guildford, Neath, Prescot and Stretford. The cost of building has varied from £30 to £80, or an average of £45 per room. About half the cottages cost under £200 each and the other half over £200 each. Rents vary from 4s. to 8s. per week and average about 1s. 6d. per room per week. Half the cottages are let at 6s. to 7s. per week and two-thirds are under 7s. per week. Most of the cottages contain four or five rooms with a scullery. In considering the relative costs of the various types of artizans’ dwellings there are 18 ART three points to bear in mind: (1) The cost of site, which varies from £1 10s. per room for cottages on the outskirts of towns to £120 per room for block dwellings in the centre of large cities. (2) The cost of development of the site by constructing the necessary roads, sewers and approaches, which varies from £4 10s. per cottage, or £100 per acre, to £45 per cottage, or £1,000 per acre, according to the nature of the works required by the bye-laws or by the specifications. Under present conditions the cost of development of building sites for cottages is generally between £200 and £500 per acre in urban districts, so that it is often a more important consideration than the cost of the site itself. (See “Town Puannine.”) (8) Cost of building which depends partly upon the varying cost of labour in different districts but also upon the type of house constructed. It will be seen from previous figures that block dwellings cost twice as much per room to build as cottages. Much depends also upon the plans and specifications. In recent years great efforts have been made by means of local cottage exhibitions to encourage improved methods of design and construction for working class dwellings. At Letchworth Garden City a cheap cottage exhibition was held in 1905, when 85 cottages were erected for competition, at a supposed cost not exceeding £150 per cottage. A second exhibition in 1907 comprised 52 cottages as follows :—Class A: Three rooms and scullery, £175; Class B, four rooms and kitchen-scullery, £200; Class C, five rooms and scullery, £240. Cottage exhibitions on municipal land have since been held as follows :— Sheffield, 1907. Forty-two cottages in three classes varying from £175 to £2285, all of which were purchased by the Corporation for the sum of £8,391, and are now let to workmen. Newcastle, 1908. Highty cottages built under the city bye-laws on municipal land, and varying in cost from £195 to £350 upon city land leased at 4d. per square yard per annum MUNICIPAL AND SANITARY ENGINEERING. ART for land covered with buildings and 1d. per square yard per annum for garden ground. Swansea, 1909, in course of arrangement. In the three last-named cases the planning of the site was a special feature of the exhibition. Rurat Hovusine in England has hardly been touched by local authorities, only 54 cottages having been built, but the famous Labourers’ (Ireland) Acts, 1888 to 1906, have had the most remarkable results in Ireland owing, first, to the power given to working men where cottages are scarce or deficient to make an official representation to the rural district council, which must be acted upon, and, secondly, to cheap money and a Government subsidy. The terms for loans have varied from 2¢ to 82% The amount borrowed exceeds £3,415,000, and the number of cottages built is over 20,684, divided as follows: Ulster, 1,668; Munster, 10,617; Leinster, 8,018 ; Connaught, 336. They are let at weekly rents varying from 9d. to 1s. 6d. per week, and their average cost has been about £150. £47,480 was received in rent for the year ending 31st March, 1906; the Government subsidy was £41,610, and the rates contributed £63,000. These sums are just sufficient to pay interest and instalments for repayment of principal amounting to £151,898. The rates are paid by the occupiers. A new Act passed in 1906 provides for loans up to £4,250,000 being advanced by the Irish Land Commission repayable on the annuity system in 684 years at 31%, for interest and repayment on prin- cipal instead of £4 11s. 8d. as formerly. The Exchequer grant of £37,000 is to be divided among the districts building or having built cottages at a pro rata amount per cottage. In future it is estimated that the cost of Irish labourers’ municipal cottages will be paid 44rds. by the Government subsidy, 48rds by the labourer, and frds. by the rates. The financial working of artizans’ dwell- ings is a matter of great importance, so the following figures derived from official returns of various local authorities have 19 c 2 ART special interest. The buildings included in the returns only represent those as to which complete particulars are available. ENCYCLOPADIA OF London County | Eight Metro- Council Com- politan pleted Schemes. Boroughs. Capital outlay £1,900,000 | £393,192 Rents received... oe 120,000 28,451 Rates, Taxes, Water and Insurance Ge om 28,000 5,557 Repairs and Maintenance 12,500 3,563 Superintendence and Sun- dries a 2 8,000 868 Total working expenses .. 48,500 9,988 Net return on outlay 3°75% 466% Twenty-two Forty-five Towns} Towns Dwell- Dwellings Built | ings Built on on Open Land | Slum Areas or under Part III. in Central Districts. Capital outlay £930,450 £991,246 Rents received si 64,681 42,084 Rates, Taxes, and In- surance .. oh si 17,490 9,046 Repairs and Maintenance 6,472 7,898 Superintendence and Sun- dries ‘ a a 2,058 2,070 Total working expenses .. 26,010 19,692 Net return on outlay 414% 2°25 % It will be seen from the foregoing that the percentages of rents on capital outlay are: London County Council, 6°3%; metropolitan boroughs, 7°2%; forty-five Part JII. schemes, 69%; twenty-two re-housing schemes, 4°2 %. The percentages of the rent that go for various expenses are as follows:—Rates, Taxes and Insurance: London County Council, 24%; metropolitan boroughs, 20%; forty- five Part II]. schemes, 27%; twenty-two re- housing schemes, 22%. Repairs and main- tenance: London County Council, 105%; metropolitan boroughs, 125%; forty-five Part III. schemes, 10°1%; twenty-two re- housing schemes, 187%. As the rate of interest on loans was in most cases 8 to 33 %, the first three groups appear to be self- supporting, and the last group (dwellings on central or slum sites in provincial towns), shows a deficiency of 1% per annum. It has, however, to be remembered that in the case ART of the London County Council, as well as some of the metropolitan boroughs and also some of the last group of provincial towns, the site has not always been charged to the capital outlay at its full cost, but in some cases at a figure called the “ housing valuation,” which represents only the value put upon the sites for housing purposes, and varies from £2,000 to £4,000 per acre. In some cases it is only one- tenth of the actual cost. If the actual cost of clearance of the slum sites be added to the capital outlay, the net return on capital out- lay would remain the same for the forty-five Part III. schemes, but would be 1% less for London County Council schemes, and 3% less for the twenty-two provincial re-housing schemes. The real justification for outlay on municipal artizans’ dwellings is the saving of life and health which follow improvement schemes. Death rates have fallen 30% in the last seventeen years for London; 3°7 per 1,000 on Plymouth Part I. areas; 10 per 1,000 in Glasgow during forty years; 17 per 1,000 for the Trowgate area ; and 35 per 1,000 in respect of slum areas cleared in Liverpool. W. T. Artesian Well.—An artesian well is a boring into the earth through which water rises. In some cases the water overflows under con- siderable pressure, at the surface of the earth, due to the natural phenomena of water finding its own level. The name “Artesian” is derived from the belief that such wells were first employed in the French province of Artois, but they appear to have been used at a much earlier date in Lombardy, Asia Minor, Persia, China, and Egypt. The principle of the artesian well will be at once apparent from the figure, where it is seen that a permeable layer A B exists between two impermeable layers D Hand F'G. Water enters the porous strata at its “outcrop” at A and B, and accumulates in the bottom of the basin until it becomes fully saturated. Upon boring a well at C, the water rises therein under a head G H, or other pressure according to the saturation level in the porous strata. The water which supplies artesian wells is some- 20 ASP times drawn from distances of as much as 60 or 70 miles. A well at Grenelle, in the vicinity of Paris, is about 1,800 ft. deep, and yields about a million gallons per day, the temperature of the water being 80°F. Several artesian wells have been sunk by the writer through about 200 ft. depth of Wadhurst clay and penetrating a further 200 ft. into the Ash- down sands of the Hastings series for public water supply purposes. The artesian rise of the water is about 100 ft. These wells vary in diameter from 113 in. to about 16 in. and are lined throughout with steel tubes, the bottom lengths being perforated. The water is raised in one case by an “ air-lift’” and in the other Permeable layer, A B, between two impermeable layers, D F and F G. cases by deep-well pumps. Large quantities of water are obtained in a very similar manner in the Colonies for agricultural and other purposes. In Queensland some 200 million gallons daily is obtained from borings, the water in many cases overflowing at the surface under considerable pressure necessitating con- trol by regulating valves. Artesian water is also largely used in New South Wales, and in the Cape of Good Hope, in the United States, Algeria and Sahara and other parts; its discovery in all quarters proving an invaluable and indispensable aid to the development of the respective countries. It should be re- membered that water occurring in the chalk and other strata is almost entirely contained in the fissures of the rock, and that borings sunk in districts where such fissures are few and far between are not likely to yield a good supply. W. H. M. Asphalte.—A native mixture of hydro- carbons, found under varying conditions and differing widely in composition. Its chief MUNICIPAL AND SANITARY ENGINEERING. 21 ASP use is aS an ingredient in numerous paving materials (patent and otherwise); also, in combination with felt, wire meshing, and crushed stone (lime-stone, sand, or granite), for producing waterproof sheeting for damp courses (q. v.), in puddling sheets as a pro- tection for underground tanks and ponds, and for providing a dry base for the footings of foundations laid in water-logged soil or ground traversed by freshets; also as a damp exclud- ing insulating material in electrical engineer- ing. For practical purposes asphalte falls into four broad groups: (1) A bituminous mass mixed with clay or marle, as in the deposits of Trinidad, Cuba, and Mexico; (2) bitumen mixed with quartz, as in the deposits of Pyri- ment-Seyssel, Clermont, &c.; (3) bitumen mixed with schist débris, as in the deposits of Autun, Allier, Dauphiné, &c.; (4) bitumen mixed with calcareous débris, as in the asphaltes of Seyssel, Val de Travers, Lobsann, Clermont, &c. The character and behaviour of the mass depend largely on the nature of the oily constituents. Oils of the coal tar group are highly volatile; on distillation they appear quite limpid, but quickly discolour, diminish in bulk, and become viscous and hard. Consequently asphaltes containing coal tar oils soon become excessively brittle, dry, and rapidly deteriorate under ordinary wear and even under atmospheric influences. For this reason the many attempts to produce artificial asphaltes by mixing coal tar with lime- stone have failed. For paving purposes it is necessary that the oil should be non-volatile, and an evaporative test is usually demanded. But this is of less importance when the asphalte is intended as a binder in preparing solid dustless macadam roads; and, therefore, for this latter purpose artificially prepared asphaltes (mixtures of petroleum and car- bonate of lime) are admissible. A proposed specification for a macadam binder of 80 per cent. asphalte contents, is as follows: (1) It shall be soluble in bisulphide of carbon to not less than 99°5 per cent. ; (2) it shall be soluble in carbon tetrachloride to not less than 99°5 per cent., as a proof that the mixture has not ASP been overheated, as this would produce car- benes; (8) when heated to a temperature not exceeding 500° F. until 20 per cent. of the mass is evaporated, the residuum shall have a pene- tration of not more than 10 mm. when tested with a No. 2 needle, weighted with 100 grs. at 77° F., on the Dow machine; (4) the com- pound shall be sufficiently liquid at working temperature 50 cubic c.m., not to take more than 200 seconds to flow out when tested in an Engler viscosimeter at 212° F.; (5) the solid contents of the material shall consist only of asphalte, and the consistency of the residue shall not be due to any other solid substance, such as paraffin. The paraffin scale of the total compound shall not exceed 1 per cent. The paraftin scale is to be deter- mined by destructive distillation of the entire compound to coke, and determination of the paraffin scale in the distillate; (6) the asphalte binder shall not contain any dirt or water, but shall consist of pure bitumen only. Tar or substances recovered from acid sludge shall not be admitted. For a binding material, he above is a rather drastic specification. For paving purposes asphalte is placed on the market in three principal forms: (1) Partly purified, made up into flat circular slabs, this is melted in cauldrons with a small percentage of bitumen to act as a flux, sand or gravel usually being added, the mass being poured out on the site to be paved, rolled out and com- pressed ; (2) in the form of powder; (8) rock asphalte—this latter has to be ground cold in a special mill. Both these forms are heated in cauldrons before use, laid while hot, pounded and smoothed with heated irons; (4) patent mixtures, usually in the form of slabs, to be melted down for laying in situ, and containing special ingredients, such as cork refuse, &c. In electrical engineering asphalte is used in a refined state (bitumen) for insulating joint boxes, lining trenches, and impregnating the fibrous outer casing of cables. (See “ Dusr Prevention,” ‘“ Foorpatus,’ “ Roaps,’ and ‘‘ STREETS.”’) Asphalte Paving.—(See “ Roaps.’’) ENCYCLOPADIA OF BAC Bacteria.—Classification and Morphology.— Reproduction.—Products of Bacterial Growth.— Influences affecting Bacteria.—Observation and Staining. —Culture.—Pathogenic Bacteria and their relation to Sanitary Problems.—Diseases due to other Micro-organisms. CuassiFIcaTion AND MorpHotocy.—Bacteria are minute unicellular plants devoid of chlorophyll. Bacteriology comprises not only the study of bacteria, but also of other micro-organisms, some of which belong to the animal kingdom. The micro-millimetre («), the thousandth part of a millimetre, is the unit by which bacteria are measured. Bacteria vary in size from O°8u to 5°Ou; they are classified according to their shapes: a bacillus is rod-like, a coccus is round or spherical, while those spiral in form are known as spirilla. Some spirilla may occur in a shorter form as curved rods, known as “ vibriones.” The cocci are found grouped in characteristic ways. They may occur in pairs (diplococci), in chains (streptococci), in clusters like a bunch of grapes (staphylococci), and some bacteriologists add a fourth group of cocci — the sarecine, which divide in three directions and in two planes. Bacteria are not capable of spontaneous generation ; they can only be produced from similar organisms. Repropucrion. — Bacteria reproduce by fission, the mother cell dividing into two organisms. Some species are also capable of reproduction by spores, which are highly refractile bodies, formed either within the cell, or, in some cases, the entire organism becomes converted into a spore. Spores possess a re- markable resistance to physical and chemical agents. Few of the pathogenic bacteria produce spores, but B. anthracis, B. tetani, B. Welchit and B. botulinus are sporulating organisms. Organisms deriving nourishment from living tissues are termed parasites in contradistine- tion to saprophytes which favour dead material. Most parasites can be cultivated on artificial media—the leprosy bacillus being a notable exception. While some organisms require free oxygen (aérobes), others exist only in its 22 BAC absence (anaérobes), and some are capable of living under either condition. Propucts or Bacrerian Growre. — The action of bacteria is generally of an analytic nature, the complex material in the media being converted into simpler compounds. Surface soil contains large numbers of aérobic bacteria which diminish with depth, few being found below five feet. Even anaérobic bac- teria are absent in the lower layers. When brought in contact with the soil bacteria, the proteins, &c., of cadavers and excreta are first converted into liquid peptone-like bodies by organisms of the proteus group. A further simplification into organic acids and simpler nitrogenous bodies having occurred, these are converted into ammonium salts by B. mycoides, &c. The nitrous bacteria convert the ammonium salts into nitrites (nitrosa- tion), while the nitric organisms oxidise the nitrites into nitrates (nitratation) which are available for plant assimilation. Legu- minous plants have nodules on their roots, which contain bacteria capable of absorb- ing atmospheric nitrogen. Some soil bacteria have the same property. Preparations of such bacteria have a remarkable effect on poor soils. Ptomines are produced in flesh foods through bacterial metabolism. The smell accompanying putrefaction is due to gases such as methyl mercaptan, which can be detected by the nose when g3qdo.500 Of a milligramme is present in a litre of air. The symptoms produced by pathogenic bacteria are mostly due to the production of poisons (toxins). If the amount of toxin be insuffi- cient to cause death an antitoxin will in many cases be developed in the blood capable of neutralising the toxin. The resistance of the blood can be raised by gradually increasing the dose of toxin until complete immunity is conferred and the blood serum of an immune animal confers the protection on an animal injected with it. Many bacteria produce gas, others form a pigment. The characteristic red colour of B. prodigiosus is utilised to ascertain the identity of watercourses run- ning underground for a distance, and is also MUNICIPAL AND SANITARY ENGINEERING. BAC sowed on the surface soil to see whether any bacteria can gain access to a well by percola- tion. Yeasts and some bacteria ferment the carbohydrates. In common with certain true bacteria, yeast cells contain unorganised ferments (enzymes) which act after extraction from the living organism. Bacteria produce the phosphorescence on mackerel and decay- ing wood. InFLuENces aFFEcTING Bacrrria. — The violet and ultra-violet rays of the spectrum have a germicidal effect, the red rays having none. The electric arc has a similar action to sunlight but in a less degree. It is doubtful if sunlight assists to any extent in the purification of water ; probably only organisms near the surface are affected to any degree. Bacteria vary in resistance to desiccation, the spores being especially resistant. Cold, while the exposure lasts, inhibits growth but does not kill bacteria. The glass apparatus used in bacteriology is sterilised by exposure to dry heat at 150° C. for at least half an hour. Tubes and flasks containing media are sterilised under pressure in an autoclave or on three successive days in a steam steriliser by an exposure on each occasion of twenty minutes to one hour. This “‘ Fractional Steri- lisation’’ is calculated to allow spores, left alive after the first sterilisation, to develop into the more easily killed bacteria. (See also ‘“‘ DistnFEcTaNtTs,” and ‘‘ DIsINFECTION.”) OxssERVATION AND Srarnine.—Bacteria can be examined with a th in. objective, although for the larger bacilli in the fresh condition a 3th in. is sufficient. A drop of liquid containing them is placed on a sterile microscope slide by means of an inoculating needle,! a clean coverslip is superimposed and the microscope focussed, using cedar wood oil if the objective be an “‘oil immersion.”’ Under the microscope bacteria appear as pale translucent t An inoculating needle is a piece of platinum wire fused into a glass rod. For liquids the free end of the wire is bent into a loop two or three millimetres in diameter. Before and after use this needle and such part of the rod as may have become contaminated is sterilised by heating in a Bunsen flame. 23 BAC bodies, some being capable of motion. Apparently they contain no nucleus. Some bacilli and spirilla have whip-like threads of protoplasm (flagella) which render them motile. Bacteria are readily stained with anilin dyes, anilin, phenol, &c., being used as mordants. A droplet of water is placed on a clean coverglass, and by means of an inocu- lating needle some of the material to be examined is added, mixed with the water, spread evenly over the coverglass and allowed to dry. The preparation is “fixed” by passing the coverglass, held by forceps, three times through the Bunsen flame at the rate of the swing of an ordinary clock pendulum. A solution of a stain is added and allowed to act for a suitable time, when it is drained off and the coverglass washed in water to remove superfluous stain when it is again allowed to dry. A drop of a mixture of Canada balsam and xylol is placed on a, microscope slide and the cover-glass gently pressed thereon—pre- pared side downwards—and examined with an oil immersion lens. Cutture.—The cultivation of bacteria on artificial media serves two main purposes: it allows the separation of various organisms (in practice a pure culture of a single organism is rarely encountered) and the manner of growth on different media is invaluable for the identification of the organisms. A medium constantly used is a nutrient broth, made from extract of meat, peptone, and salt. This is too acid and is made neutral to phenol- phthalein, and then 10 cubic centimetres of normal hydrochloric acid are added to each litre of the neutral broth (a reaction of + 10 on Eyre’s scale). This reaction is acid to phenol-phthalein but alkaline to litmus—a suitable reaction for most organisms. (See also “ BactERIoLoGyY or WaTER”’ and “ Bacts- RIOLOGICAL EXAMINATION OF DISINFECTANTS.’’) Milk and many other liquids are also used. The solid media are also very numerous — solidified blood serum and ascitic fluid, potato and various jellies are used; two of these jellies are made by adding to the nutrient broth, above described, either ENCYCLOPADIA OF BAC 10 per cent. of gelatine or 14 per cent. of agar. The former is used for temperatures about 22° C., and the latter for blood-heat cultures. Gelatine and agar media are used for the isolation of various organisms — some of the material to be examined being mixed with the liquefied media, which, after being poured into covered glass dishes (Petri dishes), is allowed to set. The individual bacilli are now isolated and on incubation each produces a colony of its own species which can be submitted to examination and sub-cultured. Tue Renation or PatHocEenic BacTeRia To Sanitary Prosuems. — The fons et origo of sanitary science is the prevention of the spread of pathogenic bacteria, and although this idea may be wrapped up in a mass of engineering problems, the principle is still fundamental. It is therefore necessary to appreciate the various ways in which infection can be carried and the means at our disposal for preventing or limiting the same. Bacteria were at one time considered to be chiefly air-borne, but with the probable exception of small-pox, it is seldom that infection is so transmitted. Bacteria certainly occur in the air, being carried on fine particles of dust; but even in sporadic outbreaks of disease other channels of infection can usually be identified. The presence of damp surfaces in preventing the rise of ‘dust rafts”’ of bacteria, conduces to the reduction of the air bacteria. The emanations of sewers have been con- sidered a predisposing cause of typhoid, diphtheria, and tonsilitis. Andrews and Hor- rocks have proved that sewer gas contains sewage bacteria and thus may not only lower the resistance of the body to disease, but may also convey the specific bacteria. Bacterial sewage systems depend on the solvent and liquefying action of the sewage bacteria on the solids (see ‘“‘Sswace Disposau”). In the filtration of water through sand, an un- satisfactory filtrate is obtained until a slimy deposit of bacteria and alge has formed on the filter bed, when a reduction of 99 per cent. of the organisms can be attained. 24 BAC The typhoid bacillus (B. typhosus) occurs in the eruption, sweat, sputum, urine and stools of enteric patients. The urine and feces by gaining access to a water supply may cause infection. The typhoid bacillus gradually dies out when introduced into water, but it appears from recent experiments by Houston that although 99°9 per cent. of the typhoid bacilli disappeared within the first week, a period of nine weeks was necessary for its total disappearance. Hence the desirability of storing water obtained from sources not above suspicion. The typhoid bacillus will live longer in sterilised than in unsterilised water and when inoculated into unsterilised water, containing little organic matter, survives longer than when the organic matter is con- siderable. Flies feeding on the dejecta of typhoid patients take up the organism and thus spread the disease. Shell-fish and water- cress obtained from polluted waters are prone to infection. The typhoid bacillus may remain latent in the body for many years without its presence being suspected and without the host giving any indications of the disease. The “ typhoid carrier” through the discharge of infected feces may thus un- wittingly cause serious outbreaks of the disease. Apparently about 3 to 4 per cent. of typhoid convalescents become chronic “carriers”? while still more are temporary “carriers” for 2 or 8 months. Although soil in this country may become polluted with typhoid, its capability of conveying the dis- ease is more restricted than in hot countries. In India excreta are buried in the ground, aud during the frequent dust storms are carried with the dust for long distances. Virgin sandy soil and peat are inimical to the growth of the typhoid bacillus and it lives longer in moist soils than in dry. It rapidly dies in a cultivated soil, owing to the antago- nistic action of the other bacteria. Typhoid can be conveyed’ by fabrics, soiled blankets, &c., producing cases through subsequent use. It is generally agreed that the clinical pheno- mena, known as “typhoid fever’? are not necessarily due to the B. typhosus, other MUNICIPAL AND SANITARY ENGINEERING. 25 BAC organisms of the typhoid-coli group pro- ducing it. The group of organisms classed as ‘‘dysentery bacilli” are found in the stools of epidemic dysentery and infantile summer diarrhea. There is no record of them being found in water. B. coli communis is a normal inhabitant of the colon of man and the lower animals. It has also been found in the intestines of carrion birds and of some fish. Apart from its pyogenic and other pathological qualities, itis of interest as an indicator of feecal contamination of water, milk, shell-fish, &«. While in some respects resembling the typhoid bacillus, it shows certain marked morphological and cultural differences. It has three or four flagella and is feebly motile, B. typhosus being actively motile and possessing eight to twelve flagella. The Spirillum cholere Asiatice, or the “Comma Bacillus,” is the specific organism of cholera. (Chicken cholera and hog cholera are due to totally different organisms.) It is found in the ‘‘ rice water’ stools and vomit of cholera patients, and may be conveyed by water, milk, uncooked vegetables, flies and fomites. Cholera spreads most rapidly when the earth temperature is high ; this is generally coincident with low ground water. Pettenkofer observes that an increase in cholera is often preceded by a fall in the ground water. In water, the cholera spirillum rapidly dies out, but while present is most likely to be found on the surface. B. anthracis, the organism of ‘‘ wool sorters’ disease’? and “malignant pustule,” forms highly resistant spores. It has been found in a catch-pit in a hide factory, in sewage and tannery effluents, in Yeo mud, and in feeding stuffs. It chiefly enters this country on Persian wool, Chinese hides, and Russian hair, the blood stains and not the dust being probably the actual carriers of the germs. The spores in the bloody discharges not only make anthrax endemic in the vicinity but are probably also distributed by wind and flood. Earthworms have been said to carry the spores from buried carcases to the surface, BAC but this is questioned. ‘‘ Rag sorters’ ”’ disease is due to another bacillus. (Shoddy is prepared by the disintegration of disused garments and other cloth likely to be contaminated with bacteria, which are mixed with some new wool and freshly woven. Such disused garments are also made into “flock” for stuffing mat- tresses. As the old material is very seldom dis- infected in any way, and is of a nature that favours the retention of bacteria, its use is attended with danger, and legislation on this point is strongly needed.) B. tuberculosis may affect the lungs, peri- toneum, the membranes surrounding the brain, the skin, bones, and lymphatic glands, producing the various manifestations of tuber- culosis. Like the leprosy and smegma bacilli, it is ‘“‘ acid-fast,” i.e., when stained with hot carbol-fuchsin, the colour is not easily removed by 25% sulphuric acid. Certain bacteria occurring in butter and fodder have the same property, and hence the presence of an acid- fast organism in milk or butter offers only presumptive evidence of tubercle. The cow suffers from tuberculosis, which, when affect- ing the udder, infects the milk. The bovine tubercle bacillus is generally supposed to be identical with the human bacillus, and when present in milk is held responsible for abdo- minal tuberculosis. The flesh may also contain this organism, and the cooking is often insufficient to destroy it. Birds also suffer from the disease, and although the avian bacillus possesses slightly different characters, organisms with the characters of the avian bacilli have been isolated from the human subject. The tubercle bacillus abounds in phthisical sputum, and it is by inhalation of either dried expectoration or the wet spray expelled when a patient coughs, that the disease is chiefly conveyed. It is also conveyed by flies, and on the bodies, particularly the lips and hands, of patients. The dust in railway carriages, public-houses, and the homes of patients, is often the cause of infec- tion. Operatives in trades in which particles of dust are produced, are very liable to the disease. The compulsory segregation of ENCYCLOPEDIA OF BAC infected persons being impossible, recourse must be had to the prohibition of promiscuous expectoration, a judicious use of disinfectants, and proscription of infected food to reduce the disease; while the resistance of the body is materially increased by improved ventilation and general sanitary conditions, prevention of overcrowding, better feeding, and alleviation of social misery. B. diphtheria occurs in the throats of per- sons suffering from diphtheria, and forms toxins which are carried by the circulatory system. It is also occasionally found in throats of healthy persons. The disease is more prevalent in temperate than in tropical climates and is conveyed chiefly by personal contact, although epidemics have been traced to milk, while it is possible that the bacteria are also carried by the dust and wind. Sewer emanations predispose to the disease. An organism simulating the true diphtheria bacillus is sometimes met with (Hoffman’s bacillus). Streptococci occur in puerperal fever, scarlet fever, sore throat, meningitis, &c. Diplococci occur in pneumonia and gonorrhea. These strepococci and diplococci are pyogenic, as also are the staphylococci found in a variety of affections. Tetanus is caused by the introduction into a wound of the B. tetani, which occurs in soil and manure. It forms spores which, when stained, give the appearance of drumsticks. Influenza is due to a bacillus. It may per- haps affect dogs and cats, and “ pink eye”’ in horses is probably due to the same bacillus. B. mallet produces glanders and farcy, and chiefly affects horses, asses, and mules. Through being bitten, or otherwise receiving the equine mucus or saliva, man may be infected and also probably by eating the raw flesh of an infected animal. In man, glanders and farcy generally occur together instead of separately as in the horse. Knackers, how- ever, possess a remarkable immunity to glanders. Actinomycosis (ray fungus) is a streptothrix — one of the higher forms of bacteria. In cattle it produces “lumpy jaw” 26 BAC and “wooden tongue” and is communicable to man. It is epiphytic on cereals and straw, which probably communicate it to animals. Madura disease in its black variety is due to a streptothrix. Quarter-evil, foot and mouth disease, and swine fever are also due to micro-organisms. DIsEasEs DUE To oTHER MicRO-oRGANISMS.— Malaria is caused by a protozoan parasite, the Plasmodium malarie. It is conveyed by mosquitoes belonging to the Anophe- line. In the body of the insect and in the blood of the host, it goes through a long cycle of changes. Prophylactic measures deal chiefly with the exclusion of mosquitoes and the destruction of their larve, which are deposited in stagnant pools, by draining and covering the surface of the pools with petroleum or insoluble tar oils. Sleeping sickness is considered to be caused by T'ry- panosoma gambiense, a protozoan organism carried by a tsetse fly. A trypanosome (Tr. Brucei) is found in nagana (tsetse fly disease of horses) and another in Surra. A trypano- some is a spindle-shaped organism, with an undulating membrane at the side and an anterior flagellum. Tropical dysentery is due to amebe. Infection takes place from water and green vegetables. The hyphomycetes are generally non-pathogenic, but Aspergillus niger, the ringworm fungi, and Oidium albi- cans are pathogenic, the latter causing the white patches occurring in the mouths of infants ‘suffering from thrush. Syphilis is attributed to a spirocheta (a spiral filiform parasite with no flagella, but having an undulating movement) known as Treponema pallidum. The etiology of carcinoma, sarcoma, hydrophobia, and small-pox is uncertain, but probably the last two are caused by protozoa. There is sufficient evidence to warrant an assumption that damp houses are a factor in the production of cancer. It is possible that the infective agent (if such there be) exists in uncooked fruit and vegetables. Acari and microscopic eels may also have something to do with the infection. W. P. 27 MUNICIPAL AND SANITARY ENGINEERING. BAC Bacteria Beds.— (See “Szwace Disposat.”) Bacteriological Examination of Disin- fectants. — Influences affecting Germicidal Value — The Carbolic Acid Coefficient — The Garnet Method —The Thread Method — The Rideal-Walker or Drop Method—The Influence of Organic Matter — The Sommerville-Walker Coefficient.—As the function of a disinfectant is to kill micro-organisms, it is obvious that the proof of such capability by labora- tory experiments indicates its value in a way that chemical analysis never can. In the case of some coal tar disinfectants chemical analysis is absolutely useless as a measurer of germicidal power, this being to a large extent dependent on physical con- ditions not indicated by chemistry. In prac- tice bacteria are met with in conditions of varying vitality and environment. Some of these conditions cannot be properly simulated in a laboratory test, but by the introduction of various forms of organic matter we are able to ascertain with a reasonable degree of accuracy what conditions will diminish the value of the disinfectant. It is first necessary to ascertain the action of the disinfectant on “naked” bacteria, i.e., bacteria unprotected by any large quantity of organic matter, and then to incorporate in the test organic matter likely to be met with in practice, and find if any depreciation has occurred. The statements often seen to the effect that a certain disinfectant when used in a particular dilution will kill a certain organism in a specified time may be regarded as fallacious. Such tests are performed by adding to the diluted disinfectant a few drops of a bacterial culture, and at the end of certain periods transferring a loopful of the contaminated disinfectant to a tube of sterile broth, labelling, and incubating. A growth (which gives the broth a turbid appearance) shows that when the “sub-culture’”’ was made from the con- taminated disinfectant the bacteria were still alive. If death had occurred no growth would have taken place in the “sub-culture,” and the broth would have remained clear. Such BAC results are worthless for the following reasons : Even bacteria of the same species do not possess an identical resistance to disinfection. The number of organisms that will be killed by a given quantity of disinfectant is limited, and the velocity of disinfection also depends on their resistancy or age. When first brought in contact with the disinfectant the mortality of the bacteria is large but gradually becomes slower, and when a curve is plotted with the numbers of surviving bacteria as ordinates and the corresponding times as abscisse, it is hyperbolic in form. The tem- perature of the disinfectant during the period of contact (the medication temperature) affects the result considerably, a rise of two or three degrees, especially above the optimum tempera- ture for the growth of the organism, very appreciably increasing the power of the disin- fectant. Similarly a culture which has been incubated at a temperature favourable to the growth will be more resistant than one grown at a less satisfactory temperature. The same remark applies to the reaction and constituents of the culture medium. THe Carsotic Acip CoEFFIcIENT. — In 1896 Moor suggested, in order to obtain some trustworthy datum of the germicidal value of a disinfectant, that at the same time as it was tested, a solution of some trustworthy disinfectant should also be tested under the same conditions. This allows a comparison between them. Carbolic acid (phenol) is the standard disinfectant usually selected for this purpose as it can be accurately standardised. (Mercurie chloride is less satisfactory and its antiseptic effect in the sub-cultures is so marked that it is necessary to add to the sub-culture tubes some sulphuretted hydrogen water to convert it into an inactive sulphide.) Such an expression of germicidal activity is known as “the carbolic acid coefficient.” As will be seen when considering the Rideal- Walker test, this method provides for the simultaneous examination of a standard carbolic acid solution, and when a strength of the disinfectant under examination is found to kill the test organism in the same time and ENCYCLOPADIA OF BAC at the same time as the control carbolic acid, it is evident that the two strengths allow of comparison. Thus should a 1 in 250 solution of a disinfectant X allow of growth up to 5 minutes and kill in 73 minutes, anda 1 in 100 solution of phenol give life and death in the same periods, the carbolic acid coefficient of X would be 252 = 2°5. Reference to a chart of a test given later will further explain this. Carbolic acid coefficients obtained by different methods often differ, and workers not adhering strictly to the modus operandi with the same test also obtain unsatisfactory results. Hence when the precise technique of the Rideal- Walker test has been followed, it is customary to specify the same by calling the carbolic acid coefficient so obtained the Rideal-Walker Coefficient. As tests on naked germs, three methods have been put forward: the Garnet, Thread, and Rideal-Walker methods. Tue Garnet MetHop.—In this test, devised by Kronig and Paul, the culture of the test organism is dried on garnets the size of a pea. The garnets with the covering of the test- organism are soaked in solutions of the disin- fectant for known periods of time, when they are removed, well washed with sterile water, and then dropped into broth tubes. A carbolic acid control is introduced, but the test is very liable to error since the organism as well as the disinfectant may be removed in the washing. Tue Toreap Metxop.—An emulsion of an agar culture in sterile water is made, and sterilised silk threads are soaked in the filtered emulsion for an hour and then dried. Four dilutions of the disinfectant and one of the control are placed in thirty water watch glasses, each dilution being put into six watch glasses. An infected thread is placed in each watch glass, and from each different dilution an infected thread is taken at the end of every 24 consecutive minutes up to 15 minutes, well washed with sterile water and placed in a broth sub-culture tube. The difficulty of washing away the disinfectant without remov- ing the organism renders the results very 28 BAC unsatisfactory, and, like the Garnet method, it is eminently unfitted for working with organisms at all sensitive to desiccation. Tae Rrieat-Watxer Mernop (The Drop Method).—This test has been adopted by most bacteriologists, disinfectant manufac- turers, and large users of disinfectants, as a standard method, the process being un- doubtedly the most satisfactory hitherto devised. A special test-tube rack is desir- able, having two tiers, the upper for six sets of five tubes for sub-cultures and the lower tier with five holes for four medication tubes of the disinfectant and one of the control. The broth tubes in the upper tier are numbered from 1 to 80. The test is usually performed on a broth culture of the typhoid bacillus, which after inoculation has been incubated for 24 hours at blood heat. Other organisms may also be used, and it should be here remarked that disinfectants show a marked selective action on bacteria, the latter being more sensitive to one: disinfectant than to another when both disinfectants may have an equal effect on bacteria of another species. The inoculating needle has a loop of 8mm. diameter, the centre part of the loop being bent down. The standard carbolic acid is best kept as a 5% solution, which has been standardised by the bromine method. The requisite dilutions for controls are made from this. The broth recommended by Rideal and Walker for cultures and sub-cultures has the following composition : Lemeco . 20 grammes Peptone (Witte). 20 grammes Salt 10 grammes Distilled water to 1 litre. It is directed to boil the mixture for 80 minutes, filter, neutralise with normal sodium hydrate solution, using phenolphthalein as an indicator, and when neutral, to add 15 e.c. of normal hydrochloric acid. This gives an acid reaction of + 1°5 per cent. (+ 15 Eyre’s scale). The broth culture used should be free from clumps. This may be attained by MUNICIPAL AND SANITARY ENGINEERING. BAC running the culture through a sterile filter paper, or, as will be found more convenient, after agitation of the tube, allowing it to stand for 20 minutes before use, when the clumps will settle to the bottom and need not be disturbed when pipetting the culture into medication tubes. As the number and, consequently, the resistance of the organism probably differs according to the method adopted for the removal of the clumps, one process should be adhered to so that the culture will not vary much from day today. All pipettes, measures, and test-tubes must be sterile. The temperature of the room should be noted and the strength of carbolic acid used as a control altered to suit. (When working with an organism of unknown strength a “ phenol table” should be made in which five strengths of phenol are tested in the same way as when a disinfectant is the subject of the test. Then a strength should be selected which gives ‘‘life” at 24 and 5 minutes and “death” at 74,10, 124, and 15 minutes.) Five sterile test-tubes, plugged with cotton wool, are placed in the lower tier of the test-tube rack. Three c.c. of four dilutions of the disinfectant (made with distilled water) are put into the first four and the same amount of the control in the fifth. Into each in succession, at intervals of 30 seconds, three drops of typhoid culture are pipetted, the tubes being agitated to disperse the bacteria through the disinfectant. Halfa minute after the fifth inoculation, a loopful is taken from the first medication tube and placed in the broth tube marked “1.” This process is repeated at intervals of 30 seconds with the other medication tubes until the first five sub- culture tubes have been inseminated. (These will subsequently show whether an exposure to disinfectant of 24 minutes has been sufficient to kill the organism.) At the time when the first sub-culture from the fifth medication tube is made, the organism in the first tube will have been exposed for 44 minutes and 30 seconds later this is inoculated into broth tube ‘‘6,” and so on until all the sub-culture tubes have been inoculated. As the tubes are inoculated they are placed in a wire basket 29 BAC and are subsequently incubated for three days at 37°C. They are then replaced in the test- tube rack and the results observed and charted. The results of an actual test are given below: BS oe Ss 2] f 5} lf an | £ Bt | ‘ fa > 6 | 3 2|)}2] gz & a|E) g 3 = | G4 F Ff F 8 @ ° on 07 |] WN 5 = | & = S 3 pu 2 2 a ef lot | +] e | aq +: a no 2 5° S minutes. 7 | 10 + | + + | + = 20 240 120 Room Temperature 15°—18° ©, Time culture exposed to action of disinfectant— 2k + + + + B. TypHosus, 24 Hours’ Brora Cunture at 87° C. growth in sub-culture (life) ; — *, Rideal-Walker Coefficient g ao oF & oS 3 a + 6 DA 3 nm oS oO OM A | BI I 3 < ch a ° i 3 : 4 aw we KO Certain disinfectants when diluted separate out into layers, having very varied germicidal powers. As such disinfectants if made up a day or so before use are liable to produce a false sense of safety, the authors of the Rideal-Walker test have requested that a 1% solution of the disinfectant under exami- nation should be made up 24 hours before testing, and the further dilutions made from this. The results obtained by the Rideal-Walker process only show the value of a disinfectant ENCYCLOP.EDIA OF BAC when possible militating organic matter is practically absent. It has served and still serves the very useful purpose of eliminating disinfectants which are practically devoid of germicidal power. But it does not exclude the hypochlorites, permanganates and other disinfectants dependent for their germicidal powers on an oxidising action, which action is preferentially expended on dead matter rather than on bacteria. Various forms of organic matter have been suggested for incorporation in the test. Hewlett and Kenwood used feces and the Lister Institute also recom- mend a 3% emulsion of dried and ground feces for the purpose. This excretion varies so enormously in composition that its intro- duction into a standard test causes hopelessly erratic results, and the plea that it represents animal matter requiring to be disinfected in practice is put out of court owing to the im- possibility of disinfecting stools by chemical means alone; moreover the feces as used in the test bear no resemblance to the article met with in practice. Milk has also been suggested as a suitable material, but the fat globules exercise a protective influence over the bacteria in a way that no other material likely to require disinfection does. Urine on the other hand has constantly to be disin- fected, and its incorporation in the test as a diluent in the place of distilled water serves to bring down the “ false coefficients” of the oxidising disinfectants. Sommerville and Walker have emphasised the necessity of using separately certain simple organic substances. They first of all dilute the disinfectant with water, in the pro- portion recommended by the manufacturers, and make the further dilutions with 1°/, solutions of blood serum, mucin, peptone, casein, gelatine, blood, or with whole urine. The disinfectant is then allowed to remain in contact with the organic matter for one hour before adding the test organism. This in some degree simulates the conditions met with in practice where a disinfectant, soon exhausted on organic matter, offers no further opposition to further additions of infected material. In 30 BAC the case of the oxidising disinfectants the germicidal power wasted on the organic matter is obviously lost, but when a lowering of the coefficient occurs with the coal-tar disinfect- ants, it is thought by some observers that this does not necessarily indicate a deprecia- tion of the disinfectant. It is possible that the disinfectant carried down by sputum or other organic matter, may still be capable of continued action. To meet the influence of absorption, Sommerville and Walker have in- troduced particulate matter in the form of granules of rice starch. The diluent consists of water and animal and vegetable matter consisting of 0°5 % of gelatine, in solution, and 0°5% of rice starch (in suspension). Results obtained with this diluent are known as the Sommerville-Walker coefficients. In all forms of disinfection, Defries’s “factor of safety’ must be recognised. Sommerville and Walker suggest that ‘‘it might be insisted that the multiple 5 be applied as a minimum to the strengths of the various disinfectants which are found to perform the same work as 1 in 100 phenol.” W. P. Bacteriology of the London Water Supply.—Sources—Districts—W orks—Results (raw waters, stored waters, filtered waters, number of bacteria, B. coli test, type of B. coli &c., remarks)—-Research Work—Reports—Sum- mary and Conclusions. 1. Sounces.—The sources of the Water Board’s supply are from (1) the River Thames (about 52%); (2) the River Lea (about 23%) ; and wells and springs (about 25 %). 2. Disrricts.—The administrative districts of supply are as follows:—Hastern, Kent, New River, Southern and Western (total population, nearly seven millions). 8. Worxs.—From the point of view of quality of water, the Water Board’s supply is best considered as the following separate waterworks :— (1) East London (Clapton, Lea Bridge) filtration works (i.e., Lea water mixed with some well-water, after prolonged storage in 31 MUNICIPAL AND SANITARY ENGINEERING. BAC the Walthamstow reservoirs; also some well- water). (2) Sunbury (Hanworth) filtration works (i.e., River Thames water after settlement and passing through roughing filters; also gravel or spring water). (3) Kempton Park filtration works (i.e., chiefly Thames water after prolonged storage in reservoirs at Staines and Kempton Park). (4) New River (Hornsey) filtration works. (5) New River (Stoke Newington) filtration works. (6) New River (Clerkenwell) filtration works (i.e., mixed Lea (New River) and well-water, slight storage in Hornsey and Stoke Newing- ton storage reservoirs). (7) Southwark and Vauxhall (Hampton and Sunnyside) filtration works (i.e., Thames water, mostly after storage in reservoirs at Walton and Hampton ; also gravel water). (8) Lambeth (Surbiton) filtration works (i.e., Thames water after storage in reservoirs at Molesey; also gravel water). (9) Grand Junction (Hampton) filtration waterworks (i.e., Thames water after storage in reservoirs at Staines and Hampton; also gravel water). (10) Grand Junction (Kew) filtration water- works (i.e., Thames. water after storage in reservoirs at Staines and Hampton). (11) West Middlesex (Barnes) filtration works (i.e., Thames water after storage in reservoirs at Staines and Barnes). (12) Chelsea (Surbiton) filtration works (i.e., Thames water after storage in reservoirs at Molesey ; also gravel water). (13) Lea Valley wells (some of these are pumped into the Lea and New River, and some are used directly for supply purposes). (14) Kent wells (all used directly for supply purposes). : (15) Additional wells (Streatham, Honor Oak, Selhurst, &c.). (1), (2), and sometimes (8). supply of the Eastern district. (4), (5), and (6). Used for the supply of Used for the BAC the New River district, and (8) really belongs to this district. (7) and (8). Used for the supply of the Southern district. (9), (10), (11), and (12). Belong to the Western district. (18). Supplies both the Eastern and New River districts. (14). Supply to the Kent district. (15). Augments the supply to the Southern district. 4, Resutts.—The results as regards the bacteriological quality of the water during the twelve months ended March 81st, 1908 (unless otherwise stated), will be considered under the following headings:—(1) Raw waters; (2) stored waters; (8) filtered waters and unfiltered well-waters. (1) Raw waters.—Average total number of microbes per c.c. (gelatine at 20—22° C., colonies counted on third day). Thames, 3,170; Lea, 6,707 ; New River, 1,639. Average number of microbes per ¢.c. (agar at 87° C., colonies counted on second day). Period of twelve months ended July 31st, 1908. Thames, 280; Lea, 882; New River, 88. Average number of microbes per c.c. (lactose bile-salt agar at 87° C., colonies counted on second day). Period of twelve months ended July 31st, 1908. Thames, 41; Lea, 34; New River, 8. B. coli test :— Per Cent. oF SAMPLES CONTAINING :— 1 or 10 or 100 or | 1,000 or } 10,000 or more more more more nore B. coli. | B. coli | B. coli | B.coli | B. coli per c.c. | per ¢.c. | per c.c. | per c.c. | per c.c. % % % % % River Thames | 83'2 | 46°8 88 | 04 = River Lea 90°8 | 46°8 | 10:4 2-4 0-4 New River 49'6 | 14:4 16 = == It will be seen that the raw waters contain a large number of bacteria, many of which grow at blood heat, and not a few in a bile- salt medium. Further, nearly one-half of ENCYCLOPEDIA OF BAC the Thames, Lea, and New River samples contain at least 10, 10 and 1, B. coli per c.c. respectively. (2) Srorep waTeRs.—As examples of stored water the Chelsea, Lambeth, and Staines (Thames water). and Lea (Lea water) stored water results may be given. The nominal number of days’ storage being about fifteen, fourteen, ninety-five, and fifty-eight respec- tively. Average total number of microbes per C.c. (gelatine at 20—22° C., colonies counted on third day). Chelsea stored water, 208; Lambeth stored water (ten months’ average), 362; Staines stored water, 175; Lea stored water, 67. Average number of microbes per c.c. (agar at 37° C., colonies counted on second day). Twelve months ended July 81st, 1908. Chel- sea stored water, 44; Lambeth stored water (ten months’ average), 52; Staines stored water, 34; Lea stored water, 11. Average number of microbes per c.c. (lactose bile-salt agar at 87° C., colonies counted on second day). Twelve months ended July 81st, 1908. Chelsea stored water, 5; Lambeth stored water (ten months’ average), 8; Staines stored water, 2; Lea stored water, 0°6. B. colt test :— Per Cent. oF NEGATIVE AND PosITIvVE RESULTS. Stored Waters. Negative. Positive. 100 100 10 1 O1 | 0-01 c.c. ¢.cC. Ce. cc, c.c. cc. % % % % % % Cols. 1 2 3 4 5 6 7 Chelsea. 42°7 | 24-7 | 19:1 | 10-1 22) 11 (13-4)* Lambeth. | 16°2 | 82°5 | 27°5 | 16:2 T5 (23-7)* Staines. 83°7 | 383-7 | 22°9 96 (9°6)* Lea. 67-4 | 26-9 | 4:5 11 we * The figures in brackets are the aggregates of columns 5, 6,and 7. The enormous bacteriological improvement in the raw water as the result of storage is 32 BAC well shown by the foregoing figures. For example, 83°2% of the raw Thames samples contained B. coli in 1 ¢.c. of water. The cor- responding figures for the Chelsea, Lambeth, and Staines stored water were 13:4, 23°7, and 9°6 respectively. In the case of the Lea the figures are still more remarkable, as 90°3% of the raw Lea samples contained B. coli in 1 cc., whereas the corresponding figure for the Lea stored water isonly 111%. As regards the latter water over two-thirds of the samples actually contained no B. coli, even in 100 c.c. Streptococcus test—The raw waters are also examined for streptococci, but these microbes are nearly always absent from 1 e.c. of the samples. (8) FInTERED WATERS (AND UNFILTERED WELL- WATERS).—Average total number of microbes per cc. (gelatine at 20—22° C., colonies counted on third day). It sometimes happens that samples of the filtered water collected from the separate filter wells at the works contain an enormous number of bacteria. The great majority of these microbes, however, are believed to be harmless, and not to be asso- ciated with imperfect filtration. To include these figures in the averages would create an erroneous impression, and so all samples containing 100 or more microbes per c.c. have been excluded from the averages given underneath :— Average Number of Microbes per c.c. (exclusive of those Samples contain- ing 100 or more). 1. East London (Lea) bs oS 13°6 2. Sunbury (Hanworth). Results for 1907—8 not available. 3. Kempton Park 25°83 4,5 & 6 New River (Hornsey, Stoke Newington, Clerkenwell) . 57 7. Southwark and Vauxhall 12°7 8. Lambeth .. < 67 9&10. Grand J unetion (Hampton, Kew) 11:2 11. West Middlesex .. 9°2 12. Chelsea .. . 63 13. Lea Valley Wells (excepting Rye Com: mon and Amwell Hill), March, 1906, to March 31st, 1908 ; ae 384 14. Kent Wells ot vs : 5°6 M.S.E. 33 MUNICIPAL AND SANITARY ENGINEERING. BAC The following statement indicates that the exclusive figures for the filtered waters were small, and the percentage reduction effected by the processes of subsidence and filtration remarkably good :— Thames. Lea New River, Raw waters (microbes per c.c.)| 3,170 6,707 1,639 Filtered waters (microbes per c.c.) 11-1 13°6 57 Percentage reduc- tion 99°6 99:7 99°6 B. coli test.—The percentage number of samples containing no B. coli, even in 100 c.c. of water, was as follows :— Percentage Number of Samples contain- ing no B. coli even in 100 c.c. of water. 1. East London (Lea) .. af .. 85:9 2. Sunbury (Hanworth). Results for 1907—8 not available. 3. Kempton Park.. 90°1 4,5 & 6, New River (Hornsey, Stoke Newington, Clerkenwell) . 83°8 7. Southwark and Vauxhall 67:2 8. Lambeth 24 i .. 197 9&10. Grand J unction (Hampton, Kew) . = ». 79°0 11. West Middlesex 82:0 12. Chelsea .. 87°71 18. Lea Valley Wells (excepting Hive Common and Amwell Hill), March, 1906, to March 81st, 1908 .. .. 92°0 14. Kent Wells 90°2 The remarkable improvement in the raw waters effected by the processes of storageand filtration may be judged by the statement that whereas the majority of the raw water samples contain B. coli in 1 ce. only a minority of the filtered water samples contain this microbe in one hundred times as much water. Type of B. coli.—As regards the type of B. cola in the raw and filtered waters, the following table shows that the filtered waters contain pro- portionately (as well as actually) fewer typical B. colt than the raw water. D Type oF B. cout. Raw Waters. Filtered Waters. Out of 2,710 speci- | Out of 3,830 speci- mens of B, coli|mens of 8B, colt isolated from 750 | isolated from 7,797 samples of raw|samples of filtered water the propor-| water (including . . tion between the|Kent and Lea Type of B, enti. typical and non-| Valley — unfiltered typical races of B. coli expressed as percentages was as follows :— well-water), the pro- portion between the typical and non- typical races of B, coli, expressed as percentages, was as follows :— Typical B. coli - (+ lactose ; + indol) 816 54-4 Non-typical B. coli: (+ lactose ; - indol) | 94} 21-1) ge. ( - lactose; + glucose)| 89 § tee 24:4 J ne 5. ResgarcH worx.—A great deal of re- search work is carried out at the Water Board’s Laboratories. As yet (1908), however, only two special reports have been published on (1) ‘“ The vitality of the typhoid bacillus in artificially infected samples of raw Thames, Lea and New River water, with special reference to the question of storage,” and (2) on “ The nega- tive results of the examination of samples of raw Thames, Lea and New River water for the presence of the typhoid bacillus.” As regards the former, the reduction in the number of the artificially added typhoid bacilli was over 99% within a period of one week, in all the eighteen laboratory experiments. A few of the typhoid bacilli, however, remained alive for from four to eight weeks. As regards the latter, 294 experiments were made with 156 samples of raw river water. The total amount of water dealt with was 29,400 c.c., containing in the aggregate, nearly 186 million bacteria. 7,829 microbes were specially studied, but none of them proved to be the typhoid bacillus. These 7,329 microbes formed but a small fraction of the millions of the other bacteria which were excluded owing to the temperature of in- cubation, the composition of the media employed, and the fact of their appearing one the plate cultures as coloured colonies. ENCYCLOPASDIA OF BAL Undue importance, however, must not be attached to negative results. 6. Rerorrs.—Reports as to the quality of the London waters are made each month, and are incorporated in the “ Monthly Reports ” of the Government Water Examiner, appointed under the Metropolis Water Act, 1871. Yearly and special reports are also issued from time to time by the Water Board. The former may be obtained from the publishers for the time being of Government Publica- tions, and the latter from the Central Office of the Water Board, at Savoy Court, W.C. 7. Summary anp Conciusions.—The Water Board supplies a population of nearly 7 million persons. The supply is derived from the River Thames (rather more than one- half); River Lea (nearly one quarter); and wells and springs (about one quarter). Speaking generally : — (1) The raw waters on an average contain between 1,000 and 10,000 microbes per c.c. ; the filtered and well-waters between 10 and 100. (2) The majority of samples of raw water contain B. coli in 1 @c.; the minority of samples of the water actually sent into supply, contain B. coliin 100 c¢.c. These results are based on the results of the examination of between eight and nine thousand bacterio- logical samples yearly. The practice of the Water Board now isto store all river water, as far as this is practicable, antecedent to filtra- tion. There are good grounds for believing that adequate storage can render an initially impure river water, relatively (if not abso- lutely) safe for domestic use. It is essential, however, to render a stored water bright, clear, and palatable, by subsequent filtra- tion. A. C. H. “ Balancing Reservoirs.” —Small reser- voirs or tanks introduced in a pipe-line conveying water with the object of reducing the pressure of the water on the lowest part of the pipes by breaking up the fall of the aqueduct, or pipe-line into independent sec- tions. (See ‘“ Warser Stpriy.”) 34 BAL Ball Valves.—Made use of to automatic- ally regulate the supply of water to cisterns and tanks, and for maintaining the water at any given level. Made in various patterns, some to open vertically, some horizontally. They all consist of a valve acted upon by a lever having a hollow copper ball at the extreme end, which floats on the water in the cistern. When the water sinks, by being drawn off, the ball drops and opens the valve, or allows it to be opened by the pressure of the water in the main. When the cistern is full the ball ‘is raised and the lever made to close the valve. The length of the lever, and the size Ball Valves. of the copper ball or float are regulated by the diameter of the supply pipe and the pressure of water in the main. The longer the lever and the larger the ball, the greater the pressure brought to bear on the valve. Ball valves should be made to resist from four to six times the pressure ordinarily pressing against them, because on quickly closing a cock, the ordinary pressure is considerably increased by the shock or water hammer. They should be tested to act to their full pressure when the ballis half immersed. The valves should be made of hard brass or gun metal, and may be faced or provided with leather or vulcanised india-rubber washers. Barometer.—People are not always con- scious of the presence of the air around them, as it is invisible; but they feel its effects when it is in motion, as in wind. Air, how- ever, has weight, which is equal to 14°7 lbs. to the square inch. It is this weight which MUNICIPAL AND SANITARY ENGINEERING. 35 BAR raises the water in the common pump to the height of about 34 ft., this being prac- tically the balance of the weight of the atmosphere. As mercury is about thirteen times heavier than water, a column of about 30 in. of mercury is held up in a tube which has been freed from air, by the pressure of the atmosphere, and such a column of mercury is used as a barometer, for showing the changes in the weight of the atmosphere. The best form of barometer is that of the Fortin pattern. This has an adjustable glass cistern in order that the surface of the mer- cury therein can be brought into contact with the ivory point which forms the extremity of the scale. In the Kew pattern of barometer (which is largely used by meteorological observers), the cistern is rigid and closed, but the error arising from the change of level in the cistern (technically termed the “ error of capacity ’’) is overcome by contracting the divisions on the scale. Every barometer has a thermometer fixed to the brass tube, in order to show the temperature of the mercury in, and the scale of, the barometer. The mode of taking an observation is this :—- First note the reading of the attached ther- mometer ; then (if the barometer is a Fortin) adjust the mercury in the cistern by turning the screw at the bottom, so that the ivory point is just brought into contact with the surface of the mercury, but does not depress it; the ivory point and its reflected image in the mercury should appear to just touch each other and form a double cone. Next adjust the vernier so that its two lower edges shall form a tangent to the convex surface of the mercury. ‘hen read off on the scale by means of the vernier to the thousandth of an inch. Having obtained the actual reading of the barometer, it now requires to be corrected for (1), index error, and (2) temperature. The correction for (1) will be found on the Kew certificate if the barometer has been verified at the Kew Observatory. The correction for (2), viz., reducing the reading to the standard temperature of 32° F., can be found in Table I. of ‘* Hints to Meteorological Observers.” D2 BAT The barometer should be fixed at such a height that the observer can read the vernier comfortably when standing upright; it must hang vertically and be in a good light. Barometers should always be very carefully handled, so as to avoid breakage, or admission of air into the tube. It is best to carry the instrument with the cistern end upwards. In the case of a Fortin barometer, the mercury should be screwed up soas to fill the tube and cistern before the instrument is taken down. Another form of barometer is the aneroid. This isan instrument consisting essentially of an elastic metal box, exhausted of air, which indicates on a dial the changes due to varia- tions of external pressure on the box, and therefore, acting as a barometer. Aneroids are very handy and useful instruments; they, however, should not be absolutely relied upon for long periods, but should be checked from time to time against a mercurial barometer. A self-recording aneroid or barograph is an interesting instrument, as it yields a con- tinuous record of the variations of atmo- spheric pressure. As the pressure of the atmosphere diminishes according to altitude, the barometer is often used for the measure- ment of heights. In comparing barometric observations made at different places, account must be taken of their respective heights above sea-level; for the higher the station, the lower will be the reading of the barometer. So for the preparation of isobaric maps it is necessary to reduce all the readings to sea- level. ‘Tables for this purpose will be found in the “Hints” referred to above. W. M. Baths for domestic purposes are made in a variety of shapes and sizes to suit special requirements. The normal dimensions of ‘full-size’ baths are :— ft. in. Length . : 5 6 Breadth at head 2 1 Breadth at foot 1 8 Depth . 1 10 These dimensions are all internal. It is usual for baths to taper from head to foot ENCYCLOP#DIA OF BAT and from top to bottom to economise water. When the users are above average size or stout, ‘parallel side ” baths should be made use of as allowing more room. Baths are made of various materials, such as zinc, copper, cast-iron, fire-clay, marble, and steel. Zine baths are not durable. They were formerly much used for cheapness, but cast-iron baths are now made equally inex- pensive, and prove much more satisfactory, and have therefore almost entirely superseded them. Copper baths are also out of date, mainly by reason that they have to be fixed in cradles and enclosed in wood to prevent them from losing their shape. They have the advantage that they do not absorb much heat from the water. ‘‘ Porcelain” or fire-clay baths are not now so frequently used as formerly. They are heavy, cold to the touch, comparatively expensive, and very liable to fracture. Much the same remarks apply to marble baths, which may be cut from the solid block or made up of slabs. The more generally useful and satisfactory baths are made of cast-iron, porcelain, or vitreous enamelled. The former are the better, but the latter are slightly cheaper. Porcelain enamelled steel baths stamped from the sheet are of recent introduction. They promise to combine the advantages of the iron baths with cheapness and light weight, but have not at present had a sufficiently long trial to warrant a judgment as to their durability. All baths should be fixed without enclosures. Baths, Open-Air.— Site—Accommodation —The Swimming Tank — Entrance Lodge — Dressing Boxes. Sirz.—This should be preferably in a public park or in some open spot. The land should be fairly level, and lend itself to enclosure without being unsightly. If the site is sur- rounded by a belt of trees so much the better. Accommopation.—After settling upon the site, the next point will be the accommodation required. This is generally as follows:— Swimming bath, entrance lodge, conveniences, dressing boxes or sheds, slipper and shower 36 BAT MUNICIPAL AND SANITARY ENGINEERING. BAT baths (sometimes). As the “open-air treat- The steps of the stage should be covered with ment” is the main feature of this type of bath, indiarubber to give a firm foothold. slipper baths are very rarely required. Steps should be provided leading into the Tue Swimminc Tanx.—This may be either bath at each corner, either of stone or teak. sunk in the ground or built on the ground. h The more convenient way seems to be the = is former. The size must be decided upon accord- St ing to the number of bathers expected. The ao HHS depth should be from about 5 ft. at the shallow ref end to 10 ft. at the deep end, the water-line being 1 ft. below the top of the coping round the bath edge. The walls will be constructed of concrete, either reinforced or ordinary concrete construction. A rough method of calculating the thickness of the wall is as follows :— — Seerion C.C.— — Secrion B.8.— Thickness at top of wall = height x ‘80 5 », middleof wall = ,, x ‘50 ” ” bottom 99099 = » x “70 ferr — Secrion A.A.— This is only approximate, but is on the safe side. To get the accurate thickness of wall, diagrams of the thrust must be drawn. __ The walls should be constructed in two thicknesses, the outér portion having wall ties embedded every yard—one to every yard super of wall face. Over this face is put the bitumen sheeting for making the tank water- tight; and the inner wall—about 6 in. in thickness—is then constructed, being held to the outer portion by the wall ties. The floor is constructed in a similar manner, i.e, in two thicknesses, having bitumen between the layers, which should not be less than 44% in. in thickness. The top layer of the concrete floor should be constructed in alternate squares, about 6 ft. sides to allow of uniform shrinkage. A handrail should be fixed round the inside of the bath, 1 ft. from the top of the coping. The coping should not hang over the edge of the bath more than 2 in. Gangways round the bath should be wide and paved with either stone or granolithic, falling away from the edge of the bath to a channel. re Diving-stages, platforms, and water-shutes should be provided. Oiled teak will be found ia the most serviceable for the diving stages. 37 — Seace 4 fac 70 aw tren — were ae eer ana 2. $C ae a = l= Sa nr ¢| dnons — FI EYATION — Details of Diving Boards at Tovting Common Swimming Bath. Design by P. Dodd, Borough Engineer, Wandsworth. ey TO) BAT If of teak, lead should be fastened to the bottom step to keep same from floating. Enrrance Lopezr.—This should contain room for the attendant and pay office. Con- veniences may be placed at each side of the entrance, having entrances both from the inside of the bath enclosure and from the outside, so that when the bath is not in use the conveniences may be used by the outside public. Accommodation should be provided for both sexes. Dressing Boxes on SHEDs.—These should be placed either round each side or along one or more sides. They may be either separate dressing boxes or one long shed with seating accommodation, and hooks for clothes. It will be found possible to use the earth excavated from the bath tank as a screen round the bath by forming an embankment. The dressing boxes or sheds may then be either on one or any of the sides. If any open shed is provided, provision should be made for temporary division into compartments when it is women’s day. Curtains will be found sufficient for this. (For Acts of Parliament, see below.) R.H.B. Baths, Public Swimming and Slipper. —aActs of Parliament—General Considerations— Swimming Hall—Bath—Corridors—Gallery— Diving Platform—Attendant’s Cabins—Water Shute — Entrances — Club Room — Pay Box— Ventilation and Warming—Slipper Baths — Superintendent’s Apartments — Establishment Laundry—Boiler House—Temporary Floor— Continuous Filtration. Acts or Partiament.—The Acts of Parlia- ment governing the provision of Public Baths commenced with the Bath and Wash-houses Act, 1846, which is an adoptive Act. This Act entitles public Authorities to erect suitable buildings for public baths and wash-houses, and also make open bathing places, and con- vert any building for the same use. After seven years’ use the public authority may sell the buildings and land, if they should find that their working is too expensive. An im- portant section is that which provides that a ENCYCLOPEDIA OF BAT copy of the Bye-Laws made in respect of this Act shall be hung in every bath-room. Section 86 provides that the number of baths for the working classes shall not be less than twice the number of the baths of any higher class if but one, or of all the baths of any higher class if more than one, in the same building. Schedule B relates to the scale of charges, but was subsequently repealed and amended. The Act was amended in 1847, extending its power to further authorities and also regulating the number of first- and second-class washing troughs on the same basis as the slipper baths referred to in section 36 of the first Act. The amended Act of 1847 contains a revised list of charges for the use of the baths. The Act was again amended in 1878 to allow the bathing places mentioned as being “open” in the 1846 Act to be roofed over. The Act also limits the period during which a swimming bath may be closed to an extent of five months in any one year beginning with November and termi- nating at March. The local authority may during that time use it as a gymnasium or place of recreation, or for parochial meetings, but not for music or dancing. The Act also contains a list of charges relating to covered swimming baths. In 1882 the Act was once more amended in order to allow of baths, &e., being erected outside the parish but within easy distance of same. The amendment of 1896 repealed section 5 of the Act of 1878 which debarred the use of the bath during the winter season for the purposes of music and dancing, but only so far as London was con- cerned, and then only after an applica- tion made to the London County Council. However, in the year 1899 section 5 in the Act of 1878, which was still in force every- where except in London, and which prevented the use of the building for music and dancing, was repealed, and the buildings could thence- forth be used for that purpose, subject to permission being obtained from the County Council of their several districts. GENERAL CONSIDERATION OF THE SUBJECT.— When considering the question of public 38 BAT baths, there are several views which might be entertained, namely, whether it is more desir- able to group the swimming baths, slipper baths, and wash-houses in one centre, than to build say, a swimming bath in one spot, generally accessible to the whole town, and to erect one or more buildings containing slipper baths in other parts, preferably congested areas. The status of the town would likewise determine whether there should be a first- and MUNICIPAL AND SANITARY ENGINEERING. BAT be free. Again the size and character of the baths will be determined by the conditions of the neighbourhood. In some places there will be a greater demand for a first-class swimming bath. In another there may be a preponder- ance of school children which will require more attention being paid to baths for their accommodation. A wash-house or public laundry will be much in demand in a poor neighbourhood, and as such, should Fie. 1.—Temporary Floor for Public Swimming Bath. Designed by R. J. Angel, A.R.LB.A. second-class bath and also a separate bath for women, or whether it would be more economical to set apart a certain day when the first- or second-class baths could be reserved for women. There is often an objection on the part of women to the latter arrangement, as it is frequently inconvenient for persons to so regulate their appointments that a swim if desired must be taken on a certain day and at a particular hour, while the men on the other hand object to being closed out on perhaps the only day of the week when their business will allow them to receive a considerable amount of attention, but its entrance and general position should be kept as far away as possible from the other portions of the building, and provision be made for the sundry perambulators, mail carts, &c., used by the customers for the transit of their laundry work. The shape and position of the site are important matters, both with regard to the initial cost, subsequent up-keep, and convenience of administration. A long narrow site will necessitate long corridors, costly in their design, awkward for the public and difficult in supervision. 39 BAT THe Swimwine Haty.—The internal faces of the walls should be of red pressed bricks as they are not liable to condensation and a glazed brick dado shoulder high should be provided. Some slight attempt at architec- tural treatment might be indulged in by forming pilasters under the roof-trusses with string courses and ornamental bands, and seg- mental arches or oversailing courses at the eaves. It is not advisable to construct any windows which will admit direct sunlight, particularly on to the water as it not only annoys the bathers but promotes vegetable growth within the bath. The roof-truss should be of iron, and its design is a matter for the architect to decide. Some roofs are sloped to an ordinary pitch, with either a flat or curved tie rod, and boarded on the underside with diagonal boarding and the usual lantern lights along the apex; while other roofs of successful design have been formed of segmental section with curved lattice principals. It is usual to form the sides of the lantern with fixed wooden louvre boards for natural ventilation, but if the bath is to be ventilated in such a manner as to free the entrance doors as much as possible from draughts and an in-rush of cold air, the plenum system seems to be the one best adapted. In that case there should, of course, be no open louvres in the roof. All glass in the roof should be wired with netting within the thickness of the glass. The artificial lights, whether gas or electric, are best kept away from the centre of the pond, and placed so as to be accessible from the gangway. The swimming bath is generally the one item which determines the whole plan, and is the making or marring of the scheme. The swimming bath should be so planned that it may be most convenient not only for its obvi- ous intention, namely, a bath to swim in, but also a bath in which competitions may take place and be viewed by the public, and in addition to this be used during the winter season as a public hall. In order to be used for the two latter purposes, convenient entrances, exits and emergency exits, both from the gallery and floor level, should be 40 ENCYCLOPADIA OF BAT provided, together with facilities for receipt of entrance fees. Tur Barn.—The best manner to form the excavation is to dig out for the exact size of the boundary walls of the bathing hall, carry- ing the footings of the walls down to the level of the bottom of the bath, utilising the inter- vening space between the wall and the bath for laying the pipes and allowing sufficient room for workmen to execute repairs. The length of the bath along the waterline, should, for racing purposes, be a fraction of a mile, thus 105 ft. 7 in. equals one fiftieth of a mile and this is for all purposes a convenient length, although some are made 132 ft. or one fortieth of a mile. A short or an odd length will be sure fo produce dissatisfaction among expert swimmers. The width should not be great, no advantage being obtained by making it anything over 30 or 36 ft. wide (numbers dividable into yards). It should be remem- bered that an increase of width means a larger proportion of expenditure in construction than would be the case with an increase in length, as heavier scantling is required for the roof, and more material both in roof covering and bath construction, both of which are expensive items. The depth of the water should vary from 8 ft. 6 in. to 6 ft. 6 in., and the bottom slope of the bath should runin an even gradi- ent from the shallow end to about 10 ft. from the deep end, the latter 10 ft. having just enough slope to drain itself. Ladies’ baths, however, should be about 50 ft. long by 25 ft. wide, and with 3 ft. 6 in. to 5 ft. 6 in. depth of water. The floor of the bath should be formed of concrete of an even thickness of not less than 2 ft. It is advisable to form the excava- tion to the same slope as the bath floor, not as is sometimes done by stepping the excava- tion in level sections and forming the top surface of the concrete on the slope. This method will exhibit a weak spot where one step joins another and tends to produce a crack due to the unequal contraction and expansion of the material. It is, however, advisable to roughen the surface of the excava- tion to avoid any tendency of the concrete to ~ NNN. BAT ‘“‘ereep.” The concrete bottom should be carried under the sides of the bath and pro- ject on the outside for at least afoot. The sides of the bath should for preference be of concrete ramped or stepped in varying thick- MUNICIPAL AND SANITARY ENGINEERING. BAT asphalte should be about an inch thick laid in two thicknesses and of:such a consistency that it will not run when the temperature of the water is raised. The interior of the bath is lined with 44 in. white glazed bricks on the Plan ot Boorded Secltons Showing method of interlocking . SS N SRN TR IRR TLR N = ———— WTR vi x aw aN WS nN Tramsrerse Trusses . PSS = : EAN iS ae a or SS - | mS Gs! 3 { | =< I< lll ss t LEA SI A Sl — SS ae et eee Bare O%I=FLOOR TART IRIE TT TANT TITIAN STP SN Longitudinal Trusses RTAngelbmimsece: wf i tet oe 7 pe Seale of Feel. : Fic. 2.—Temporary Floor for Public Swimming Bath. Designed by R. J. Angel, A.R.I.B.A. nesses from 4 ft. at the base to 18 in, at the top. Buttresses at intervals should not be built, but the wall should be constructed of continuous thickness, each diminution of thickness being perfectly horizontal. The inside face of the concrete should be left rough to provide for a layer of asphalte being put as a waterproof coveting over all. This 41 sides, varied sometimes with a coloured (green) band along the top courses. It is not neces- sary to tie this 43 in. lining into the main body of the work. The bottom of the bath may be either “brick flat,” brick-on-edge, or thick tiles, the whole very carefully jointed with Portland cement compo. It is advisable to fill the bath with water after the asphalte BAT has been finished and before the brick lining has been commenced so as to test for water leakage. It is, of course, assumed that the earth forming the foundation of the bath is firm and secure, any defective portion being dug out and the hole filled with concrete. There is no advantage to be obtained in using reinforced concrete in either walls or bed, as it does not need so much as a “ collapse”’ to destroy the utility of the work, a simple crack or fissure being quite sufficient to ruin the watertightness of the bath, and this is just as likely to occur with reinforced work as with- out it. Especial care must be taken in build- ing-in all connections to pipes. It is as well to have a double flange to such connections, one placed on the inside of the bath and the other outside, and packing the concrete in between. All such connecting pieces should be built in as the concrete is laid. Overflows and scum troughs should be formed on the sides and more particularly at the deep end ; and also places where bathers can spit, although in some of the newer baths this latter has been omitted, but whether provided or omitted the tendency to spit exists so that it is better to provide for it than to allow bathers to expectorate in the water or on to the gangway. A handrail of galvanized iron tubing about 24 in. diameter should be placed about 2 in. clear of the water. The top of the gangway should be about 15 in. above the water line. It is assumed that there will be a passage formed around the walls of the tank itself for pipes, &c., so that the floor or gang- way around the tank will form the ceiling or covering to it. This gangway should be of steel girders in concrete and covered with some non-absorbent and non-slippery paving material. York flags and slate have been used, but both these are undesirable; certain qualities of red tiles are better, and one bath in London has a flooring of rubber tiles, but this has a tendency to allow water to percolate between the joints. Great importance must be paid to the non-slipperyness of the paving material. The curb around the bath may bea 4 in. finely tooled or rubbed York stone with ENCYCLOPAEDIA OF 42 BAT a round nosing. This gangway should be from 4 ft. to 4 ft. 6 in. wide, and if chairs are to be placed along the gangway during enter- tainments it should be 5 ft. wide. Consider- able space should be allowed at either end as it is there people mostly congregate—there should certainly be a not less space than 12 ft. at the deep end as races generally start from here and the opposite end may be 6 or 8 ft. wide. The gangways should have a slope from the water’s edge towards the dressing boxes, and a shallow channel be formed next to the boxes, with trapped galvanized gullies at intervals. The dressing boxes should only be ranged along the long sides of the bath and should be raised above the gangway by a 24 in. to 8 in. step. The floor of the dressing boxes should be of maple as this is the best wood to use where the floor is constantly wet. The size of the boxes ought not to be less than 3 ft. 6 in. by 8 ft. 6 in. for the first-class baths and 8 ft. by 2 ft. 9 in. for the second- class. The framing should be of pitch pine or teak, framed with as few internal angles as possible, of light scantling compatible with strength, and filled in with panels in prefer- ence to either beaded or V-jointed boarding. The door should be about 4 ft. 6 in. high and in the case of the women’s bath there should be a rail and curtain provided to fill up the space to the top of the box. The width of the doors need not be more than 27 in. and the remaining portion of the front may be carried up to the top of the box. In some of the more recent baths the door is also carried up for the full height, but the upper panels are in the form of a grill. In the latter case the latch which is provided should be opened on the inside with a knob and on the outside by an attendant’s key. Thedoor, and sometimes the framed divisions, are kept off the ground about 8 or 4 in., but the latter in some locali- ties is open to objection as it leads to the temptation for articles, such as boots, clothing, &c., which may be on the floor being stolen by persons in the adjoining box. In the public baths at Camberwell and Hoxton the framing is made collapsible and folds back BAT against the wall, the seat also being hinged, allowing of a considerable area being thrown into the hall for public meetings. A fixed seat (capable of being unscrewed), a slatted footboard, two hooks, and a mirror complete the furnishing of the dressing box. No steel or ironwork should be used for the fittings, even the butt hinges on the doors should be of brass, so as to dispense with liability to rust. The feet of the uprights should be let into galvanized sockets set in the concrete floor to protect the wood from'damp. There should be two w.c.’s and urinals for each class of ‘bath, and it is advisable that they should be in a compartment leading off the main hall. A foot bath about 18 in. deep should also be provided somewhere near the entrance so as to be under the control of the attendant and supplied with warm water, its size being about 4 ft. by 8 ft. and have an outlet for the rapid discharge of water. A wooden seat should be ranged around three sides where several bathers may sit together and cleanse their feet before entering the bath. This is especially useful where schools attend the baths. A shower bath, if provided, should be separated from the foot bath, it can then be used indepen- dently and need only be sufficiently large for one person to stand in. Most public baths are now provided in either the first- or second- class divisions with a gallery for the public to view entertainments. This is mostly done in the first-class bath. The gallery should comply with the local regulations with respect to safety of places of public entertainment. The regu- lations in force in London are mostly followed by the provincial towns and are set forth in an amended form dated 18th November, 1906, and entitled “Regulations made by the (London County) Council with respect to the requirements for the protection from fire of theatres, houses, rooms, and other places of Public resort within the Administrative County of London.” The chief points affecting public baths when used for entertainments are that each gallery accommodating not more than 800 persons must have two exits each MUNICIPAL AND SANITARY ENGINEERING. BAT 4 ft. wide. There shall be no recesses along the walls within 5 ft. from the floor; all stair- cases must be of stone or other incombustible material and 4 ft. wide, with steps having 11 in. treads and 6 in. risers with no winders, and not less than three steps in a flight or more than fifteen without an intervening landing. All doors shall open away from per- sons leaving the hall and have panic bolts fitted and be hung in two leaves. Swing doors for the interior are preferable. All doors leading out to be properly marked with the word Ext. Corripors AND Passacges.—The corridors and passages throughout the building are best lined with glazed bricks, and the floors covered with Terazzo or Mosaic tiles, as they are easily cleaned. GaLLery.—The design of the gallery should be such that the water may be seen for its full width by all persons when seated. This will probably mean that the steps carrying the seats must be fairly steep. There should be nothing movable, and all timbers, especially the gallery front, should be extra strong to provide against danger arising from the public pressing forward. There should be no means of communication between the body of the hall and the gallery, which should have its own separate entrance and emergency exits. The gallery could very well be carried around each of the four sides of the hall, supported over the boxes by thin columns designed to coincide with the divisions between the com- partments, but at either end of the bath, where there are no boxes, the columns should be omitted and cantilevers used. Divine Puatrorm.—A diving stage is pro- vided at the deep end of the bath in the form of three steps, the bottom step being about 2 ft., the next 4 ft., and the top 6 ft. above the gangway level. Sometimes there is only the one provided, at a height of about 2 ft. 6 in., and this as long as possible. ArrENDANT’s Capins.—A cabin for the atten- dant, stores for used towels (or a shute for same to the basement), should be provided, and also accommodation for brushes, buckets, 43 BAT ke., &c. These compartments are usually near the entrance. Warer-SHute.—A shute is also a useful adjunct to the bath, formed of teak 24 in. wide by 3 in. thick, with sides projecting 3 in. above the surface. The shute is hung on rods from the roof principals, a spray is fixed along the top end, and the shute is reached by a fixed ladder. Entrrances.—The entrance to each of the bathing halls should be through a short vesti- bule having folding doors at each end so as to cut off all draughts, and screen the hall from observation. The entrance is generally at the deep end of the bath. Cuus Room.—In baths of any distinction, there should be a room for the use of clubs and committees, designed so as to be acces- sible both from the bathing hall and also from the corridor outside. Also an artistes’ room may be provided somewhere near the deep end of the bath. Pay Box.—The pay box is generally at the front of the building, and so placed as to divide the first from the second-class entrances, each entrance serving both the swimming and slipper baths in their respective class. It is advisable to provide a separate pay box for the women’s slipper baths (and also for their swimming baths if one is provided). Their entrance should not be through the same door as the men except on days when the women use either the first- or second-class swims, in the absence of a special bath being provided. If properly designed, the men using the slipper baths and the women passing into the swimming bath on their special day will be effectually separated. It is as well to so place the first- and second-class swimming baths that they should be divided with the same division wall; this will economise the piping and simplify the construction, and as a door of communication could be provided it will be found very useful on gala nights, to swim off the first heats of a race in the otherwise vacant bath, while the entertainment is pro- gressing in the other. VENTILATION AND WarMinc.—The ventilation ENCYCLOPAIDIA OF BAT of the large bathing hall is a matter which should receive keen attention. Unless great care is exercised draughts will ensue, or else an unpleasant steamy odour will exist, especi- ally when large numbers of bathers are using the water. When schools are bathing this smell is very evident. To efficiently ventilate so large a hall when used either for bathing purposes or public meetings, it is quite useless to depend on natural ventilation. On the one hand, the air may be exhausted by an electric or water-power fan (the water being used either for flushing or in the bath), placed in the roof and dry warm air admitted by Tobin’s tubes, placed 6 ft. above the floor, or the Plenum system could be adopted, whereby dry, warm air could be admitted at the eaves line of the roof, and expelled through aper- tures near the base of the wall, which are connected continuously to ducts passing through the subway. ‘There are advantages and objections to both systems. In the first, the distribution of the fresh air may be un- equal and unpleasantly severe in the neigh- bourhood of the inlet, and cause an inrush of cold air at the entrances each time the doors are opened, while in the second instance, vermin may get into the duct, especially at baths where large numbers of lower class school children bathe. Mr. Aldwinkle, F.R.I.B.A., has overcome the objection of the large amount of cold air which accumulates in the upper part of the roof of the hall, by discharging warmed air above the line of the eaves, on the Plenum system. Hot water pipes on the low pressure system are frequently laid along the sides of the hall, behind the dressing boxes—useful on occasion of public meetings, and also at certain times of the year when the hall is uncomfortably chill to bathers. Waitine Room.—Adjoining the entrances there should be a waiting room for each sex and each class of bathers, awaiting their turn to use the slipper baths. The slipper baths should be accessible immediately out of this room, and long corridors avoided. Supper Barus.—It is necessary when pre- paring the design to recollect that portion of 44 BAT the Act which requires twice the number of second-class baths to be provided as there are in the first-class. The size of a slipper bath- room is about 6 ft. wide by 6 ft. 6 in. long. The baths are placed in pairs on either side of the dividing partition. It is best to design the arrangement, if it is possible, so that the room containing the slipper baths may be about 17 ft. wide, and have windows on each side. This will allow a row of bath-rooms to be erected along each outer wall, lit by direct daylight, and separated by a central corridor 4ft. wide. The flooring may be of concrete, granolithic or mosaic. The partitions are generally 6 ft. 6in. high and lin. thick. It is not advisable for the division to be fixed so as to leave a space at the floor line. Articles of clothing may drop and get kicked into the next compartment, or be stolen. The space causes a considerable draught, and there is not that idea of privacy which is. desired. Moreover, in washing one bath, the adjoining one gets wet. Enamelled slate is the best material for both division and door. Marble looks much better but is more costly, and is very liable to fracture along the veins. If the doors, which should be about 27 in. wide, are made about a fin. less in- width than the opening, there will be no fear of their break- ing, especially if a rubber buffer be also fixed. The top and bottom of the slate divisions, and also the door, should have a cast iron grooved capping to connect each width together, and the several widths of slate should be dowelled together with copper or gunmetal dowels. The room containing the slipper bath-rooms should be at least-12 ft. high if there is a flat ceiling, but an open roof is to be preferred, with a closed lantern light over, which will adequately light the central corridor. There should be an external window to each bath-room if possible. Where the exigencies of the site do not allow of all classes of slipper baths being on the ground floor, it is usual to place the first-class on the floor above. The baths are either porcelain or the newest type of enamelled iron, and should be of the pedestal pattern. Porcelain is often MUNICIPAL AND SANITARY ENGINEERING. BAT objected to on account of its coldness. A wooden top should be provided over the bath, of unpainted yellow pine, 14 in. thick; also a seat, and hooks for clothes, and a slatted footboard. Within the large room containing the several slipper kaths, there should be w.c. and urinal accommodation and, situated near the waiting room, an apartment should be provided for the attendant. Each bath-room should be connected with this room by an electric bell. If the relative position of the room will permit, there could be provided with advantage, a shute for soiled towels from the bath-room to the establishment laundry. The room containing the slipper baths should be amply lit by artificial light. If by gas, one bracket could be fixed so as to serve two baths. They will probably be kept alight the whole evening, but if electricity be available, a light could be provided in each bath, each controlled by a separate switch. The locks for the bath- room doors should be of a simple kind, capable of being drawn back with.a knob from inside, and opened with a key by the attendant. These slipper baths should be warmed with pipes or hot air as previously described. SUPERINTENDENT'S APARTMENTS. — There must be a suite of apartments for the bath superintendent, generally consisting of six or seven rooms and arranged in the front of the building on the upper floor. EstasuisHMent Launpry.—There must also be an establishment laundry where the towels and bathing costumes are washed. This room is generally in the basement, and contains a mechanical washer, a boiling and rinsing tank, a hydro extractor and mangle, all driven by machinery. Also a set of drying horses, con- taining about twelve divisions according to the size and requirements of the premises. The heat might very well be circulated by a small ‘motor fan. In all respects the horses should be constructed in the manner described under that head in the article on Public Wash- houses. The motive power for all the machinery might with every economy and convenience be electricity, if it is available, as it is most important to economise labour and 45 BAT do away with constant attendance of the staff. The boiler-house should be so placed that there may be a good height for circulation of water to the various baths. It should also be so placed that a boiler can be taken in and out without causing much damage to the building. Convenience for taking in coal should be considered. Store Room.—A store room for towels, bathing costumes, soap, &¢., should be pro- vided and fitted with clean wooden racks. The room should be heated and ventilated. Tue Borter-Hovss.—lIt will probably be found that three boilers will be required, of Cornish or Lancashire type, with a length of say 30 ft. and a diameter of 6 ft. to 6 ft. 6 in. each. This will be a guide to the dimensions of the room required. The boilers will be required to supply steam for the swims, hot water for the slipper baths, and hot water and steam for the wash-houses. The water in the swimming bath is generally heated by injecting steam into the bath full of water, or, it may be, by circulating the water through a calorifier, which can be done with spent steam supplemented with a small quantity of live steam, which is certainly the cheapest and most satisfactory way of keeping the temperature even and properly distributing the warmed water. Ample storage for coal must be provided. Each of the boilers should be capable of doing the same work and be of similar construction. A large storage tank for cold water must be provided with enough head to quickly supply all water which may be required for the slipper baths, laundries, boilers, &c. The circulating pipes are laid to the swimming bath along the subway arranged around the tank, and all other pipes and wastes are laid in channels formed so as to be capable of easy inspection and covered with chequered plating. It is a great con- venience to place a 2 in. pipe across the width of the swimming baths at the shallow end with perforations for spraying cold water along the surface of the water towards the deep end, and so driving out any scum which may collect. The fittings for supplying hot ENCYCLOPAEDIA OF 46 BAT and cold water for the slipper baths should be of a simple character and capable of pro- perly mixing the hot and cold water. Such fittings are, of course, controlled from outside the bath-room by the attendant. Tue Temporary Fioor.—If the bathing hall is to be used as a place for public meet- ings, the bath must be covered over with a substantial floor. It is important that the substructure should be strong and the boarded covering framed so as not to creak when persons walk across it. The floor which is illustrated was designed by the author with these objects in view. The trusses arranged across the bath were in three sections, the headpiece 9 in. by 3 in., the sill 6 in. by 3 in., uprights 7 in. by 24 in., struts 5 in. by 23 in. The top of the headpiece was notched to receive joists which were 7 in. by 24 in. and 18 in. apart. These joists were also partly notched to fit on to the trusses and were in as long lengths as could be obtained, but so that their ends “ broke joint.’ The top surface of the joists was level with the gangways around the bath, so as to allow the wooden floor to cover the entire area. Between these cross trusses there were placed two rows of longi- tudinal trusses having 6 in. by 8 in. head, sill and uprights, and 6 in. by 14 in. cross bracing screwed on to each side. Hach truss was secured to its neighbour by a hasp and staple— the staple, however, being in the form of a peg which secured itself when turned. It was desirable for dancing that the joints of the boards should be in the direction of the length of the bath. The flooring consisted of 6 in. by 14 in. tongued and grooved boards, screwed to 6 in. by 13 in. cross bearers. The floor was formed into sections 6 ft. by 4 ft. Three bearers were provided to each section, and as the end of each bearer projected 2 in. beyond the side of the boarding, each section became interlocking and self-securing, and its united weight kept it rigid. A specially formed section, tapered down, was provided near the doorway and the joint between the wood section and the tiled floor covered with a mat. A trap-door in one section gave access to the BAT bath where it might have been necessary for an entrance to be obtained to wedge up. It is important that a floor of this kind should have a special place in which it can be stored away, as each section should be laid flat and kept from twisting by the weight of the members above. Each part of the floor is numbered and laid in its place according to plan. Continuous Finrration oF THE WATER IN THE Swiuuinc Baru.—lIt is impossible to MUNICIPAL AND SANITARY ENGINEERING. BAT instance the general run of one filling of the bath with water, which will probably remain fit for use for three days. It may be con- sidered quite pure for say one or two hours ; at the end of a day it will present the appear- ance of being different from drinking water, but at the end of three days it becomes necessary to discontinue its use, and yet some swimmers bathe in it up to the last moment. The plant in question never allows the water to get beyond the impurity of an ordinary Fic. 3.—Continuous Filter. work a public bath so that it will be self- supporting in the matter of current expenses. The capital charges are heavy and the cost of maintenance and repairs also very great, consequently everything should be done to lessen the latter as much as possible. But it is not with that object principally in view that a system of systematic filtration has been adopted ; it is for the purpose of keeping the water at one degree of continuous purity that the installation has been in use. Take for bath water two or three hours old, and the water used with this system remains in use at the Rotherhithe Baths, where the author has installed the scheme, for three or four months at a time, including the summer season. The results have been tested both chemically and bacteriologically by eminent analysts and pronounced perfectly satisfactory, while the minor question of economy is equally gratifying to the Council. The following advantages are claimed for 47 BAT continuous filtration :—(1) The water is never allowed to get into an unclean state, such as may be the experience of the last bather in water ready to be thrown away under the old system. (2) The water is uniformly heated throughout at all times, and those cold areas which exist during the first hour or two in water heated after filling are avoided. (8) A total absence, even in a crowded bath, of that close ‘“‘body’’ smell so well known in the atmosphere of most public swimming baths which are much used. (4) A continuous current of water is maintained through the bath. (5) Economy of water. (6) Saving of time of the employees attending in the early hours of the morning to heat up a fresh bath. In the purification of the water there are three different processes engaged, viz. (1) mechanical, (2) biological, and (3) chemical ; and although the result is the same, viz., the conversion of complex organic compounds into simpler ones, it is difficult to apportion the exact share which each takes in producing the final result. In the first place, there is the mechanical cleansing of the water from the coarser impurities by the filter. This is self-evident, and needs no explanation. Naturally, the finer the material in the filter, and the thicker the layer through which the water has to pass, the more effectual this will be. The next process, the biological, also takes place in the filter and is probably due to the activity of anaérobic organisms in its interstices. These organisms assist in split- ting up the complex organic matters mentioned through their various stages, viz., ammonia and nitrites, into the end products known as nitrates. The periodical cleansing of this filter by “live” steam, no doubt, puts a tem- porary check on this action, but when the water is put through the filter again, the spar will soon regain a fresh supply of anaérobes. The third cleansing process (chemical) is that due to the exposure of the water to the atmosphere by the aérator on the roof. This is principally one of oxidation, in which the greater portion of the organic matter will be destroyed by the combination of the atmo- ENCYCLOPADIA OF 48 BAT spheric oxygen with it, the final products being water, carbonic acid, and an innocuous resi- due. Saline ammonia and any volatile animal products in the water will also be got rid of during this process of aération. This, no one who takes the trouble to visit the aérator can doubt, for the sense of smell will convince him that a number of such products are freely given off. The following is a description of the work- ing of the scheme :—The water is first put into the first- and second-class baths direct from the main, and then alternately allowed: to gravitate to a strainer, which eliminates such solid particles as portions of bathing costumes, grit, hair-pins, &c., ke. The water is afterwards raised by pumps to the aérating tower, which ig fixed on the roof, by which means the whole of the water is broken up and exposed to the atmosphere, and thus it receives a fresh supply of oxygen. The water then descends and passes through the filter, which purifies it. Then it passes through a heater, which is worked by the spent steam from the pumps and from other parts of the building, producing a temperature of 74° Fahr., and after this, the water is delivered into the shallow end of the bath, again fit for bathing. This process is continuous. The filter is cleansed about every second or third day, by passing about 2,000 gallons of water and live steam the reverse way through the filtering media, and washing the accumulation out into the sewer. The first- and second-class baths are worked alternately, and the plant will deal with 20,000 gallons per hour ; the water in the large swim being changed every four-and-a half hours by this process of circulation. As the baths are situated near manufacturing works, there is a tendency for dust to blow in through the louvre ventilators during the night, and settle on the water; therefore a spray is used each morning to clean off the top surface, and it also replenishes any water lost by evaporation and that used in the emptying of the filtering chamber during the periods of cleansing. The various parts consist of (1) A strainer BAT to intercept particles likely to obstruct the pumps. (2) Two pumps to deliver the water to the aérator. (3) An aérator to oxygenate the water, situated on the roof. (4) A filter capable of filtering the water, provided with means of cleansing the filtering surface when required. (5) A heater-condenser capable of condensing the steam used by the pump, and of raising the temperature of the water from about 50° to 74° F., when supplied with auxiliary live steam. Aérator.—The aérator consists of cast-iron “A” frames supporting a copper perforated Fie. 4.—Aérator. pipe. These ‘‘A” frames are connected to- gether by means of light girders at intervals, and fixed to these girders are perforated zinc trays, having sufficient number of perfora- tions to allow the required amount of water to pass through in a large number of very fine streams. The aérator is fitted with three of these trays. The bottom of the aérator con- sists of a galvanized sheet-iron tank to receive the aérated water. ‘The end frames of the aérator are boarded in, and the sides are fitted with a number of louvre boards, so arranged that the air can have free inlet and outlet to the water, and that any water M.S.E. 49 MUNICIPAL AND SANITARY ENGINEERING. BOI splashing on to these boards will run back again into the tank. Rough plate glass is now being substituted for wood in the louvres, so as to admit more light to the water. Filter.—The filter measures 14 ft. by 6 ft. 6 in. by 5 ft. 6 in. deep, and is of sufficient surface to deal with 20,000 gallons of water per hour. The filter tank consists of cast-iron plates. The filter is arranged inside with a rib which supports a couple of filter plates of wrought iron, these filter plates having a sheet of wire gauze in between, and so arranged that the holes in the plates are opposite one another. In that part of the filter below the filter plates a cast-iron pipe is connected to a valve on the outside of the filter. This cast-iron pipe has a large number of 14 in. wrought-iron pipes branching out under the whole of the filter surface, these pipes having a number of very small holes arranged in them, so that the delivery of air for flushing purposes may be distributed as evenly as possible on to the surface of the filtering material. The filtering material consists of gravel of special quality, about 18 in. or 19 in. deep, supported on the above-mentioned plates. The cost of the plant and builders’ work was £965; at present the scheme shows a saving of £188 5s. 4d. on the year’s working. R. J. A. Bell's Water Filters.—(Sce ‘‘ Mecuanicau FIntration.”’) Benching.—A raised step at the bottom of a manhole so formed that any liquids falling on same may flow off into the drain. Boilers.—A satisfactory steam power plant must, in addition to having an efficient engine, also have an economical boiler, the design and setting of which should be such as to use the heat generated to the best possible advantage with a minimum cost for fuel. Different types of boilers are required for different powers and conditions of working, and it is necessary to investigate boiler efficiency as distinct from that of the engine E BOI in order to allocate to the proper quarter any wastes taking place. The principal types of boiler in use are the Cornish, the Lan- cashire, the Galloway, the Babcock and Wilcox, and other forms of water-tube boilers. In the Cornish boiler there is one central flue containing the furnace, with side-flues and bottom-flue. This type works at a pressure of about 80 Ibs. per square inch, is only suited for comparatively small powers ranging from 40 to 150 h.p., and is made from 4 ft. to 6 ft. 6 in. diameter. The Lancashire boiler is similar to the Cornish in general arrange- ment and setting, but has the distinguishing feature of two central flues instead of one. These boilers are made in sizes varying from about 80 h.p. (14 ft. by 5 ft. 6 in.) to 390 h.p. (80 ft. by 8 ft. 6 in.), and for working pressures up to 160 lbs. to the square inch. Lan- cashire boilers are steady steam producers, have a large water capacity, and are easily accessible. For ordinary waterworks pumping purposes and for other general use it is the most serviceable and economical form that can be used. Galloway boilers have two circular furnaces, extending about one-third the length of the boiler, and which open into a wide flue, in which are inserted Galloway tubes. Pockets placed at each side of the wide flue just beyond the furnaces contract the area and divert the furnace flames towards the centre tubes. These boilers have evaporated over 12 lbs. of water per pound of coal. Water-tube boilers are usually classed in two main divisions, viz., those with large tubes and those with small tubes. The Babcock and Wilcox boiler, with inclined tubes connected into headers at each end, and these in turn communicating with the steam drum, is an example of the first division, whilst the Yarrow and the Thornycroft boilers, having a number of small tubes communicating with upper and lower drums are examples of the second class. Water-tube boilers have a small water capacity, are quick steaming, give systematic circulation of water, are light and portable, and are suitable for the quick generation of high pressure steam. Their ENCYCLOPADIA OF BOI disadvantages are liability to smoke with bituminous coals, smallness of thermal capacity and unsteadiness of steaming, increased complication and cost of repairs, and the necessity of using pure water to avoid incrustation of the tubes. Bower Erricirency.—The weight of water evaporated by a boiler from a given tem- perature per pound of fuel used is in practice taken to represent the efficiency of the boiler in the same way that the weight of steam used by an engine per i.h.p. hour is regarded as the measure of its efficiency. A more accurate statement of the efficiency of the boiler is made by separately calculating the heat units given to the water and the heat units obtained by the combustion of 1 lb. of coal, so that the ratio, Heat units given to the water Heat units from coal ae a aenr ys A much higher percentage of efficiency may be obtained from a good boiler properly set and fired, than from the steam engine. A boiler when worked with the best fuel under the best conditions will deliver to the engine as much as 75 % of the theoretical heat of the coal. The combustion of a pound of pure carbon yields 14,500 heat units, which, if fully used, will evaporate into steam at atmospheric pressure 15 lbs. of water from 212° F. In practice, the evaporations of boilers range from about 7 lbs. up to about 13 lbs. of water per pound of combustible according to the type, arrangement, and efficiency of the boiler and furnace and the quality of the coal. An average evaporation of 10 lbs. of water per pound of coal is ordin- arily considered a satisfactory result. In addition to the ordinary Lancashire boilers, others giving first-class evaporative results are, the Galloway breeches boiler, the Babcock and Wilcox water-tube, and the Climax water-tube boiler. In seeking econo- mical results in a steam generating plant it must be remembered that such a plant consists of two parts, the furnace and the boiler, each of which must efficiently perform its share of the work. The function of the 50 BON furnace is to properly consume the fuel and to procure the greatest amount of heat from a given weight consumed. The function of the boiler is to utilise the fullest possible quantity of heat thus generated in the furnace and to transfer the same into useful effect by evap- orating the maximum possible of water into steam. W. H. M. Boning Rods.—A set of boning rods consists of three exactly similar T-shaped wooden frames. Boning rods are used by drain layers, paviours, and other workmen in performing simple levelling operations, such as setting outa level line, extending a gradient, or ascertaining the intermediate levels between two points. To set out a level, one boning rod is erected at the starting point and another some feet away from it and astraight edge laid across their tops; the second boning rod is raised or lowered until a spirit level, placed at the centre of the straightedge shows it to be exactly horizontal. A third boning rod is set up at an equal distance from the second and the process repeated, except that the straightedge should be reversed. The second boning rod (No. 2) may now be removed ; Nos. 1 and 8 will be truly level as any error in the straightedge or spirit level will have been neutralised. A gradient can be set out by first obtaining a level line and then raising or lowering the third rod to the required distance. A line can be extended by sighting across the tops of two boning rods and raising or lowering a third until the tops of all three are exactly in line. Similarly, intermediate levels may be determined by placing boning rods on the outside points and sighting on to a third one between them. In actual work pegs are driven into the ground for the rods to rest upon and obviously the height of these pegs will indicate the variation of the ground surface. (See ‘‘ LevEt- LING, GENERAL PRINCIPLES OF.’’) E. L. B. Borewells.—Bored steel-lined tube wells are now very largely employed for access to underground water for public supply and also 51 MUNICIPAL AND SANITARY ENGINEERING. BOR for numerous trade purposes. Given average success, water obtained in this way commonly costs from 8d. to 4d. per 1,000 gallons inclusive of interest on capital and working expenses. Unless the water-bearing capacity of a district has been well tested by previous borings, the initial steps towards obtaining underground water is necessarily accompanied by consider- able risk, as, although the geological features Fie. 1.—Drilling Apparatus. may seem favourable, nothing short of the expenditure of the necessary money of sinking a fair-sized trial boring, followed by continued pumping operations, can he relied upon. Greatimprovements have been made of recent years for expeditiously sinking borings of this character. They are now made almost exclusively by percussive mechanism with the aid of a great variety of ingeniously contrived tools adapted for piercing the various classes of strata met with. A typical modern surface plant, as used by the well-known firm of EB BOR C. Isler & Co., for raising and lowering the tools in the boring is shown in Fig. 1. It consists of wrought-iron tubular sheer legs and winch, and is well adapted for expeditious sinking and convenient of transport. Steam- winch may also be fitted. A considerable variety of tools are employed in connection with such a plant for the purpose of meeting the various emergencies of the work as they arise. The principal of these, as illustrated in Fig. 2, are :— 1. Clams for suspending and screwing tubes. 2. Worm auger for loosening compact soils. 3. Clay auger. 4 & 5. Flat chisel for rocky and hard strata. 6. Auger nose shell for bringing soils broken up by the chisel. 7. Flat bottom shell for sandy soil. 8. Shoe-nose shell. 9. Latch tool for picking up pipes from a bore-hole. 10. Spring dart for same purpose. 11. Bell screw for cutting thread on rods broken in bore-hole. 12. Bell box for picking up rods in case of breakage. 13. Spiral worm for extracting broken rods, &c. 14. Swivel rod. 15. Crow’s foot for extracting broken rods. 16. Rod joints. 17. Spiral worm for extracting rods. 18. V-chisel for rocky strata, &c. 19. T-chisel for ditto. 20. Rimer for enlarging bore-hole. 21. Lifting-dogs for raising rods. 22. A and B, rod tillers for working rods. 23. Hand dogs for screwing rods. 24. Spring hook. 25. Boring rod with screwed ends. A complete set of tools for boring to 400 ft. deep, with wrought-iron sheer legs, fitted with the necessary gearing and fast and loose pulleys, costs about £150. Drilling through sand, gravel, clay or soft rocks is also very expeditiously done by what ENCYCLOPADIA OF 52 BOR is known as the hydraulic washing system in which the boring rods and chisel are hollow to enable water to be pumped downwards through them, which has the effect of washing all débris to the surface, thus obviating the necessity of removing the tools from time to time to the surface, for clearing, &c. The rods and chisels are lifted and dropped as in the ordinary percussion system, the water being forced down at the same time. In suitable soils this is one of the most efficient Lao aS Gal Fig. 2.—Drilling Tools. and expeditious methods available. Boring through rocks or solid formations is more advantageously done by means of the Rotary Shot Boring gear shown in Fig. 3, which has been designed to replace the more costly method of diamond rock drills. The shot is fed into the hollow boring rods and carried downwards by means of water, past the core, and eventually under the crown. The system is suited for the penetration of the hardest rocks. The cost of boring depends largely upon the depth and character of the strata to be passed through, but in gravel, clay, chalk or other soft strata for depths not exceeding 500 ft. the price may lie between 30s. and 60s. per foot according to circumstances. In rock similar work may cost from 40s. to 80s. BOR per foot, for borings not exceeding 12 in. in diameter, and exclusive of lining tubes. Where lining of the bore is necessary wrought- iron lap-welded steel-socketed tubes are used, the approximate prices of which are 6 in. internal diameter 10s. per foot, 84 in. diameter 17s. per foot, and 114 in. diameter 25s. per foot. Other well-known methods of boring which have been successfully employed are the C.ISLER'S IMPROVED STEAM ROTARY ROCK BORING GEAR. Fie. 3.—Drilling Process in operation. Kind- Chaudron deep- boring system, the Dru deep-boring system, Mather & Platt’s system, the American rope-boring system, and deep-boring by diamond drills. The water from borewells is raised either by means of an “‘air-lift’’ or by the employment of steam-driven deep-well pumps of the ordinary type. For further information, see also articles, “ Wetis, ARTESIAN WELLS, ABYs- SINIAN WELLS, UNDERGROUND WATER, AND AIR-LIFT.” W. H. M. MUNICIPAL AND SANITARY ENGINEERING. ARTESIAN WORKS LONDON. 53 BOS Boston, U.S.A., Sewage Disposal at.— Boston, Massachusetts, U.S.A., is a city of somewhat over half a miilion inhabitants, situated at the upper end of an elliptical harbour, about twelve miles long and six miles wide. A considerable number of smaller cities and towns are clustered thickly about the larger municipality, making the popula- tion of Greater Boston about 1,250,000. The metropolitan district as a whole covers an area of nearly two hundred miles; and it is intersected by three rivers, the Mystic and the Charles, which discharge at the upper (N.W.) extremity of the harbour, and the Neponset, which enters on its south- westerly side. Originally the sewers of the city dis- charged at various points (seventy or more) along the water front. At times of heavy rain coinciding with high tides the sewage backed up, and created objectionable conditions in the lower part of the city; and at almost all times there was a serious nuisance in the inner har- bour, as the sewage was borne back and forth by the tide. In 1875 a joint engineering and medical commission made a study of the problem and recom- mended the construction of two main systems of intercepting sewers, one for the region south of the Charles river, including most of Boston proper, and the other for the cities and towns north of the Charles. The development of the former plan, the Boston Main Drainage Works, was begun almost at once, in 1877, and was com- pleted in its general outlines by 1884. The main outfall sewer for this district discharges at Moon Island, near the middle of the harbour. The construction of the Main Drainage Works C.ASLER2 C? BOS has been carried out under successive city engineers, J. P. Davis, H. M. Wightman and William Jackson; Eliot C. Clarke was principal assistant engineer in charge of construction up to 1884. Meanwhile the State Legislature of Massachusetts appointed various commissions to consider the wider problems involved, notably the Metropolitan Drainage Commis- sion of 1881 and the Massachusetts Drainage Commissions of, 1884 and 1885. In 1889 the State Board of Health prepared a general plan for a system of intercepting sewers to serve the region north of the Charles, and to dis- charge at Deer Island at the mouth of the harbour. A special board of Metropolitan Sewerage Commissioners (Hosea Kingman, Chairman) was created by the State Legisla- ture to construct and operate the works, outside of the Boston Drainage District, the costs being apportioned on the several com- munities involved. Howard A. Carson was Chief Engineer to 1895; William M. Brown has had entire charge of construction and maintenance since that date. The Commis- sion constructed first an intercepting sewer along the south bank of the Charles for the region to the west of Boston. This entered into the Boston Main Drainage system from 1892 to 1904; and the sewage thence passed to Moon Island. The North Metropolitan system for the cities and towns north of the Charles River was essentially completed in 1895; and has since discharged at Deer Island. In 1895 a sewer was begun in the Neponset Valley; and in 1899 construction was begun on a general high-level system for the communities to the south and west of Boston. This system was completed in 1904. It takes most of the sewage which originally passed from the Metropolitan sewer on the south bank of the Charles into the Boston Main Drainage Works, and carries it round the south side of the harbour to discharge at Nut Island near the harbour mouth. The entire system thus includes three main divi- sions—the North Metropolitan sewer, dis- charging at Deer Island; the Boston Main Drainage Works, discharging at Moon Island ; ENCYCLOPADIA OF BOS and the South Metropolitan high-level sewer, discharging at Nut Island. The North Metropolitan sewer serves certain areas of Boston, and the cities and towns of Winthrop, Chelsea, Everett, Malden, Melrose, Cambridge, Somerville, Medford, Winchester, Woburn, Stoneham, Arlington, Belmont, Wakefield, Lexington and Revere. The total area is 90°50 square miles and the total popu- lation January 1, 1908, was estimated at 498,640. Of this population 422,065 are estimated as contributing sewage. The mileage of local sewers connected January 1, 1908, was 624°74, and the number of connections 65,786. The total flow of sewage in 1907 averaged 64,300,000 gallons per day. In constructing the North Metropolitan system, it seemed best, in order to avoid deep excavation in unfavour- able ground, to provide for pumping several times with low lifts at each station. The system has three main branches extending to the northern, western, and southern portions of the area. The sewage from the western portion (4,000,000 gallons per day) is lifted 184 ft. at Alewife Brook, and that from the southerly portion (82,000,000 gallons per day) is lifted about 10 ft. At East Boston, and again at Deer Island, nearly the entire volume of the sewage is pumped, the lift being 15 ft. at the first station and 6 to 15 ft., according to tide, at the second. The equip- ment at the last two stations consists in each case of three submerged centrifugal pumps with impellers 8-25 ft. in diameter driven by triple-expansion Reynolds-Corliss engines. The cost of pumping is $:1079 per million foot-gallons at Deer Island, and $0718 at East Boston. Between these two pumping stations the sewage passes in an 8'5-ft. inverted siphon of steel, 264 ft. long, under Shirley Gut. After pumping at Deer Island the sewage Is disposed of by continuous under- water discharge through a 6}-ft. outfall sewer of concrete and brick. The point of discharge is 1,860 ft. out from the shore line at high water, and in a powerful current setting in and out through the mouth of the harbour. Engineering problems of considerable interest 54 BOS arose in the construction and laying of the Shirley Gut siphon and the outfall sewer. Screening, carried out at the various pumping stations of the North Metropolitan system, intercepted in 1907 rags, paper, &c., to the amount of 2422°2 cu. yds. or 2'8 cu. ft. per million gallons of sewage. The high-level sewer of the South Metro- politan system now serves about a quarter of the city of Boston and the cities and towns of Brookline, Newton, Watertown, Waltham, Milton, Hyde Park, Dedham, and Quincy. The total area included is 102 square miles, and the population, January 1, 1908, was estimated at 325,090. Of this population 188,150 are estimated as now contributing sewage. The mileage of local sewers connected was 479°51, and the number of connections, 26,019 on January 1, 1908. The total flow of sewage for 1907 averaged 40,600,000 gallons per day. The sewage from the northern part of the high-level system, amounting to 23,000,000 gallons a day, is pumped at Ward Street, the lift being about 40 ft. The pumps are of reciprocating type with plungers 48 in. in diameter and a 60-in. stroke, operated by vertical triple-expansion Allis-Chalmers engines. From Ward Street the sewage flows by gravity to the outfall at Nut Island. The flow from the southern and eastern part of the district enters for the most part by gravity, although about 3,000,000 gallons a day are pumped at Quincy. The main outfall sewer is 11 ft. 3 in. by 12 ft. 6 in., and it discharges off Nut Island by two 60-in. cast-iron pipes, having an aggregate length of 10,844 ft., and laid under the bed of the harbour. Screens are located at the pumping stations and at Nut Island, and the total screenings removed in 1907 amounted to 2735°6 cu. yds., or 50 cu. ft. per million gallons of sewage. The screens at Nut Island are four in number, two in each duplicate channel of the screen room. They are about 12 ft. square with clear openings of 2 in. between the bars, and are operated by small reversing engines. The third and central system of the three MUNICIPAL AND SANITARY ENGINEERING. BOS which discharge into Boston Harbour, is the Boston Main Drainage Works, which serves the central portion of the city itself (E. 8. Dorr, Chief Engineer). The area is small, only about 18 square miles. The popula- tion in this area, however, was estimated at 358,372, January 1, 1908, and practically all of the houses are connected. There are 530°48 miles of local sewers connected with this system. The number of individual con- nections is not accurately known, but may be placed somewhere between 35,000 and 40,000. The average daily flow of sewage in 1907 was 87,660,000 gallons. The figures for the whole city of Boston, including the sewers which discharge through the North and the high-level systems as well as the Boston Main Drainage Works, are as follows:—Population, January 1, 1908, 614,632; total area, 42°5 square miles; total length of sewers, 729°26 miles; average flow of sewage, 124,200,000 gallons per day. The sewage of the Boston Main Drainage Works flows by gravity to the Calf Pasture in Dorchester. At the Calf Pasture it is lifted 36°5 ft. and discharged through a tunnel under Dorchester Bay to the main outfall sewer on Moon Island. Here, as Moon Island is situated near the centre of the harbour and not, like Deer Island and Nut Island, in strong currents of deep water, the sewage is stored in masonry tanks and discharged only on the out-going tide. Before pumping the sewage is screened by passing it through iron cages working in vertical shafts. The screenings removed in 1907 amounted to 577 tons. After pumping, and before entering the tunnel, the sewage passes through two deposit sewers, 8 ft. wide and 16 ft. high, which run side by side for a distance of 1,260 ft., terminating in each case with a dam which keeps a level high enough to ensure a current velocity not ex- ceeding 1 ft. per second. The deposits are moved by a travelling scraping and flushing machine, operated by the current, and are delivered to a sludge tank from which the liquid flows back into the sewer. The sludge removed from the tank is towed out to sea by 55 BOS scows. It ordinarily amounts to 10,000 cu. yds. per year or 4°5 cu. yds. per million gallons of sewage. The pumping station is equipped with three high-duty engines, two of which are compound engines, the plungers of which are 48 in. in diameter, with a 9-ft. stroke and a nominal capacity of 35,000,000 gallons a day. The third is a triple-expansion engine, the plungers of which are 60 in. in diameter, with a 10-ft. stroke and a capacity of 72,000 gallons a day with seventeen revolutions per minute. There are also two low-duty engines with 45-in. plungers and a 4-ft. stroke. The nominal capacity of each engine is 25,000,000 gallons a day. The tunnel under Dorchester Bay, between the deposit sewer and the outfall sewer, is of brick, 7,160 ft. long, and it has an inside diameter of 7°5 ft. The outfall sewer itself is 5,900 ft. long, and of horse-shoe section, 11 ft. high and 12 ft. wide. The tanks in which the sewage is stored at Moon- Island are four in number, and cover an area of about 10 acres. Their bottoms are of con- crete, and their walls of granite blocks, laid in cement. The total capacity of the four tanks is about 50,000,000 gallons. They can be flushed out by introducing sewage under high velocity at either end of the tanks. Along the nearer end of the tanks run two sewers, one above the other, the upper being the sewer which discharges sewage into the tanks; the lower, the one which empties the tanks into the bay. There are two sets of gates for filling and emptying and flushing the tanks ; one set is controlled by electro-pneumatic switches, operated by compressed air, and the other set is controlled by a line of shafting. The whole system is driven by a turbine run by the sewage flow. The method of opera- tion is to allow the reservoirs to fill for ten hours and to discharge during the second and third hours of the outgoing tide. The total amount of sewage discharged into Boston Harbour from the three main outlets averaged, in 1907, 192,500,000 gallons a day. The sewage of the Boston Main Drainage Works is studied daily at the Sewage Experiment ENCYCLOPADIA OF BOS Station of the Massachusetts Institute of Technology. The following table shows the average analyses for 1905—1907. ComposITION oF Boston SEWAGE. PARTS PER MILLION. Suspended Solids. Total,)Fixed. Organic Nitrogen Total Dissolved. Oxygen Consumed.* Total Dissulved. Turbidity. Sediment. Free Ammonia. o1 58 ra 09 oS 56 43 I<} aq 9 HB bo on 135 44 * 30 minutes, 100°, The general results of this method of disposal have, on the whole, proved fairly satisfactory. The sewage discharged at Moon Island spreads out on the surface (the dis- charge is 1 ft. above low water), and is very obvious for an hour or two within an area of half a mile or a mile in diameter. Some nuisance is undoubtedly caused to passing vessels, and it is said that real estate in the neighbourhood has been injured in value. The Massachusetts State Board of Health made careful investigations of the condition of the harbour in 1900, and again in 1905, and showed that the chemical and bacterio- logical evidences of pollution were manifest on the out-going tide only in a narrow path extending for two miles and a half from Moon Island, and on the incoming tide, only in the immediate vicinity of the outfall itself. At Deer Island and Nut Island where discharge is continuous, under water, and in a strong current, conditions are better. In 1907 the Board of Health pointed out that the most serious pollution of Boston Harbour at present is not at the main outlets at all, but in the upper portion of the harbour, where a con- siderable amount of sewage still finds its way in by various unauthorised channels. It is, of course, probable that the concentra- tion of population and the rising level of sanitary standards will ultimately make some other method of disposal desirable, at least for the Moon Island outlet. In view of this contingency the Sewage Experiment Station of the Massachusetts Institute of 56 BRA Technology has for six years been carrying on experimental studies of the purification of Boston sewage with the following general results. The most suitable method for purify- ing the sewage from the city proper would be by filtration through trickling or perco- lating beds. These should be 8 ft. deep and constructed of 14 in. to 2 in. stone.. They might conveniently be located on Thompson’s Island near the present Moon Island outfall and would occupy an area of 50 acres. It seems from the experiments so far conducted that it would be more economical to apply the sewage directly to the beds without septic treatment, remov- ing only screenings and heavy detritus. After filtration the trickling effluent must, however, be subjected to a sedimentation of two hours for the removal of suspended solids. At the same time bacterial purification may be attained by disinfection with chloride of lime, using about five parts of available chlorin per million gallons of sewage. Preliminary estimates place the cost of filtration (including capital charges), at about five dollars and a half per million gallons, and the cost of disinfection at about one dollar and a half per million gallons. It is quite possible that the extension of an outfall sewer to the outer harbour with an under-water discharge, pre- ceded by careful screening, might prove more economical and equally satisfactory. C. HE. A. W Bradford Sewage Disposal. — Poruna- tion, ArEA, &c.—The City of Bradford has a population of about 300,000 (1901 census 279,767), the area being 22,800 acres. For sewage disposal purposes, this is divided into ten districts, each having separate sewage disposal works, the most important being at Frizinghall. At the other works the sewage is purified as follows :-— 1. Eccleshall.— Chemical precipitation and land filtration, 100 acres (clay). 2. Greengates. — Chemical precipitation, straining filters (coal), followed by circular filter 7 ft. deep (coal). ‘ MUNICIPAL AND SANITARY ENGINEERING. 57 BRA 3. Idle. — Broad irrigation, aluminaferric being added to the sewage. 4, Heaton.—Septic tanks and contact beds. 5. Thornton.—Chemical precipitation (alu- minaferric) and land filtration. 6. Thackley.— Broad irrigation. 7. Sandy Lane.—Aluminaferric circular pre- cipitation tank, followed by shallow filters (engine ashes). 8. North Bierley—Septic tanks and artificial filters, area six acres, distribution by fixed jets, and also circular distributor 236 ft. diameter. 9. Lower Wyke.—Sewage treated by the Brighouse Corporation. 10. Frizinghall.—In addition the Corpora- tion of Bradford take and treat the sewage of the Yeadon Urban District. This latter, together with that from Frizinghall and the first named five districts, will be conveyed to the Esholt works, which are being carried out by the Corporation of Bradford at an estimated cost of £1,250,000, including cost of 1,800 acres of land recently purchased. VotumE or Szewacre.—The volumes treated at the different works vary, and the trade refuse contained determines the preliminary method of treatment in use. The largest volume, 13,000,000 gallons a day (dry weather flow) is dealt with at Friz- inghall. This sewage comes from the centre of the city, and is more affected by liquid trade refuse than any other. It contains some 6,500,000 gallons of liquids from the pro- cesses of wool scouring, dyeing, &c., and in consequence is highly charged with fatty matters and organic matter in solution. The fatty matters brought down in the sewage amount to as much as 25 tons a day. The oxygen absorbed from permanganate in four hours at 80° F. is about 20, and the albuminoid nitrogen 3 parts per 100,000. Trearment.—The sewage is passed through detritus tanks which remove 10 tons per day of heavy matter, and through screens, each consisting of six sets of tynes set in a com- mon shaft, and caused to revolve in the sewage, and provided with an automatic BRA cleaning device. Sulphuric acid is then added to the sewage in such quantities as to give an excess of about 5 parts per 100,000 of free sulphuric acid. In this way the sludge is precipitated, being deposited in settling tanks worked in series on the continuous flow system. The sludge produced contains an average of 78% of moisture, and 7% of fatty matter. Stupce.—The sludge israised by compressed air into the sludge pressing houses, where it is screened, acidified with sulphuric acid, heated to 100° C by exhaust steam in open vats, and then passed through sludge ‘“‘rams”’ into 64 filter presses. The presses are heated by steam, and the whole kept hot during the process of filter pressing. In this way the fatty matters are kept fluid, and pass away from the presses with the press liquor. The resulting cake contains 27 % of moisture, and is sold for manure at 3s. 6d. per ton f.o.r., or used for fuel on the works. The fatty matter is separated from the water, purified, and sold. Tank Errivent.—The effluent water from the precipitation tanks, which is acid in reaction, is at present run off into the river. The high content of soluble organic matter in this effluent is now the difficulty to contend with. Fiirration.—With regard to filtration, the methods at present in use at the Frizinghall works, and which are necessarily only of an experimental character, are the result of the work of several years. A large amount of experimental work has been done, the work including researches on the effect of filtration of (a) acid tank effluent (as discharged from the tanks); (b) tank effluent neutralised with lime, magnesium, barium salts, &c.; (c) tank effluent made slightly alkaline; (d) tank effluent after a secondary precipitation ; (¢) septic tank effluents; (f) tank effluent con- taining a large quantity of added sulphuric acid. The different kinds of material tried have been very numerous, amongst others tried being coal, coke, cinders, shingle, and soil. ENCYCLOPEDIA OF 58 BRA The depths of the beds varied from 12 in. to 7 ft. 6 in. Any work on the purification of the Bradford effluent must be judged from the standpoint of the high content of soluble organic matter in the tank effluent. The results obtained prove that the Bradford effluent can be efficiently purified notwithstanding the acidity, and they further prove that the acidity of a tank effluent has no very marked detrimental effect on the purification effected in a filter bed. In confirmation of this fact, which is quite contrary to the view of most authorities to-day, two series of experiments were carried out. In the first, two filters of similar material were worked side by side under the game conditions, one filter treating acid tank effluent, and the other treating similar effluent, which had been neutralised with lime. An average of 111 analyses made of each effluent showed a difference of only 0°11 parts per 100,000 of oxygen absorbed in favour of the filter treating neutral effluent. In the second series, a filter of cinders was supplied with tank effluent containing added sulphuric acid varying in amount from 25 to 60 parts per 100,000. The filter was worked for several months, and notwithstanding the very large amount of acid, satisfactory results were obtained. A large portion of the acid was neutralised in the bed, the acidity of the filter effluent varying between 7 and 29 parts per 100,000. The oxygen absorbed figure was rather higher and the albuminoid ammonia figure always lower than in ordinary filter effluents. As regards the question of nitrification, the Frizinghall analyses show that with the ex- ception of one set of experiments in 1906-7, nitrification does not take place unless the acidity of the tank effluent is neutralised in the bed. In the experiments referred to, the effluent was one from a coal bed, and in the average of over 180 analyses, although the effluent showed a slight acid reaction, the nitrates averaged between ‘1 and 1°5 parts per 100,000. Bactrertotocica, Worx.— During the last 18 months bacteriological investigations have BRA been made at Frizinghall on the crude sewage and effluents. The chief result of the work so far has been to show that the effluents from the filtration of Bradford sewage can be brought to the provisional standards suggested by Dr. Houston in the Second Report of the Royal Commission on Sewage Dizposal. Summary.—On the basis of the experimental work done at Frizinghall, therefore, it is held that the acidity of a tank effluent does not exert any marked detrimental action on its subsequent filtration, either chemically or biologically ; nitrates, however, are not formed, and their absence points to the fact that nitri- fication is not essential to the efficient purifi- cation of this sewage. The researches are being continued, and the bacteriological aspect of the question more thoroughly investigated. The new sewage works at Esholt necessitate the construction of an outfall sewer nearly 34 miles long and 10 ft. diameter, constructed in tunnel for a continuous length of 2? miles. Also an intercepting sewer 12 miles long, chiefly egg-shaped in cross section 8 ft. 6 in. by 2 ft. 6 in., constructed in tunnel for one- third of a mile, and a pumping plant capable of raising 2,000,000 gallons per day to a height of 120 ft. At the Esholt end of the tunnel the sewage will be delivered into detritus tanks of 1,000,000 gallons capacity, screened, mixed with acid, and passed into precipitation tanks of 19,500,000 gallons capacity, arranged with two divisions so that a second dose of chemicals can be added if necessary. The tank effluent water will then be passed on to 60 acres of filters 6 ft. deep, rectangular in plan and arranged in half-acre beds, and on to 411 acres of land laid out for filtration purposes. The storm water will be passed through tanks of 11,500,000 gallons capacity, and on to 50 acres of land. The buildings and works necessary for the treat- ment of sludge will cover an area of about 34 acres. The minimum volume of sewage to be dealt with is 15,000,000 gallons per day. : J. G. Brazing.—(See “ Piumsine.”) MUNICIPAL AND SANITARY ENGINEERING. BRI Bricks and Brickwork for Sewers.— The best materials procurable at a reasonable cost should be used in the construction of sewers, as it is most necessary that they should be constructed and remain watertight, be capable of resisting the crushing pressure exerted by the superincumbent earth, and withstand the erosion caused by the sand and pebbles being carried along the invert, in addition to being unaffected either by the sewer- gas or the chemicals present in the sewage of manufacturing towns. Bricks for sewers may be either wire-cut or pressed, the former being commonly used for the crown and the latter for the invert, they should be well burnt in a kiln, uniform in size and shape, with sharp arrises, free from lumps of lime and pebbles and as non-absorbent as possible. They should be comparatively tough and have considerable hardness, while the faces should be true to permit of joints not exceeding zs in. as a maximum. The colour of the bricks is immaterial, and smoothness of sur- face is not an essential characteristic except in the invert, provided the excrescences on the exposed face are not sufficiently large to inter- fere with the flow, as a thin layer of sewage quickly forms a smooth face on the interior of the sewer. The best bricks to use are Blue Staffordshire, Ruabon, or Buckley, which will generally absorb less than 4% of their weight when soaked in water. Gault bricks, although absorbing nearly 20% of water, may be used on account of their hardness and durability provided they are not perforated, or have frogs formed in them, as is frequently done to reduce their weight. Staffordshire brindles, which are an opff-pro- duct of blue burnings, and are variegated in colour according to their more or less exposed position in the kiln, are also suitable. Broken bricks, burrs, place bricks, grizzles, or chuffs should never be used; soft. bricks would quickly wear away. Any individual bricks which do not come up to the standard, if not too numerous, may be used for backing. Bricks for sewer work should be tested for absorption, hardness, crushing, and freedom 59 BRO from lime. The absorption test which to a certain extent is a general guide to the quality of the brick, can be quickly made as follows :— Thoroughly dry the sample brick, weigh it, place in boiling water and boil for 20 minutes, then allow the brick to cool in the water, and after being carefully wiped dry, weigh it again. Generally speaking, no brick should be used in sewer work which absorbs more than 10% of its weight in water. Another method of testing is to soak the sample _ brick in a strong solution of sulphuric acid for a few days, when, if no loss of weight occurs and the brick otherwise stands the test, the con- signment may safely be used in the construc- tion of the sewers. Brick sewers are usually built either oval or circular, the former section giving a quicker velocity with a small flow than the latter, and usually a better class brick, such as a best pressed blue Stafford- shire, is used in the invert. Where bricks of different kinds are used they should all be of the same size to properly bond together. The bricks are laid in 44 in. rings, of which there should never be less than two, unless the outer part of the sewer is formed of concrete. Cement mortar (1 part cement, 2 sand) should be used for jointing, and the joints should be struck as the work proceeds. Bricks for cir- cular works of less radius than 8 ft. should be specially moulded to the required taper to prevent wide joints on the extrados, and the various sizes should be stamped with a dis- tinguishing mark. H. A. Broad Irrigation.—(Sec “Szwacr Dis- POSAL.”’) Bryan’s Jets.—(See ‘ Jzrs.’’) Building Construction in its Sanitary Aspect.— Walls—Papering—Floors— Windows — Ventilators —Chimney Flues —Cupboards— Partitions—Position of W.C.—Water Supply— Dustbins — Insanitary Conditions.— The site and aspect of the house demand the first consideration, but these will be dealt with under a separate heading later on. The pre- ENCYCLOPADIA OF BUI vention of damp rising in or penetrating through the walls, or downwards through the roof, will also be dealt with in a special sec- tion. Many important details of construction remain which will now be reviewed. Watis.—Concrete under the footings of the walls is only necessary when the soil is of irregular density or has insufficient supporting power without it, and the foundation is then widened so as to reduce the intensity of the pressure to half a ton or one ton per square foot. Modern bye-laws, however, usually require that not less than 9 in. of concrete shall be placed below the brick footings, extending 6 in. beyond them on each side, irrespective of the soil below, as in Fig. 1. The num- ber of courses in the footings is equal to the number of half bricks, or 44 in., in the thick- ness of the wall, each projecting 21 1in. beyond the course above, so that the bottom course is twice the width of the base of the wall. Brick walls and porous plastering are very beneficial to the health of the inmates of the dwelling; they allow of the passage of a considerable quantity of air without any feeling of draught; they absorb the surplus moisture in the atmosphere of the rooms, and do not allow of condensation on the surface when a rapid rise of temperature takes place, as happens with stone walls, cement plastering, or var- nished papers. Stone walls have sometimes a half-brick lining, or a thick coat of plaster- ing, which promotes the dryness of the rooms. Bricks should be hard burnt but not too dense, and should not be glazed except where they require occasional cleansing, or are used to reflect light. In poor neighbourhoods the external walls at the back of the premises should be lime-washed every twelve months, and all sculleries should be washed and dis- tempered at the same time. Limewash is composed of fresh burnt chalk lime, with a little alum init to prevent it from rubbing off too readily. Internal plastering should be put on in three coats, the first consisting of slaked chalk lime with 1 to 14°times its bulk of clean sharp sand, and 1 lb. of ox hair to every 2 cu. ft. of “stuff;” this is called the 60 BUI “ pricking up ” coat. The second, or “ floating ” coat, consists of slaked lime with a little white hair added. ‘he third, or “setting” coat, consists of pure slaked lime without hair, and with about 25% of: plaster of Paris to expedite the setting and give a slightly harder face. Stone lime, or hydraulic lime, must not be used for plastering as it is apt to contain hard particles, which slake slowly and cause “blowing” or blistering. Paprerinc.—The most hygienic papers are those known in the trade as “sanitary” papers. They have a smooth surface that does not collect the dust and they may be cleaned with dough or wiped lightly with a damp cloth without injuring the paper. Highly-coloured papers should be avoided, as they may con- tain arsenic, especially those having bright green in them. Before re- papering a room the old paper should be stripped off and the wall scrubbed down and any damage to the plaster- ing made good. Old houses, especially in poor neighbourhoods, have frequently seven or elght thicknesses of paper on or less decomposed state, and the junc- tions with the mouldings round the doors and windows gaping open and forming a breeding and harbouring place for fleas and bugs. Fioors.—The basement floors of dwelling- houses, and ground floors where there are no basements, are usually of deal battens on fir joists for the living rooms and kitchens, and of concrete and tiles for sculleries, or concrete alone for cellars. The concrete should be composed of 1 part of Portland cement, 2 parts of sand, and 5 or 6 parts of broken stone, hard brick, clinker or flint gravel. Coke breeze is too porus to use for the aggregate in concrete next to the soil. The fir joists are supported on sleeper walls at intervals of 4 to 6 ft. The external walls should have air bricks inserted about every 6 ft. to ventilate the underside of the wooden floor; without this precaution dry rot is very liable to occur. MUNICIPAL AND SANITARY ENGINEERING. “ “ey “es Vt 14¢ 7077, the walls, with the paste in a more [zZZ BUI A continuous course of perforated glazed tiles is sometimes adopted for this purpose, but they let in too much air and cause a draught through the joints of the flooring. All floor boards should be well seasoned to prevent shrinkage and a consequent opening of the joints which would let dust through to collect in the space below. Double floors for upper stories, consisting of common bridging joists in one direction upon which the boards are nailed, and ceiling joists in the opposite direc- tion upon which the ceiling laths are nailed, not only make a stiffer floor, but allow the C07. AAG 204707 2a 7070; NK AAZAAA\ | dine. Fig. 1.—Ordinary Foundation to Brick Wall, » 2.—Section through Window Sill. », 8.—Elevation of Chimney Breast. air to circulate from air bricks which should be placed in the outer walls. Skirtings should be plastered at the back to obstruct the passage of vermir ; this also reduces the risk of fire travel- ling quickly up a lath and plaster partition. Floors should not be covered with an imper- vious material, such as oil-cloth or linoleum, unless well ventilated below. Carpets should not extend to the walls, it is much more sani- tary if a space of 18 in. all round is left un- covered and stained. The floors of school rooms, hospitals, and public buildings generally, should be formed of hard wood blocks laid on mastic with close joints, so as to leave no crevices for the collection of germs. If these floors are properly prepared 61 BUI and beeswaxed they will be non-absorbent and readily cleaned. Any floors that are washed should be dried as quickly as possible by free ventilation from open windows. Winpows should bear some proportion to the floor area, height and shape of the room, and various rules are given by different authorities; for example, Sir W. Chambers— breadth of window should be one-eighth of the sum of the breadth and height of room, and height of window 2 to 23 times its breadth. Joseph Gwilt—1 ft. super of light to every 100 cu. ft. contents of room. Sir Douglas Galton—1 ft. super to every 50 or 55 cu. ft. in hospitals. Robert Morris—area of window surface should equal the square root of the cubic contents of the room. J. 8. Adams— width of window should equal the side of a square whose diagonal is the height. A com- mon rule is to make the window area one- eighth to one-tenth of the floor area. The window-sill should be 18 in. to 86 in. above the floor, average 80 in. The head of the window should be carried up as near the ceiling as possible, say within 12 in. of it, and should be made to open. Above the ordinary inside bead along the bottom rail of the lower sash, there should be a piece of wood 3 in. deep, to permit of the bottom sash being raised to that extent without exposing the opening, as in Fig. 2. This permits of free ventila- tion at the meeting bars without objectionable draught, and is known as the Hinckes-Bird system of ventilation. VENTILATORS.—Open fire-places are the best ventilators in a dwelling-house, but these generally require to be supplemented by Arnot valves in the chimney flue or into a separate ventilating flue carried up alongside. Objection is sometimes made to these valves from the dirty stain surrounding them, which is generally alleged to be due to smoke escaping from the chimney, but is really due to the dust in the air impinging upon the wall owing to the momentum of the particles carrying them in straight lines instead of allowing them to deflect with the air current. Rooms without fire-places should have a ENCYCLOPADIA OF BUI Sherringham inlet ventilator, Tobin tube, pipe flue, or perforated zine square from ceiling to roof space. FFire-places should never be closed by a board and the register door of stoves should always be left open. Curmney Fives should not go straight up but be gathered over the wing in the chimney breast and carried up the side as in Fig. 3. The usual size is 14 in. by 9 in., this being the smallest size the ‘‘ chimney boys” of the eighteenth century could climb, but 9 in. by 9 in. is sufficient in the majority of cases. A chimney pot on top, of a smaller sectional area than the flue, causes the escaping hot air and gases to leave with a much higher velocity and with little increase of friction, so that there is less tendency to a down draught. Chimney tops should be carried higher than surrounding buildings, or there will always be a tendency to smoke, but a smoky chimney is sometimes due to the want of an inlet for fresh air to the room. Cupgpoarps should be of dwarf construction, say 8 ft. high, or should be carried up to the ceiling, or a second cupboard fitted above ; a cupboard 6 or 8 ft. high leaves a space on top for dust and rubbish to collect. Partirions.—Lath and plaster partitions are commonly used because they are cheap and can be utilised to support the upper floors, but they are readily attacked and destroyed by fire. A brick-nogged partition, where the spaces between the uprights are filled in with common bricks, is more sound-proof and fire-resisting, and where no superincumbent weight has to be carried the ‘ Mack” partition, of solid porous slabs, is to be recommended. Position oF W.C.—The inside w.c. should always be against an external wall with the soil pipe outside. There should be a window to open, not less than 2 sq. ft. in area, and also an air-brick high up with an orna- mental grating inside, which is always open. It is an advantage if the door is at least 1 in. off the floor. If the apartment can be shut off from the house by a lobby with a cross current of air it will keep all smell away 62 BUI from the house. A w.c. must not be entered direct from any living room or place where food is prepared. Water Suppiy.—tThe service pipes should be laid 2 ft. below the ground to avoid the effects of frost, and in addition to the stop- cock in the foot-path required by the water company, another should be placed imme- diately inside the house. The supply to the cistern should preferably be carried up an internal wall, but if it must go up on the inside face of an outer wall it should be boxed in, the space being filled up with cocoa-nut fibre. All exposed pipes in the roof should be lapped with gaskin and covered with canvas. Haybands form a cheap substitute. Old carpet used for this purpose simply harbours moth. Cisterns should not be placed under floors, but in a cistern room in the roof or attics. For moderately hard water, say, over 10 degrees of hardness or grains of lime salts per gallon, they may be of galvanized iron, or of wood lined with lead or zine, but for soft water they should be of slate with cement joints, not red lead, which is poisonous. A cover should be provided to keep out dust, leaves, birds, beetles, and mice. Some glass slates or a skylight should be provided in the roof and the cistern should be cleaned out at least once a year. Many writers on hygiene say that drinking-water cisterns should be cleaned out every month, but it is really safer to have it done properly once or twice a year, than to have the duty performed oftener in a perfunctory manner. The overflow pipe should be 2 in. from the top and should discharge in the open air, where any leakage would be seen, and not on to a roof to be carried away by the rain water guttering. The w.c.’s must not be flushed direct from the drinking-water cistern, but should have three- gallon waste preventer cisterns fed by a ball cock in each. Dust Brns.—Fixed dust bins should in no case be allowed, portable covered galvanized iron sanitary bins, holding 2 or 3 cub. ft., should be provided in towns, where they MUNICIPAL AND SANITARY ENGINEERING. 68 BUR can be emptied weekly by the authorities. In the country the animal and vegetable refuse may be burnt or dug into the garden, and the ashes used for making up paths. Insanitary Conpirions. — The principal sources of unhealthiness in dwellings are: building on made ground, a wet sub-soil, damp walls, rotten floors, insufficient depth below floors, dead vermin, drains untrapped or leaking, want of ventilation, ventilating shafts improperly placed, poisonous wall papers, non-removal of old papers, leakage of gas, broken slates and defective gutters, low ceilings and small windows, fire-place open- ings closed, flues blocked up, polluted water supply, foul cisterns, non-removal of house refuse, and want of cleanliness. The chief enactments which give public control over these matters are the Public Health Acts, 1875 and 1891, The Housing of the Working Classes Act, 1890, The London Building Act, 1894, and the various bye-laws of the county and district councils. H. A. Burial Grounds and Cemeteries.—Sani- tary Requirements of Cemeteries—Size of Grave Spaces—Purchase of Land for Burial Grounds— Power to Appropriate Land — Disused Burial Grounds—Repairs to Fencing Surrounding Burial Grounds. SanitaRy REQUIREMENTS OF CEMETERIES. — In 1888 the Local Government Board issued a ‘‘ Memorandum on the Sanitary Require- ments of Cemeteries.” It embodies the views of the official medical advisers of the English Government as to avoidance of dangers to health. Itis stated that the soil of a ceme- tery should be of an open porous nature, with numerous interstices; easily worked, yet not loose; free from water or hard rock to a depth of at least 8 ft., and sufficiently elevated above the drainage level of the locality. Loam and sand are the best; clay and loose stones the worst soils. It may be taken that a distance of 200 yards is amply sufficient to prevent any injury to health from a well-kept cemetery, so far as regards noxious matters transmitted through the air. The BUR Burial Act of 1855 prescribes 100 yards as the minimum distance between the burial places and human habitations; the Cemeteries Act, 1847, 200 yards. The drainage of a cemetery should not be allowed to enter a stream from which water is drawn for domestic use. The Acts and regulations prescribe no limit of distance for water supplies within which a cemetery is not to be established. There is no power to prevent anyone from sinking a well on his own property, as near to a ceme- tery as he pleases. The regulations of the Home Office prescribe that no unwalled grave shall be reopened within fourteen years after the burial of a person above twelve years of age, or within eight years after the burial of a child under twelve years of age, unless to bury another member of the same family, in which case a layer of earth, not less than 1 ft. thick, shall be left undisturbed above the previously buried coffin ; but if on reopen- ing any grave the soil be found to be offensive, such soil shall not be disturbed, and in no case shall human remains be moved from the grave. Size or Grave Spraces.—The size of the grave spaces is 9 ft. by 4 ft. = 4 square yards, for an adult; and for a child under twelve 2 square yards, viz.: either 44 ft. by 4 ft. or 6 ft. by 3 ft. They allow for the hole dug for an adult to be 7 ft. by 2 ft. In any case it is important that each grave should be at least a foot distant from the nearest grave on every side. The minimum allowance of space in a cemetery should be about a quarter of an acre per 1,000 inhabitants. This allows the graves to be re-used every fourteen years. Purcuase oF Lanp ror Buriat Grounps.— A burial board, with the vestry or vestries of the parish or respective parishes for which the board is appointed to act, may purchase any lands, including, if necessary, any ceme- tery belonging to any company or persons, or in lieu of providing a burial ground may contract with any company or persons entitled to any cemetery for the interment therein of the bodies of persons who would have had ENCYCLOPADIA OF BUR rights of interment in the burial grounds of the parish or parishes for which the burial board acts. No approval, sanction, or authori- sation of the vestry is requisite where the town council of a borough, or a local board, or improvement commissioners have been con- stituted a burial board by Order in Council. Where the vestry refuse or neglect to authorise the necessary expenditure for providing a burial ground and building the necessary chapel or chapels thereon, the Secretary of State may on appeal authorise the expendi- ture, the borrowing of money for the purpose, the purchase of land, &c., without any further sanction, approval, or authorisation of the vestry. A burial board may lay out and em- bellish any burial-ground provided by them in such manner as may be fitting and proper, and may build on any land to be pur- chased or appropriated, according to plans approved by the Bishop of the Diocese, a chapel for the performance of the burial service according to the rites of the Church of England. : Power to Appropriare Lanp.—A Town Council of any borough may appropriate for the purposes of the Burial Acts any land be- longing to the body corporate of the borough, or vested in any trustees, or others for the general use of the borough, or for any specific charity, provided that when any land so appropriated is subject to any charitable use it may be taken only on such conditions as the Chancery Divi- sion in the exercise of its jurisdiction over charitable trusts shall direct and appoint. Disusep Buriat Grounps.—It is not lawful to build upon any disused burial ground, ex- cept for the purpose of enlarging a church, chapel, meeting-house, or other places of worship. Repairs to Fences Surrounpine Burra Grounps.—Any urban authority constituting a burial board may from time to time repair and uphold the fences surrounding any burial ground which has been discontinued as such within their jurisdiction, or they may take down any fences and substitute others in lieu thereof. A. 0. FE. 64 CAL Calorifier.— A chamber having tubes through which steam is projected for the pur- pose of heating the surrounding water. Camp Sanitation.— Camp Site — Camp Space—Water Supply—Kitchens and Ablution Places—Disposal of Excreta.— All camps may be regarded as hastily constructed towns, in which the tents or huts represent so many houses, while their sanitation depends upon orderly habits governed by corporate and individual discipline. The selection of a camp site is dominated largely by the facilities which exist ' for obtaining water. This is particularly so in regard to temporary encampments, but where camp sites are likely to be occupied any length of time the feasibility of bringing the water to the camp must be as much considered as taking the camp to the water. Tue Camp Sirge.—The proper location of a camp, as a matter of importance in maintain- ing the health of the occupants, demands in- telligent consideration. It is a good rule to select the site as if for continual occupancy, and, if possible, on high ground, since not only is the surface drainage better, but exposure to air currents facilitates evaporation. Situations at the base of hills are usually damp, and only acceptable if a deep transverse ravine inter- cepts the drainage from the adjacent high ground. No encampment should be placed in ravines or dry beds of water-courses; simi- larly valleys and punch-bowl depressions are objectionable. The vicinity of marshes or irrigated lands should be avoided, while locali- ties to which surface or subsoil water gravi- tates are undesirable for obvious reasons. An abandoned camp site should never be utilised except under circumstances of great necessity—soil contamination is certain, and there is a strong probability of its specific infection. -As regards actual soil, it may be said the more porous the better ; but if a camp must be located upon an impermeable soil, the area affording the best surface drainage and the least dust should be chosen. Apart from the accessibility to water, the golden rule in the selection of camp sites is—choose areas M.S.E. MUNICIPAL AND SANITARY ENGINEERING. CAM which are not only dry, but clean, that is, have not been occupied recently for other encamp- ments, and are not fouled or in any way encumbered with the recent filth of man and animals. Tue Camp Spacr.—Owing to physical diffi- culties connected with the locality, this is subject to variation, but the main principle to be borne in mind is that each tent or hut should be separated from its neighbour by an interval equal to its own height. The risk of camp life, however, lies not so much in ex- cessive density of population on the gross superficies as in overcrowding of individual tents or huts. This is a matter of great diffi- culty, and often dependent upon financial con- siderations. So far as possible, each occupant of a tent or hut should be allotted an available space of 20 square feet in order to minimise the facilities for direct infection from man to man which camp life does so much to foster. All tent walls should be looped up daily for at least three hours, and during the absence of the occupants, so that the tent area may be disinfected by fresh air and sunlight. Where huts are used the doors and windows must be opened daily to permit of aération. In perma- nent camps all tents should be struck and their enclosed ground area sunned or aired for eight hours every week; if the space permits the tents should be shifted to a new site once a month. The excavating of soil within a tent area should be forbidden as tending to impede ventilation and cleanliness. If floor-boards are not available the ground inside tents may be covered with straw or tarpaulin, but whatever is employed it must be turned out, aired and cleaned daily so long as weather permits. Blankets and bedding must be sunned and aired each day. Whenever possible, special accommodation should be provided in all camps for the eating of meals and the storage of food. The eating, storage or retention of food in the living tents or huts must be dis- couraged, as the facilities for contamination in these crowded places are great. If food must be retained or stored, every endeavour must be made to keep it in closed tins or boxes so 65 ¥ CAM that flies may not gain access to it. All food remains, particularly if not likely to be utilised in a few hours, should be either burnt or buried. Water Svuppity.—The general principles affecting this question need not be con- sidered here except to emphasise the need of scrupulously safeguarding the sources of supply from casual contamination by men or animals. When the circumstances permit, water for animals should be taken at a point distinct from that supplying men; in the case of running water the animal’s drinking place must be below that whence the water for men is taken. In camps water is either available from some stand-pipes or from natural source of supply. In each case it is distributed by tanks on wheels or other vessels such as pails, canvas tanks, barrels, or cans. If water is stored in camp the vessels must be protected from dust and other contamination by suitable covers. Individuals should not be allowed to drink direct from the taps of water-tanks, or from the rims or spouts or other receptacles used for carrying or distributing water. Kircuens anp ABLutiIon Puaces.—The cook- ing of food in camps presents no serious sani- tary problems—at best it must be crude and rough. The most important details which need attention are:—(1) That kitchens be located well away from latrines, urine pits, or other receptacles for refuse and garbage. (2) All sullage water must be made to pass into pits from which it can drain away along suitably dug trenches. This waste water is greasy and, if allowed to pass direct on to soil, soon makes a felt-like scum which attracts flies. A useful procedure is to fill the recep- tion pits or the upper ends of the drainage channels with grass or coarse brushwood. If the greasy water be poured on to this material the grease and other solids are entangled, allowing the clearer liquid to run freely away. The grass, or brushwood, loaded with fatty matter, is conveniently burnt daily and re- placed by fresh cuttings. In all camps the system of washing up cooking utensils needs careful supervision, a separate washing-up ENCYCLOPEDIA OF CAM place being allocated for this purpose. ‘This should be provided with as much boiled or filtered water as circumstances permit. If sand is used for cleaning vessels this should be previously baked over a fire. The whole process of washing up and sand-baking should be under the supervision of a sanitary orderly. The ablution places need to be located con- veniently near the tents or huts, and the soiled and soapy water therefrom drained away and disposed of on similar principles to those in- dicated for kitchen sullage water. In standing camps, unless the physical conditions of the soil and the gradients are distinctly favourable for a rapid absorption and soaking away of all sullage and ablution water, it will be advisable either to shift the location of the kitchen and washing places every few days or to collect this liquid in air-and-water-tight receptacles. Such receptacles should be placed on raised plat- forms for the better protection of themselves and the ground beneath them, and should be emptied daily and the contents disposed of outside the camp area. Before being returned to use they should be cleaned and smeared over with a cloth soaked in crude creosote oil. Disposat or Reruse.—Kitchen refuse and the various other items which go to make up the ordinary refuse from camps should never be thrown upon casual ground, but placed in- variably in special receptacles conveniently located for the purpose. In temporary camps these receptacles best take the form of pits, but where these are employed the contents must be covered over each day with at least 6 in. of fine earth, the constant endeavour being to protect the material © ~ from flies. In more permanent camps all this garbage and refuse should be placed in closed metal receptacles, the contents of which must be removed and disposed of daily. On no account, unless necessity compels, should the solid and liquid refuse be mixed. Carts or vehicles for the removal of refuse to the place of disposal should be of special design and capable of preventing any escape of their con- tents. The final disposal of this material is often a matter of difficulty. The location of 66 ee CAM the place should be always outside the camp area and placed to leeward of prevailing winds, and remote from the kitchens and source of water supply. There are two possible methods of disposal—burial or burning, The former is suitable where the amount of material is not excessive, but when much refuse is present the labour necessary to dig sufficiently large pits is prohibitive. In these cases destruction by fire is the only means of disposal; in fact, it may be said that burning is the ideal mode of disposal in all cases. Theoretically this is so, but practically it is difficult to carry out, mainly on account of the natural dampness of the material. Various portable destructors have been proposed and used, probably the best for fixed encampments is that of Horsfall. In the absence of special destructors much can be done by means of improvised crematories. When crude mineral oil is available its incor- poration with the material constitutes an effective aid to its combustion. The construc- tion of a simple grate by laying iron rods or railway rails so as to form a grid or platform, on lateral supports built up of sods or bricks is successful in the combustion of camp refuse—its utility is enhanced if a series be built, arranged concentrically round a central cone of rails or rods stacked or bound together. Cremators of this kind can be built of any size at little cost. One measuring 10 ft. in diameter is capable of burning two tons of damp refuse daily, and, if care be exercised, on to the burning mass the contents of latrine buckets can be thrown and incinerated without local offence. On the same principle a similar erematory can be constructed by lining a circular shallow pit, say 3 ft. deep and 12 ft. in diameter, with large stones, and heaping other stones in the centre to form a pyramid to a height of 6 ft. If ordinary wood be used to start the fire, a freely burning furnace can be maintained by judicious feeding with refuse. Its stones soon become intensely hot, and serve to dispose of liquid and damp material with rapidity. In any devices of this kind the great essential is to secure a draught of air under and through the material to be MUNICIPAL AND SANITARY ENGINEERING. CAM . burnt, and the damper the mass the greater the 67 need of air. An improvised refuse destructor of a simple nature can be made by digging two trenches intersecting at right angles ; each trench should be 9 in. deep, and any length from 5 ft. Over the angle of intersection a shaft is built up of sods, a few pieces of iron hooping, or other resistant material, supporting the shaft where it crosses the trenches. A fire can be quickly lighted at the base of the chimney and fed steadily by throwing rubbish down the shaft. Assuming the refuse be added with ordinary care and the potency of the draught trenches maintained by judicious raking, an enormous amount of combustible material can be disposed of in a few hours. Modifications of this type will naturally suggest themselves. DisposaL or Excreta.—This question is vital to the sanitary interests of all, but pro- vided ordinary intelligence be exercised, it presents fewer difficulties than might be expected. The general location of latrines will depend upon the direction of the prevail- ing wind and the position of the water supply, the rule to be observed being to leeward of the camp and in such a position that no possible fouling of the water supply can result. The construction of these places must not be delayed until tents or huts are fixed, but completed as soon as possible, to safeguard casual fouling of the camp area and its vicinity. Under ordinary circumstances, latrines may be put 100 yards distant from the tents or huts, but always as far as possible away from the kitchens and other places where food is prepared or stored. The extent and type of latrine accommodation in camps will vary according to whether the area is for temporary or permanent occupation. For temporary camps the allowance should be 5%, and in those intended for long occupa- tion at least 8%. These figures may be taken to represent either yards or seats, according to circumstances. The multiplication of latrines is undesirable, as one or two fairly large ones are easier of control than several smaller ones, and soil pollution is also more F 2 CAM localised. In permanent camps, latrine accommodation will best take the form of pail-middens with dry earth, fitted with rough wooden seats. For the reception of urine, iron tubs should be provided, these being placed adjacent to the ordinary latrines for day use, and during the night at selected points convenient for the tents. The contents of these several receptacles will need daily removal in covered and water-tight carts to points well away from the camp area, to be disposed of by burial in the earth. If portable middens, such as pails, are not provided, then the seats must be placed over pits or trenches specially dug. Whatever form the latrine takes, its successful conduction depends abso- lutely upon rigid adherence to the rule that the excreta must be quickly and completely covered over with earth, and this depends, again, upon the enforcement of individual sanitary discipline, adequate personnel, and competent administrative control and super- vision. For ordinary or more or less tempo- rary camps, the usual latrine is a trench, provided or not with a seat. Some 20 ft. of trench, 2 ft. deep and 16 in. wide, is the common allowance for each hundred persons. For temporary encampments and where the provision of a rough seat is impossible, a preferable arrangement is to provide a series of short trenches in parallel, across which the user straddles; each trench should be 8 ft. long, 1 ft. wide and 2 ft. deep, with the interspace between each trench not more than 24 ft., preferably less if the soil permits, so as to preclude use otherwise than in the straddling attitude. Every latrine needs to be surrounded by some form of screen, also roofed in if possible, and the soil removed from the trenches must be broken up and carefully piled to the rear, whence it can be scattered as needed over the deposits. All displaced grass sods, too, should be carefully stacked in rear of the loose earth, so that when the trench is filled in these grass sods can be replaced and the soiled area made neat and wholesome. In wet weather, latrines should be protected by a shallow drain to ENCYCLOPADIA OF CAN prevent ingress of surface water. So soon as the contents of the trench reach within 6 in. of the top, it should be filled in, the turf replaced and new ground taken up by digging fresh trenches. Some kind of implement, such as a spade, scoop, or tin should be by each trench for replacing earth at each time of use. Kicking the soil in by the foot is certain to be a failure and should be dis- couraged as conducive to imperfect covering of the excreta and consequent slackness. Notices should be displayed prominently within all latrines impressing upon users the necessity of covering their dejecta before leaving with earth. Failure on their part to adequately cover their excreta should be made a matter of discipline and entail some punish- ment or disability. If difficulty is experienced in getting this essential act properly carried out, an alternative is to place a man within the screen, provided with a spade, and direct him to cover each deposit with earth as each depositor moves off. A tour of such duty should not exceed two hours, and might well be limited to one hour. A modification of this disciplinary method is to place a sanitary patrol or policeman over the latrine to see that each user thereof fulfils his duty to himself and his neighbour. So long as the sanitary foresight of the masses remains at the present low level, the latrine sentry, how- ever great the sentimental objections may appear, is a necessity, and the only safeguard against fecal diseases which spread in camps from this point. The care and conduct of latrines in camps must be ever regarded as a disciplinary matter, and unless it is so regarded these places will be the foci of disease in all climates. Consistent practice on the lines explained will result in the latrine being no more offensive than the ordinary ablution place. When this is so, the incidence of filth-originated or dust and fly-borne disease in camps can be reduced to a minimum. R. H. F. Candy Mechanical Filter. — (See “MecuanicaL FIurration.’’) 68 CAN Candy Settling Tank.— This consists of a flat-bottomed sewage precipitating tank in which the upward-flow principle has been applied, and which admits of-the sludge being removed by the hydrostatic head of water within the tank, the sludge-pipe rising to a level 18 in. below the tank top-water level. The sludge is removed by a revolving perforated sludge-pipe pivoted at the centre of the tank floor. This, together with a rubber squeegee passing over the floor and a similar vertical squeegee for the walls of the tank, is worked by means of a worm-gear at the ground surface level. Hard substances are apt to jam between the squeegee and the floor of the tank, but if the sludge is removed daily the tank on the whole works well, and the growths of bacteria and deposit of sludge on the sides, which cause trouble in the Dortmund tank, are prevented by regularly working the revolving squeegees. Carbolic Acid, or phenol, C;H,OH, is a colourless crystalline solid, very hygroscopic, and having a characteristic odour. It melts at 42° C., boils at 182° C., and has a specific gravity of 1084 at 0° C. It is not very soluble in water, a saturated solution at 15° C. containing about 5 °/,, but phenol itself dissolves water, taking up nearly one-fourth its weight at 15° C., forming an oily liquid. The liquefied phenol of the B.P. consists of 100 parts of carbolic acid with 10 parts of water by weight. It has a caustic action on the skin and mucous membrane. Carbolic acid is produced during the decomposition of a variety of substances ; practically all the phenol of commerce is obtained from the distillation of coal. Com- mercial carbolic acid is a dark oily liquid containing higher homologues and not miscible with water, and requires some 500 times its volume to dissolve it. Until recently it has been widely employed for the preparation of disinfectant fluids and powders, and has the merit of showing no great diminution of MUNICIPAL AND SANITARY ENGINEERING... CEM germicidal activity in the presence of organic matter either in solution or in suspension. Absolute phenol has been adopted as a standard germicide for the testing of disinfectants. (See “ DistnFEcrion.’’) Catch Pits. — Depressions, hollows or sump holes made use of in drainage and sewage disposal works for arresting sand and other such detritus which may pass through drains. The matter to be detained sinks to the bottom of the pits by gravitation, while the liquid and lighter solids of the sewage pass out through the overflow. , Catchment Area.—(See “ Watrer-SHep ”’ and “ Warer Suppty.’’) Catchwater Drain.— Open ditches or catchwater drains are artificially cut along the contour lines of hillside slopes for the purpose of intercepting the flow from rainfall and preventing damage which would other- wise be caused by the water rushing to the foot of the hill-side. The water thus inter- Catchwater Drain. cepted is passed down from one catchwater drain to another by means of properly con- structed conduits of masonry, brickwork, or piping, and so safely conveyed to the required point of discharge. Cement, Portland—Portland cement is so called from its resemblance to Portland stone. It is an artificial cement composed 69 CEM of various ingredients intimately mixed, calcined and ground, finally consisting of about 83% clay, 68% lime, 8% iron, mag- nesia, &c.; the clay (silicate of alumina) confers the property of hydraulicity. The materials used are chalk and clay by the wet process, and limestone and clay, or shale, by the dry process; the wet process is usually employed on the Thames and Medway. The approximate proportions are 1 of clay to 8 of white chalk or 4 of grey chalk; the quality depends upon the care taken in the manu- facture. Under-burning produces a greater bulk from a given quantity of material, and the specific gravity is thereby reduced ; less fuel and grinding are required, and a quick setting cement is pro- duced, but it never reaches the same strength as if better burnt. The heavy cements are always slower in setting, but have greater ulti- mate tensile strength. Light cements may be used for rendering, but a fairly heavy cement is necessary for all work of importance. Over-burnt cement is slow and irregular in setting. Cement which is over-limed expands in setting, that which is over-clayed contracts. The setting of Portland cement is due to the crystallisation of a compound silicate of lime and alumina, together with the evaporation of surplus moisture, and in course of time the formation of a small amount of car- bonate of lime by absorption of carbon dioxide from the atmosphere. The specifi- cation of weight by Imperial striked bushel is now obsolete, and a specific gravity of 3°1 is required instead, taken with a specific gravity bottle. Of late years cement has been ground much finer than formerly, giving it more covering power and enabling it to take a larger quantity of sand, or, conversely, reach a higher strength. The residue on a sieve Te es + r | trot ~ x [7O°thick ie ee eae JO- - = - 4] ame k Standard Briquette for Testing Portland Cement. ENCYCLOPADIA OF 70 CES 180 x 180 = 32,400 meshes per sq. in. must not exceed 12%. The British Standard Speci- fication for Portland Cement revised to June, 1907, is generally adopted. Figure shows the dimensions of a standard briquette. The tensile tests on briquettes 1 sq. in. net section are, 7 days from gauging 400 lbs., 28 days 500 Ibs. If the 7-day test comes out higher than 400 lbs., there shall be an increase over 500 lbs. at 28 days, varying from 25°% down to 5%. Three grades of cement are recognised — “ quick-setting,’’ in which the final setting time is not less than 10 nor more than 30 minutes; “medium- setting,’ in which the time is not less than 4 hour nor more than 1 hour; “ slow- setting,’ in which the time is not less than 2 hours nor more than 7 hours. Final setting occurs when the Vicat needle fails to make an impression. The Le Chatelier test for expansion is considered to be of great importance. Accelerated or boiling tests are frequently adopted to ascertain the soundness of cement. H. A. Cemeteries.—(See “ Burtan Grounps anp CEMETERIES.” Cesspool, Self Emptying Septic. — Forms of self-discharging septic-tank cess- pools are being largely used both in urban and rural districts of France. These are improvements introduced respectively by Bezault and Degoux on the old Mouras siphonage cesspool. The Bezault type con- sists of an air-tight cesspit, divided into two unequal sized chambers by a vertical partition reaching nearly to the ceiling, and perforated towards the base. The soil and rain-water pipes enter the larger section of the tank vertically, but with horizontal outlets to prevent any violent commotion on the intro- duction of fresh matter. ‘The discharge pipe enters the smaller compartment horizontally, but has the end turned downwards, and at the elbow there is a small ventilation outlet. The sewage is collected in the larger section, where it undergoes liquefaction as the result CES of aérobic bacterial activity, air being intro- duced whenever any material enters the cesspool. The liquefied and drained sewage enters the smaller section, and as soon as the liquid reaches the level of the horizontal discharge pipe siphonage takes place, and any accumulation of gas generated during bacterial action is removed by way of the ventilating orifice with the flow of the effluent. Asa rule the purification is not carried very far in such a cesspool, but the effluent is entirely free from flocculent matter, is prac- tically odourless, and in a fit condition for distribution over a contact bed or for broad irrigation. It is impossible for any nuisance from sewer-gas to arise. In the Degoux type there are also two compartments. The first is a water-tight pit, into which the soil pipe discharges vertically. The discharge pipe is horizontal, with end bent downwards, the orifice being protected by a grid or other contrivance to prevent the aspiration of paper or solid matter during discharge by siphonage. This pipe communicates with the top part of the second water-tight tank, which contains a bacterial contact bed, composed of three or more layers of slag broken up into different sizes, resting on a perforated plate, placed a few inches above the base of the tank. Over the filter is an air-inlet pipe. The effluent is discharged through a large valve at the base, and this discharge pipe is provided with a small ventilating shaft, fitted with a vaned cowl, the shaft being carried up above the eaves of a house, or to a sufficient elevation to avoid the causing of any possible nuisance. The discharge of effluent is sufficiently rapid to ensure the necessary supply of air to the contact bed and the dispersal of sewer-gas. The eftluent, which is slightly opalescent, is inodourous and claimed to be imputrescible, but sanitary engineers object to its being discharged into any stream before refiltra- tion upon beds or land. The Degoux type has been employed. successfully in connection not only with dwelling-houses and factories, but also for the collective treatment of sewage from houses and cottages on estates and from villages. MUNICIPAL AND SANITARY ENGINEERING. CHI Cesspools.—Now out of date, yet, fre- quently made use of, and permissible if properly constructed and placed. Cesspools may be simply sunk in a porous soil, such as chalk or gravel, and lined with loose brick- work. In this case the sewage merely soaks away when liquefied. Ata safe distance from dwellings and sources of water supply, there is no objection to this type of cesspool. Other cesspools, which are preferable, are those which are made water-tight and from which an overflow pipe conveys the liquid sewage to some convenient and safe spot for ultimate disposal, which may take the form of land irrigation or treatment on suitable bacteria beds. Many such cesspools which in former years were blindly constructed on right principles are in existence, and have proved satisfactory even though their very position had been forgotten. The essentials in cess- pools are a suitable capacity, and placing the inlet and outlet pipes so that sewage entering the cesspool is immersed, and the outflow quite liquid. When, as is frequently the case, the inlet and outlet are placed at the same level, the sewage merely passes from one to the other, thus leading to blockage and nuisance. If both are dipped to about the centre of the contents of the cesspool the heavier solids fall to the bottom while the lighter float on the surface, and only liquid is allowed to escape. In time the solids liquefy by bacterial action and are displaced by fresh solids. A cesspool so constructed closely resembles a “Septic Tank ’’ as to which see “Szwace Disposau.” Chimney Shafts.—Tall chimney shafts, as used for factories and engineering works generally, are usually built of brickwork, but more recently iron and reinforced concrete have also largely come into use. Perforated radiated bricks are employed in the Alphons Custodis system of construction, which also has been largely used in this country of late years. These shafts are of thinner outer walls than the ordinary recognised English mode of construction, and are consequently of less 71 CHI weight and cheaper to build. The usual practice in this country is shortly as follows :— the brickwork to be not less than 9 in. thick at the top and for 20 ft. below, to be increased 43 in. in thickness for every additional 20 ft. of height measured downwards. The batter to be 24 in. in every 10 ft., or an inclination of lin 48. In circular shafts the outside width or diameter at the base to be jth of the total height, and in square shafts to be not less than zoth of the total height. No cornice or other projection should stand out more than the thickness of the brickwork at the top. The firebrick lining is to be additional to the thicknesses of the ordinary brickwork as pre- scribed by the above-named rules. This lining should not be bonded in with the brickwork of the outer walls, but be built quite free in order that it may expand and contract without affecting the outer walls. The height to which this lining should be carried up depends upon the heat of the gases and the fluctuations of temperature within the shaft. Usually, in a shaft 150 ft. high the firebrick lining may be advantageously carried up to about 70 ft.: from the bottom of the inlet flue at the base. The top of the shaft may be provided with a cast-iron cap, which is preferable to stone, as the latter is very liable to deteriorate, especially when held together with ironcramps. Cramps, if used, should be of gun-metal, and continuous gun-metal rings are sometimes adopted in circular shafts to bind the stone courses in chimney caps. Special care should be taken to see that the shaft stands upon a thoroughly sound foundation. It is usual to provide an extended base of Portland cement concrete from 3 to 10 ft. thick, according to the necessities of the site, in order to thoroughly distribute the weight of the shaft over a large area. The brickwork foundation is then commenced upon this and gradually tapered up to the proper size or outside diameter of shaft at the finished ground level. A shaft should be built and allowed to settle before connecting up to the main flue to avoid fracture in the brickwork. For the same reason it is advisable shafts ENCYCLOPEDIA OF CHL should stand alone without connection with any surrounding buildings. The circular form of chimney is best and most economical, as the same amount of material covers a greater area, and the effect of wind pressure on the structure is less. Taking the effect of wind pressure upon a square shaft as 1, the effect upon a hexagonal shaft may be taken at ‘75, on an octagonal shaft ‘7, and upon a circular shaft °5. In practice it is customary to provide shafts of sufficient weight and stability to withstand a wind-pressure of 56 lbs. per square foot of surface exposed, an allowance which was recommended by the Board of Trade Committee on Wind Pressure, and which is well in excess of anything likely to be realised. In calculations for stability of shafts no value is attached to the tensile or adhesive strength of the mortar, the weight of the shaft alone must be adequate to resist overturning, so that even during the most severe gale of wind there should be no tension set up in any part of any bed-joint. If a chimney is designed with the thicknesses of brickwork prescribed in the first part of this article its stability will be ensured. Chloride of Lime, or bleaching powder, CaCl,0, dissolves in water (except the im- purities) forming chloride and hypochlorite of calcium, the latter only being available as a disinfectant or oxidiser. The powder should be dry and should contain about 4rd of its weight of “available chlorine” (that belonging to the hypochlorite). It keeps for some time when protected from light and air, which cause it to deliquesce and spoil, while CO, liberates hypochlorous acid, giving rise to the odour. It is a bactericide and an oxidiser acting approximately thus: (1) when alone (a slow action), CaClO = CaCl, + O: (2) with hydrochloric and some other strong acids, immediately, CaClO + 2HCl = CaCl, + H.O + Cl, (free chlorine): with weak sulphuric and other acids, 2CaCl,O + H,SO,4 = CaCl. + CaSO, + 2HCI10 (Hypochlorous acid). When mixed with whitewash the surface remains damp, owing to the calcium chloride. For 72 CHL _ sprinkling use 1 part to 10 or 12 of water ; for washing the person 1 to 100. For disinfecting rooms several applications of the 1% solution are needed.1 If strong it corrodes metal fittings, and it has sometimes perforated the siphons of water closets, but after the Maidstone typhoid epidemic in 1897 the water pipes were sterilised with a 1% solution of chloride of lime acting for 48 hours, and no corrosion was observed. Traube in 1894 stated that a quantity of chloride of lime containing one milligramme of available chlorine destroyed in 2 hours all the bacteria in a litre of water (a proportion of 1 per million), but it has since been proved that the amount required is much greater, and such as to make the water hard and undrinkable. Hypochlorite of soda, in the form of “ Chloros,” or electrolytic, can be used in- stead, and the writer has found that 1/25,000th to 1/30,000th part of available chlorine in either of the three forms killed B. typhosus in 10 minutes. The strength of commercial hypo- chlorites in available Cl (normal 83 %) must always be known, and they must be used in pro- portion to this figure. Comparative tests with bleaching powder and electrolytic chlorine for the sterilisation of water and sewage effluents show that the latter is cheaper and more efficient, and it is probable that electrolytic plants will be installed in those cases in which a permanent treatment is required. Itis even possible to disinfect crude sewage, as, for example, that from a hospital, prior to bacterial treatment, but in this case the cost is pro- portionally higher. Schumacher, and Dunbar and Korn, conducted some elaborate trials at Hamburg in 1904 with bleaching powder, and established the quantities necessary for the sterilisation of sewage, whilst Chloros has since been used by the London Water Board for Hertford Sewage, and Rideal has similarly used “‘oxychlorides ” (sodium hypochlorite prepared electrically) on the Guildford sewage with satisfactory results. (See “ HuEctrRozysis.’’) 1 The Board of Agriculture and Fisheries prescribes “21% (minimum) solution of chloride of lime con- taining not less than 80% of available chlorine.” Diseases of Animals (Disinfection) Order of 1906. MUNICIPAL AND SANITARY ENGINEERING. CHL In the United States the Department of Agriculture in Bulletin, 115, has further in- vestigated the subject, comparing the effect of copper sulphate and chlorine for the disin- fection of sewage effluents for the protection of public water supplies. At Ilford bleaching powder has been used for sterilising the effluent from the sewage works after chemical precipita- tion. About 5 parts per million of available chlorine and a storage of about 2 hours re- moves nearly all the bacteria, including B. colt and any typhoid bacilli present, from an ordinary sewage effluent after bacterial treatment in a modern percolating filter. S. R. Chlorine in Water and Sewage.— Chlorides in water (and sewage) are usually recorded as chlorine. High chlorides, unless derived from rocks or from the sea (which contains about 1°9% of Cl), point to contamina- tion by urine, which dontains up to 1% of NaCl, as distinguished from that by feces, which contain much less, hence the chlorine figure is sometimes a valuable index of the pollution. The urineaverages about 13 litres per head per day, with a mean chlorine of about 0°45 % or 450 parts per 100,000, whereas in most ordinary waters the chlorine is only 1 to 2 parts; in weak domestic sewages it is about 7, in stronger ones it may be 40 or 50, and a common average is 10. For comparing sewages it is often useful to calculate the analyses to a uniform Cl figure, say 10 parts, and the ratio of the Cl to the amounts of the different forms of nitrogen shows the progress of the purification. We may note that (1) rain, unless it has passed over a polluted surface, always diminishes the Cl; (2) a decrease in the Cl of a well may indicate surface infiltration; (3) a good well yields a fairly constant figure. The Massachusetts reports give maps of “‘Isochlors,” or lines on which the subsoil water shows equal Cl, but in many countries agriculture renders these illusory. In rivers and estuaries, and on coasts, Cl determinations enable us to trace the course of sewage and of fresh or salt water 73 CHO (as recently at Dublin, Southend, and other places), and also the infiltration of the sea into water pipes and wells, as at Eastbourne, and the passage of trade effluents. (See ‘‘AwaLysis, CHEwicaL”; ‘‘ EFFLUENTS AND Sranparps oF Puriry”; “ Water, CHEMICAL ANALYSIS OF.” Cholera.—Cholera is a specific infectious disease characterised by violent diarrhea and collapse, causing a heavy mortality, often reaching 50 %, amongst those attacked. In certain parts of India it appears to be continuously prevalent, ‘‘ endemic,” and from time to time it follows the routes of travel to the most distant parts of the world. Sometimes it travels slowly along the route of caravan traffic, at others it travels more rapidly along the course of rivers, and at others it is carried rapidly by ships from port to port. Several times during last cen- tury it entered British ports, and in 1832, 1849, 1854, and 1866, wide-spread epidemics occurred; but in 1866 the invasion was far less serious than on previous occasions, and since that date although the infection has been several times imported the secondary cases have been few in number and practically confined to the port of entry. The disease is due to a specific poison, a toxin, produced by a spirillum, the cholera bacillus, during its growth in the large intestine. The organism does not produce spores, and it can readily be grown in nutrient broth and on various solid media. It apparently lives only a short time in water, but may survive a long time in soil under favourable conditions. The evidence, however, on these points is very conflicting. Like the infection of typhoid fever, it is chiefly disseminated by water, milk, and articles of food and drink; but it can also spread from person to person, and it is especially prone to prevail where the sanitary conditions are unsatisfactory. The spirilla are rarely if ever found in the blood or the urine of the patient, but the rice water stools contain them in myriads. From surfaces which have become contaminated flies may convey the infective ENCYCLOPAEDIA OF 74 CHO material to water, milk, &c., and so cause spread of the disease; but doubtless water supplies are most prone to pollution from the washings of soil which has been fecally contaminated. The last epidemic m Europe, which occurred in Hamburg in 1892, was- due to the use of unfiltered water from the river Elbe. Altona, lower down the river, using still more grossly polluted water from the same river after careful filtration, practically escaped until by an accident a little imperfectly filtered water was allowed to enter the mains when a small outbreak quickly occurred. The Hamburg epidemic resulted in the loss of over 8,000 lives within a period of about three months. The mortality amongst those attacked was over 40 %. Within two to five days from the ingestion of the specific poison, the first symptoms of the disease appear, and frequently the early cases of an epidemic are so mild in character as to be regarded as ordinary diarrhea. The later occurrence of typical and rapidly fatal cases clears up the diagnosis. In districts liable to invasion any outbreak of diarrheal disease, however mild, should be carefully watched, or the train may be laid for an extensive outburst before the real danger is realised. Wherever pure water supplies have been introduced the ravages of cholera have been held in check. Thus in Lahore the average death-rate from cholera fell from 1:07 per 1,000 population to 0°07 after the provision of a public water supply, whereas the death-rate increased in the district around, where the water supplies remained as before. The annual pilgrimage of Mohammedans te Mecca almost invariably brings cholera in its train, though the great attention now paid to the wells en route has considerably reduced the risk of a serious epidemic. Cases of cholera can only enter this country through the ports, and the Local Government Board has issued regulations for the prevention of such importation Any vessels coming within three miles of the coast of England 1 Pp, H. A., 1875, s. 180; P. H. (Port) A., 1896; P. H. A., 1896. CIS and Wales, and having a case of cholera (or yellow fever or plague) on board must hoist at the mast-head a large yellow and black flag. All vessels from foreign ports are boarded by Customs officers, and if, upon inquiry, they have reason to suspect that a ship is infected, it is ordered to be moored in a place set apart for the purpose until the medical officer of the port has boarded and examined the passengers and crew. A vessel is deemed to be infected in which there is any case of cholera (or yellow fever or plague), or in which there has been a case whilst it was in, or since it has left the port of departure. The medical officer of health can detain the vessel for a period not exceeding two days. Infected persons must be sent to a hospital, suspected persons may be detained two days to enable a diagnosis to be made, whilst those who are well must be permitted to land, pro- vided they give their names and addresses, and intended destinations. These names and addresses are sent to the sanitary authorities for the districts into which the persons are going and the medical officers of health for the respective districts then exercise such supervision as may be deemed desirable until the danger period is past. In some countries vessels are detained in quarantine for a con- siderable period, but the experience gained at British ports has shown that such prolonged quarantine is totally unnecessary whilst it seriously dislocates trade, and causes heavy pecuniary loss to shipowners and passengers. During the day or two’s detention the vessel can be disinfected, and bedding, clothing, &c., be submitted to steam for sterilisation, the bilge water pumped out, and all water receptacles disinfected. The master of the vessel must carry out or permit to be carried out neces- sary disinfecting and cleansing operations and must burn or otherwise destroy all infected articles if ordered to do so by the sanitary authority or medical officer of health. J.C. 7. Cisterns (Vessels for the Storage of Water in Buildings).—Although drinking MUNICIPAL AND SANITARY ENGINEERING. 75 CIS water is best drawn direct from the mains, where mains and a constant supply are avail- able, water must be stored in all cases for eventualities, such as during periods of frozen mains or repairs. Oisterns are constructed of a variety of materials which should be selected with due regard to the characteristics of the water to be stored. Soft water absorbs lead and this material must therefore be avoided if the water has any tendency to act upon it. Zine lined and galvanised iron cisterns are also undesirable in connection therewith, al- though less objectionable than lead. Copper lined cisterns, unless tinned, are even more objection- able, as copper isa metal which is attacked very energetically by water and air, and the salts of copper are very dangerous. Tin, however, has a great affinity for copper,and forms a very durable and protective coating when thoroughly applied. Tinned copper is therefore probably the best metallic lining which can be used for cisterns intended for the storage of water having a tendency to act upon metals. Other suitable cisterns which are safe and desirable with all kinds of water are, enamelled iron cisterns made in sizes to hold from 40 to 500 gallons of water; porcelain enamelled stoneware cisterns made of capacities up to about 60 gallons, and fireclay salt glazed cisterns which are obtainable in Cisterns. sizes ° cIS sufficiently large to hold from 400 to 500 gallons of water. With all these it is neces- sary to exercise care in selection, as the enamelling or glazing is frequently rough or fractured. Stoneware or fireclay cisterns are for this reason oceasionally apt to prove slightly porous. Slate cisterns are also good, and come next to stoneware cisterns in clean- liness and suitability for the storage of water. They are, however, heavy, costly and liable to leak. Their joints should be made with materials other than red or white lead, as the oxides of lead are soluble in most waters and, of course, poisonous. Black wrought-iron cisterns, painted or washed with lime or cement, are occasionally used. The cement or lime-washing, however, soon wears off, and needs frequent renewal; whilst painting is not always suitable owing to the lead con- tained in the paint. If iron cisterns are used the safest and most lasting protective coating would be a quick-drying asphalte varnish, of which two or three coats should be applied. Cisterns, and especially such of them as are connected to taps for supplying drinking water, are amongst the most important of the sanitary fittings of a house, and require at least as much consideration as water closets, or other sanitary appliances. They should be placed in apartments kept exclusively for the purpose and chosen with the utmost care. The room or rooms in which they are placed should be well lighted, warm in winter and cool in summer, and as far removed as pos- sible from those portions of the house in which sanitary fittings or bedrooms are situated. All care must be taken to prevent the pollution of the water by dust, vermin or foul air, for which purpose each cistern should be provided with a close fitting removable cover. When vermin and dirt are the only impurities to be guarded against, a wooden lid, constructed of tongued and grooved boards or of matchboarding, will be sufficient; but if there be the slightest possibility of contamina- tion by foul air or gases—such as from bed- ENCYCLOPADIA OF CLE absolutely air-tight, both in itself and in its fixing to the cistern. The ideal cistern, as was pointed out by the Commission on the Kast London water-supply, would be a mere local enlargement of the service pipe, perfectly closed except for a minute valve, and preferably of a conical shape, so as to be self-cleansing. Such cisterns are upon the market (see Figure, p. 75). In order to efficiently guard drinking water against aérial contamination, it is also essen- tial that all ordinary cisterns containing such water should have their overflow pipes arranged to discharge into the open air at some point at which the overflow pipe is not exposed to emanation from drains, sanitary fittings, or other sources of polluted air. Nor must any water closets, urinals, or housemaids’ slop- sinks be flushed directly from the service pipes or from any cistern containing potable water. The latter would be liable to be polluted by means of foul air conveyed to them from the sanitary fittings through the flushing pipes; whilst, in the case of service pipes, there is a strong tendency for foul air to be drawn into these when emptied through any cause. It is for these reasons that most sanitary authorities require the fittings mentioned to be flushed from separate cisterns. The requirements of water companies and corpo- rations, by which it is necessary to provide water -waste preventing cisterns, are also beneficial, although, perhaps, framed mainly for the prevention of waste. For details of these see “‘ Waste Preventers.” G.J.G.J. Cleaning Eye.—A round aperture on a pipe, usually in the nature of a branch socket, rooms or from ventilation pipes on drains or = from the house—then the lid should be CLI provided for cleaning purposes and fitted with a movable cap or cover capable of being closed air-tightly. Cleaning eyes are usually pro- vided on waste pipes; also on disconnecting traps for giving access to that ,portion of the drain whicn lies between the trap and the sewer. (See also ‘‘ Access Pipzs.”’) es vz 4 o" tees ata a Fig. 3. Clinker from Destructors.— (See ‘‘ Dz- STRUCTORS.”’) Coagulents.— (See “ Fiurration.’’) Coarse Beds, Bacterial.—(See “ Snwacz Disposat.’’) Cocks.—A valve or tap for controlling the flow of water through or from a pipe. Strictly, a cock is a fitting having a conical plug with its axis at right angles to the flow through the pipe and provided with a slot or opening which, when in the direction of the flow, permits water to pass through. When the slot is at right angles to the flow the water is turned off. Cocks are not desirable fittings as they shut off the water too suddenly and give rise to the percussion known as water hammer when the water is under pressure. (See also ““ VALVES.’’) Colloidal Matters in Sewage.—The substances in sewage which are not removed by ordinary filtration or sedimentation are of two kinds, (1) colloidal, amorphous, of con- siderable viscosity, and almost incapable of diffusion, like albumen or gum; and (2) crystal- loid, capable of crystallisation and diffusion, and much less viscous, like, typically, common salt. unstable condition, and Graham, whose work first made the difference distinct, introduced the terms still in use of “sol” for their apparent solution, and “gel” for the MUNICIPAL AND SANITARY ENGINEERING. The former are in a more or less COL gelatinous result of their coagulation or change; the words are frequently extended into “hydrosol” and “hydrogel” to include in them the presence of water. Although most of the colloids are organic, probably all solids in conjunction with liquids are capable of assuming, at least temporarily, the colloidal state: that is (1) they may be in such a fine state of division as not to be separable by filtration ; (2) they leave the liquid clear or only slightly turbid, so that their presence may be solely detectible by the ultra-microscope—that is, by a concentrated beam of reflected light; and (3) they can be flocculated and precipitated by addition of small quantities of chemical substances, also sometimes by heat, and sometimes by adhesion to surfaces. In forming a “gel” a colloid always combines with and entangles a considerable amount of other substances present ; this property, especially when it affects matters in solution is called ‘“ adsorp- tion,” and is a conspicuous feature of methods of precipitation of sewage by the inorganic “gels”? of ferric oxide and alumina, obtained by adding an acid salt like ‘‘ alumino-ferrie,” and then:lime. In this case, since a number of organic.substances prevent the precipitation of metallic oxides, it is necessary to ascertain the quantities by trial, in order that the effluent should not contain more than traces of the precipitant. It is possible by suitable chemicals to greatly decrease the colloids in sewage, but with considerable expense and an excessive sludge. A large portion of these colloids are deposited in simple sedimentation, if time can be allowed, but this deposition is greatly accelerated by their property of adhesion to surfaces. In filtration a slimy layer forms on the material, and acts mechanically,*by entangling suspended matter, and biologically by the large number of organisms growing in it (“‘Zooglwa’’), which occasion chemical changes in the liquid passing through, and if properly managed effect a great purification. At the same time the working of filters is largely influenced by the viscous properties of the colloids, acting by (1) causing 77 COL the liquid itself to flow more slowly; (2) diminishing the capacity on account of the gelatinous deposit on the medium; (3)retarding the previous deposition of suspended matter. Hence the advantage of a preliminary passage over surfaces, as in the Scott-Moncrieff culti- vation tank or in Travis’s ‘ hydrolytic ” arrangement. Besides the mucous matters in domestic sewage, a number of other viscous substances are often added by manufactures and may necessitate some form of chemical precipitation. Blitz’s work on the different polarity of the colloids, the gummy and the albuminoid class being electrically negative, and the metallic hydroxides positive, helps to explain why definite quantities of precipitants are necessary, and why electric currents, passage over surfaces, or addition of electrolytes can cause coagulation. Anaérobie action in septic tanks, and defective aération in filters increase the amount of colloid matter in the state of “hydrosol,’ which also usually becomes higher with increased temperature, while high nitrification generally coincides with low colloids in the final effluent. The amount of these substances in sewage has been determined by dialysing the filtered liquid through parchment, or through porous porcelain (Thorp): upwards of 30 to 50°/, of the organic matter will not diffuse and is there- fore colloid. A similar figure is obtained more rapidly by precipitating by basic ferric acetate. Fowler for his ‘‘Clarification Test’’ adds to 200 c.c. of the sample 2 ¢.c. of a 5°/, solution of sodium acetate and 2 c.c. of a 10°/, ferric ammoniumalumsolution, boils fortwominutes, cools, filters, and analyses the clear liquid. O’Shaughnessy found (Birmingham sewage) that the matter which separates on allowing a clear septic tank to stand has only a faint odour, is extremely stable, and even when incubated with water under the most favourable circumstances decomposes with extreme slow- ness. These properties sharply distinguish this matter from the.original sewage sludge. He mentions incidentally that the colloid matter usually present in land effluents is very small in quantity and contains much mineral matter ENCYCLOPZDIA OF COM consisting mainly of ferric hydrate and silica. Other investigators ' have shown that the pro- ducts of a proper septic fermentation and sedi- mentation of sewage resemble the humus of peat, are practically inoffensive, and contain about 7 parts of carbon to 1 of nitrogen, associated with iron and other inorganic matter. 8. R. Columbaria. — (See “ Crematortia CoLUMBARIA.’’) AND Combined Drainage System.—The com- bined drainage system is that in which the surface-water from a district is carried away by the same sewers which convey the sewage. Most English cities and towns are drained on this system, the original practice having been to turn sewage, rain-water, and even subsoil- water into the same set of sewers. The points urged in favour of the combined system are that it is simpler and cheaper to have one set of sewers than two, and that the rain-water admitted to the sewers is valuable for flushing them. Its disadvantages are the excessively large sewers which it generally necessitates, and the consequent sluggishness of the dry- weather flow in them; and the difficulty of dealing with large volumesof storm water at the outfall. Whether the sewage is to be purified on land or in artificial works, it is important to keep the flow within moderate limits; and where it has to be pumped, the admission of surface-water will generally entail a very large addition to the cost of this operation. The “combined system ”’ is therefore very generally discarded in favour of the “ separate system ” (which see), though for various practical reasons it is seldom possible to carry out the latter in its entirety. The washings from the roads, especially after a long spell of dry weather, are often fouler than the sewage. London is a good example of a city sewered on the combined system. A. J. M. Commin Separator, (Sewage Dis- posal).—This consists essentially of a shallow 1 Adeney, “ Trans. Roy. Dublin Soc.,” Sept., 1895, and Aug., 1897 ; Rideal, “‘ Brit. Assoc. Reports,” 1901. 78 coOM MUNICIPAL AND tank with grit chamber of sufficient capacity to steady the flow of sewage so as to permit of the heavier suspended solids sinking and the lighter matters rising. The object of the “separator” being to thus remove the coarser suspended solids in the sewage in order to render the liquid portion capable of further treatment upon bacteria beds or by other means. With the object of assisting in the settlement of the solids, the flow from the tank is divided over the edges of a large number of small channels at the surface all set SANITARY ENGINEERING. level with each other, thus forming a long length of weir, and the velocity of approach of the sewage sought to be secured is such as to ensure the precipitation of the finely divided solids. Like ordinary settling tanks, these “* separators ” should be provided in duplicate for continuous work so that a section may be cleared daily. A ‘separator ” 33 ft. x 18 ft. : is considered capable of treating 30,000 gallons per hour. A separator plant is in use at Dorchester where the tank is divided into four compartments, the sludge from one of which is emptied daily by first removing the whole of the supernatant water. The popu- lation of Dorchester is about 10,000 and the dry weather flow, which is diluted by leakage into the sewers, 45 gallons per head. The grit chambers in connection with the separators are reported to remove some 4 or 5 tons of stiff sludge per day and the separator another = of a ton. After leaving the “ separator ” the sewage passes into what was formerly a septic tank, now used as a sedi- mentation tank, in this way a further 2 to 3 tons of sludge is removed daily, due appayr- ently to the much larger capacity of the septic tank. Since the Dorchester plant was con- structed improvements have been introduced with the object of overcoming the difficulties in working experienced in that installation. (See also “ Kussei-SEPARATOR.’’) Compensation Water.—When the water- shed of the upper reaches of a stream is appropriated by a public water authority, a definite statutory obligation is usually imposed 79 COM upon such authority to deliver into the water- course flowing from the watershed proposed to be utilised for purposes of a public supply, a stipulated quantity of water daily for the use of millowners, agriculturists, and others interested in the water-rights of the stream. The water so supplied is known as “com- pensation water.” (See “‘ Warmer Suppty.”) Compressed Air.—Compressed air is ex- tensively used for transmitting power to distances, raising water from boreholes, lifting sewage by displacement, &c., &e. According to the well-known law of gases, the pressure of a quantity of dry air is inversely pro- portional to its volume, provided its tempera- ture remains the same; thus if a cylinder full of “free” air, i.e., air at atmospheric pressure (14°7 lbs. per square inch), were compressed by a piston, without increase of temperature (isothermally), to half its former volume, the resulting pressure would be 29°4 Ibs. per square inch. When air is compressed, however, its temperature is raised, and, unless the heat due to the work of compression could be abstracted during the process, such compression would not be performed ‘‘isothermally’”’ and the above conditions would fail to be realised. If the temperature acquired by compression is retained, the rise of pressure will be more rapid than the inverse ratio of the volume, and will assume the proportion known as “adiabatic” (no heat passing). As this heat will be dissipated after the air leaves the compressing cylinder, a proportionate shrinkage in volume and loss of pressure will take place, with the result that a corresponding amount of work will have been wasted. From this it is evident that the more closely compression follows isothermic conditions, the more efficient will be the process. To remove the heat, compressor cylinders and, in some cases, the pistons, are water jacketted ; but as air is a slow conductor of heat this is only a partial remedy. A further attempt towards economy consisted in spraying water into the cylinder, but the latter and similar CON plans were open to practical objections. The best solution of the difficulty was to divide the compression into two or more stages and to cool the air between each stage in a kind of surface condenser. As the difficulties of cooling during compression increase with the pressure, it is usually advisable to employ ‘stage’? compression for pressures over about 70 lbs. per square inch. The air, after being compressed, may be stored in receivers if the work is of a nature to require it, and may be conducted considerable distances with slight loss. In employing compressed air as a motive power behind a piston (as steam in an engine) the air is, when practic- able, allowed to expand until at the end of the piston stroke it is nearly down to atmospheric pressure. As air is heated by compression it will, conversely, be cooled by expansion; this leads to a further loss in the motor, and may also cause trouble at the exhaust ports by freezing the moisture contained in the air. The air is, therefore, re-heated before it enters the motor, usually by passing it through a jacket or coil heated by some inexpensive fuel. The gain in efficiency far outweighs the cost of re-heating. (See ‘‘ Arr CompREssor.’”) E. L. B. Concrete.—Formerly lime concrete was largely used for foundation work on land, but it is now unknown, if we except the occasional use of lias lime for the purpose. This is due to the abundance and low price of Portland cement which sets well under all conditions and produces a far better result. Concrete is generally described as consisting of a matrix and aggregate, the matrix being Portland cement and sand in the form of mortar, and the aggregate the large material forming the bulk of the mass, such as stone, gravel, brick, &e. The proportion of cement used is the main element of cost and it is therefore kept down to the lowest limit consistent with the strength required in the mass. Where the mass is subject mainly or wholly to compression a weak mixture only is necessary, say 1 part of ENCYCLOPEDIA OF CON cement to 8 of the aggregate; this would apply to concrete in heavy retaining walls and under the base of ordinary walls. For basement floors where it is subject to irregular loading and unequal expansion of the soil below, 1 to 6 is more suitable, but for modern reinforced concrete work 1 to 4 is found necessary. The aggregate may be varied according to what is available, broken stone, brick, furnace slag, flints, flint gravel, shore ballast, pumice-stone, or coke breeze. The limitations, however, should be made that coke breeze should only be used for dry situations such as upper floors, and that only brick, furnace slag, pumice-stone, or coke - breeze should be used for fireproof or fire-resisting floors. Red ballast from burnt clay is of no value for concrete. The material used should be graded, that is, of various sizes from 4 in. up to 1 in. as a maximum for fireproof floors and reinforced work generally, and up to 2 in. asa maximum for other work. The character of the aggregate determines the proportion of sand, which should be sufficient to fill the interstices, and the cement should then be sufficient to coat every particle of sand and aggregate and fill up the smaller interstices. Generally speaking, this will give mixtures of 1: 2: 4, that is, 1 cement, 2 sand, 4 ageregate, for floors and reinforced work, and 1: 24 or 3: 6, to 1: 3: 8, for other purposes. Mrxine.—For hand-mixing a wooden plat- form should be laid down to avoid any earthy mixture, say, a dozen scaffold boards laid side by side ona level piece of ground. An open frame or box with no top or bottom, 3 ft. square and 18 in. deep (inside dimensions), should be used to measure the large aggregate; this will contain 4 cu. yd., equal to 134 cu. ft., when filled level. ‘Then a similar frame, 2 ft. by 2 ft. by 14 ft. deep, if placed on top of the other and filled with sand would give the right proportion for ordinary foundations. Then 24 cu. ft. of cement will be required, or 12 bushels, and this is usually the total amount contained in a two-bushel sack of cement, so that the sack 80 CON of cement is emptied on top of the sand without needing any box to measure it. The boxes are then removed, and two men standing on opposite sides shovel the material over so as to mix it. A second pair of men continue the process, until the colour is uniform ; then they turn it back again while it is being watered through a rose so as to moisten it completely throughout the mass without washing any cement away. It is then filled into barrows and wheeled away at once to the trench; if the trench is shallow it may simply be tipped in, but if deep the concrete should slide down a trough. Not more than 1 ft. thickness should be laid at one time, and it should be lightly rammed to consolidate it. It was formerly the custom to specify that it should be thrown from a height of not less than 10 ft., but it was found that this caused all the large stuff to go to the bottom, and where any of that previously laid had begun to set it caused disintegration. Each batch of concrete should be used within one hour of mixing and should not be disturbed afterwards. In important works the voids in the aggregate should be carefully measured in order to ensure that the mixture shall be in the best proportions to secure final solidity. This is done by taking a zinc-lined box of given capacity with an outlet tap in the bottom, filling it up with an average sample of the ageregate, then filling with water and making up the water to the level of the top as it soaks into the material, then running off and measuring the unabsorbed water, which will represent the voidsin the mass. For machine- mixing there are two classes of apparatus, the continuous mixers and the batch mixers; the latter are the better type. Machine-mixing is only profitable on large jobs and then the cost is much reduced. Some authorities recom- mend that the cement and sand should be made into mortar before mixing with the aggregate, but the preliminary dry mixing of all the materials is more usual. Lavine Promenapes. — After paring the surface to a level and filling and ramming any soft places with ashes or dry brick M.S.E. MUNICIPAL AND SANITARY ENGINEERING. 81 CON rubbish, a layer of 8 in. of broken. brick should be put down and rolled to a level surface, well watered, and then the concrete laid in portions 10 ft. or 12 ft. square, each portion divided from the adjoining one by a wood strip, or, better still, a strip of sheet- iron, smeared with soft soap, which can be more easily withdrawn. These, which are known as expansion boards, are removed as soon as the concrete has set, and the joint is then grouted up if too wide to leave. This method is generally effective in preventing the unsightly cracks which so disfigure some pavements. The chief point is to have the cement thoroughly air-slaked before use and to see that it is neither over limed nor over clayed. Neat cement floating should be applied to the surface while the concrete is still moist, to secure proper adhesion. Concrete IN Heavy Worx.—In concrete dams and heavy walls, engineers require the cement to be as slow setting as it can be made without detracting from its strength, so that initial stresses may, as far as possible, be avoided by the mass being able to adjust itself before it becomes too rigid. H. A. Condensers.—(See “ Sream Encines” and “ INDICATORS.”’) Condensing. — Condensers are of two principal classes, viz., jet condensers and surface condensers. The jet condenser con- sists of an iron chamber of almost any con- venient form in which the exhaust steam from the engine cylinders and the cold water spray which is injected to meet and condense the incoming steam may be freely mixed. The bottom of the chamber, or “ hot-well,” in which the condensed water accumulates, is in communication with an air pump (which may be worked from the engine piston rod), the object of which is to draw off the water and any air or vapour contained in the chamber. From the hot-well the water is returned by means of a suitable feed-pump to the boiler, thus securing a considerable thermal advantage over the use of cold feed. The steam inlet pipe into the condenser consists a CON of a plain pipe entering at the top of the condenser, and the cold spray is injected through a perforated pipe or rose carried well into the centre of the condenser so that the water may be well distributed and the steam on entry immediately condensed. The jet condenser is made of about one-third the capacity of the cylinders exhausting into it. In the surface condenser the cooling water and the steam do not come into contact, but are separated from it by the large surface of a number of small metal tubes contained in an outer casing of cast iron. The cooling water circulates through the tubes, the exhaust steam is condensed around them, and the resulting hot water is removed by the air- pump to the hot-well, from which a feed- pump delivers it back to the boiler. Where surface condensers are used in connection with waterworks pumping plant, it is unneces- sary to have a separate circulating pump to force the cooling water through the condenser, as the water pumped by the main engines may be made to circulate through the condenser. Owing to the quantity thus passing through, the water is not heated to any appreciable extent. The advantages of condensing are two-fold. In the first instance the engine has the advantage of exhausting into a partial vacuum of say 27 or 28 in. instead of against the atmospheric pressure, and the fuel consump- tion is also economised by the return of hot feed to the boiler instead of cold. For surface condensers allow a tube surface of $ sq. ft. to 75 sq. ft. per pound of steam condensed per hour for circulating water not exceeding 65° F. at inlet, or, another rule is a tube surface of 1 sq. ft. to 18 sq. ft. per 1.H.P. with tubes $ in. or # in. diameter and go in. thick. (See also articles “ InpicatoR”’ and “Steam Enaine.’’) Conder’s Sulphate of Iron Process of Sewage Purification.— This system was advocated by the late F. R. Conder, M.I.C.E., who proposed that a solution of iron should bs added to the sewage of each house by the 82 ENCYCLOPEDIA OF CON use of an instrument called a “ ferrometer.” A small stream of water flows through the ferrometer, dissolves the sulphate of iron, and carries it into the sewers. A slice of lemon is placed weekly in the instrument to add a vegetable acid. It was also proposed to place trays of sulphate of iron in the street man- holes, the chemical being dissolved by a small stream of water. The system has been tried upon a small scale at Chichester Barracks and in Bermuda with satisfactory results, but is not suitable for dealing with the sewage of a town. The cost of installation and royalty is put at about £36 per 100 people, and of chemicals at 6d. per head perannum. The cost of labour, attendance, and the removal of the resulting deposits from sewers would appear to be a bar to the extended use of such a system. Condy’s Fluid.— Condy’s Green Fluid” is a strongly alkaline solution of sodium manganate, NaeMnO., with much sodium chloride and some permanganate. ‘The “Red Fluid” is a purer sodium permangan- ate. Crystallised potassium permanganate, KeMn,0g, which is pure and fairly cheap, is preferable to either, but as a disinfectant it is still very costly, and, moreover, unsafe, on account of its almost immediate destruc- tion by organic matter. The writer had unfavourable results with street watering.' (See “ DISINFECTANTS.) Connections—House Drains to Sewers. —That portion of the drainage of a building which lies between the disconnecting trap of the drain at its outlet and the public sewer. This drain is frequently laid by the local authority, as it involves the tapping and connecting up to the sewer and the taking up of part of the highway. The cost of the work, however, falls upon the owner of the house. Conservancy System.—The conservancy system of excrement disposal is that in which the nightsoil is retained in pans or pits, instead 1 «Sanitary Record,” July 27th, 1900. CON of being carried away in pipes, as in the “Water-carriage System.” In some cases the dejecta are received in large built pits, into which the household ashes are sometimes thrown, and which are emptied periodically. Another and better plan is to use pails or pans, which are removed and cleansed at short intervals. In earth-closets the dejecta, as deposited, are covered with a little dry earth. The conservancy system is largely employed in country districts, the nightsoil being used as a manure. It also survives in a number of large towns in the Midlands and North of England, and in the Colonies, but it is unfavourably regarded by the health authorities, and its supersession by the water- carriage system is merely a question of time. The main point in its favour is that it con- serves and returns to the soil the manurial constituents of the excreta. On the other hand, the retention of fecal matter near houses is offensive, and even dangerous, more especially in view of the action of flies in conveying infective material from the closets to the larder. A. J. M. Contact Beds, Bacterial.—(Sce “ Suwace Disposat.’’) Conveniences, Underground. — Acts of Parliament—Points to be Noted—Site—Exca- vation — Walls — Drainage — Roof — Staircase — Ventilation — Sanitary Fittings — Plumbing, &c. — Attendant’s Cabin — Framing — Locks — Lighting—Oost. Acts or Paruiament.—Power to borrow money for the purpose of providing under- ground conveniences and lavatories within the metropolis is contained in sect. 105 (2) (a) of the Public Health (London) Act, 1891, and, in the provinces, the Public Health Act, 1875, sect. 89, gives an urban authority power, if they think fit, to provide and maintain con- veniences, while the Public Health Acts Amendment Act, 1890, sect. 20, gives the urban authority power, if they think fit, to make regulations for the management thereof, and to make bye-laws as to the decent conduct MUNICIPAL AND SANITARY ENGINEERING. 83 CON of persons using same. Also the urban authority may let the convenience for a term not exceeding three years, or may charge such fees for the use of the water closets as they may think proper. Points to BE Notep.—When choosing a site for an underground convenience (and only such are referred to in this article) the following points should be considered :— 1. Central position with regard to the necessity for such a structure. 2. Position with regard to lines of traffic. 3. Available depth with regard to sewers and risk of flooding when sewers are surcharged. 4. Stability of founda- tion. 5. Absence of gas, water, and other mains or facility of diverting them if encountered. Sirz.—Persons requiring the services of such a structure usually seek them in large open spaces, and since, owing to their con- struction, they form a useful landing-place or refuge among the traffic, it isin keeping that the position should be chosen with great care, and that they should be so placed as to be en route from the corner of one street to the corner of another, and yet allow at least two lines of traffic to pass along each of their sides, and their proximity to tramway lines should not be less than 9 ft. 6 in. to the nearest rail. Excavation.—In forming the excavation great care should be taken in view of encountering the mains belonging to the various gas, water, and other companies, as damage to same might unduly prolong the work, and cause an unnecessary interference with the street traffic. The question of the existence of such mains should be fully gone into before the scheme has finally been decided on, as it sometimes happens that a diversion may either be impossible or very costly, and the subsequent alteration of the convenience render it the less commodious and inconvenient in administration. When arranging details prior to commencing the work, it will be found convenient, in a work on so restricted a space, to have all material delivered at one end and the débris carted away at the other. Also rather than extend G2 CON the area of the enclosure to provide for a fore- man’s office and so impede the traffic, it may be found possible to erect it on a low scaffold overhead. ‘The excavation should be the neat width of the outside walls, and no footings should of course project beyond the outside face of the outer walls. ‘The depth of concrete under the walls should be 12 in. to 18 in., according to the local conditions of the sub- soil, and project beyond the internal face of the wall for at least 12 in. Wauus.—The walls are generally constructed of an outer thickness of 12 in. of Portland cement concrete, and faced on the inside with 14 in. or 18 in. of brickwork, between which and the concrete backing is a vertical damp- proof course of asphalte, with also one laid GK lon SSG Viectin SOWIE \\ method of Veniilation Fig. 1. horizontally. Occasionally the whole of the wall is composed of concrete, which should be formed in two thicknesses, with the vertical damp-proof course inserted as previously mentioned. The inside face of the walls where constructed of brickwork is often of glazed bricks, but as these have to be fre- quently cut for fixing pipes, plugs and hold- fasts, the subsequent making good often presents an untidy finish. It is preferable to cover the rough brickwork or concrete with 2 in. tiles of brick pattern, thus obtaining a finer joint than with bricks, and a better finish may be obtained to soffits and scribing than by the use of glazed bricks. Some con- veniences have been faced with opal glass tiles as supplied under various trade names and of different makes. The use has been attended with more or less success. It is thought by some engineers that the vibration of the street traffic has a tendency to crack the tiles, ENCYCLOPADIA OF CON although the fineness of the joints, choice of colour, and ease with which they can be cut to fit around awkward corners is an argument in their favour. The floor should be con- structed of concrete, and covered with tiles. Dratnace.—The drainage of a convenience is a matter of supreme importance. No such structure should be built which cannot allow of an adequate fall in the drain from the interceptor to the sewer, and also be at such a relative level above the sewer that no back flow may occur from flooding, due to rainfall, rise of tide, &c. There are two possibilities likely to occur with every convenience, namely, the risk of flooding, due to (1) the flow in the sewer, and (2) stoppage in the inter- ceptor, and to deal with this until the outlet of the drain may be free there must be con- structed a storage chamber under the floor of the convenience of a size calculated to be sufficient to retain the sewage until the diff- culty has been removed. The storage capacity of the chambers in the convenience illustrating this article is represented by two connected tanks, each 3 ft. deep, and holding together 1,800 gallons, and serving to retain the water from 9 w.c.’s, 11 urinals, 3 urinettes, and 4 lavatory basins. Of course when the outward flow from the drain is restricted, the attendants minimise the use of the wash-basins and the automatic flush to the urinals as much as possible. The chambers, which are practi- cally large manholes, may be faced with glazed bricks, and are formed on the invert, with white glazed half round pipes, and cement benchings. One chamber should be constructed in each of the male and female compartments, and each w.c. connected thereto direct. The urinals and lavatories may be grouped in sets, and each set also connected direct. A sparge pipe should be fixed around each chamber at the top, and connected with the water supply, and be under the control of the attendant—this is to wash down the sides of the chamber after the retained waste water flows off. As this pipe will be at the furthermost extremity of prob- ably a shallow manhole, it will be difficult of 84 CON access; therefore it should be of copper, as this is not liable to rust either inside or out. Air-tight manhole covers should be provided to each chamber, and it is usual to make pro- vision for tiles to be let.in the top to match the general tiling of the floor. The waste from the w.c.’s, lavatories, &c., should dis- charge into a manhole after leaving the storage chamber and before passing through the interceptor. A penstock should be placed on this pipe so as to prevent the waste from entering the manhole, when required, thus impounding it in the storage chamber. The reason for this being that in case of the flluminaled Stgr jit “1 MUNICIPAL AND SANITARY ENGINEERING. Lamp Post \ Verditator CON his chambers have become so filled that they overflow on to the floor of the convenience. To cope with this the author has devised a ball and lever arrangement fixed in one of the chambers, and so made that when the ball floats owing to rise of water it will raise a rod connected with an electric bell which will act as a warning to the attendant. Roor.—The roof is the one portion of the structure which will probably give a consider- able amount of trouble and annoyance to those concerned, either from leakage due to outside moisture or from sweating due to condensation of internal moisture. The convenience should (ah Vi LOO KO or Kr Ko MEMES 5 % ETE te Fe ice hig Paty te SIND SUNT TW RT ‘ Fs SSG | of “4 T Z * : Mer Wormer - ea “8 talory + RN i tre we. = we 3 a al “ ; Ww pe a ae TI SEG sigs i W225 mae IR) rage EN 11) ty ‘Ds E £ < £ 4 Scale of Feet. Fia. 2. interceptor being stopped, the waste from the w.c.’s, lavatories, &c., may be retained, and the manhole pumped dry so as to allow the obstruction to be removed from the inter- ceptor. A penstock should also be fixed over the interceptor, so that it may be closed down at a time of flood in the sewer, to prevent the sewage finding its way either into the manhole or the convenience. This is extremely useful at night, if the penstock is closed down before the attendant leaves. The manhole containing these two penstocks should be accessible only from the surface of the ground outside. There are occasions when the sewer may be in flood, or the interceptor be stopped, and the attendant be unaware of the fact until he discovers that be so designed that the roof may be about 10 ft. 6 in. above the floor. The construction of the roof should be of wrought iron or steel joists carrying prismatic lights, and care should be taken that a sufficient gradient is’ given to the frames containing these lights to throw the water off as quickly as possible. Large areas of prismatic lights are subject to considerable expansion and contraction during the varying temperatures, and as this is the main cause of leakages, arrangement should be made whereby the lights should be divided into sections and so reduce the ultimate con- traction and expansion. The joints between the frames should be made with a pliable cement. Should any part of the convenience 85 - CON be under the carriageway, the design of the roof will require more attention than other- wise, as provision must be made for heavy motor traffic. ‘I'he construction in this case might consist of steel girders supporting brick arches, with the crown and haunches filled in with concrete, or reinforced concrete might be used instead and the top of the concrete then be paved with wood blocks or asphalte to form the surface of the road. That part of the roof which contains the prismatic lights and is not available for vehicular traffic should be formed a step higher than the road and surrounded with a wide granite kerb, heavy cast-iron guard- posts, and granite spur stones. Various devices have been tried to deal with the condensation of the moist internal air in relation to its corrosive action on the iron-work. The most successful method is to cover the paint and varnish with fine cork dust while the varnish is still wet. Starrcase.—The rules covering the en- trances and exits are such as would suggest themselves in any ordinary building. If two staircases cannot be provided, one for the entrance and the other for the exit, the width of the single stair should be sufficient to allow of two persons passing one another. The top step should be so placed as not to come within a distance of about 3 ft. from the carriage- way, soas to prevent a person stepping directly in front of the traffic. The staircase should be formed with easy steps and as few winders as possible, but owing to their narrowness and the great amount of traffic, the treads will be subject to considerable wear, unless some of the various patent treads are used, such as are to be found on the market, but whichever form is adopted they should be so fixed as to be capable of renewal expeditiously and without much damage to the surrounding work. A considerable amount of water will flow down the steps both during rain and when washing down. A channel with a grating over it should therefore be fixed at the bottom, having a pipe connected to the manhole so as to carry away any water that may flow down. The staircases are usually ENCYCLOPADIA OF 86 CON protected with ornamental pailings about 5 ft. high, having a padlocked gate at the entrance. To screen the interior of the convenience it is customary to cover the pailings with wired rough plate glass. Owing to conveniences being frequently burgled at night-time, either for the sake of the brass fittings or the money in the automatic locks, it has been found necessary to construct a collapsible gate at the foot of the staircase and also. a horizontal grating, level with the top rail of the palings, having a portion so made as to slide backward and forwards, and when drawn towards the gate and locked it forms an effectual cage, entirely covering in the staircase and pre- venting people climbing over for unlawful purposes. VENTILATION.—Various methods are adopted to ventilate the inside of the convenience. A ventilating column may be fixed on the wall dividing the male from the female sections, having a revolving fan, driven by electricity or water. In the latter case the waste water may be used for flushing the urinals. The column is generally utilised as a lamp-post for lighting purposes, and may be of an ornamental character. Another method of ventilating may be by a continuous iron grating about 6 in. or 9 in. wide fixed level with the top of the prismatic lights, thus forming an opening all round the structure. Rain and dirt which will go through are caught in a heavy pattern cast-iron gutter, and the water is delivered into the drains through a square section rainwater pipe, chased into the wall. Splashing of water and a direct line of vision into the convenience from the outside is prevented by a 6in. to 9in. width of zinc or sheet iron placed at a suitable angle so as to drip into the gutter. Fre- quently both methods of ventilation are used in conjunction with one another. Sanitary Firrines.—The sanitary fittings for a convenience are made in many designs and of various shapes, and it must be left to the fancy of the engineer to choose for himself. It is preferable to adopt a design that can be easily cleaned in all its parts and renewed if CON broken. The urinals may be formed with an open channel attached, the latter being covered with a galvanised or brass grating. The division between each stall may be St. Anne’s or other marble or even polished and oiled slate, or it may be of the same material and colour as the urinal itself, and the urinals should be 24 in. from centre to centre. he w.c. pans should be quite self-cleansing, with one flush, the “wash down” type being the best. The w.c. compartments generally MUNICIPAL AND SANITARY ENGINEERING. CON the opposite direction to aw.c. Some of the patterns also have a perforated grating on the trapped outlet instead of the free-way of a w.c. trap. As a rule the purpose and method of using a urinette is not understood by those who enter a women’s convenience, and they are frequently put to the purpose of a w.c., hence their existence becomes either useless or a nuisance. In many of the conveniences where urinettes have been fixed, the usual wooden door has been dispensed with, and \ = rang gthte Weed satire whine emis ese trareen eR a ET ar a ES Scale of Feel. Plait —— 2 See are see Verlual damp proof Course = RST ANGE rmsne E.— Fie. 3. s measure about 6 ft. by 8 ft., and are divided by marble divisions 1} in. or 1} in. thick and 7 ft. to 7 ft. 6in. high. An addition to the women’s section has been made recently in the form of a ‘‘ Urinette.” This has been an attempt to do away with the objection that a man may use a urinal free, while a woman has to pay for a similar purpose. These urinettes are in form similar to a w.c. pedestal ; some patterns are narrower than the w.c. pan, the intention being that the users may stand over it with their face towards the wall or in waterproof sheeting hung as a curtain in place thereof. Puumsine, &c.—The plumbing and fittings should be of the best and simplest of their kind. The water supply to each section should be separately under control to enable any par- ticular part to be shut off for repairs. A tap should be provided inside each of the con- veniences with nozzle for a hose pipe, likewise a hydrant should be fixed outside and suited to the same hose pipe for washing down the roof and steps. Hot water should be provided 87 CON in each of the lavatories by a geyser. Also the attendant should have a stove for warming and cooking. ATrEeNDANT’s Capin.—The attendant’s cabin should be made as large and airy as possible, and so placed as to command a view of the whole of the convenience and the staircases, and be provided with a wooden floor. Much more space ought to be given to the attendant than is usually done. We frequently find that he is provided with so small a compartment that he experiences the greatest discomfort when in it. Framine.—The general framing, doors, &e., of the inside should, for preference, be of teak, as owing to its nature it is non-absorbent and proof against damp. The w.c. doors may be made so as to leave a few inches of space at the bottom above the ground, or the bottom panel may be in the form of louvres, so as to allow a current of air to circulate within. Items not to be forgotten are the provision in the w.c.’s of toilet-paper holders and hooks for coats. In the lavatories—mirrors, towel rails, coat-hooks, brushes and combs. In the atten- dant’s cabin—cupboards for personal articles, storage for towels, soap, &c., and safe drawers for money, &c. A speaking tube should con- nect the attendant in the male and female sections. Locxs.—The locks to the w.c. doors may be either of automatic penny-in-the-slot type, or else locks having a registering number, in which case the user pays the attendant and the lock indicates the number of times the door has been opened. Bent coins have caused considerable inconvenience and damage to the former type of lock. Licutine.—lf the illumination of the con- venience is by gas, care should be taken not to place the brackets too close to the prismatic lights, as the latter have been known to chip owing to the heat. The placing of the lights over the w.c.’s may be economically done by making one bracket serve two closets. Should electricity be used, it may be found convenient to so arrange the switches which are controlled from the cabin that certain of the lights may 88 ENCYCLOPADIA OF CRE be switched off when not required. The stair- cases should be well lighted and an illuminated sign is sometimes fixed over the entrance. It is also desirable if the convenience be lit by electricity to also have at least one gas bracket available in case of the current failing. Cost.—The convenience illustrating this article cost, without diversion of mains, £2,500, or 3s. 6d. per foot cube. R. J. A. “Coombs” Pneumatic Ejector.—(See ‘* HJECTORS.’’) Cosham Precipitating Tank. — This form of preliminary preparation tank of the “Natural” Purification Company was first adopted at Nuneaton. It may be constructed either on a circular or rectangular plan, and consists of a series of seven or eight separate compartments through which the sewage flows successively on its way to the outlet. The communications between the compart- ments are formed by ‘ flocculent flues” or submerged exits, the object of which is to hold back floating matter. These, together with a number of cross walls, assist the precipitation within the tank and economise the chemicals employed. The sludge is removed from the bottom of the tank by a siphon terminating a little below the top water level within the tank. Cremator (Jones’).—This consists of a small independent high temperature furnace usedin connection with town refuse destructors for the purpose of cremating and rendering harmless the objectionable fumes known as the empyreumatic vapours which arise during the earlier stages of the process of burning town’s refuse. It was introduced in 1885 by Mr. C. Jones, M.I.C.E., of Ealing, but since that date considerable advances have been made in the process of disposal of refuse by burning mainly by the adoption of high temperature destructors of greatly improved design, thus rendering the employment of an independent cremator unnecessary. (See “ DusrRuctoss.’’) CRE Crematoria and Columbaria. — General Survey — Catafalque — Incinerating Chamber— Chimney Shaft—Furnaces—Columbaria—Site of a Crematorium—Cost of Crematoria. In the general arrangement of the plan of these buildings it is of the utmost importance that due regard be given to the relative positions of the chapel and the incinerating chamber, so that the coffin can be transported from the chapel to the crematory as quickly as possible. The chapel or hall should be planned with a minimum floor area of 1,200 super. feet. It will be found that this is the least permissible, for when the catafalque and necessary seating is provided there will remain little waste space. Provision should be made in the chapel for the reception of urns; they may be stored in niches in the walls, in the floor, or in the sides of the catafalque. In some cases a columbarium is provided under the chapel in the basement. This is found in the. Liverpool Crematorium. A system of electric inter-communication between the chapel and the incinerating chamber is necessary; a bell-push placed either on the clergy’s desk, or in the floor near it. This is provided so that he may inform the engineer in charge when the moment arrives for the body being removed from the chapel to the cremating chamber. THe CataraLque.—The catafalque or table upon which the coffin is placed during the service should be situated near the cremating chamber. In most of the English crematoria it is situated so as to project longitudinally into the chapel. This position has many dis- advantages. It is far preferable to place the cremating chamber at the side of the chapel, so that the coffin passes out at the side, and the opening between the two apartments is not facing those who are assembled to witness the last rites. The catafalque in general use is, in size, about 12 ft. long, 3 ft. 8in. wide, and 4 ft. high. The top is fitted with an apparatus worked by means of an endless chain, which conveys the coffin from the catafalque to the carriage in the cremating chamber. The coffin is transported MUNICIPAL AND SANITARY ENGINEERING. CRE to the furnace upon a carriage fitted with the same apparatus. The opening in the wall through which the coffin passes should be the full width of the catafalque, and about 2 ft. 6 in. to 3 ft. high. It should be fitted with a pair of wrought-iron doors, grills, or curtains. Incineratine CHamber.—The incinerating chamber, which adjoins the chapel, is governed in size by the number and type of furnaces to be installed. When provision is made for one furnace only, then the chamber should have a minimum width of 20 ft. and 25 ft. inlength. This will be found sufficiently large for any furnace. When two or more furnaces are provided then the superficial area will be increased in pro- portion. The cremating chamber should be well lighted and ventilated, and constructed of such materials as will allow of it being kept perfectly clean. Cuimygry SHart.—The chimney shaft should be situated in as close proximity to the cremating furnaces as possible; the internal measurements at the base being at least 2 ft. square. The shaft should be erected to a minimum height of 60 ft. A pilot -fire is necessary at the base of the chimney shaft for any fumes not consumed in the furnace, to pass over. Many forms of pilot fires have been constructed, but, for general purposes, if a small grid is formed, having open bars for holding a small fire, it will meet the purpose for which it is provided. A small iron door and frame will, of course, be provided for access to the pilot fire. Funnaces.—There are two types of furnace employed for burning human bodies—the reverberatory and the regenerative. In the former a tongue of flame coming directly from the flue is deflected on to the body. In the latter, gas is produced from coke, and then burnt in the chamber where the body is placed. Both methods are equally effective, but the latter furnace is much more costly to con- struct. It lends itself, however, to a more satisfactory means of collecting the ashes, and is in keeping with popular sentiment. There are four patent cremating furnaces on the English market, three of which are in use. 89 CRE They are the “Simon” coke furnace, the “Tousil Fradet,” a gas furnace, and the ‘Carbon Oxide’’; another patent furnace is that of Messrs. Goddard, Masey, & Warner. ENCYCLOPEDIA OF CRE consists of three chambers, the two lower of which are surrounded by air passages. The lower chamber contains a coke fire, and the upper or cremating one is that in which the body is reduced to ashes. The fire is lit some time before the eoN t r vl % \ : eo “HAART f a BN ‘al 4 ‘ ~ . AY ‘| apparatus is to be used, and is supplied with air in the usual way. Before the introduction of the coffin containing the body the air supply to the coke fire is greatly restricted, and after the body has been placed in the furnace a separate supply of heated air is introduced. Owing to the re- stricted air supply under the fire the product of combustion is largely , carbonic oxide, which immediately on the addition of hot air burns into carbonic acid. The incine- rating chamber is thus filled with gas of an intensely oxidising character, in a state of incan- descence. The process occupies about one hour, at the end of which time there remains only the residue of the bones, consisting of grey pumice-like fragments. As the body is reduced to ashes, the remains fall through the grid into the chamber below. At the com- pletion of the operation they are swept by an asbestos brush into Scale of Keer 4 ARTA i 7 * 7 7 an urn. ‘Two inspection holes are provided at the head of the furnace; one overlooking the chamber containing the body, the other the chamber which receives the ashes. These are provided so Metres 2 ° 5 10 . 6 Aen ie fi ‘ Fic. 1—Design by M. Formége, Chief Architect Paris Municipality. Messrs. Henry Simon & Co.’s furnace, which is in use in the principal crematoria of this country, is made in two distinct types. The older one is of the regenerative type, and that the engineer in charge may watch the progress and so regulate the working of the furnace to suit the progress of reduction. This furnace is erected in two storeys. When this furnace is adopted it is advisable to form an opening in the floor clear of the same, so that any expansion or con- traction which takes place will in no way wt 90 CRE affect the main structure. In the later type of the ‘‘Simon” furnace it is not necessary to have a basement, the whole being fixed on one level. This type is somewhat longer than the former owing to the firing portion being at the end instead of below. With this furnace the fuel used is coke only, and the heat is brought more directly into con- tact with the body. There is consequently a saving in the pre- liminary heating of the brickwork and flues previous to the operation. The construction is simple, and the furnace is built to withstand the contraction and expansion which takes place in all intermittently- fired furnaces. This furnace can also be arranged, with slight modi- fications, for heating with coal gas. The Carbon Oxide Company’s furnace, which is heated by coke, is fixed in the Golder’s Green and Woking Crematoria. Little information can be obtained of this furnace, but judging from inspection it appears to work satis- factorily. The construction is similar to those furnaces pre- viously described. Messrs. Tousil, Fradet & Company’s furnace is in use at the Leeds and Bradford Cre- matoria. This type of furnace has been in operation for some years in the crematoria at Paris, Rouen, Rheims, and Lyons. The heating is performed by gas, introduced through Bunsen burners at the rear of the chamber containing the corpse. The products of com- bustion pass out at the side near the front or entrance of the chamber. The hot gases are then conveyed along flues and pipes underneath the furnace in such a way as to highly heat the air supply to the burners, as well as a separate air supply that is arranged to enter the chamber at each side of the 91 MUNICIPAL AND SANITARY ENGINEERING. PA//AGE PA/AGE RETORT B PAs/AGE COLYMBARIYM COLVMBARIVM , AGH oT CRE body at the later stages of the process, when desiccation has been completed and inflammable gases are being given off from the body. The air supply to the Bunsen Recenvine VAYLT 1B MICHEL 18 VEsTIBVLE SACRISTY oo Setee he PLATFORM __ VE/TRY COLVMBARIWM PASSAGE VE/TIBYLE --__-- Fic. 2.—Crematoria, Portland, U.S.A. burners is controllable, as is that sup- plied separately to the sides of the in- cinerating chamber. Messrs. Tousil, Fradet & Company also use a special mechanical apparatus for introducing the coffin into the CRE incinerating chamber, and for removing the ashes. Cotumparia.—In planning a columbarium provision should be made for the requirements of the poor as well as for those who are ina position to pay large fees; little distinction, however, should be made between the two. Where the former niches are enclosed with plain stone or marble slabs, the latter will be finished with wrought iron, copper, silver, or gold grills. The niches or receptacles should be formed to hold from one to five urns in a WING < S&, st 41, & R oo, x OPLERIES 1, o STAIRS ROTVNDA % ny VESTIBULE ENTRY Fig. 3.—Columbarium, Oddfellows’ Cemetery, San Francisco. single compartment. In constructing the niches, the materials employed should be such as will occupy the least amount of space. The urns in use are known as the “ Box” or ‘Vase’ shape; the first-mentioned measures 16 in. by 8 in., and is 8in. high. The box urn being generally used, provision is made, with few exceptions, for this. The fronts of the niches are enclosed with marble or glass slabs, or grills made of iron, copper, or other material. Many beautiful examples of the latter are to be seen in the columbarium at Golder’s Green, London. These grills are held in position by detachable copper or iron ENCYCLOPAIDIA OF CcUL fittings. The interior of the niches may be plastered, distempered, or otherwise artisti- cally decorated. When the grill of the niche is fitted with a lock, then the superintendent of the columbarium is supplied with a dupli- cate key, so that he may periodically clean the compartment, and if required, cover the urn with flowers. Sire ora CremaTor1um.—The Cremation Act of Parliament (2 Ed. VII., ¢. 8.), states that ° no crematorium shall be constructed nearer to any dwelling than 200 yds., except with the consent, in writing, of the owner, lessee, and occupier of such house, nor within 50 yds. of any public highway, nor in the consecrated part of any burial-ground of any burial authority. No crematorium shall be erected until the plans of the site thereof have been approved by the Local Government Board, and no human remains shall be burned therein until such time as the burial authority has certified to the Home Secretary that the crematorium is completed and properly equipped for the purpose of the disposal of human remains by burning. Cost or Crematoria.—The cost of the crematoria in England has varied con- siderably; that at Woking cost £5,022; Leicester, including a chapel for inhuma- tion services, and various other buildings, £13,830; Birmingham, £5,000; Liver- pool, £8,000; Ilford, £7,000; while the municipal crematorium at Hull cost £2,700 only. A.C. F. “Cultivation Tank ” (Scott-Moncrieff).— In lieu of an ordinary septic tank, Mr. Scott- Moncrieff has used what may be described asa tank full of flints, with the object of providing anchorages for the cultivation of colonies of anaérobic bacteria throughout the mass of the sewage. In such a tank the sewage enters at the bottom and filters upwards through the stones which are carried on a grating, and escapes at the top by means of a suitable‘ overflow, near the level of the inlet. ‘This tank effluent is then distributed over the 92 DAL uppermost of a series of nitrifying trays of boxes with perforated bottoms, and filled with coke of the size of beans. The system was first tried on a practical scale at Ashtead (1891), and has been adopted at the Caterham Barracks, and many other places at home and abroad. The separation of the anaérobic from the aérobic organisms is well provided for by this method of treatment, and importance is attached to this feature as forming the desired liquefaction of the sewage, and the satisfactory nitrification of the final effluent. For large installations, however, the question of cost would appear to be an important factor, inas- much as it is cheaper to provide a given capacity in a clear tank than in the interstices of materials such as flints filled into the tank space; also, any undigested matter is more readily removed from the ordinary open tank than from a cultivation tank. The sewage would, in most cases, doubtless require screen- ing and rough sedimentation before passing into the cultivation tank. Dale’s Muriate of Iron Process of Sewage Purification.—This process em- ploys a concentrated solution of perchloride of iron for the disinfection and deodorisation of sewage. Damp Buildings, prevention of.—The first thing is to obtain a fairly dry site, or to drain it as described further on, under the heading of sub-soil drainage. If the soil is retentive of moisture, the walls should rest on lias lime or Portland cement concrete, to retard the rising of moisture, and the whole site between the outer walls should be covered with similar material, 6 in. thick, the compo- sition of which has already been described. It is generally considered advisable before laying the concrete to put 3in. or 4in. of good brick rubbish over the surface of the ground and lightly ram itso as to leaveitin a perma- nent porous layer, but there is some doubt as to its actual utility. The inner cross walls and sleeper walls may be built on this layer of concrete. MUNICIPAL AND SANITARY ENGINEERING. DAM Wauts.—The basement or semi-basement walls may be protected from the external earth in contact with them by a layer of bitumen, or asphalte, or even by tarring, as in Fig. 1, or by making a cavity wall as Fig. 2. Where there is no basement, a horizontal damp- proof course is inserted 6 in. above the ground level as in Fig. 8. The horizontal damp-proof course may be Callender’s pure bitumen, Robinson’s roll asphalte, patent asphalted sheet lead, a double cotirse of slates in cement, or horizontally perforated glazed tiles. Where the walls are subject to spray, or a very moist atmosphere, they are built hollow, a 44 in. skin being placed outside the ordinary wall and bonded to it as in Fig. 4. At the window and door openings, bricks must be bonded across the cavity in the wall; and over the top of the door and sash frames, sheet lead must be built in and carried beyond the woodwork on each side to prevent moisture dropping on it. The cavity must in all cases be ventilated by air-bricks, or perforated tiles, as shown at the bottom, and similar openings at the top of the wall. The brickwork should be composed of thoroughly well-burnt bricks and good mortar. An ordinary building brick should not absorb more than one-sixth of its weight of water when left in for 24 hours, and a foundation brick of best quality should not absorb more than 6 °/,. Other means of preventing damp from passing through a wall are covering it with hanging tiles or slates, coating it with Szerelmey liquid or with Fluate, or painting it. At the top of a wall the moisture is prevented from travelling downwards by an impervious covering of stone coping, Portland cement coping, blue brick lumps, or brick-on- edge in cement, having underneath it a layer of slates or tile creasing. Projecting copings, cornices, window-sills, &c., must be throated on the under-side to throw off the drips of water clear of the walls. Roors.—The most usual coverings for roofs are slates and tiles. Slates are split off from a naturally formed clay rock with cleavage planes, and, when of good quality, absorb very little moisture. Stood in a pail of water 93 DAM over-night to half their depth, the water should not have risen 1 in. on the face in the morning. Slates are of various sizes, the most general being Countesses 20 in. by 10 in., laid with a lap of 8 in., and a visible margin or gauge of 8 in. if head nailed, and Fig. 1. Floor level panacea ENCYCLOPAEDIA OF DAM 10 in. or 103 in. by 6 in. by 4 in, are generally used for house roofs. They should be slightly curved in the length so as to lie closely at the ends, and be laid with a lap of not less than 24 in. and margin of 34 in. to 4 in., a3 shown in Fig. 6. The pitch of a Fic. 3. 2’ covity — floor level Galvd. tron j = wall tre — I 2tod to every yor (all plate = S’concret Pertorated Bey A Sort Stoneware DPC: Cement /s Gam, wae" ales Ground level L] Va ee ge mT ! 9 3 I ~ 8 S y : ae : fa i | | | ap 82a: ke 6p | | l ‘ee ANG ¥ eta Water _level Masonry (120 les per cub, Fre. ENCYCLOPEDIA OF DAM these points will be the curve of stability when the reservoir is empty. When the reservoir is full the method will be as follows: taking the part down to line A the pressures due to the head of water will be in the form of a triangle with a base at A of 62°5 x 20 = 1,250 lbs. The total pressure will then be xe = 12,500 lbs. acting at right angles to back of wall through the centre of gravity of the triangle. This pressure must be combined with the weight of the part considered, and where the re- sultant cuts line A will be one point in the curve. The part from A to B must next be considered, and the pressures due to the head of water will now vary from 1,250 lbs. at A to 62°5 x 40 = 2,500 lbs. at B. The total pressure acting through the centre of gravity of the quadrilateral will be VO F 2000 x 20 87,500 lbs., and this amount must be combined with the resultant from the first portion. The resultant thus formed is then combined with the weight of wall from A to B, and another point in the curve will be given where the resultant of the last — 62/6" - Fic. 3.—Principles of designing Modern Dam. to the stress, allowing for the weight of the superincumbent parts as well as for the increasing thrust of the water as a greater depth is reached. The principle of designing and calculating the main stresses of a modern masonry dam is exemplified in Fig. 3, which shows a conventional section of a dam 70 ft. high. The curve of stability when the reservoir is empty will be found by first dividing the section into any convenient number of parts as shown by the dotted lines A,B,C,and D. Find the centre of gravity of each part, and through each centre of gravity drop a vertical line to cut the assumed base line of each part. The curve drawn through step cuts.line B. In a similar manner the other divisions of the wall may be worked out and other points found, through which the curve of stability when reservoir is full may be drawn. Other information may be given upon the same diagram, such as the maximum com- pression produced in the masonry at each level where the position of the curve has been found. Fig. 4 shows a cross section through the Vyrnwy dam with the principal figures of the stresses, and a pressure diagram below it showing the distribu- tion of the load upon the foundations. This masonry dam with a flood water head against it of 129 ft. is a magnificent piece of engineering with considerable claim to architectural merit. Besides the main stresses 98 DAM referred to above two others have received considerable attention in recent years, viz., the shear stresses and the upward pressures due to penetration of water below the masonry. The most important contribution to the subject of shear in masonry dams was given by Prof. Unwin in a series of articles in Engineering Fig. 4. Wino! 026 tons rt a flood Water Level as SENS NN SYN x VQy MUNICIPAL AND SANITARY ENGINEERING. DAM dam about 34 ft. high in the Hudson Water- works, New York. This dam was built in alternate 50-ft. sections at one time, with a tongue-and-groove tar joint between the sec- tions. After the first lift of the forms had been filled, a 3-ft. layer of concrete was placed in one section on one day, then permitted to % I Ws s \ 4a 2 4 OR § 2 iN gd 3 ; N Mf GIVE LS 1 SA A MED We 4900 | COLCA TASO TOL LOA TE Lette ore CLO MAGGIE “ttre POLOOL DA pe LEELA LS OOVMAAD AP Gg EF ! CoG agipttltet te Cite ! ( SOL thy LOS EC OG Ler COL TOY 1, COPS OOS UO LES CLC 27/8 tons LVL TTS ' Eaaae Wy Gases Wy ' L614 65 LGUs 7 64 \ | 142227 | CGE OCT G oo & I! ! $65074 z 4 ‘/, s 5 bipgsgeeae Bo Lasse x GUM OU N. s @& 174224 el AAA OO ga 26574,5 | NS 2AA4 tp trt, & a 122774 t ALLOA, (no y eee yg rer | NM MN Aes i “O04, TLE =! + 127777 a2 ms LALOEAS ALY, %, Dy 44,7474 ! | | COLLET ol : LECCE es 1,00 y Ll Am D222 807; tity ny OA | AAA ALE sy 1, 0p < v CM tt G4 4 VOGT LOU AT AA tll DG GF: , TT, bY O Att le | ' OP AMAA LOLOL LLL 6 Y Y LOUL lle titi; yy 1 EOC GAAS 7 j f i 48 L,Uitrit Y cS PV/406 Fe a iS Tos i) T| | 7 60°8/ ft. — r| | : yt ee 8; Nc tflyt § Nem ola ih UPS, Fe, as I "= So GR Fic. 4.—Section of Vyrnwy Dam. for April 21, May 12, and June 80, 1905, and the upward pressures have been discussed somewhat fully by correspondents in The Engineering Record during June and July, 1908. In consideration of the enormous stake in life and property connected with the design of dams, these matters are of very serious import, but they are rather beyond the scope of the present work. Concrete Dams.—Fig. 5 shows a cross section through the spillway of a concrete 99 Fie. 5.—Section of Spillway of Dam. set a day while a 8-ft. layer was placed in an alternate section, after which another 3-ft. layer was placed in the first section, and so on. The surface of each layer was thoroughly brushed and cleaned, then wetted and covered with a thin coat of 1:2 Portland cement mortar before the next layer was placed. The concrete used in the dam was mixed quite wet in the proportion of 1 part of Hudson Port- land cement, 2°8 parts sand, and 54 parts broken stone, these proportions having been H 2 DAM found to give a slight excess of fine material. The sand was found to contain from 6 to 8 °/, of loam. Thorough tests were made to discover, if possible, the effect of the presence of the loam, and, as good results were obtained in the tests, the sand was used. In the early part of the work the broken stone was screened, but the greater part of the concrete was made with crusher-run broken stone, in which the largest pieces did not exceed 24 in. in their greatest dimension. Ferro -Concrete Dams. — The Ambursen Hydraulic Construction Co. of Boston, Mass., give a remarkable section of a reinforced Fic. 6.—Section of Ferro-Concrete Dam in Pleasure Park. concrete dam erected by them in a pleasure park, shown in Fig. 6. The principal promenade leads right through the dam, in at one end and out at the other; the interior of the dam is treated as a grotto, being decorated with rock-work, moss, ferns, &c.; the stiffen- ing division walls are perforated by arches, seats are placed in each bay, and the whole is lighted by electricity. The main point about such work is that it must be not only strong, but must be waterproof; to obtain this the mixture must be rich in cement, not leaner than 1: 2: 4, with fine aggregate and plenty of water. Lime has been added to the cement used in mixing concrete for reservoir walls with the view of preventing the percolation of ENCYCLOPEDIA OF DES moisture and rendering the wall waterproof. There is some evidence that it is efficient, but until more is known about the action of free lime in cement it would be wiser to adopt more usual means, such as using a richer mixture of cement towards the face, or pro- tecting it with one of the bituminous com- pounds, externally or a little way in from the face. H. A. Deacon’s Meter.— (See “ Water Suppty.”) Deep Well Water.—(Sce ‘“ UnpErcrounp Water,” “‘WELLs,” and ‘“ WaTeR Suppty.”’) Deodorants, or substances which re- move smells, must be carefully dis- tinguished from true disinfectants, many of which, however, are also deodorant. To get rid of a bad odour or to mask it by a stronger one does not necessarily indicate that disease-producing organisms are at the same time affected, and mere deodorants are often an evil by causing a false sense of security. Charcoal and dry earth absorb most odours, but have little or no action on bacteria. On the other hand many perfumes and aromatic bodies not only mask bad smells but also cause oxidation and are inimical to bacteria, and therefore may act as real disinfectants, but not in proportion to their odour. In chlorine and oxone the two powers are strongly developed. (See ‘¢ DISINFECTANTS.”’) Destructors. — General: the “ Destructor System ” of dealing with Refuse—The Variable Composition of Refuse—Quantity of Refuse— Different Types of Destructors—Accessory Plant —Dust-Catcher, Boilers, Economisers—Thermal Storage—Kemarks on the Design of Destructor Plants—Recent Improvements in Destructors— Production of Steam Power—Money Value of Refase Fuel at Combined Destructor and Electric Stations — Total Costs of Burn- ing Refuse, including Capital Charges.— The term ‘destructor’ is applied to a high 100 DES temperature furnace specially designed for the disposal of town refuse by burning. The system was introduced about the year 1870, and has since been subjected to great modi- fication and improvement. It may be said that during the past 40 years the destructor system has had its birth, has grown into maturity, and has latterly been pursued to an extent which has enabled the practice to be reduced to certain well-understood general principles. Many years of practical experience has led to the design of efficient types of destructors, has shown what is the true calorific value of average town refuse, so that manufacturers are now able to give definite and reliable guarantees of performance such as both users and makers may with a reason- able degree of certainty expect to realise. The mere disposal of the refuse is not, as a rule, the only consideration kept in view in a modern refuse destructor station. A com- plete installation for a population of, say, 50,000 persons may cost from £5,000 to £6,000 to erect, according to local circum- stances, and, in addition to the destructor cells proper, usually includes machinery and plant for the removal and disposal of the residual clinker, for its crushing and manufacture into paving slabs, bricks, mortar, or other saleable products, also steam and engine power for actuating the various plant required at such a station. It will, therefore, be evident that the working expenses, maintenance, and depreciation of a fully equipped installation must necessarily be considerable, and that with the view of reducing this annual expense to a minimum it becomes necessary to turn to account any and every by-product or resi- dual material which can be really diverted to profitable use. Tse VARIABLE Composition or Town Reruse. —The material dealt with in destructors is of variable composition. It not only varies widely in different localities, but the summer and winter supplies of refuse in any town is rarely of the same calorific value. A destructor installation must therefore be adapted to cope with this unavoidable fluctuation where a MUNICIPAL AND SANITARY ENGINEERING. DES fairly steady and uniform demand for the surplus heat available for motive power pur- poses exists. The constituents commonly met with in the refuse include, ashes and cinders, small pieces of coal, dust, waste paper and cardboard boxes and packings, straw, shavings, rags, vegetable and animal matter, scullery and kitchen wastes, bottles and. preserved food tins, broken crockery, glass, bones, &c. The amount of cinders, ashes, and coal is not large, and has a tendency to decrease of recent years, owing to the extended use of gas fires, and the consumption of ready-made artificially preserved tinned and bottled foods. Contrary to what may be expected, the house refuse of the poorer districts of a town very usually contains the largest proportion of cinders and coal, which obviously formed the most valuable parts of the refuse from a calorific standpoint. This is probably due to the greater extrava- gance or want of care of the poorer classes in the sifting out of cinders from their household refuse, and its retention for further use, and also to the fact that the refuse from these quarters is more strictly household refuse with a much smaller admixture of garden and vegetable waste. As may be anticipated, the refuse of the coal mining districts of the northern and Midland towns possesses greater calorific value than that of the southern and eastern counties, but the distinction is not always so marked as might be supposed hav- ing regard to the relative prices of coal in different quarters. The quantity of refuse to be dealt with from a given population is a matter requiring investigation when designing a destructor installation. In London this amounts to from 4 to 5 ewt. per head per annum, or to from 200 to 250 tons per 1,000 of the population per annum. In the neighbourhood of the Metropolis varying amounts have been reported, viz: 24 cwt. per head per annum at Leyton, 34 cwt. at Hornsey, and as much as 7 cwt. at Haling. In the north of England the total collected, exclusive of street sweep- ings, has been put at 8 cwt. per head per annum. On the average from 5 to 10 ewt. 101 DES per head per annum must be allowed for. The weight of refuse is also variable, and great discrepancy will usually arise in estimates based upon so many “ loads”’ col- lected per annum. The “load”? may range from 10 ewt. to 1 ton, though from 12 to 14 cwt. is commonly about the weight of an ordinary good one-horse load of average house refuse weighed in fine weather. Much A oN P S. Ry Ir ti \ ro: Sot YPPING het Pld TFORMS BBN SV ARTRTINVAS ENCYCLOPADIA OF DES employed be of the most perfect type for the primary purpose of burning the refuse, without thereby giving rise to nuisance or incon- venience to the neighbouring public. The secondary object of the plant must be to take the fullest possible advantage of the heat given out by burning the refuse for the generation of steam. In that way the cost of collecting and disposing of the material may PALL EL VY ] | SOOO, << LLL L ‘4 SE ! 2 Ege se Fic. 1.—Section of Fryer’s Destructor. depends on whether the refuse is wet or dry, and whether it is collected from shop properties, or residential quarters. Shop refuse is usually of a light character and consists largely of paper, shavings, boxes and packings, and is of but little calorific value. A population of, say, 50,000 persons will produce domestic household refuse at the rate of about 40 tons per day. As it is essential that this material should be satisfactorily and economically disposed of day by day, it is of first importance that the furnaces and plant be reduced. Some general idea of what may be regained in this connection may be gathered from the following calculation :—Forty tons of refuse per day, or about 12,500 tons per annum, giving an evaporative efficiency at the rate of 1lb. of water per pound of refuse (a result readily obtained in practice), will develop a steam-power of 1,400,000 I.H.P. hours annually, calculating upon a steam con- sumption for condensing engines of 20 lbs. of steam per I-H.P. per hour. Then, allowing 3 lbs. of coal as the fuel consumption per I.H.P. hour, this gives an equivalent of about 102 DES 1,880 tons of coal per annum, showing the refuse in this case to be from one-seventh to one-sixth the value of coal for steam-raising purposes. Dirrerent Typzs or Destrucrors.—Since Mr. Fryer erected his destructor in Man- chester, in 1876, many different designs of furnace have been introduced, as experience has directed attention to numerous important points where improvements could be intro- duced. The principal furnaces to which attention should be directed are those of “Fryer,” “Warner,” ‘“ Horsfall,” “‘ Meldrum,” “Beaman & Deas,” the ‘‘ Heenan’”’ twin-cell, and the “Sterling” destructor. Fryer’s Destructor (Fig: 1), as already mentioned, is one of the earliest types, and for a long time formed the basis of several subsequent designs. It consists of a block of cells or furnaces, usually arranged ‘back to back”’ in pairs. Each cell measures in- ternally about 9 ft. by 5 ft., and is covered by a fire-brick arch 8 ft. 6 in. in height above the grate area. The furnace floor slopes at an inclination of about 1 in 3, and the area of the fire grate is 25 sq.ft. This destructor ordinarily deals with from 4 to 6 tons of refuse per cell per 24 hours, and is known as a low temperature destructor. The outlets for the products of combustion are at the back of the cells near the refuse feed-opening, which is an undesirable arrangement. Warner's Destructor (Fig. 2) is similar to Fryer’s in general arrangement, but differs therefrom in many points of detail. It pro- vides special charging hoppers, dampers in the flue, dust-catching arrangements, rocking fire-bars, and a modified position of the outlets for the escape of the products of combustion. The cells are 5 ft. wide by 11 ft. deep, the rearmost portion consisting of a fire-brick drying hearth. The grate area is MUNICIPAL AND SANITARY ENGINEERING. ‘DES 25 sq. ft., and the amount of refuse consumed varies from 5 to 8 tons per cell per 24 hours. Horsrauu’s Desrructor (Figs. 8, 4, 5) has been on the market for a great many years, and is well known both in this country and on the Continent of Europe. It was probably the earliest type to work at really high tempera- tures, and many improvements have been made in its design where experience has shown them to be necessary. It will be seen from the illustration that the general arrange- ment of the Fryer type has been followed in the Horsfall design ; but that there are many Fig. 2.—Warner’s Destructor and Boiler. important modifications, such, for example, as those of the arrangement of flues and flue outlets for the products of combustion and the introduction of a blast duct through which air is conducted to the closed ashpit. The feed holes are placed at the back of the furnace, whilst the flue openings for the removal of gases are situated at the front of the cell, so that the gases from the drying refuse pass on their way tothe main flue over the hottest parts of the fire and through a red- hot reverberatory arch. The steam jet, a feature in the Horsfall furnace, forces air into the closed ashpit at a water-gauge pressure of 103 DES about $ in. to 1 in., thus producing a tempera- ture of from 1,500° to 2,000° F. The blast air is conveyed on its way to the grate through cast-iron boxes at the sides of the furnaces, as shown in the figure, the boxes also having the further object of preventing the clinker adhering to the sides of the cells, the removal from which causes damage to the brickwork by the clinkering tools. The Horsfall furnace deals with from 8 to 10 tons per cell per 24 hours. Considerable improvements and additions in accessory details have been made Feeding Hole ENCYCLOPADIA OF DES removing the fine ash, and two Meldrum steam jet “blowers” are provided to each furnace capable of supplying any pressure of blast up to 6 in. water column. The pressure usually used does not exceed 13 irs. The furnaces are arranged for hand feeding from the front, but hopper feeding of the customary type can be adapted if preferred. The flue gases pass away to the boilers and from thence are further utilised in an air-heater or continuous regenerator consisting of cast- iron pipes from which the air is delivered Freding Floor or nie o LM > Y pope RS cas rt jer fun Flue eo ee Ze ZY Ash: Pit Blast }. y Blast Ash Pot ; Flas YY Flue Sh pL eB Z nt = Line ee % Lo “fe 57 ’ : i ofr “Le Y ’ (tif Yfit WL LLELLLLLILPAL ALLL FEES LLL SLT TTL Fic. 3.—Section of Horsfall’s Destructor. in connection with this type of furnace during recent years. Me.prum’s Destructor (Fig. 6) differs in general arrangement from the types already referred to. It is a modern high-temperature destructor, now widely adopted, and capable of giving good steam-raising results. This destructor is practically one long cell, fed and clinkered at four or five different furnace mouths, according to the number of grates installed, and by this means an approximately uniform temperature is maintained through- out. The ashpits are each closed air-tight by a cast-iron plate and air-tight doors for through the Meldrum “ blowers” at a tem- perature of about 300° F., thus assisting to keep up the temperature of the furnace and facilitate combustion. High-pressure Lanca- shire boilers of large capacity are usually ‘ provided for the accumulation, during periods of light demand, of a reserve of steam. Storage is obtained by using the difference between the maximum and minimum working steam pressure and the permissible fluctua- tion of water-levels in the boiler. From 50 to 60 lbs. of refuse per square foot of grate area per hour are consumed by the Meldrum furnaces, as compared with about 22 lbs. per 104 DES square foot in the low temperature destructors. Installations of the Meldrum type have been largely adopted where a special feature of the destructor station has been to produce the MUNICIPAL AND SANITARY ENGINEERING. DES this destructor, with Lancashire boiler and regenerative apparatus, is shown in the plan (Fig. 7). In the section (Fig. 8) a water- tube boiler and hot-air duct leading to the regenerator is shown. A plant of this type is in use at Gloucester, consisting of two ‘‘twin-cells.” A “twin-cell” comprises two furnace-grates, each of Cc DUSTCATCHER & CHIMNEY CI TIPPING PIT FFICE STORES { Fic. 4.—Section of 4-Cell Tub Fed Plant by Horsfall Destructor Co., Ltd. utmost steam power possible for purposes of sewage or water pumping, or for electric light or power generation. Braman & Dua’s Destructor is another high-temperature furnace, the patents of which are now in the hands of Messrs. Meldrum Bros., of Manchester. The special features are the flat grate area of 25 sq. ft., and the sloping drying and feeding hearth immediately below the feed hopper on the tipping platform. At the back of the cells is a high temperature combustion chamber, placed between the cell proper and the main flue. A secondary air supply also meets the fumes as they pass over the fire-bridge. The destructor is fitted with a powerful air blast, and is generally installed in conjunction with Babeock & Wilcox water-tube boilers. This destructor will consume about 20 tons of refuse per cell per 24 hours, and is a good steam generator. “ Heenan” Twin-cett Destructor (Figs. 7, 8, and 9) is one of the most recent destructors, and is built by Messrs. Heenan & Froude, of Manchester. The standard arrangement of 39 sq. ft. in area, with a fire-bridge between. Hach pair of cells are capable of cremating 25 tons of refuse in 24 hours, and are worked together. A maximum amount of clinker of 25 °/, of the refuse is guaranteed. The furnaces work at a temperature of over 2,000° F.: that of the flues before the boilers is from 1,400° to 1,800°, and after the boilers from 400° to 700°. One Babcock & Wilcox boiler is pro- vided to each pair of cells, and the weight of water evaporated from and at 212° F. per pound of refuse burned is from 1°25 lbs. to 2 lbs. Forced draught is produced by an electric fan of 12 B.H.P., running at 950 revolutions per minute. About 125 H.P. is obtained from the refuse when burning 150 tons weekly. The cells are fed through an iron uN Fic. 5.—Section of 4-Cell Tub Fed Plant iby Horsfall Destructor Co., Ltd. shoot at the back, and the clinkering is done from the front of the furnace. The cost of the destructor was about £4,150. 105 DES Tue “ Srertine’’ Desrructor has of recent years been installed at Hackney, Bermondsey, Gravesend, Heston and Isleworth, and other places. The destructor and electricity works inaugurated at Hackney in 1901 are amongst the largest combined destructor and electric stations yet put down. The estimated cost of the destructor alone was £22,000 for dealing with about 38,000 tons of refuse yearly. The plant consists of twelve cells arranged in three groups, each group having a central supple- mentary combustion and dust-depositing ENCYCLOPADIA OF ir DES careful attention, both from a sanitary as well as an economical point of view. The whole of each day’s refuse is burned within the 24 hours. The electric energy consumed by the elevators and distributors is about ‘35 of a kilowatt-hour per ton of refuse elevated, and the amount of the lift is 43 ft. from ground level to the storage bins. The forced draught is obtained from three centrifugal fans driven by 15 H.P. “Rhodes” motors. The guaranteed capacity of the destructor is 160 tons of refuse per day of 24 hours. The “Sterling” a a a Fic. 6.—Meldrum’s Destructor. chamber, three Babcock & Wilcox water-tube boilers, fired by heat from the destructors, and built for a working pressure of 250 lbs. per square inch; three fans, each driven by an electric motor, for providing the necessary ‘forced draught; three elevators, also driven by electric motors, for raising the refuse and delivering it into high-level refuse storage bins, whence it is drawn down as required into the cells; a large Green’s economiser ; and a complete range of flues and by-passes which permit the gases to be taken through the boilers and economiser, through the boilers alone, through the economiser alone, or direct to the chimney shaft without passing through either boilers or economiser. The best means of handling the refuse has received destructor may be generally described as a compound furnace, having at least two cells, each with a drying hearth, a grate, and a closed air-tight ashpit, combined with a special chamber placed between the cells. This chamber serves the purpose of a supple- mentary combustion and dust-depositing cell, and is made large enough for the reception of infected mattresses, bedding, and even of an entire ox. Calculating upon the basis of 1 lb. of steam per pound of refuse fed into the cells, the “Sterling” furnace (two cells), burning 2,800 lbs. of refuse per hour, will give 140 I.H.P. continuously per pair of cells at 20 Ibs. steam per LH.P. Steam-blast is not recommended by the makers, and the furnaces of this type 106 wieaeaams 5 pati ae” DES are assisted hy forced draught produced by a fan. Accessory Puant at Destructor Insrat- Lations.— Much auxiliary plant is now in use for the complete equipment of a modern destructor station. Such accessories are mainly designed to ensure the following points :—(1) The complete combustion of the refuse and gases given off; (2) The avoidance of all possibility of nuisance in carrying on the working of the destructor ; (8) the reduc- tion of working expenses by labour-saving devices, and the introduction of means of utilising the residuals produced on the works, including the profitable employment of the sur- plus heat; (4) and the reduction of wear and tear and maintenance ex- penses generally. The utilisation of clinker from destructors has given scope for a variety of plant, such as mortar mills, crushers, slab- making machinery, for example, as that of Messrs. C. & A. Musker, Ltd., of Liverpool, and . artificial stone - plant as made by Messrs. Field- ing & Platt. Messrs. Musker have also introduced a brick-making plant, as now used by Bradford and Liverpool Corporations. The approximate cost of a 6,000-brick plant is £1,900, and of a 10,000-brick plant £2,300. The cost of production of the bricks averages from 12s. to 14s. per 1,000. For the purpose of manufacture of clinker into bricks, slabs, &c., the material as it leaves the furnaces must first be crushed to suitable sizes. A suitable machine for this purpose is the Cox & McTaggart clinker-crushing plant, consisting essentially of a pair of grooved rollers with removable faces made of specially hard metal and chilled, driven by heavy and powerful gearing. MUNICIPAL AND SANITARY ENGINEERING. — Heenan Twin Coll Hopuse Destructor wih, Lancushurc Boiler Fic. 7.—Heenan’s Destructor. DES At Kensington a plant costing about £6,000 has been installed for making road-paving blocks. The treated clinker, after crushing, is mixed with 15% of Trinidad asphalte and a certain proportion of: fine dust, and then pressed under two tons to the square inch into paving blocks 8 in. by 3 in. by 8 in. and 4 in. deep, for use upon secondary roads. At Liverpool, trials have been carried out in the construction of labourers’ dwellings of crushed clinker steel armoured concrete for walls, roofs, and floors. After mixture with cement the materials are filled into moulds to ‘form large slabs representing a complete side, floor or roof of a room. At Fulham a plant was put down by Messrs. Fielding & Platt at a cost of £2,365 for the manufacture of bricks and flags in con- nection with a 12-cell ‘‘ Horsfall”’ destructor completed in the year 1900. The materials manufactured have been sold to the various departments at the following prices :—bricks 35s. per 1,000; paving flags 4s. per square yard; mortar 10s. 6d. per cubic yard, at the works. Artificial slabs, concrete bricks, mortar, &e., are also made on a large scale at the Bradford Corporation Works, where nearly 60,000 tons of refuse are dealt with annually 107 DES ENCYCLOPAEDIA OF DES by the destructors, at a cost for labour of the objectionable quenching of the hot about 114d. per ton. material within the building is avoided. An improved system for the easier removal The use of forced draught is an important | Bowden Hor Ain Ovor HEENAN Reruse DESTRUCTOR — 35 Cet. PLAntT — Fic. 8.—Heenan’s Destructor. of clinker from the furnaces has been adopted and essential detail in all destructor stations. at Blackpool, Bradford, Hanley, Fulham, In the “Meldrum” system the air is delivered and several other places. The arrangement into a closed ashpit by means of a steam jet consists of an overhead railway with clinker blower of special construction, used in con- N RS Strorace iT Hoprer ELL = Firing Space]. x rege ys Dee ay PT 68 Boy i bie 8 A Reet ZLIPMERING jee os SQ an. vs . ee at 7 Hor aie Z ei > ae > =): : AIR Sed -' 2 i ie Buer \G* Og he | 7% %, Cross SECTION THROUGH CELL Fic. 9.—Heenan’s Destructor. buckets suspended upon a rail leading direct junction with special made fire bars spaced from each furnace to the cooling space or only ;4, in. apart, and thus enables steam to crushing machine. The handling of the be economically raised with materials contain- clinker is thus reduced to a minimum, and _ ing only a small percentage of combustibles. 108 DES The proportion of steam used in the forced blast is about 15°/, of the total raised. At the set of six new cells built at West Hartlepool in 1903 was installed a system of forced draught on the Horsfall new “ hot- blast system,” in which each side air box in every cell contains its own separate steam blower, so that no condensation of the steam in the passages is possible. The air tem- perature in the ashpits is increased to over 400° I¥., which materially quickens com- bustion. A special form of superheater has also been adopted for heating the steam to MUNICIPAL AND SANITARY ENGINEERING. DES of the site, some form of top-feed closed hopper system is, on the whole, preferable, provided the mechanical devices adopted are quite simple in construction and work smoothly in daily use. The fires, however, should not be too suddenly fed with large charges of green refuse, otherwise the diffi- culty of maintaining a steady steam pressure will be increased, and some risk of imperfect combustion of gases incurred. With hand- feed at the furnace mouth the cost of an inclined roadway and raised tipping platform is dispensed with, and there is also an advan- orem be ede Gey oe ail aIR CONDUIT Fic. 10.—Leyton Destructor. Section through Cell and Boiler. the jets, increasing the efficiency of the blast. and reducing the quantity of steam consumed. Improvements have been made of late years in the feeding arrangements to destructor cells in order to avoid the handling or storage of the refuse, to avoid nuisance, and to save cost of labour. Of these arrangements may be cited the apparatus of Boulnois and Brodie, the “feeding hoppers ” of the Horsfall Destruc- tor Co., and the special feeding arrangement adopted by Messrs. Meldrum Bros. for dealing with fish and slaughter-house offal. Unless there is some special local reason for adopting a hand-fed arrangement, such as the exigencies tage, when combined with the continuous grate and divided ashpit arrangement, that the feeding in of small quantities of refuse does not very materially affect the tempera- ture of the cell, as in the case of a large charge such as a ton or a load. The “dust catcher” is an important. feature in installations of the Horsfall type, and has for its object the prevention of the escape of fine dust from the chimney shaft into the atmosphere. It consists of an outer annular chamber and an inner well. The flue gases enter the outer chamber and swirl rapidly round it, thereby throwing off the suspended dust against the outer wall. 109 DES Clearing doors are provided for periodically removing the dust thus deposited within the. chambers. Other accessory details connected with destructor plants include counterbalanced fur- nace fronts, back-feeding or charging doors, water-sealed feed-opening doors, dampers, and furnace lining blocks. The principal accessories for heat utilisa- tion include various forms and settings of boilers, regenerators, economisers, and super- heaters. Borners.—The boilers mostly used are of the Lancashire and the water-tube type. The Lancashire boiler, where there is a fairly uniform demand for steam, is a reliable steam raiser, and for steady work has much to recommend it. The thermal capacity is large, and a steady steam pressure can be maintained. Water-tube boilers, are, how- ever, largely used in connection with destruc- tors, as the steam power is very generally applied to the generation of electricity, in which connection the water-tube boiler is well adapted for coping with the sudden demands for steam often required in the generation of energy for lighting and motive power. Water-tube boilers have a small water capacity, a relatively large heating surface, and are, therefore, quick steaming boilers, but their small thermal capacity tends to unsteady steam production, and this class of boiler is liable to smoke with bitu- minous coal, so that smokeless fuel must be used. The use of pure water is also neces- sary to avoid incrustation in the tubes. The Babcock & Wilcox water-tube boiler has been largely used in connection with destructor stations, and has been found well suited to the work. The Stirling boiler is also em- ployed in a similar connection. Economisers, ReGeNERatToRS, &c. -— To secure the full value of available heat in the flue gases, in addition to using boilers of large heating surface as compared with their water capacity, it is necessary to provide ‘“economisers”’ and ‘‘ regenerators ” through which the -gases pass on their way to the ENCYCLOPADIA OF DES chimney shaft. This cooling of the gases must not, however, be carried too far, other- wise the chimney draught will be impaired. A temperature of some 350° to 450° F. on entering the chimney may be regarded as satisfactory. “EKconomisers” are placed in the main flue leading to the chimney shaft, and the hot flue gases thus utilised to heat the feed-water to the boilers. Green’s and Hudson’s econo- misers are much used for this purpose. The Green economiser is a flue-heated feed-water heater, by means of which the lot gases may be reduced in temperature from 650° F. to 850° F., and the feed-water heated some 150° to 250° F. In the Meldrum system as installed at Sheerness, a Sugden superheater is placed in the down-take immediately behind the boiler, and arranged to give about 125° F. of superheat to the steam. Bevond the super- heater is provided a Meldrum’s “ regenerator,” or continuous air-heater, so that in addition to actual steam-raising the hot gases are further utilised for superheating the steam, and then for heating the air supply for combustion up to a temperature of about 350° F. THERMAL Storace.—The object sought in the storing of heat energy is to accumulate surplus heat during hours of light load, as, for example in electric central station work, so as to utilise this stored energy through the hours of towering peak load. The thermal storage installation originally put in at the Shoreditch combined destructor and electric light station was subsequently altered to store the hot feed-water instead of storing the actual steam, as was originally intended, and in this modified form has done good service. In 1904 an installation of thermal storage was put down by the Kensington and Knightsbridge and the Notting Hill Electric Light Companies for the purpose of increasing the capacity of their plant at their joint station at the Wood Lane Works. Large hot water-feed cylinders were placed over the steam drums of the existing water-tube boilers and immediately below the 110 DES water storage tanks. The main idea of the system is to increase the rating of the boilers at the hours of peak load by feeding the boiler with water at boiler temperature during those hours, this water having been previously heated to the desired temperature by live steam during the hours preceding the peak. _ Remarks on tHe Desten or Destructor Puants.—The proper design and capabilities of the refuse destructor and its accessory plants have not been well understood until within comparatively recent years. The utilisation of refuse as fuel is an essentially practical subject and one in which every “improvement” must be submitted to a prolonged practical test before’ it can be pronounced as good. The best results of to-day are obtained through a knowledge of the failures and defects of the past. Like most mechanical apparatus and inventions, that destructor plant is best which is simple, strong, and easily worked, if combined, of course, with efficiency. It would be unwise to lay down any hard and fast rule as to a particular type of plant as being absolutely the best for all cases and localities. Due regard must be had to the conditions of the case and local requirements. The choice of plant and the general design of a station requires to be entrusted to an engineer experienced in such matters in order to ensure the best results. The following general obser- vations, however, will be a guide :— The temperature in the cells must be sufficiently high to reduce the refuse to an entirely innocuous clinker, and all vapours given off should pass through an adjoining red-hot cell, or through a chamber whose heat is maintained by the ordinary working of the furnaces themselves to a temperature of from 1,500° to 2,500° F., so as to pre- vent the escape of noxious gases. To maintain a uniformly high temperature, the destructor requires to be so worked that whilst one set of cells is recharging, another -set is at a full red heat. The furnaces and plant require to be strong, simple, and easily worked without stoppages, MUNICIPAL AND SANITARY ENGINEERING. DES and should contain no mechanical complica- tions. The installation should withstand variations of temperature and readily admit of being repaired. The plant must admit of being understood and worked by stokers of average intelligence, so that its continuous working may be ensured, and that the cost of working may be kept as low as possible. Clinkering and recharging requires to be done as speedily as possible to prevent the inrush of cold air, which would reduce the temperature of the main flues and the calorific efficiency of the refuse. Where boilers are provided for stoking with both refuse and coal, a system of dampers should be arranged so that when coal fuel is in use only the refuse cells may be shut off from the boilers; otherwise the cold air passing through the cells and into the coal furnaces will materially reduce the calorific efficiency of the coal. The chimney draught must always be assisted by forced draught from fans or steam jet to the extent of from 1:5 in. to 2 in. of water-gauge pressure in the ashpit. In districts where the question of nuisance from the chimney shaft is of importance, boilers must not be placed immediately over a furnace in such a way as to present a large cooling surface to the gases, for then their temperature would be reduced before they have been rendered wholly innocuous. If steam power is an important part of the system, ample boiler capacity and hot-water storage feed tanks should be provided; also the flue gases may be utilised in heating the air supply to the grates and the feed water to the boilers. For a high fuel efficiency a large proportion of CO. should be sought in the cells, with as little excess of air or free oxygen as possible. Considering the somewhat trying nature of the work, a destructor station should be worked in three eight-hour shifts where the plant is running continuously. A bath-room in connection with the works will be found not only a boon by the workmen, but a hygienic necessity. In order to derive the full advantage of 111 DES good points of design, it is necessary that the furnaces and plant be carefully and intelli- gently worked, and the efforts of the firemen should be towards obtaining a good, hard vitreous clinker, and perfect cremation of the whole of the refuse without the escape of unconsumed vapours of any kind; also the inrush of cold air into the cells and flues must be avoided as much as possible, other- wise the calorific results obtained will be low. The great improvements which have taken place in the design and management of destructor plants have contributed materially to the carrying on of such works in the midst of populated districts with a minimum of inconvenience to the neighbouring inhabitants. The introduction of a good forced draught and high temperature furnaces has enabled larger quantities of material to be dealt with, and with less risk of allowing unconsumed vapours to escape into the atmosphere. Tue Cost or Burnine Rerusz differs widely, according to local circumstances; at Battersea the cost is as much as 2s. 10d. per ton, whilst at Bradford it is burned for about 6d. per ton. Under ordinary circumstances a cost of Is. per ton for labour, supervision and small repairs is a fair average figure. The amount of refuse burned per cell per hour materially affects the cost of burning. For purposes of comparison the best way of stating the duty of different types of furnaces is to state the performance of the furnace in pounds per square foot of grate area per hour, as the furnaces have varying grate areas, and to give the consumption in tons per cell is some- times apt to mislead. The ordinary low tem- perature destructor, working without forced draught, deals with about 20 lbs. of refuse per square foot of grate area per hour, and this gives, for a grate area of 25 sq. ft. each furnace, a duty of between 5 and 6 tons per cell per day of 24 hours. This consumption is low, and with forced draught may be greatly increased. The Beaman & Dea’s furnace at Canterbury has been found to deal with as much as 77°5 lbs. per sq. ft. of grate area per hour, and the same type cell at Llandudno ENCYCLOPEDIA OF DES deals with 71°7 lbs. per sq. ft. per hour. The consumption in the Meldrum furnaces at Rochdale is 66 lbs. per square foot per hour. The amount passed through the furnaces depends largely, however, on the mode of stok- ing, upon the degree to which the material is thoroughly cremated, and the frequency of the removal of clinker. The amount of residue clinker produced is usually between 25 °/, and 33 °/, of the material dealt with, Its ultimate disposal is a question of consider- able importance in built-up districts, where the ordinary outlets for the material are not available, as the cost of cartage or barging to the suburbs of the town is almost pro- hibitive in many districts, as is the case in Shoreditch, where the total residue amounts to 82°8 °/,. Recent Improvements. — Some of the principal improvements made in destructor installations during recent years, include:— 1. The use of high temperatures within the cells and combustion chambers and the reduc- tion of cold air-leakage into the furnaces. 2. Increased durability of the furnaces under high temperatures, and the avoidance of defects caused by contraction and expansion owing to frequent variations of temperature. 3. The employment of hot-blast and forced draught, and the reduction of power used in its working. 4, The extraction of the full calorific value from the refuse, and the interception and utilisation by means of boilers, economisers, or feed-water heaters, superheaters, regen- erators, hot-blast draught, &c., of all heat given off by its combustion, and its fullest possible application to the performance of profit-yielding work. 5. Improvements in the uniform mainten- ance of steady steam pressures and in the generation of high-pressure steam. 6. The practical application of ‘thermal storage’ in the employment of hot water-feed cylinders, thus affording a certain elasticity of output of power. 7. Improvements in the handling of the raw refuse, in the stoking and charging of the 112 DES MUNICIPAL AND furnaces, and in the removal and disposal of clinker, fine ash, &c. 8. The reduction of working and mainten- ance costs by the employment of the various improvements mentioned; also, some reduc- tion of initial capital for a given capacity of plant. 9. The employment of all possible means of full utilisation of residuals created at the works and of any marketable material occur- ring in the refuse. 10. Various sanitary improvements in connection with the handling and storage of the refuse, and the prevention of dust or smells from the chimney shaft and destruc- tor station generally. Propuction oF Sream-Powsr.— Various recent destructor installations, where the production of steam-power is an important consideration, show that, on the whole, an evaporation of from 1 lb. to 2 lbs. of water per pound of refuse represents the full avail- able calorific value of town refuse for power production, and it is not usual that this average can be maintained over long periods of working under ordinary conditions. A few of the comparatively recent power-using installations, taken at random, are—(1) the ‘* Horsfall ”’ system at West Hartlepool Elec- tricity Works, Fulham Electricity Works, Accrington Electricity Works, and Beckenham Electricity Works; (2) “‘Meldrum’s”’ system at Cleckheaton, Burnley, Darwen, Port Glasgow, Wandsworth, and Plumstead ; (8), the ‘‘ Hee- nan” system at Blackburn, Gloucester, and Wakefield; (4), the ‘‘ Sterling’? destructor system at Bermondsey and Hackney. The amount of power obtained per ton of refuse varies with the character of the material collected in the particular district concerned. Taking the average of the mean results of six towns in the vicinity of coal-producing areas in the North of England an evaporation of 1°6 lbs. of water per pound of refuse is shown, as against 1°32 lbs. average evaporation of six destructors in the South-east. The difference is, however, often much more marked, as the refuse in some towns is of an unusually rich M.S.E. SANITARY ENGINEERING. DES character. At Warrington the Beaman & Deas furnaces are reported, after prolonged test, as generating 8 lbs. of steam per pound of refuse throughout the year, owing to the refuse containing some 60°/, to 70% of cinders. At King’s Norton the average refuse has been analysed and found to contain 386°8 % of carbon, 7°3 % of oxygen, and 12°12 % moisture, and yielded 4,500 British thermal units of heat per pound, or nearly one-third the value of average Welsh coal. Ordinarily, average town refuse is found to contain from 1,500 to 3,000 British thermal units per pound, and to possess a calorific value of from one-tenth to one-fifth that of average good coal. At Llan- dudno, the refuse is of very low calorific value, especially during summer, and here the Beaman & Deas furnaces (as used at Warrington above mentioned) give an evapora- tion of only about ‘7 Ib. of water per pound of refuse. A low value was also obtained at Royton (Lancashire) where, upon careful calorimeter test, only 997 British thermal units were obtained per pound of refuse. Money Vauus or Reruse Fug. at comBINED Destrucron anD Execrric Stations. — For many years past there has been a growing confidence in the utility of modern destructors as power producers in addition to being mere destroyers of refuse as evidenced by recent combined installations at such districts as Liverpool, Nottingham, Wolverhampton, Preston, Hackney, Bermondsey, Fulham, Plumstead, Woolwich, and others. From recent results of several London combined destructor and electric stations it appears that the money value of the refuse fuel per unit of electric current generated varies from about ‘7d. to ‘9d. per unit, and that under ordinary working conditions from 20 to 40 units per ton of refuse are at present obtainable, but that over limited periods much higher outputs have been generated. However, in the investi- gation of the value of destructors to electric or other power stations one of the main difficulties is that of procuring trustworthy statistics on a uniform basis such as can be usefully compared one with another. 113 I DET Toran Costs or Burninc REFUSE, INCLUDING CapitaL Cuarces.—The quantity, or rate, at which refuse is burned by a modern destructor commonly lies between 50 lbs. to 60 lbs. per square foot of furnace grate area, and the cost of dealing with the refuse on this system varies on the average as follows:— Per ton of refuse. s. a. sd. Labour of burning and handling, including stokers, feeders, yard- men, &e. . i ‘ 0 8 to 110 Supervision, repairs, removal of clinker, stores, water, rates and taxes. . 2 - Ba .. 0 6 to 0 9 Capital charges (interest and redemp- tion) .. 6 to 1 9 Perton of refuse burned .. 1 8 to 4 4 | ADVISABILITY OF COMBINING DESTRUCTOR AND Eectric oR OTHER Powsr-usinc UNDER- TAKINGS.—There has been much difference of opinion in many quarters as to the advisability of installing refuse destructors in conjunction with power-using stations of various kinds; but generally speaking, it may be stated that, where there is refuse which must be disposed of and works to which some form of motive power must be supplied, experience has shown that the modern refuse destructor is of a certain real commercial value as a power producer, and that, where suitable conditions exist, the outlay involved in its application to that duty is fully justified by the results obtainable, not forgetting at the same time, its useful sanitary function as a means of refuse disposal. (See also articles on ‘“Rerusge Disposau,”’ and ‘‘ Rerusz CoLLEc- TION.” W.H.M. Detritus Tank.— (See “Szwace Disposat.”) Disconnecting Trap.—A trap fixed upon the outlet end of a house drain to break aérial communication between the drain and the public sewer, or other sewage outlet. Discon- necting traps are best fixed in manholes, in order that they may be readily reached. In the alternative a shaft reaching to the surface of the ground may be provided. It is desirable ENCYCLOPAEDIA OF DIS also that a sweeping eye be available on the outlet end of the trap, to afford access to the drain between the trap and the sewer, &e. The standing level of the water in disconnecting traps should be at least 3 in. below the inlet drain, in order that a cascade may be formed by sewage passing into it. This will have a tendency to break up accumula- tions in the trap, and greatly assist in keeping it clean. Disconnecting Trap. Disinfectants.—Disinfection in the mo- dern sense may be regarded as having had its origin in the year 1862, when Pasteur, in response to an offer of the Academy of Science of Paris of a prize for ‘‘an attempt by means of suitable experiments to throw new light on the question of spontaneous generation,” demonstrated the possibility of sterilising any substance whatsoever. Previous to the work of Pasteur in France and Koch in Germany little had been done in investigating the life cycles of bacteria with a view to ascertaining their relation to disease. Koch’s method of isolating pure cultures of micro-organisms published in 1881, and his discovery of the tubercle bacillus in the following year, in- augurated a new era in preventive medicine, and for the first time in the history of that subject made the study of disinfection rational. In the light of the knowledge furnished by this and later bacteriological work the mode of action of disinfectants became plain ; heat, whether dry or moist, destroyed infective bacteria; the problem of the resistance of spores was solved; and a significant dis- tinction was drawn between antiseptics which inhibit the growth of microbes without de- stroying them and disinfectants which kill them outright. It was also found that deodo- rants for the most part which merely mask or absorb odorous gases and vapours possess 114 DIS neither the properties of disinfectants nor of antiseptics. In order to successfully carry out the work of disinfection it is clear that the life history, source, environment, and specific properties of the infective agent must be fully known, as also the nature and mode of interaction, chemical or physical, which obtains between it and the disinfectant. The germicidal efficiency of a chemical disinfectant is often determined as much by physical conditions as by chemical structure ; and to-day an efficient disinfectant, in addition to such germicidal efficiency, must be capable of penetrating various forms of organic matter containing bacteria, must be free from corro- sive action on the skin and on metals, must be innocuous to man and the higher animals, must be homogeneous in all conditions of dilution or emulsion, and must largely retain its germicidal properties in the presence of organic matter. Chemical disinfectants in the liquid state are obviously much more effective than in the gaseous or solid condition. The efficiency of a disinfectant liquid depends to a degree on the concentration of its active principle, and also on the particular form in which the active principle occurs. In the present state of knowledge it is impossible to state exactly how the micro-organism is killed. In certain instances it is probable that death occurs through coagulation of the protein of the cell, in others through its disruption. In solutions the degree of ionisation, and in emulsions the viscosity and size of the particles, influence the rate and completeness of penetration of the cell, and thus of the germicidal efficiency. The temperature of the disinfectant, within certain limits, influences directly the efficiency. Attempts have been made to reduce rate and efficiency of disinfection to mathematical form, but until very much more is known of the chemical and physical factors involved in this complex problem such work must remain unsatisfactory. In the case of simple and stable acids efficiency is approximately proportional to the 115 : MUNICIPAL AND SANITARY ENGINEERING. DIS degree of acidity. In alkalies the nature of the metal forming the base and not the degree of alkalinity appears to govern germi- cidal efficiency. The efficiency of certain organic acids has been found to be inversely proportional to the molecular weight. Sulphurous acid ‘obtained from burning sulphur in a moist atmosphere, or from the liquefied gas, produces a slow disinfection of a very uncertain character, even in laboratory experiments. Although a committee of Ger- man experts unanimously condemned this disinfectant nearly a quarter of a century ago, certain British sanitarians still employ it, for what reason one cannot conceive other than that of the ancient witch doctor, that the more abominable the potion the more certain the cure. Of the halogens and their compounds, chlorine is most commonly employed. It may combine directly with the protoplasm of the organism, thereby coagulating and killing it, at the same time decomposing offensive gases of putrefaction, such as sulphuretted hydro- gen, phosphoretted hydrogen, and ammonias ; or, which is the more common and important action of chlorine, in the presence of water it combines with hydrogen to form hydrochloric acid and liberates oxygen ; this nascent oxygen kills bacteria and burns up putrescent organic matter. In a fluid like urine, which consumes large quantities of chlorine, excess must be maintained until the last germ is destroyed, that is, the smell of chlorine must be per- ceptible and persistent for some time. The age and vitality of the organism influence the length of time required for sterilisation. Inti- mate contact between the gas and the centre of the infected mass must be assured, and in this requirement chlorine in common with all gases largely fails as a disinfectant. In chloride of lime and hypochlorites the avail- able or active chlorine is that present in the free state or as hypochlorite. Chloros is a solution of sodium hypochlorite said to con- tain 10°/, by weight of chlorine. In the process of disinfection by these bodies hypo- chlorous acid is formed from hypochlorite by 12 DIS the addition of an acid or by spontaneous action of atmospheric carbon dioxide; the hypochlorous acid splits into hydrochloric acid and nascent oxygen, which latter acts as the disinfectant. The great fall of germicidal power which the hypochlorites experience in the presence of organic matter militates greatly against them as disinfectants. Hermite solution may be regarded as the magnesian equivalent of chloride of lime. Sommerville and Walker (see Lancet, Octo- ber 27, 1906) conclude that the available chlorine in this fluid diminishes on standing, is rapidly destroyed in the presence of organic matter, and does not later reappear. The Rideal-Walker co-efficient of the fluid was found to be 0°6; using urine as the diluent, with a minute’s contact 0°075; and with urine as the diluent and an hour’s contact, less than 0°01. The hypochlorites of this fluid, like all other hypochlorites, are unstable, and in presence of organic matter untrustworthy disinfectants. Perchloride of mercury has been largely used in surgery, and is a powerful disinfec- tant; but it is also a powerful poison, doses of 0°2 gramme per diem rapidly causing disas- trous effects. It dissolves in fifteen parts of water, and in less alcohol and ether. If the dissociation of metallic ions in a solution of mercuric chloride be reduced by the addition of a salt, such as sodium chloride, its germi- cidal power is likewise reduced. A dilution of 1 in 1,000 is recommended for non-sporing bacteria, and 1 in 500 for sporing bacteria. The biniodide of mercury is also used in surgery, is less poisonous than the per- chloride, and is said to be of higher germicidal efficiency. Other salts of mercury in use are mercuric cyanide, mercuric salicylate, and mercuric thymolate—all poisonous, difficult of solution, and, as they coagulate albumin, unable to penetrate albuminous envelopes. Where the organism is enclosed in a protein or fatty envelope those disinfectants which can be suspended in liquid soaps are to be selected, and it should ever be borne in mind that the solution or penetration of the protein ENCYCLOPADIA OF DIS or fatty envelope may require a much larger expenditure of energy on the part of the disinfectant than the killing of the micro- organisms within. In all such work it is obvious that the “ oxidising” disinfectants (permanganates, peroxides, hypochlorites, &c.) are undesirable. In a set of experiments carried out by Sommerville and Walker a 20% solution of permanganate of potassium which gave a co-efficient of 50 in water dropped to 1°3 in a 1% solution of peptone, and a 10% solution of chloros, acting under the same conditions, fell from 21 to 0-2. Oxygen, ozone, and peroxide of hydrogen labour under like disadvantages. Oxygen, the natural disinfectant, burns all organic matter into carbon dioxide, water, &e., and in the ordinary or molecular form acts slowly. It is highly active when liberated in the nascent state from permanganates, peroxides, &c. The intensity of its action, however, militates against its disinfectant properties when the bacteria which it is intended to kill are embedded in organic matter, seeing that it spends its energy on the latter. Ozone readily decomposes into mole- cular oxygen and nascent oxygen, and is mostly prepared for disinfection purposes from air by the passage of an electric dis- charge. Peroxide of hydrogen is readily prepared from a peroxide of an alkaline earth and an acid: BaOy + H2.80.,= BaSO, + H202 This is a syrupy liquid which readily decom- poses into water and nascent oxygen. Of organic bodies the paraffin and aromatic series furnish the disinfectants most impor- tant in practice. Formalin, a 40% aqueous solution of formic aldehyde, is the most important of the paraffin group. It may be used in liquid or gaseous form, but the gas is practically useless unless precautions are taken to obtain in the room to be disinfected the necessary degree of moisture, tempera- ture, quantity of formaldehyde (which should be not less, perhaps, than 100 grammes per 1,000 cu. ft.), and complete sealing from the outside atmosphere. Of the aromatic series the best known is 116 DIS phenol. It is generally stable in the presence of organic matter, butis poisonous and caustic, and for the disinfection of spores useless. Crude carbolic acid consists of cresols and higher phenols in various proportions, depen- dent on the source of the tar. Cresols are with difficulty soluble in water, and in alcohol or oil have little germicidal power; they are much depreciated in efficiency by proteins. The addition of salt solution or mineral acid enhances the disinfectant values of phenol and cresols, and the latter may be conveniently dissolved in alkalies. A number of saponified neutral tar oils, known commercially as soluble carbolic acid, soluble creosote, &c., is met with in practice, but the efficiency in all cases is low. Lysol appears to be a solution of cresols in fatty acid saponified with addition of alcohol. It produces a clear solution in water. Izal is described as a preparation of oxidised hydrocarbons obtained from coke ovens. It is much less poisonous and caustic than phenol, and has a much greater germi- cidal power. Cyllin is described as prepared from certain members of a new series of oxidised hydrocarbons extracted from coal-tar, and is emulsified so as to be miscible in all proportions in water. Its toxicity is extremely low, and germicidal efficiency high. Cofectant, a still more modern preparation, is exquisitely emulsified and of high and con- stant efficiency. Its toxicity is negligible. Disinfectant powders may have some value when they possess a soluble base, otherwise, except as deodorants, they are useless. The only practicable base is lime, and as this is incompatible with phenol, it is necessary to use a high class disinfectant of different type ; such disinfectant may be found in the aroma- tic group. It must not be forgotten, however, that the germicidal powers of the best possible powders are necessarily small when compared with liquids. Experimental work on the bacteriological standardisation of disinfectants during the past five years has brought to light the superior efficiency of certain emulsified coal- tar products. It is possible to prepare such MUNICIPAL AND SANITARY ENGINEERING. DIS emulsions so as to possess a germicidal efficiency fifteen or sixteen times that of phenol, when tested by the Rideal-Walker method, or ten to twelve times that of phenol, when subjected to the Sommerville-Walker test. Until recently the merest empiricism has characterised the use of disinfectants. In future, discrimination will be used in selecting a suitable type of disinfectant for a particular form of work, and in order to obtain the best results all the conditions attaching to the work to be done will be intimately studied. It has been amply demonstrated that, except in a very few cases, the quantitative estima- tion of the so-called active chemical principle furnishes little information concerning germi- cidal efficiency. Previous to 1908, when Rideal and Walker brought forward their bacteriological method of testing disinfectants, too much attention had been paid to the quantity of chemically active principle present in disinfectants, whilst the form in which it existed was practically ignored; chemical analysis was accordingly the main criterion by which the value of a preparation was esti- mated. In bacteriology, as in all sections of biology, the estimation of effects produced on any unit or set of units by external conditions involves the careful consideration of a number of variable factors. But if in a given series of experiments one observer considers the time of application of the agent the only important factor, a second the proportion of culture to disinfectant, and so on throughout, no two results can be compared. Uniformity of pro- cedure in every step of the investigation must be a sine qué non where comparison of results is required. ideal and Walker in their method lay it down as axiomatic that in selecting any particular process to be employed as a standard the following factors must be considered :—(1) Time of medication and incubation. (2) Age of the bacterial culture ; the resistance of different micro-organisms varies in different degrees according to age. (3) Choice of medium and its reaction ; broth cultures possess certain advantages 117 DIS over cultures raised on solid media; the standard broth used for the growth of the B. typhosus possesses an acidity of + 1°5°/o. (4) Temperature of medication; within certain limits the higher the temperature at which disinfectants act the greater the germicidal efficiency. (5) Temperature of incubation ; all organisms have an optimum temperature of growth at which temperature they are most vigorous. (6) Variations in vital resistance of the same species ; sub-cultures of organisms on different media possess different degrees of resistance, as do also cultures obtained from different sources. (7) Variations in vital resistance of different species; for the most part disinfectants give different co-efficients when tested against different organisms. (8) Proportion of culture to disinfectant; the slightest deviation from uniformity in this factor makes the test worthless. The efficiency of the disinfectant is expressed in terms of phenol doing the same work as the Rideal-Walker co-efficient. Whilst much has been written on methods of estimating avail- able chlorine in bleaching powders, crystallis- able phenols, cresols, tar oils, and water in preparations of carbolic acid, &e., &c., it cannot be too emphatically stated that all such tests are vain, and that direct appeal to bactericidal powers alone avails. (See section dealing with Bacteriological Examination of Disinfectants.) With a view to imitating conditions that ob- tain in practical disinfection, Sommerville and Walker, in 1906, attempted to grow the B. typho- sus in various forms of sterile organic matter, such as urine, blood, blood serum, mucin, gelatin, pus, &c., and then to add the various disinfectants in suitable dilutions to measured quantities of these organic media, and finally to plant out in broth after the manner of the Rideal-Walker method. But several trials demonstrated that the B. typhosus grew so feebly in these media that it was impossible to obtain uniform results. Later they pointed out that uniform results could be obtained by diluting the disinfectants under test with an emulsion of ‘5°/, gelatin and °5°/, rice starch. ENCYCLOPADIA OF DIS The starch was used to meet the influence of adsorption. The presence of this amount of animal and vegetable matter lowered the co- efficients of different disinfectants to different degrees, but in each case always to the same degree. It is not to be concluded that the figure obtained (Sommerville- Walker co-efficient) indicates in any measure the quantity of disinfectant to be used in any given case; it merely shows the relative fall of co-efficient of a disinfectant under the conditions of admixture with organic matter described, as compared with phenol under the same con- ditions. In this, as in many other problems in which exact quantitative data cannot be obtained, a liberal use must be made of “ the factor of safety.” D. $8. Disinfection Stations and Appliances. —1. Local authorities have power to provide and equip disinfection stations and to disinfect free of charge any articles brought there for the purpose. They must exercise their power to disinfect or destroy any articles as to which | the Medical Officer of Health or any other legally qualified medical practitioner certifies that their disinfection or destruction would tend to prevent or check the spread of any dangerous infectious disease, unless the master or owner of the house undertakes the duty within 24 hours from receiving notice from the local authority and carries out his undertaking. For the purpose of such disin- fection the local authority may enter any premises by day (6 a.m. to 9 pm.). The disinfection must be carried out at the cost of the local authority, under the superintendence of its Medical Officer of Health, and compen- sation must be given to the master or owner of articles which have been damaged unneces- sarily in the process of disinfection. On the application of any person, local authorities may pay the expenses of disinfecting any bedding, clothes, or other things which have been exposed to infection, provided such disin- fection is carried out by the local authority or under its direction. 118 DIS On notification from any person that a book in his possession belonging to a public or circulating library has been exposed to notifi- able infectious disease, the local authority must cause such book to be disinfected or destroyed, paying to the proprietor the value of any book destroyed. When a person suffering from a notifiable infectious disease has been driven in a public vehicle without the knowledge of the owner or driver that the person was so suffering, the owner or driver may require the local authority to disinfect the vehicle and its contents free of .charge. The local authority may provide apparatus for destruction of vermin, and allow it to be used free of charge by any persons declaring themselves to be infested with vermin. Such apparatus consists essentially of a steam disin- fector for clothing and baths for persons. Ships or boats in rivers, harbours, or other waters within the jurisdiction of a local authority, are reckoned for disinfection pur- poses as houses, the master, or other officers in charge, being deemed the occupier. If not within the district of a local authority the Local Government Board may prescribe a district to undertake the duty, and in default of such prescription it must be undertaken by the nearest district. Admiralty and War Office property are exempt from the jurisdic- tion of the local authority, unless by consent. The Local Government Board may authorise or require any two or more local authorities to combine for the purpose, inter alia, of disinfection. In addition to the normal powers and duties of a local authority, of which the effect is summarised above, special regulations may be made by the Local Government Board on the occurrence of cholera or any other epidemic, endemic, or infectious disease, or on any part of England appearing to be threatened or being affected by any formid- able outbreak. These regulations may be revoked or modified, and the period of their application extended or abridged; and the local authority of any district within which or part of which such regulations are declared MUNICIPAL AND SANITARY ENGINEERING. DIS to be in force must superintend and see to their execution, and appoint and pay any necessary medical or other officers, and do all things necessary. For practical purposes, a local authority has, therefore, to provide for the disinfection of all articles liable to retain infection, whether in normal times or during epidemics; and in view of the difficulty of ensuring proper disinfection of goods, such as rags used for industrial purposes, they may find it expedient to undertake such disinfection for themselves. 2. The construction of a disinfection-station should fulfil the following conditions: (a) The disinfection room should be divided into separate chambers for infected and dis-infected material respectively. No direct passage of men or material from the infected to the dis- infected side should be possible except through the steam disinfector itself. For this purpose the room is divided by a solid wall or parti- tion through which the disinfector projects in each direction. A window may be let into this wall to enable persons employed on one side to see and signal to those on the other. The best means of providing access from the infected to the disinfected side is to arrange exits on the side wall of each space leading into lobbies which communicate through doors with a bath-room fitted with a water-basin. Each of the lobbies has a set of overalls and felt slippers for each man, which he puts on as he passes into the corresponding side of the disinfection room, and takes off as he passes out from it, washing his hands and face as he passes through the bath-room. At the end of the day the clothes and slippers are passed through the disinfector and returned to their proper places. The use of overalls and of washing is of some importance in reducing the risk of disinfected objects becom- ing reinfected. Its chief value, however, lies in the fact that at the cost of comparatively little trouble it is an automatic drill for the disinfector attendants in the caution which they must exercise if their work is to be effective. (b) The space allotted to the infected side should be no greater than will 119 DIS accommodate the goods to be treated, facilities for storing, and thus delaying their treatment, being undesirable. The disinfected side, in which the working fittings of the disinfector should be arranged, should be of ample size, with convenience for airing and storing dis- infected objects. (c) The internal facings of all walls, floors, and ceilings should be smooth, impervious, free from angles and as far as possible from joints, unaffected by damp, and ENCYCLOPADIA OF DIS separate as in the case of the infected and disinfected sides of the disinfection room. All surfaces in a collection van should be water- proof and free from seams and angles, so that it can be thoroughly washed with a strong soap-disinfectant at the end of each day. Where only one van is used, or no separation is maintained between vans for collection and for delivery, the van after disinfection at the end of the day should be kept on the disinfected HJ. MARTEN . (A.M, Inst. C.E.) Surveyor, EASTERN DISTRICT. oo — 98" 27 nt MET. BORO. WANDSWORTH. * i Te A A (ZL | ot (ae r r PLZZ. Ur AT Yj a Ly HK J rij ry ZB v} Ge Ly aN IIE Woon fu LO i “Y y Al | tp pile LZIIIZZ y : Y, VAN Steen Arai Formatin | j | Y Hh ChanaEe. Wy \ CHAMBER. p V Des ] 8 Tm Y Le Fer ogres) t ‘l A ol [| core | gee | jf“ LLL 7 wy y DISINFECTED CHAMBER. INFECTED B CNAURER: S Gua vat Qrodl Z Gy pont pal Y Z J | Gren EE siccer: theasnbor Y ] ] Crain ey rales || il Y LS eleey |... @e- L) y 4 © Disinrecren | b/ f Cs Steam ae ‘ol Y g Van SHEp. P\ prsctteneesees 4 ; A I | Seam Chambery Ee ee y sy" AIT CL =z Ly +ZZZB ZL a ee S eee Wi 4S5°0* Fic. 1.—Disinfecting reely guttered and drained so as to allow of copious flushing. (d) All parts of the building should be well lighted; skylights should pre- ferably be double to avoid the risk of condensa- tion and dripping. The windows, &c., should be arranged to give thorough ventilation, but to avoid draughts in the neighbourhood of the disinfector and the disinfected clothes. It is convenient as well as desirable on other grounds to have two vans, one being reserved for collection of infected goods and the other for delivery of disinfected goods. Where this is practicable, the stables should be kept Station, Tooting, 8.W. side. Where the van does more than one journey in the day, it must be washed with strong soap-disinfectant after each journey. The courtyards should be asphalted or con- creted to allow of free flushing. 3. The most important equipment in a disinfection-station is the steam-disinfector. Considerable use was made of steam-disinfec- tion before the facts which affect their efficiency were known ; and very many stations are equipped with steam-disinfectors which give no certainty of real disinfection, and are probably doing some mischief through the 120 DIS false confidence which they engender. Com- plete disinfection of all organisms in practical conditions can be obtained only by the use of saturated steam, free from air and applied at a pressure of 10 to 20 lbs. per square inch for a period which for ordinary objects varies from The omission of any of 15 to 30 minutes. PIPE FROM MUNICIPAL AND SANITARY ENGINEERING. Ih” Ar Pree DIS originally in the disinfector must be displaced by or blown out with the steam which enters ; that is to say, the steam must be applied as a current until the air in the chamber has been removed. The use of what is sometimes called a “vacuum,” but in fact is a partial vacuum only, removes a part of the air. A FOR FOR EXHAUST a: FROM PIT AT LOWEST END Fig. 2.—Showing Plan of Disinfecting Machine and arrangement of Steam Pipes. these conditions may at any time cause failure of disinfection. This danger is the more serious because, when failure occurs, it is seldom possible to trace the return case to the real cause ; and expense may be incurred through continuance of an epidemic and through precautions against some innocent assumed cause, which might have been spared by correct design of the disinfector. To obtain steam free from air, the air “good vacuum ” of this character corresponds to some 20 in. of mercury, and thus leaves one-third of the air in the disinfector; a mix- ture much less efficient for disinfection than pure steam. Apart from the air in the dis- infector, a certain amount will remain in the pores of the mattresses and other thick objects ; this air is removed by periodically blowing off steam from the disinfector after it has been allowed to reach the necessary pressure and 121 DIS has remained at it for a few minutes. Satu- rated steam is usually obtained from an ordinary vertical boiler. It should be passed through a separator before being admitted to the disinfector, so as to avoid the admission of pre-formed water, which retards the penetra- tion of heat and the ultimate drying of the objects under treatment. When the boiler ENCYCLOPADIA OF DIS in each operation should always be secured independently of the attendant. While involv- ing no sensible addition to the cost of working and not much to the first cost of the plant, the use of this precaution is convenient to the attendant in giving him a record of what he is doing. It is still more convenient to the officer responsible for the station, not only in \e “+ qi ol 3, % JAGGED BoLTrs 6°4LOnG INFECTED | ; ae }-— - —— af | I . | | | kK— 3° Mn _—— ne | gl — vo ; T ° eS | S wre 1 Sf, gis cis T DISINFECTED & ¥ dig aus ‘sy Goons = fay SIS C= ah I Qly Wa S116, ry Vet Sie at! “ g k— 751.1 el | I CLOSED WINDOW — IN ONE PANE WOOD OR /RON COVER FOR FIXED 4:6° from Pir NOT SUFPLIED BY GROUND LEVEL MAG C°L? Fic. 3.—Plan of Disinfecting Machine. forms part of the disinfector, care must be taken to see that the steam is not superheated by excessive transmission of heat from the furnace-gases through the shell of the steam- space. This defect occurs in many self- contained disinfectors, and prevents uniform heating and complete disinfection. It also gives rise to scorching of goods, which subjects the authority to claims for compensation. The assurance that all the necessary con- ditions for true disinfection have been attained giving him direct proof that the disinfector has been worked efficiently, but also in enabling him to exhibit this proof to others. The most satisfactory way of obtaining this control is to connect a by-pass from the dis- infector to a gauge which, when the steam in the disinfector is free from air, permits the steam m the by-pass to enter a recording pressure-gauge, on which it traces a curve indicating the pressure attained and the period of exposure. When the operation is 122 Gooos DIS interrupted, as, for instance, on blowing off for the ejection of air from the pores of mat- tresses, the by-pass closes automatically, and the freedom of the steam from air has to be verified again before the steam can pass to the recording gauge and give credit for further disinfection. The apparatus is usually arranged to be worked merely by pushing or NOTE. AFTER DISINFECTOR 15 1 POSITION THE SPACE BETWEEN ARCHWAY & DISINFECTOR TO BE FILLED /N WITH 8RICK, WITH A LAYER OF FELT PLACED BETWEEN. DISINFECTOR € BRICKWORK MUNICIPAL AND SANITARY ENGINEERING. DIS detached and the pores to be filled with dry air more readily than after they have cooled. Where considerable variations are likely to occur in the amount of work to be done at a station, it is possible to economise in steam by installing two disinfectors, of which one serves to do the normal work and the other the excess. In such installations it is usually IM [== rial 1 1 Ke "i dee l i | y I 13 . . Xx . \ . “iE teed ? ae i 2 | poe eT is Si 4 $ | | t 1 Vat y FOR CHAMBE, Eas EXHAUST fiz eee = =S5 ; a | IR f LEVEL g-— 2- pp) ¢ 2°2" | Fie. 4.—Section of Disinfecting Machine. pulling a button, and its use involves no skill whatever. In most disinfectors means are provided for drying thick objects, and it is very important that they should be rapid and efficient, so as to avoid scorching and damp- ness. Immediately on removing the objects from the disinfector they should be thoroughly shaken and hung up or laid out to air, as their relative high temperature enables the film of steam which hangs about them to be better to have two sizes of disinfector, say 7 ft. 6 in. by 4 ft. 3 in. diameter and 9 ft. by 6 ft. diameter. An alternative method of getting excess of work out of a disinfector is to have an auxiliary drying closet, which is used to relieve the disinfector for the period ordinarily occupied in drying. With this arrangement the drying closet must be larger than the volume of the disinfector which it relieves, as the transfer of goods from the 123 DIS disinfector to the closet entails a certain amount of condensation anda proportionately longer period of drying. Given such a closet, the work done by a good disinfector may be approximately doubled when it is relieved from the duty of drying. A drying closet may be worked with a fan or by natural ventilation, and is best furnished with “horses ’’ to draw out as in laundry practice. The disinfector should drain into a steam trap, to avoid nuisance and loss from escaping steam. If drying coils are used with steam at a higher pressure, a separate steam-trap will be required. If the exhaust from the disinfector is a nuisance, it may be fitted with a condensing silencer. The disinfector and boiler should be thoroughly well lagged to reduce the loss and inconvenience due to escape of heat. A disinfector should always be warm before goods are put in it for treat- ment, and they should be removed as soon as the operation is over. Where the funds necessary for a disinfector for absolute dis- infection are not available, a low-pressure or a non-pressure disinfector must be used. The design of such a disinfector must be such as to drive the fastest possible current of steam through the disinfecting chamber. Longer time must be allowed both for disinfection and for drying them in disinfectors working at higher temperatures. Such disinfectors are perfectly sufficient for dealing with enteric fever, diphtheria, cholera, and certain other diseases associated with sporeless organisms. There is no evidence that they can be depended on to disinfect from small-pox, scarlet-fever, or measles. Steam for a disinfector may be derived from a neighbouring destructor station. In this and other cases in which steam is brought to the disinfector from a distance the efficiency of drying and, to some extent, of disinfection depends largely on the pipe-run being well designed and the pipes thoroughly lagged. 4. The accessory appliances needed for a disinfection station are: (a) convenient racks for airing and stacking disinfected objects. The best airing racks are of steam-heated ENCYCLOPADIA OF DIS tinned copper pipes. They are more costly than wood, but take less labour to keep clean, last longer, and are much more rapid in operation. (b) A small tank for chemical disinfectant, such as permanganate of potash, so that spots of organic matter may be damped before steam- disinfection, to prevent them from leaving fixed stains. (c) A boiling tank for objects too stained with organic matter to make it desirable to go over them with cold disin- fectant. Such a tank is preferably made in two parts, one over the other, communicating by two tubes which enter the lower tank at different levels, and arranged so that the liquid contents of the lower tank boil up into the upper tank and there steep the clothes, &e., circulating continuously from lower to upper tank, and ultimately falling back into the lower tank at the end of the operation. This construction ensures the constant expo- sure of the clothes to boiling water ; and by putting washing soda in the lower vessel both the temperature of the boiling water and its cleansing power are raised to a very valuable extent. Where practicable the tank should be arranged like the disinfector through the partition wall, the goods being slid in under water from the infected side and taken out on the disinfected side. (d) A spray disinfector for dealing with objects such as furs, leather, &e., which cannot stand steam. (e) Hose and flushing apparatus enabling all parts of the station to be flushed down. (f) Bath and basins for attendants with hot and cold water. If cleansing of persons is undertaken, two other separate baths, for men and women respectively, should be provided in a room adjacent to the disinfector room, so that the clothes of persons may be disinfected and deverminised while they are in the bath. (g) A store for the utensils (spray-disinfectors, brushes, bottles, soap, &c.), served out to the house-disinfectors in their daily rounds. (h) An incinerator for burning objects not worth disinfection. W. Dz. Distemper.— A water paint made by mixing refined chalk with water and an 124 DIS agglutinant such as ordinary size, colour being added when desired. Ordinary white- wash is an example of a distemper. Of late years ordinary distempers are being used less than formerly, their place being taken by washable water paints or distempers. (See “Paints AND PaIntING.”’) Distributors, for Sewage.—An essential feature of the ‘‘ percolation bed” for the dis- posal of sewage lies in distributing the liquid uniformly, and at a suitable rate, over the whole of the surface of the bed, so that it may percolate through by dripping slowly from particle to particle of the filtering material and thus become thoroughly exposed to the air and the nitrifying influences of the bed. This object is accomplished in a variety of ways, that most generally adopted being distribution by means of a continuous rain- like shower from revolving “sprinklers” working in a horizontal plane on the Barker’s mill principle, or by means of “jets” or nozzles placed in rows of fixed pipes carrying the sewage under a head of from 5 to about 10 ft. In some cases the same object is sought by the employment of distributors travelling on rails and carrying a series of buckets or nozzles arranged to embrace the full width of the bed. At small works distri- bution has also been affected, with varying degrees of success, by means of balanced trays or tippers, and sheet-iron gutters or troughing. Whatever form of distributor is adopted, it is important that it should distri- bute the liquid uniformly without interrup- tions from wind, frost, or other atmospheric conditions, that it should not easily stop through clogging of small holes and that it should be easily and quickly cleaned. It should be self-adjusting to variations of flow, and the bearings and central moving parts” through which the sewage is admitted should be of special and appropriate design. The means first adopted for distributing sewage over percolating filters consisted in the use of a fine surface material over which the sewage was flushed and distributed by flooding. The MUNICIPAL AND SANITARY ENGINEERING. DIS result, however, was not satisfactory as the top layer and coating greatly impeded aéra- tion and led to unevenness of distribution. Trials were also made with both wooden and iron troughs provided with holes and notches placed over the surface of the bed at intervals of 2 or 8 ft., but the difficulties of keeping these level and the notches clear contributed largely to unevenness and cost of distribution insomuch that the system is found almost impracticable except for small installations. A greatly improved iron trough and tipper arrangement has been introduced by W. E. Farrer, of Birmingham. With the object of securing more constant and uniform distribu- tion than is obtained by troughs, a distributor, constructed of a special form of corrugated iron sheets, was introduced by F. Stoddart, of Bristol, and over this the sewage runs from the main carrier into small channels formed by the corrugations. The sheets are punched with numerous holes to allow the sewage to drip through uniformly on to the beds from a great number of small points thus provided. It is necessary, however, that the sheets should be absolutely level and the holes kept clear from obstruction by frequent brushing. At Lichfield, about the year 1898, a system of perforated pipes, working under pressure as suggested by Mr. Garfield, was introduced and has since been working satis- factorily. The ‘“ jets’? work under a head of 7 it., and the sewage is discharged in fine sprays by the use of small metal plates placed over each jet upon which the liquid impinges and is thus scattered over a wide area. The whole series of distributing pipes are so arranged that they can be turned through an angle of 45° and the jets thrown first on one side of the tube and then on the other, thus securing a good and even distribution. A somewhat similiar arrangement is in use at Chesterfield, but here the quantity of sewage is varied from time to time by an automatic ejector. The liquid as it impinges on the iron plates over the holes in the distributing pipes is thrown in a circle all around, the radius of which narrows as the head or pressure from 125 DIS the ejector diminishes, so that each part of the filter is alternately sprinkled. Perforated distributing pipes are also used successfully at Brownhills and Pelsall in Staffordshire. Here the available head is less than a foot and no effort is made to spray the jets, but the surface of the filter is formed into low Fig. 1.—Gjer’s & Harrison’s Nozzle used at Salford. ridges between which the distributing pipes are placed. At Salford, sprinkling filters were first constructed in 1899, and have been added to from time to time. The precipi- tating tank liquor is passed through roughing filters of 2 in. to 4 in. mixed gravel, to hold back suspended matters find- ing their way through the tanks, and is then distributed over percolation beds of clinkers of an average depth of about 5 ft., by means of 4 in. fixed pipe distributors in which sprinkling “jets” are placed working under a 4 ft. head. Figs. 1 and 2 illustrate the description of nozzles used. The Salford aérating filters deal with the roughing bed liquor at the rate of 500 gallons per square yard on filters 5 ft. deep, or equal to 278 gallons per cubic yard of filtra- tion material ; in some cases this rate, though large, has been exceeded. Fixep Spray Jers.—The best example of the extensive use of fixed spray jets of good pattern is on the works of the Birmingham Fic. 2. Sewage Spray Nozzle, used at Salford. ENCYCLOPADIA OF DIS Tame and Rea Drainage Board at Curd- worth and Minworth. Here large areas of rectangular filters have been constructed over which the tank liquor is distributed by means of fixed pipes fitted with Bryan’s jets (Fig. 3) as supplied by Jones & Attwood, Engineers, of Stourbridge. The distributing pipes are of 3 in. diameter, spaced 9 ft. apart, and carried by cast-iron chairs on the surface of the clinker. The pipes are of a light iron hot water weight 5% in. thick, with bosses for the jets cast on at 4 ft. 6 in. centres. These LZ Fic. 3.—Bryan’s Fixed Jets, as used at Birmingham. bosses carry brass sprinkler jets. The head or pressure at the jetis about 7 ft. 6 in., giving a discharge of 400 gallons per square yard per day. This rate, however, is reduced by plugging some of the jets or by regulating the valve on the main supply pipe. In some cases there is an arrangement of distributing pipes and sprinklers suitable for, working with alternate jets (Fig. 4). A sprinkler is placed in each alternate hole and the intermediate holes are stopped with wood plugs, or shut off by turning the centre plug in the adjustable head form of the jet. The dark circles represent the distribution when working one set of sprays, and the light circles give the effect when using the alternate jets, thus securing good and uniform distribution. The arrange- ment of piping, spacing, &c., may be modified 126 DIS to suit any shape of bed, head of pressure available, or rate of distribution required, and 2 VALVES TO WASHOUTS MUNICIPAL AND SANITARY ENGINEERING. DIS this limitation does not obtain and other circumstances are favourable, distribution by 4°VALVES TO WASHOUTSS, LL LLL <3, “ont v6.7 4/DIMY PIRE—P Fic. 4.—Diagram of Jones & Attwood’s Distributing Pipes and Sprinklers. before planning a system of piping for any given scheme of beds, the safest plan is to experiment with a few lengths of piping and jets under the actual head available in the permanent works so as to accurately arrive at the proper spacing of pipes required and the rate of discharge per square yard of bed. As the liquid descends in a fine spray it passes down into the filter and induces a light current of air to follow, thereby maintaining the aérobic conditions required for the proper oxidation of the sewage. There is no doubt that the fine spraying greatly assists the oxidation of the liquid, but there is risk of nuisance from smell if septic sewage is used— a danger which disappears when dealing with average domestic sewage treated whilst fresh. The minimum head consumed in the working of the jets is from 5 to 6 ft. for securing the best results, a consideration which may prohibit the use of this system in situations where the available fall is limited. But where this means has many advantages. Under suit- able conditions it is economical and simple in construction as compared with other methods Fic. 5.—Arm Jet Sprinkler, H.S. Type, Hinged - Saddle and Clip, with Brass Arm, Cone, and Nozzle. of distribution, requires no skilled labour in attendance, possesses no working or moving patts, and where the sewage undergoes 127 DIS proper preliminary preparation, requires but little attendance under ordinary working conditions. In addition to Birmingham, this mode of distribution is used by the Corpora- tions of Tunbridge Wells, Darwen, Carlisle, Crieff, and others. Spraying nozzles were adopted at Birmingham, after careful comparison of various methods, as being the least costly system of distribution for large areas of filters. There is practically no reasonable limit to the size or shape of beds to which this system may be applied, but there is a certain drawback in the necessity of workmen walking over the surface of the filter to attend to the jets. The “ Arm jet” shown in Fig. 5 is the most effective in distribution, and gives no trouble as regards stoppage— ENCYCLOPEDIA OF DIS type of distributor, ingenious application has been made of the “‘ Barker’s Mill” principle. The revolving distributor consists of a number of perforated iron pipes radiating from a central pillar through which the sewage is supplied. The holes in the distributing pipes being all Candy - Whittaker Secinkler t ensali N ee NH y NH Fic. 6.—Sewage Spray Nozzle, adopted at ===_e=sn RK Columbus, Ohio. C 0 this latter feature being a great advantage. 7 " EE A solid plug of sewage water issues BR A cts ; through the “‘ brass nozzle”’ fixed in the Check ring NAN Check rig distributing pipe and impinges upon the, | ie NZ “brass cone,” held in any desired position rece tereury Seal by an adjustable arm soas to regulate the a quantity discharged and width of spread. CESS A These jets are in use at the Birmingham PTTL P sewage works, and on percolation beds at H ] ; f U one of the sewage farms of the Tunbridge 4 ‘3 Y Wells Corporation. A “jet” of the form yy shown in Fig. 6 has been adopted at Columbus, Ohio. The rotary and travelling systems of dis- tribution, whilst overcoming some of the drawbacks attendant upon theabove-mentioned methods, atthe same time create new objections peculiar to these systems. With a view of overcoming the difficulty in regard to the pro- vision of motive power for driving the rotary Fic. 7.—Candy Distributor. on one side the reaction of the escaping jets of sewage liquor causes the pipes to revolve around the central supporting pillar thus dis- tributing the liquid over the circular area commanded by the length of the arms of the distributor. Much care is required in properly apportioning the sizes and spacing of the 128 DIS discharge holes in the arms in order to secure uniform distribution over the whole surface of the filters. The outer ends of the arms obviously travel over a much greater area than those parts nearer the central pillar, so that the number and size of the perforations must be proportionate to the distance from the centre in order to secure equity of dis- tribution as far as possible. The difficulty of uniformity of distribution is particularly marked in rotary distributors of large diameter as the rate of discharge neat the central pillar differs widely from that at the outer extremity, and, in order to, meet this as far as possible, the perforations near the centre are widely spaced, whilst those at the outer end are very close together. Another attempt to meet the same difficulty is to have some of the arms perforated for distribution on the outer extremity only of the filter with a lesser number perforated for the inner or central ring only. Even with these adjustments some portions of the filter will be sprinkled at a higher rate of discharge than others. Another point requiring careful consideration arises from the fact that the sewage is ad- mitted through the fixed pivot at the centre of the filter, and difficulty has been experienced in providing a suitable joint between this pivot or supply pipe and the arms revolving around it. In Adam’s ‘‘ Cresset”’ distributor the central’ joint or coupling is a simple air- lock trap, formed by the locking in of a body of air between the outer and inner annular spaces of the lower tank and the body of the distributor which is suspended over and dips into the water seal below. Thus the cylinders shown revolve in water, and loss by friction in the centre joint is reduced to a minimum. The illustration also shows the cross-head where the weight of the distributor is mainly carried by independent bearings of hardened steel balls running in steel grooves. These ball-bearings and races may be removed and replaced without dismantling the apparatus. The distributor is well balanced, but if any settlement should occur the ‘‘ head” may be pushed over by the adjusting screws, thus M.S.E. MUNICIPAL AND SANITARY ENGINEERING. DIS avoiding the taking down and re-setting of the distributor. A simple method of lifting the weight of a sewage distributor off its bearings for clean- ing or repair consists in the provision of a vertical screw at the top of the central standard. Fig. 7 is a section of the central pillar of the “ Candy-Whittaker” distributor of the Patent Automatic Sewage Distributors, Ltd., London. To raise the weight of the distributor clear of the bearings it is simply pushed round in the reverse direction to that in which it rotates when working, when the top block from which the distributor is suspended raises up the screw and so clears the bearings accessible for repair, cleansing, or renewal. The ball-bearings again take the weight as soon as the distributor is lowered by starting to revolve in its ordinary working direction. Another feature of this distributor is the provision of a “‘ mercury seal” for the central joint which is quite water-tight so long as of sufficient depth. A gun-metal ‘‘check-ring’’ is also provided to prevent the forcing out and loss of the mercury through any sudden increase of sewage pres- sure beyond the weight of the depth of seal provided. A ‘‘moisture-proof oil seal” is arranged atthe top of the central pillar for the purpose of preserving the ball-bearings carrying the weight of the distributor, and these bearings again are run in an oil bath. This distributor is very extensively used by a great number of public authorities, and the results of much practical experience have been em- bodied in its design. In the circular distributor made by Geo. Jennings, Ltd., the centre joint is above the level of the sewage in the revolving arms instead of below as in the previous cases, and the sewage is discharged from the central supply pipe into an annular trough, to which the distributing arms are connected, by means of siphons. Farrer’s “Facile” siphon fed distributor may be connected direct to the septic tank, and thus works with a minimum loss of head. The construction of the joint with the central 129 K DIS supply pipe in the circular distributor of the Ames-Crosta Sanitary Engineering Company is shown in Fig. 8. It is formed of two gun- metal rings with annular grooves and projec- tions as a seal against the escape of the liquid. One ring is fixed to the supply pipe and the Fic. 8.—Ames-Crosta & Co., Sectional Sprinkler Pillar. other to the revolving distributor. Between the rings is placed a rubber or metal dia- phragm. The weight of the distributor is carried on ball bearings in the top of the centre pillar, which are readily accessible by means of a raising screw for lifting the dis- tributor off its bearings. It is claimed that ENCYCLOPAEDIA OF DIS the distributor will work with so small a head as 8 in. Scott Monerieff’s circular power-driven distributor, erected for experi- mental purposes at Hanley, produced an excellent effluent owing to the efficient dis- tribution secured by its means, but it proved costly to maintain and was replaced by a power-driven distributor of a lighter design introduced by Hartley & Son, of Stoke-on- Trent. Hartley, Causton, & Co., of Stoke-on-Trent, have introduced a power-driven eircular sewage distribuior as illustrated in Figs. 9, 10, and 11, which may be seen in use at the Hanley sewage works. The electric motor is fixed at the end of the distributor as shown, and travels on a rail around the outside wall of the bed: the arms are carried at the centre on ball-bearings. The sewage flows through a stuffing-box centre tube upwards to the balancing arm and the main distributing arm at the same time. The sewage is distributed through a number of sectional distributing tubes arranged in échelon to facilitate cleans- ing. The horse-power required to drive the distributor is less than half-horse power per acre of bed, and the apparatus can be regu- lated to increase or decrease the dose of sewage from the smallest quantity to 2,000,000 gallons per acre per day. Rotary distributors are also made by Mather & Platt, Ham, Baker & Co., and others, and one of the turbine ring-drive type is manufactured by the Septic Tank Co.,Ltd. At Worcester, a self-propelled’ Candy-Caink sprinkler (Fig. 12) of an unusual type is in use. The sewage of a population of 50,000 persons is first prepared in two disin- tegrating tanks, each having a capacity of nine hours’ dry-weather flow, and is then lifted to the filters by two 45 h.-p. electric motors and two 90 h.-p. gas engines fed from a suction gas plant. The tank liquor is treated on six circular percolating filters, each of 200 ft. diameter, upon which the sewage is delivered by means of Candy-Caink distributors, fitted with Caink’s patent jets. These filters are of washed local gravel 8 ft. in depth. The storm water beds can also be used as straining 130 DIS DIS MUNICIPAL AND SANITARY ENGINEERING. ‘sroyngiysiq, Lope ‘OT “LL NW1d “ a advilduvd YOLOW ONI i aac 3 f= wiv OL orang wive 7 + L2ViNOD ONIATONIS ‘6 OL K2 131 ENCYCLOPADIA OF DIS or mechanical filtration beds for removing the fine suspended matter from the percolating bed effluent, and there are also 17 acres of land available. The sprinkler has only one distributing arm and this is supported by three wheel carriages running on three con- centric tracks, one in a small well at the centre, one near the circumfer- ence of the bed, and one at an intermediate posi- tion. The distributor is supplied by means of a siphon from a stand-pipe at the centre of the filter. The siphons from all the distributors are connected by means of air pipes carried to the engine- room where they connect with a vacuum chamber, and the beds are thus readily controlled by opening and closing the necessary taps or valves in the engine-room for the purpose of starting the siphon feed to each bed as required. The distributors were supplied by the Patent Automatic Sewage Distributors, Ltd., of Westminster. Ns! genann pp-\\\ SECTION.AB. “FO al C TO MAIN TUBE. VALVE OPEN zziza\\ PP = BRUE & | PLAN SHEWING RELATION OF SECTIONAL TUBES f ag A OO} Ve SSSECTIONAL OEFLECTORS HTM JoscosreHIIR Fic. 11.—Sectional Distributing Tube of Hartley Circular Sewage Distributor ee ae C PP FS In another type of 2 a rotary distributor for —— circular beds the rotating A) . ta arms are fitted as small water wheels, with a number of buckets or troughs around the cir- cumference and extending throughout the length of the arm. The apparatus INTERIOR OF SECTIONAL MM — DEFLECTOR PLATE SECTION.A.B. fi DOOR OPENED FOR CLEANING | 182 be DIS is supplied with sewage, by means of a feed pipe from the centre of the filter and rotates upon circular rail tracks at the centre and MUNICIPAL AND SANITARY ENGINEERING. DIS aérating from time to time. The water-wheel type of distributor is less satisfactory than the rotary and fixed spray type in this respect, Fic. 12.—Sewage Distribution at Worcester: Self-propelled Candy-Caink Sprinkler. periphery of the filter. The ‘“ Fiddian”’ distributors for circular filters as introduced by Birch, Killon, & Co., engineers, Man- chester, are of this type, and one is in- stalled at Fazakerley for the Liverpool whilst the initial cost and maintenance is also heavy. Siphonie feeds to distributors are oftentimes troublesome through risk of “air- locking,” and the introduction of mechanical Corporation. The propelling power for the class of distributor shown in Fig. 18 is also developed on the principle of the water wheel, but instead of taking a circular path the apparatus travels backwards and forwards over filters of a rectangular shape, thus securing great economy of space as compared to the circular form of bed. The most effective method of applying sewage to bacteria beds is in the form of a small jet or fine spray, and in selecting a distributor it should not be one of the type which dashes the sewage on to the bed in bucketfuls so as to cause rapid down- ward flushes through the bed. The dis- advantageous effect of this is minimised by using a fine top layer over the surface of the bed, but this will usually need cleaning and Fic. 13.—Ham, Baker's Travelling Distributors. joints between the fixed and moving parts of such apparatus, as by means of an ordinary stuffing-box and gland, causes much friction and resistance to the rotary movement of the distributor. Efforts have also been made to 133 DOR develop power for driving distributors by passing the sewage through a turbine inter- posed between the central supply pipe and the distributing arms, but the advantage would appear to lie with the ‘“‘Barker’s mill” principle inasmuch as the reaction of a jet issuing from the distributor arm at a distance from the centre of rotation must be more effective than a similar jet escaping close to the centre and with a very short leverage through which to act. The influence of the wind has an important effect upon the working of moving distributors propelled by a small head only of sewage liquor, and in some cases they are frequently brought to a standstill, thus permitting the liquid to pour upon the filter at one spot and stream through the bed to the effluent channel in an untreated condition. The effects of continued severe frost and snow occasionally derange the working of distributors, but where they can be kept in full use throughout the 24 hours the warmth of the sewage itself is generally sufficient to prevent freezing. If the distributor is not in full use it is best drained off dry to avoid bursting of pipes, &c., should freezing of the water contained therein occur. The distribution of the sewage by all existing forms of distributors may at times be far from perfect, especially where only a limited amount of attention is given, so that it becomes import- ant to have sufficient depth of bed to distribute and equalise such imperfections. W. H. M. Dortmund Settling Tank.—This is a circular conical-bottomed precipitating tank first tried at Dortmund, in Germany, by Carl Kinebihler, and afterwards at the Chicago Exhibition. The sewage, after preliminary settling in an ordinary horizontal tank, passes down a vertical central downpipe about 3 ft. 6 in. in diameter, to a depth of some 30 ft., where the sludge settles in the conical shaped bottom. Radial arms are provided at the upper end of the conical portion of the bottom of the tank for the purpose of dis- tributing the sewage evenly throughout. As it consolidates the sludge in the apex of the ENCYCLOPADIA OF DRA cone is pumped out by a 6 in. suction pipe. This type of tank, like others which are off- shoots of the same original idea, embodies a good principle in the continuous upward flow of the sewage with a downward movement of the sludge, but in practical working has not given the satisfaction first contemplated by many, inasmuch as the sludge does not always gravitate into the cone but floats or settles on the sides, where it decomposes. Colonies of bacteria also form, and these together with the putrid sludge pass off with the effluent. Matters may, however, be improved by removing the sludge daily, by adopting a revolving scraper for cleansing the internal surfaces of the tank walls, and by having the tanks in duplicate. Dosing Tank.—The name “ dosing tank” is applied to a small chamber placed between the precipitating or settling tanks and the contact or percolating beds for the purpose of accumulating a sufficient volume of liquid for distribution on to the filters in cases where the flow of sewage is small during certain periods of the 24 hours. Where a rotary distributor is used, in the case of a small works, the flow may fall during the night to such an extent that the distributor will not revolve, and in these circumstances the sewage is stored in a ‘“‘dosing tank” from which it is discharged in bulk, by means of a siphon or other suitable contrivance, on to the filter beds, which are thus afforded inter- mittent periods of rest. Drainage—Cast-iron.—Cast-iron drain- age differs from ordinary house drainage only as regards the materials of which the under- ground drains are constructed. It has many advantages over stoneware drainage, whereas only one drawback may fairly be urged against it, and that is the question of cost, which is about 80 °/, more than that of stone-ware ; but having regard to the security obtained by the use of iron, it is, doubtless, the most economical material in the long run. Apart from having a longer life than stone-ware drains, in itself a great advantage, cast-iron 134 3 # ‘ “3 ? ies yee i ae DRA drains are also superior in other respects. In the first place the pipes are made in longer lengths, there being a joint every 9 ft. in an iron drain as against every 2 ft. in a stone- ware drain. As itis generally accepted that the fewer joints there are in a drain, the Fie. 1. fewer chances there are for imperfections, the advantages of iron over stoneware would be in the ratio of 44 to 1. It follows from this also that the time occupied in laying a given length in each material, and conse- quently the cost of labour, is distinctly in favour of theiron drain. Secondly, the joints of iron drains can be made in all weathers and in all soils, which is a great consideration in the case of drains constructed during periods of frost or rain or in water-logged ground— conditions which would seriously interfere with the making of stoneware pipe joints. In the third place, there is a greater likelihood of a stoneware drain giving way, owing to pres- sure, settlement of the ground, or to vibration, such as that produced by an underground railway or by heavy vehicular traffic, by reason not only of the increased number of joints and correspondingly increased number of points of possible rupture, but also because of the more brittle nature of the materials of which both the pipes and the joints are made. In the fourth place, iron drains may be laid in MUNICIPAL AND SANITARY ENGINEERING. DRA a variety of ways which would be impracticable in the case of stoneware drains. They may be fixed openly against walls or suspended from ceilings (see Fig. 1) where the lowest floor of the building is below the level of the public sewer, or they may be laid, subject to proper fixing, above the floor of a basement or in a culvert. They will be as safe there as if laid underground, and possess the advantage that every portion will he easily accessible and visible. On iron piping the manholes may be made on the piping itself, as shown in Fig. 2. This will obviate the necessity for constructing air and water- tight brick manholes. A further advantage of cast-iron over stoneware drains is that the former do not require continuous con- crete foundations except in cases where the ground is particularly bad. In most cases it will be sufficient to provide a concrete pier about 1 ft. square and from 6 in. to 12 in. deep according to the nature of the ground under each socket. All cast-iron pipes used in drainage work should be made of good tough grey iron of the second melting run from the cupola. The pipes should be cast with sockets downward and with an extra head of at least 1 ft. of metal. All pipes above 4 in. in diameter should be inclined My \ 4 wt Fig. 2.—Access Pipe or Hatch Box on Iron Drain. at an angle of 45°. The pipes should be straight, true in section, even-in thickness of metal, perfectly smooth inside, and free from air and sand holes and other defects. Their sockets must be strong, deep, and sufficiently wide all round to leave room for caulking up 135 DRA the joint ; whilst the spigots of the pipes must be provided with a bead on the end. This bead causes the spigot of one pipe to lie in the socket of the other in such a way that the pipes are concentric when joined. The bead will also ensure an equal annular space all round the inside of the socket, and help to keep the lead used in making the joint from running into the interior of the pipes. The walls of the sockets should not be less than } in. thicker than the walls of the pipes, whilst the internal diameter of the sockets should be from 4 in. to # in. larger than the external diameter of the pipes, so as to leave a suffi- ciently large annular space all round the pipes for the lead joints. The pipes must be capable of withstanding a pressure of 200 ft. head of water, and must be coated, both inside and out, by some anti-corrosive solution, such as Dr. Angus Smith’s composition, to prevent deterioration through oxidation. For the proportions and weights of cast-iron pipes see article ‘‘ Cast-1ron Prpxs.” The joints of iron drains should be made with molten lead well caulked whilst cooling. G.J.G. Jd. Drainage, House.—The objects to be attained in carrying out a perfect system of house drainage are:—1. The disconnection of the drains from the public sewer or other outfall. 2. The disconnection of the rain and waste-water pipes from the house drains. 8. The thorough ventilation of the whole drainage system. 4. The entire and immedi- ate removal of all matter discharged into the drains. 5. The provision of means of access for inspection, testing, and ‘cleansing of the drains. 6. The construction of the entire system in such a manner and of such materials as shall preclude the possibility of leakage of either liquids or gases. 1. Of these requirements the first is attained by breaking direct aérial communication be- tween the drain and sewage outfall by the insertion of a ventilated disconnecting trap (see article ‘“‘ Disconnectinc Traps”) at the outlet end of the drains. For convenience of ENCYCLOPADIA OF DRA cleansing, &c., this trap is best fixed in a manhole; the drain or drains discharging into it terminating in an open channel running into the trap. This disconnection is desirable for the protection of the house drains against infection from sewers, be that infection merely one of fouled air, of dangerous gases, or of germs of disease. 2. Secondary disconnection is effected by breaking the direct communication between waste-water and rain-water pipes and the drains by the use of gully traps. These are placed at the heads or inlets of all drains that do not take water closets or soil pipes, and serve to shut out from the waste and rain- water pipes, all vitiated air generated in the house drains themselves. The pipes may be discharged over or beneath the gratings of the gullies, but must in all cases have their open ends above the level of the water standing in the traps, which latter must be fixed in the open air. It occasionally happens that a waste pipe or rain-water pipe must of necessity pass down in the interior of the house. In such a case it should be continued below ground in a horizontal position (at a proper fall) to the exterior, and there discharged over a gully. Should this arrangement prove impracticable, the gully may be fixed within the building, but as there is a chance of its water-seal evaporating and consequently of foul air being liberated, the gully must be hermetically sealed at the ground level and the waste pipe provided with an air inlet opening terminating in the open air. 3. The third object named as being neces- sary to ensure a sanitary system of drainage is ventilation. This is essential in the first place to secure proper disconnection, and secondly, for the oxygenation of the interior of the drains or pipes, and for the dissemination of such gaseous products as may be generated in the drains or waste pipes. For proper ventilation there should be both inlets for fresh air and outlets for vitiated air. Moreover, if ventilation is to be complete, the inlets and outlets must be, as far as practic- able, at the extreme opposite ends of the 136 DRA drains or pipes to be ventilated. It is, more- over, necessary that the inlets and outlets should be at appreciably different levels, since there will otherwise be a tendency to equili- brium due to the collection of the heavier gases, such as carbonic acid gas, at the lowest points of the drains, &c. Soil pipes, having in any case to be carried up above the roof of the building upon which they are fixed, provide convenient and inexpensive up-cast ventilation shafts, and are, therefore, usually made use of for the purpose. If it is possible to so arrange the soil pipes that they may ventilate the whole drainage system, no other up-cast shafts will be necessary. Taking the case of a small house, or of an ordinary town house, for instance, if the soil pipe is at the head of the drain, through-ventilation is attained by the provision of an air-inlet at the opposite end of the system. In cases where the soil pipe is centrally placed a second up-cast shaft will be necessary at the head of the drain, or alternatively an air-inlet at each extremity of the system. This latter method is not permitted by the by-laws of many towns. In other cases, where one or more long branch drains exist, the head of each must be provided with a ventilation shaft. This arrangement, however, involves the splitting up of the air-current drawn through the inlet, and tends to produce inefficient ventilation as the air usually travels through the path of least resistance, and possibly woula only occasionally reach some of the outlet shafts under favourable cireum- stances. It is desirable, therefore, in an extensive drainage scheme, to subdivide the system by judicious trapping and to provide a separate air-inlet to each section. Short branch drains require no special provision for ventilation, as the flow through them will as a rule suffice to displace the air contained therein and so bring it under the influence of the air-currents in the main drains. Ventila- tion shafts, other than soil pipes, should not be less than 4 in. in diameter, and should preferably be constructed of lead piping. Cast-iron pipes, although frequently used, MUNICIPAL AND SANITARY ENGINEERING. -Cases. DRA being cheaper, are not desirable, as they are acted upon by gases occasionally present in drains and also rapidly deteriorate by rusting. Soil pipes should not be less than 84 in. in diameter, nor more than 4 in., and may be made of drawn lead piping of not less than 8 lbs. to the superficial foot, or of heavy cast- iron piping. In the case of soil pipes washed by sewage, the iron is protected from deteriora- tion by the slimy film which soon forms on their interior. That portion of the pipe which lies above the highest closet and receives no sewage should, however, be of lead in all All outlet ventilation pipes should be carried up full bore, above the roof, and terminated well out of the way of windows and chimneys. Their openings should be protected against blockage by domical copper wire guards. Cowls are not necessary, nor advisable, as they frequently only serve as shelters for birds’ nests. Inlet ventilation pipes should be arranged to have their openings in positions where they are not liable to cause annoyance should there be a back-draught from the drains. They may then be simply protected by open gratings. The mica flap valves frequently made use of for shutting off occasional back currents from the drains are not desirable fittings, as they are very liable to get out of order, and, either to leave the inlets open at all times or to permanently close them. The proper ventilation of waste pipes, by which is under- stood the discharge pipes of sinks, baths, and lavatories, is important, not only to prevent them from becoming foul, but also because the traps of fittings discharging into them are liable to lose their ‘‘seal,’’ should the waste pipes be unventilated (see ‘“‘SrpHonace”’). The not unusual practice of constructing waste pipes with hopper heads, into which the dis- charges of various fittings are collected, is not desirable, because if ventilated near windows considerable nuisance arises. The pipes should be continued up to above the eaves of the roof for ventilation in a similar manner as soil pipes, and the branches from the fittings connected to the main stack pipe. 137 DRA This, of course, is only necessary in the case of waste pipes from fittings fixed upon the upper floors. Short waste pipes from fittings on the lowest floor are sufficiently well venti- lated by the provision of ‘‘ puff” pipes carried to the exterior. Where a number of fittings discharge into a stack pipe common to all, the trap of each fitting, other than the highest one on the stack, must be further ventilated by an anti-siphonage pipe, which may be branched into a main ventilation pipe taking them all and carried up to the eaves inde- pendently (as shown in the illustration under the article “ SrpHonace”’), or branched into the ventilation pipe from the waste pipe above the level of the highest fitting on the stack. This applies also to the traps of water-closets where a number of these fittings discharge into one soil pipe. 4. The immediate removal of the sewage discharged into the drains is dependent upon proper gradients, suitable dimensions, and efficient flushing arrangements. In size, the drains should be as small as practicable, as this will tend to cleanliness and a rapid discharge. Thus a flow of sewage which will cause a 4-in. drain to run full and to be self-cleansing on account of the thorough flush which it receives, will not even half fill a 6-in. drain; while a 9-in. drain would only run about one-quarter full. As the mean velocity of sewage flowing through a drain varies directly (up to a certain point), as the depth of the flow of sewage, the drain in which the sewage flows deepest (i.e., the smallest drain) will have the greatest scouring and cleansing flow. Moreover, in an un- necessarily large drain, which is never properly flushed, there is room for splashing and for the deposit of sewage matter, a condition of things which is opposed to true sanitation. In design- ing a system of drainage the probable flow of sewage should be carefully calculated, as also should the possible amount of rain-water to be removed. Should a small drain, say a 4-in., be found insufficient to take the whole flow, it will be desirable to provide a small drain for the sewage proper and a certain amount of ENCYCLOPAEDIA OF DRA the rainfall, and to lay a second drain for the removal of the remaining rain-water. This course is preferable to the laying of a large drain which would only be thoroughly cleansed during periods of heavy rains. No less im- portant than their sizes are the gradients of the drains. It should be borne in mind that even the smallest drain (which in practice should not be less than 4 in. in diameter) will only run full, or nearly so, under exceptional circumstances. During dry weather, for instance, the flow through the drains will consist merely of excrementitious matter and waste water, the bulk of which will be delivered into the drains spasmodically through waste pipes considerably smaller than the drains. It is, therefore, necessary in laying a drain not only to make use of small piping, but also to lay it at gradients which will provide it with a self-cleansing flow, that is, with a flow sufficiently deep to float fecal matter to the outlet. In an excessively flat drain the flow of sewage will be so sluggish as to permit the deposit of the heavier portions of the sewage. In an excessively steep drain, on the other hand, the depth of the flow may be so small as to be insufficient to float the larger particles of sewage to the outlet of the drain. Both extremes must, therefore, be avoided. The most suitable falls for drains are those which will impart to the sewage a velocity of 8 ft. per second when the drain is flowing quarter full, or, what is equivalent thereto, a velocity of 4 to 5 ft. per second when flowing full or half full. These falls are roughly :— For a 4 in. drain 1 in 40. a ‘its. 1 ,, 50. » 6in. ,, 1 ,, 60. » gin ,, 1 ,, 90. These gradients should, as far as possible, be adhered to in all cases. Where the fall available is not sufficient to give these gradients throughout the system, the branches should be 1388 DRA so laid and the main drain given a somewhat smaller rate of fall and provided with means of flushing, rather than sacrifice the self-cleansing gradients of the branches, which cannot be coveniently flushed individually. As already stated it is only occasionally that any con- siderable volume of sewage is discharged through a house-drain at one time. During the periods of minimum flow, therefore, even the best of drains will be far from self-cleansing, and it is therefore desirable that all drains should: be periodically and efficiently flushed. Automatic flushing is of the greatest assistance, not only in keeping a drain free from deposit, but also for the removal of grease, and should be made use of whenever possible. The great point in drain flushing is to discharge the available water periodically, automatically, and in suitable quantities, at a rate of, say, from 2 to 4 gallons per second. For this purpose appropriate apparatus (see “ FLusHine Tanxs”’) are necessary in order that the water may be collected and retained until the desired quantity has accumulated, and then suddenly discharged into the drains. Under such a system on the one hand, the merest dribble of water may be made use of, while on the other 40 or 50 gallons of water may. be made more efficient than 1,000 gallons discharged in a small continuous stream. Flushing tanks should be fixed at the head of the main drain where the drainage system is a small one, and at the head of each of the most important branch drains where the system is extensive. If possible, it should be arranged that one tank discharges into the drain taking the flow from the scullery sink, as this is frequently highly charged with grease. The discharge pipes of the tanks may be connected to the drains through back inlets or ordinary gullies, or they may be attached to the arms of flushing rim gullies, that is gullies provided with flushing rims and made specially for the purpose. The capacities of the tanks must necessarily depend upon the diameters, lengths, and gradients of the drains upon which they are provided. Broadly speaking it will be found that the following MUNICIPAL AND SANITARY ENGINEERING. DRA volumes of results :— water will give satisfactory . 80 to 40 gallons. . 40, 60 ,,. . 60,, 100 ,, For a 4 in. drain . 2? 29 5 3? ord oP bed 6 7 7 5. As a broad principle, every pipe and connection comprised by the drainage system should be made accessible throughout, for the purpose of enabling stoppages to be located and removed without loss of time and without damage to the component parts of the system. It permits also of the inspection, cleansing and testing of the drainage system, enables leak- - ages to be located and rectified without un- necessary laying bare of drains, and therefore brings all that would otherwise be out of sight and out of reach under perfect control. In vertical piping such as soil pipes, waste pipes, and pipes above ground generally, means of access are provided in the case of iron pipes by the use of suitable access pipes made for the purpose. They consist of pipes, straight or bent, fitted with removable lids which are capable of being closed air-tightly. (See “Access Prpz.”) In lead pipes access is provided for by the insertion on the pipes of screwed brass caps and sockets. These open- ings into the pipes must be suitably placed so that the fullest advantage may be derived from them both for the removal of accumula- tions, where such are liable to take place, and for the insertion of a cane or brush for clean- ing purposes whenever that should become necessary. In underground piping, that is in the drains proper, access is provided by means of manholes which should be placed at all important changes of direction, and also on straight lengths of drain wherever these are considerable. All branch drains should be arranged to join the main drains in these manholes, and the drains to or from them laid in perfectly straight lines from point to point. Manholes should be constructed of brickwork in cement upon proper cement concrete foundations, and should be made perfectly water-tight up to the ground 139 DRA level. This is arrived at by rendering the surfaces of the manholes with cement or by lining them with slabs of plate glass. Man- holes constructed of glazed bricks are not desirable, because, although capable of being made water-tight, the joints of the brickwork favour the accumulation of dirt. The man- holes, which should be situated in the open, must be covered at the ground level with air- tight iron covers and frames. Should a man- hole of necessity have to be placed within a building, a double cover, capable of sealing itself by the condensation arising from the drains, must be provided, or other means adopted to ensure that the covers shall be permanently air-tight. Through these man- holes all drains should pass in the form of open channels shaped out of concrete and rendered in cement, or properly shaped glazed stoneware channels set in cement. It is desirable that the branch channels should be at a slightly higher level than the main channel into which they deliver. The branch channels should, further, invariably discharge in the direction of the outlet of the manhole and should be so placed that the discharge of one does not enter any of the channels on the opposite side of the manhole. The most con- venient proportions for ordinary manholes are :— For manholes 1 ft. 6 in. or less in depth— 2 ft. by 2 ft. between 1 ft. 6 in. and 2 ft. 6 in. in depth—2 ft. 6 in. by 2 ft. above 2 ft. 6 in. in depth— 3 ft. 6 in. by 2 ft. 6 in. 9 oh a2 Ped When over 7 ft. 6 in. in depth the upper portion of the manhole may be contracted in size by constructing an arch at a height of 5 ft. above the invert of the drain; a shaft 2 ft. by 2 ft. in the interior being carried up to the level of the ground. The construction of an ordinary manhole is shown on page 77. 6. Construction. — Upon this is depen- dent, more than upon anything else, the health and well-being of the inmates of the ENCYCLOPADIA OF DRA house in connection with which the drainage system has been provided. The entire system must be water-tight to prevent the pollution by sewage of the subsoil and foundations, and in many cases also the pollution of the water-supply to the house or other buildings in the vicinity. It must also be air-tight to preclude the possibility of polluting the air. The materials made use of in drainage con- struction are cast-iron and stoneware. For the former, which has many advantages, see article ‘‘Dratnace, Cast-Iron.” In the case of stoneware pipes, only those of best quality should be made use of. Harthenware or fireclay pipes must be avoided entirely, as they are usually absorbent and are not as tenacious and strong as stoneware piping. Nor are they, as a rule, burnt at a sufficiently high temperature to become vitrified. The stoneware pipes used should be salt-glazed, highly vitrified, perfectly smooth inside, straight, true in section, even in thickness, free from sandholes, cracks, and other defects, and should be provided with strong deep sockets so as to allow of proper joints being made (see “ Stoneware Pipz Joints”). They should be tested to a pressure of from 20 ft. to 25 ft. head of water. Stoneware pipe drains should in all cases be laid upon a continuous cement concrete bed at least 6 in. thick, and in width sufficient to pro- ject on each side of the drain a distance at least equal to the external diameter of the drain. After being tested and found per- fectly water-tight, concrete should be filled in on each side of the drain so as to pre- clude the possibility of lateral movement. Where a stoneware drain passes under build- ings or roads or in other similar positions, it should be entirely surrounded by concrete to a thickness of at least 6 in. In each case where the drain passes under a wall a relieving arch should be built over it so that there may be no pressure on the drain. Soil- pipes may be constructed of iron or of lead. In the case of the former the piping should be of at least “medium” strength (see ‘‘ Prpzs, WeIcaTs AND Diwenstons or Cast-Iron”) and 140 DRY the joints made with molten lead well caulked. Lead piping should be hydraulic drawn and at least 8 Ibs. weight to the superticial foot. Where the pipe has unavoidably to be fixed inside a building, piping of 10 lbs. strength should be made use of. In either case the joints should invariably be of “ wiped” lead. Ventilation pipes should, as already stated, always be constructed of lead. Hydraulic drawn lead piping is also the material to be used for all waste pipes, and the joints in this case should also be of ‘‘ wiped”’ solder, except where the pipes are of some length and intended to take hot water. Under these circumstances “expansion joints’’ are per- missible in order to allow free movement to the pipes when under the influence of expan- sion and contraction, which would otherwise soon cause them to break. Rain-water pipes should be of galvanized iron—the ordinary painted rain-water pipe being liable to choke from internal rust. The joints of these pipes should be made with red lead putty. On com- pletion of the drainage system, each and every component part should besubjected tothorough tests, as to which see article ‘‘ DRain- TESTING.” It is also desirable that all drainage systems should be tested periodically, so that defects may be discovered and remedied before they reach a serious stage. (See “ PuumBine.”’) G.J.G. J. “« HARTH- Dry Earth System.—(See CLOSETS.”’) “Dry-weather flow” of Sewage.— This phrase means the ordinary daily average quantity of true sewage from any given population, free from augmentation by rainfall and subsoil soakage. The quantity should therefore approximate closely to the amount of the water-supply to the same population, and, in a well sewered district, commonly amounts to from 25 to 80 gallons per head of the population, but “trade MUNICIPAL AND SANITARY ENGINEERING. DUS wastes” and special local conditions may alter this amount in certain cases. Ducat’s Filter.— This is an aérating filter for sewage treatment constructed with external walls of 8 in. drain pipes, laid with the outer ends 3 in. higher than the inner to prevent sewage leaking outwards. Aérating layers of drain pipes are placed at intervals throughout the depth of the filtering material, which latter consists of 4 in. to 4 in. vitrified clinker. The object aimed at is that air should continually pass laterally through the filter with a view of keeping the same regularly at work without intermission. Another feature is that crude sewage is claimed to be dealt with, but experience teaches that under nearly all circumstances some form of preliminary preparation such as screening and settlement of the raw sewage is needed. The direct oxidation of the sewage by currents of air produces considerable cooling; the system therefore requires to be supplemented by hot- water pipes fed by a boiler situate in a heating chamber adjoining. The Ducat system has been experimented with at Leeds, Market Drayton, Hendon, Sutton, and also at the Tattingstone Workhouse, near Ipswich. Dundrum Settling Tanks.—Mr. Kaye Perry has used tanks to which this name is applied. The tanks are three in number each 7 ft. square by 16 ft. deep, and containing 5,000 gallons of sewage each. The liquid enters near the bottom to each tank in succession, and by the upward flow principle of the Dortmund and other tanks the heavier suspended matters are left behind. Dust Bins.—Receptacles provided in con- nection with dwellings for the collection of ashes and other house refuse. These bins should only be used for dry refuse; cabbage leaves, food scraps, paper and similar material liable to decomposition being better disposed of by burning, in which householders should be encouraged. Dust bins frequently consist 141 DUS of a brick or wooden pit from which the refuse is shovelled out when about to be removed. This involves much dust and nuisance and must be considered insanitary. Better bins are those generally known as “sanitary,” which are made of galvanized iron and are provided with a light-fitting lid to exclude rain, as moisture favours decom- position. These bins may be bodily removed for emptying. Preference should be given to those that are round in shape or have rounded corners, aS being more readily cleaned. Another form of sanitary bin, much used in the North of England, is one made of metal and hinged in an aperture in a boundary wall in such a way that ashes may be thrown in from the house side of the wall, while the emptying may take place from a passage at the back of the wall by simply tipping over the bin. Dust Prevention.—Surfacing Roads—Oiled Roads—Dust Palliatives—Apparatus.—The dust problem is a very ancient one, but has only assumed an acute form since the advent of motor traffic. Dust has a deprecating effect upon everything with which it comes in contact, and is a source of great danger to the public health. It not only predisposes to diseases of the lungs, but as a carrier of disease germs is a greater source of danger than mud. To permanently cure the evil would involve greater expense than our local bodies are prepared to involve themselves in. Moreover the vast number of roads which have been formed of macadam only allow of certain palliative measures being adopted. Many engineers suggest a system of roads in duplicate, one for heavy and the other for light traffic, each road surface being made of materials suitable to withstand the strain set up by passing vehicles. This system is, how- ever, prohibitive on the ground of its great expense. Before treating of palliatives for existing surfaces, we will deal with systems that have been generally adopted for the prevention of dust in making new roads. ENCYCLOPHDIA OF DUS Many systems have been employed, among them being wood-paving, tarred macadam, and many patent systems of binders, asphalte, &c. In every case success largely depends on the foundation of the road, and the reader is referred to the article on ‘‘ Roaps, Streets, AND Pavements” for further consideration of this point. It will be well to point out that only the best materials should be used and the work carried out in the best possible manner. Systems or Surracinc Roaps.—Woop-Pav- 1nc.—This has undoubtedly decreased the dust in main thoroughfares, though much still arises from horse droppings, &c., but if properly ordered as pointed out in the article on “STREET CLEANSING,” part of the dust may be speedily removed. Tar Macapam.—This method of surfacing roads for dust prevention has been largely adopted with varying results. The materials used are generally limestone or ironstone slag, the latter being stronger than limestone. Care must be exercised over the tar, as upon it depends very largely the success of the surface. In hot weather owing to bad tar or unsuitable stone being used, or defective mixing of the materials, the surface becomes sticky and dangerous. There is little doubt that the best way of drying the stone is by placing it in specially heated ovens, the stone being turned over at intervals to ensure it being thoroughly dried and heated. The tar should in all cases be boiled, and if it is of poor quality a little pitch will improve it. The mixing of the tar and the stone requires very careful attention. Engineers have different methods of mixing, for instance: (1) Cold stone and cold tar. (2) Cold stone and hot tar. (8) Hot stone and hot tar. After the foundation of the carriage-way has been thoroughly rolled and consolidated, the tar macadam may be put on in one or two layers. The usual depth is about 4 in., consist- ing mostly of two layers. The bottom layer is about 24 in. in depth and consists of stone 142 DUS 2 in. to 24 in. gauge, well rolled; the top coat is about 14 in. in depth, and consists of stone % in. to lin. gauge. This is then thoroughly rolled and covered with fine shingle. SzaLeD Roaps.—These are roads which are surfaced with “binders” such as “Tarvia.”’ In such instances not only has dust been reduced to a minimum, but the cost of cleansing has also been reduced. The system of binding Coating of Road ee. MUNICIPAL AND SANITARY ENGINEERING. DUS covered with a mixture of dehydrated gas tar and refined rock pitch, in the proportion of 8 lbs. of pitch to a barrel of tar. This mixture is poured over the surface in a boiling condition and sprinkled with lias lime. This is then covered with a layer of tar concrete about 14 to 2 in. in thickness; this also being sprinkled with lias lime, and before rolling covered with macadam to a depth of yes grouted with hot Tar Compound ond Fic. 1.—Single with “ Tarvia,” as suggested by the manu- facturers, is as follows:—The road surface is levelled and covered with a mixture of Tarvia and chippings about $ in. in thickness, 1 cu. yd. covering about 36 superficial yards. On the top of this layer, a coating of 2 in. roadstone is laid, and in such a manner that 1 ton covers 11 or 12 superficial yards. Clean Road Macadam, machine broken with riddle 2g holes made into Tar YOON Ss 2’Layer of Quarry Siftings Sealed Road. 3 to4in. The whole is then rapidly rolled, to adjust the layers, and afterwards slowly rolled and lightly watered. The effect of this method is to force the fine tar concrete into the top surface covering, thereby filling the interstices and binding the surfaces together. The road surface has stood well and reduced the amount of dust considerably. Another Foundation grouted Concrete with Hot Tar Cogpound whe Fic. 2.—Double The whole is then lightly rolled, the effect of which is to force the binder up into the top surface thus filling in all the interstices and providing thereby a waterproof surface. The operation is completed by a top sealing with hot Tarvia. Dry chippings are then spread on the surface and the whole well rolled. A system that has been adopted in Penzance is as follows :—After the old macadam has been scarified and carted away, the surface is NRE FC pg oe Sealed Road. method adopted at Penzance for coating the surface of gradients, with due regard to the dust evil, was the use of a preparation of dis- tilled tar, rock pitch, and lias lime, under the coating of macadam. The surface being thus rendered impervious to wet, and, while retain- ing its rigidity, afforded a good foothold for horses. Before calling attention to some of the dust palliatives and machines on the market, there are one or two methods 143 DUS of dressing the finished surface of the road- way to reduce the amount of dust. The materials used form a tar cement and in some cases consist of tar, pitch, and lias lime. The material should be applied to the road sur- face in a hot condition, and when laid should be sprinkled with fine stone chippings about #th of an inch, and the whole well rolled. It will be found that this material forms a cushion to the road surface, and reduces wear and tear. Another method which has given excellent results and is inexpensive is as follows:—The road surface should be thoroughly brushed and kept dry to receive the material. The mixture is made of sand, chippings and shell, added to which is a quantity of tar. The whole is then mixed to a mastic state, and then sprinkled over the road surface to a depth varying from 4 in. to 3 in. The surface is then sprinkled with shell and rolled with a hand roller. The cost of this material laid is about 24d. per superficial yard. Dust palliatives still occupy an impor- tant position in connection with the problem of prevention of dust, as many of our roads are of macadam, and the expense involved in removing the top surface and substituting one that will minimise the amount of dust, such as tar macadam, as- phalte, &c., would be prohibitive, and the attention of engineers has, therefore, been directed towards less costly methods. Dust Patuiatives.—In order that these may be successful, road surfaces must be thoroughly swept and freed from dust and the work of treating the surface carried out in fine, dry weather; otherwise the first heavy vehicle passing over the treated area will begin the work of destruction and in a short time the whole surface will be rendered very unsatisfactory and present large quan- tities of objectionable, dangerous mud. Crupe Tar has been extensively used as a dust palliative with excellent results. Care must be exercised in the boiling of the tar, as more than 3 % of water in the tar causes trouble during the boiling. The tar is heated ENCYCLOPAHDIA OF DUS to about 200° F., poured on the road, and then brushed into the surface, or spread by the aid of special machines. After the surface has been thoroughly treated, fine chippings are sprinkled over it—these being more suitable than sand. The action of the traffic causes the tar and chippings to form an impervious cushion on the surface of the road. The work should be carried out during warm weather. The cost works out at 1d. to 8d. per super yard. A good and effective method, and one which adds considerably to the life of the road, is to cover the surface with tar at the beginning of the summer and another coat in Septem- ber, this method keeping the tarred cushion surface of the road in good condition during the winter, thereby making it easier to prepare the surface for the next summer’s coat of tar. Distituep Tar, from which the light oils and other compounds have not been extracted, is an exceedingly good dust preventer. Distilled tar thinned by the addition of the residuums of petroleum oils in the pro- portion of 1 pint of petroleum to 2 gallons of coal tar is a good palliative, when mixed and applied cold. The treated surface should be sprinkled with fine chippings. The same preparation with the addition of 1 pint of lias lime to the above proportions of petroleum and tar gives a thicker material which is almost as readily applied. CarBURETTED WaTER-Gas o1L Tar.—This material is largely used in many districts where water-gas is manufactured. It is a much thinner liquid than coal tar, and can be sprinkled over the surface by means of an ordinary water cart. Heating is not necessary, it being applied cold. Fine chippings should be sprinkled on the surface. Before treating of other palliatives, a word or two may be necessary about the boiling and distilling of crude tar. Care must be exercised in the process so that the material is not burnt or overheated. The water will rise to the surface and can then be removed by the use of a flat tinshovel. Overheating destroys 144 DUS the essential oils in the. tar and the work invariably results in failure. APPARATUS FOR SpreaDING Tar.—There are many machines for spreading tar, that have from time to time been placed’ upon the market. In smaller districts, where economy has to be exercised, it will be found that an ordinary street watering cart, fitted with a special tar spraying attachment in place of the sprinkler box, will be found useful, where the work is finished by the hand broom. Where only small quantities of work have to be done, a small apparatus such as the Simeon’s tar-spraying and painting machine, or the machine supplied by the P. A. S. Distributors, Lid., will answer the purpose. The latter machine is also capable of doing large quan- tities of work, and an experiment recently witnessed by the writer proved highly satis- factory. The cost of the machine is about £45. It is claimed by the manufacturers that boiling over of the tar is prevented. The Figure opposite is a rough line section through the boiler. The tar is placed in the internal section and percolates through perforations in the sides into the lower cavity of the external drum. The tar in this section when brought up to the required heat is drawn up the pipe and pumped by a hand pump into the distributor. This dis- tributor has three or four sprays attached to an arm. This arm is attached to a single wheel which is worked by one man. By this arrangement, the man working the sprays can walk forward and keep to a line, no por- tion of the work having to be traversed by the man. Each spray will cover about 15 in. at each application, the combination of four covering about 4 ft. The cost of the tar and men’s time spreading, fuel, carriage, &c., is about 3d. per super yard. The machine which has given the best all round satisfaction was invented by Mr. Thomas Aitken, a gentleman who has given the subject of road construction more than ordinary attention, and whose tar-spraying plant has received the highest commendation. The “Tarspra”’ apparatus can be attached M.S.B. MUNICIPAL AND SANITARY ENGINEERING. DUS to an ordinary water van, drawn by either horse or tractor. This apparatus is con- structed with an air receiver, into which air is pumped and kept at a constant pressure of 100 lbs. per square inch on the pressure gauge. Tar is then pumped into this receiver, increasing the pressure to about 220 lbs. The tar is sprayed on the road through a series of nozzles at a constant pressure of about 200 lbs. per square inch. Cc To Pump SECTION OF PATENT CANTAR, CONTINUOUS-HEATING, SAFETY TAR BOILER O1is.—Oil has been largely used as a dust preventer, petroleum being used some eight or nine years ago in America. The oil should be highly heated and put on the road during a very hot day, and afterwards covered with sand. Undoubtedly the best method is to treat it in the same way as a tar binder, a hard and firm covering being thereby obtained. Other coatings of oil can then be sprinkled on the surface to fill up the inter- stices remaining, and to give a smooth impervious surface. All petroleum oils are not satisfactory, and only those should be used which have an asphalte base. It has been contended that when the wet season commences, the surface thus ‘treated becomes very greasy, and objectionable mud is formed, necessitating thorough cleans- ing of the road surface. 145 L DUS ProprieTrary Preparations. — There are many patent preparations for dust prevention on the market, but only a few can be men- tioned. ‘* Akonia”’ is the patent process of Mr. Dan de Liebhaber, and has been used with considerable success in a large number of districts. The following advantages are claimed for this material by the patentee :— “ Akonia”’ is cheaper, in most cases, than ordinary watering when applied at the rate of 250 applications a year. It is not only a dust preventer, but also acts as a road preserver and improver, by rendering the surface hard and smooth, thereby diminishing the dis- integration of the macadam, and reducing the cost of scavenging. It is absolutely odourless, and free from emanations of any kind, uninjurious to health, does not damage tyres, metal, clothes, horses’ hoofs, &c., or render the road slippery and cloggy. It does away with the mud which invari- ably follows ordinary watering, and renders the road less muddy in wet weather. It requires no special appliances beyond an ordinary water cart, and can be kept for any length of time without losing its properties. ‘“*Hahnite’’ is an insoluble liquid, which oxidizes when sprayed on to the road and forms an impervious and durable coating over the surface. It is claimed for “ Hahnite” that it preserves the road, causes no injury to tyres, varnish, horses, or pedestrians, reduces the sound of traffic, acts as a disinfectant, pre- vents dust from rising, and minimises the formation of mud. The use of this material compares favour- ably with ordinary street watering, and is applied to the road by a street watering cart. Caleium chloride, which is manufactured at Northwick, Cheshire, is an excellent dust preventer. A small quantity of these crystals are placed in an ordinary watering cart, and allowed to dissolve in the water, thus forming a cheap dust palliative capable of producing good results, and of considerably reducing the cost of watering. (See ‘‘ Roap WatERING.’’) R. H. B. & F. L. ENCYCLOPEDIA OF ECO Earth Closets.—Useful apparatus in the country, but unsuitable for use on a large scale or in populous districts, owing to the quantity of suitable earth required. Where water-closets are not practicable and the con- ditions are favourable, earth closets form the best substitutes, as the earth made use of not only keeps the excreta dry, but also deodorises it and disintegrates the organic matter and converts it into the condition in which it naturally exists in fertile soil. It is essential that the earth used should be suitable. It must be dry, finely sifted, and of a loamy nature, and from 1 to 2 pints must ‘be spread over the excreta whenever the closet is made use of. An earth closet may simply consist of a seat fixed over a suitable recep- tacle, which is easily removed for emptying ; the earth being in this case stored in a box and applied by hand with a trowel. A better apparatus is that in which the earth is applied automatically, as in the case of Moule’s earth closet. In this a hopper is provided behind and above the seat capable of storing a sufficient amount of earth to last for some little time. Connected with this is a valve into which a measured quantity of earth falls, and which, being worked by a handle or by a lever connected with the seat, distributes the earth over the excreta when the handle is pulled or a person rises from the seat. When the handle is released or a person again sits upon the seat, the valve is recharged with the requisite amount of earth. No moisture other than that of the excreta and urine should be admitted to the closet. The apartment in which an earth closet is fixed should not have any direct communication with a dwelling. It should be well lighted and ventilated, and should be provided with an impervious floor raised some few inches above the ground level. Economisers or Feed-Water Heaters. —Accessory appliances used in connection with steam boiler plants for the purpose of effecting a saving in fuel by utilising the waste heat in the flues for the purpose of heating the feed- water to the boiler. This object is achieved 146 ECO in different ways—(a) by intercepting and utilising part of the heat of the gases from the boiler furnaces as soon as they leave the boiler; (b) by passing the feed through a vessel jacketed with exhaust steam, or using live steam in asimilar manner. In principle, the “economiser”’ is really a supplementary boiler working within a low range of temperature and whereby a saving of fuel can be secured, say, from 10 to 15%. For example, a boiler working at a steam gauge pres- sure of 150 lbs. per square inch with boiler- feed at 32° F., will consume 1,198 thermal units per 1b. of water evaporated, as com- pared with 1,018 units when using feed-water at 212° F., thus showing a saving of 15 % of the heat required. To secure the greatest real economy the temperature of the feed- water should be at a maximum with a minimum of fuel-cost. One of the best- known appliances for realising the advantages to be gained by the first method (a) is ‘‘ Green’s fuel economiser,”’ which is a flue-heated feed- water heater. It consists of sections or rows of cast-iron tubes (44 in. diameter by 9 ft. long) fixed in an enlargement of the main flue. The accumulation of soot which takes place on the pipes is removed by slow-moving scrapers (the invention of Mr. Green) upon their external surfaces. The size of economiser required for any given plant is calculated on the evaporative capacity of the boilers, but approximate rules such as the pro- vision of one pipe for every three I.H.P., or 4 pipes per ton of coal per week of 56 hours, are useful guides. The hot flue gases may be reduced in temperature from 650° F. to 850° F., and the feed-water heated some 150° F. to 250° F. Each pipe has 10 sq. ft. of heat absorbing surface and a water capacity of 64 gallons. Another useful apparatus is the “‘ Hudson economiser ” which is also a steam condenser, is of simple con- struction, and has no tubes, so that renewal of parts is reduced to a minimum. This apparatus extracts the grease from the exhaust steam before coming in contact with the cold feed. The purified steam thus obtained comes 147 MUNICIPAL AND SANITARY ENGINEERING. EJE in direct contact with the cold feed entering the top chamber of the apparatus through a spray, the water being nearly boiled. Softened water is thus obtained, free from oil, at from 200° F. to 210° F., for purposes of boiler feed. The apparatus thus possesses the further advantage of preventing incrustation on the interior of boiler shell or tubes. Exhaust-steam feed-heaters are also largely used, and an average economy of about 15 % is obtainable between a cold boiler feed at 55° F. and water at 212° F. In the “Row feed-water’”’ heater a patent indented tube is used which is claimed as being twice as efficient as an equal amount of plain tube surface. For good water, not liable to scale, the steam circulates around the outsides of the tubes through which the water passes. For bad water this order is reversed. Efflorescence.—This is a term applied to a peculiar powdery substance which occa- sionally appears on the face of new brick or stone work. As a rule it arises from an excess of salts in the bricks or stone, which become dissolved in water from heavy rain. Usually the efflorescence consists largely of sulphate of magnesia. The cure is difficult, but a periodical washing down with diluted hydrochloric acid, applied by means of a sponge, is to be recommended. ec Ejectors. — Hydro-pneumatic “‘ ejectors,” for lifting sewage by the employment of compressed air, now often replace centri- fugal and lift pumps, and, in suitable circumstances, have many advantages for such work. The principle upon which the apparatus works will be understood from an inspection of Fig. 1, which is a sectional diagram of “Coombs” pneumatic ejector as installed for raising crude sewage, and other liquids, by compressed air. The apparatus consists of a wrought-steel or cast-iron body or container C., provided with inlet and outlet sewage flap valves I. V. and O. V., sluice valves S.V.1and S. V.2, for disconnecting the ejector, and two floats T. F., and B. F., which operate the automatic valve A. V. which controls the L2 EJE supply of compressed air and the exhaustion of same after ejection of the sewage. In actual work the sewage flows from the gravita- tion sewers into the container C., through the inlet flap valve J. V. until it is full, when the top float T. F. rises and opens the automatic valve A. V. to the compressed air supply, closing it to exhaust at the same time. The sewage is then discharged through the outlet flap valve O. V., by the pressure of the compressed air, and the body of the ejector is quickly emptied. When the container C.is nearly empty, the bottom float B. F’. falls and closes the automatic valve 4. V. to com- pressed air supply, and at the same time opens the valve to exhaust, so allowing the com- pressed air to escape, after which a fresh charge of sewage flows into the con- tainer, thus beginning another cycle of operations as above described. The working of the apparatus is automatically re- peated so long as there is a flow of sewage and a supply of compressed air. Attendance is only required at the ejector chamber for periodical inspec- tion. The rate of discharge depends upon the time of ENCYCLOPADIA OF EJE air as a motive power is not found economical in fuel costs, but this does not apply to the same extent in the case of ejectors lifting sewage as ordinarily applied. The total cost under all heads of expenditure must be con- sidered in estimating the value of the system in any given case. For ejector work, low pressures such as from 15 lbs. to 25 lbs. are the normal conditions met with, and the percentage of loss is much less than in the case of higher pressures. For greater pressures two-stage compression is necessary, but ejector work is generally below the limit for the advantageous employment of stage compression. Con- siderable improvements have been made of recent years in the compressors filling, and the ejector will automatically adapt itself to the variations of sewage flow. LHjectors are sometimes placed in pairs, and may be arranged to work either independently or alternately so as to give a continuous delivery of sewage. The compressed air for actuating the ejector is commonly produced at some central station and transmitted to the ejectors in different parts of the district as may be required. The air mains consist of cast-iron pipes, as used for water supply purposes, with spigot and socket joints, caulked with lead and yarn. Generally speaking, the use of compressed Fic. 1.—‘‘ Coombs” Pneumatic Ejector. (Daniel Adamson & Co.) employed, and the modern high-speed com- pressor, with mechanically-operated valves, gives a much greater efficiency than the earlier type of low-speed compressor fitted with lift-valves. In the drainage of many towns it is an advantage to be able to divide the area into a number of independent drain- age areas, and to such a condition the ejector system favourably lends itself, as the ejectors can be conveniently worked from one central compressor station. The system is applicable, in general, where low-level sewage has to be 148 EJE lifted to higher parts of the district, into intercepting or outfall sewers, for delivering sewage in low-lying areas out to sea during any state of the tide, and also in level country where to secure self-cleansing gradients deep and ex- pensive cuttings would be involved in a purely gravitation scheme of drainage. The mode of fixing an injector in a brick underground chamber and connecting it with the gravitation sewer on the one side, and with a rising or delivery main on the other, is shown in Fig. 2. LLU MUG GHE fiji EX Tr ee ~~ Fie. 2. ““Coombs”’ Ejector in Chamber. In the actual working of the ejector, there are certain advantages which tend to facilitate the raising of sewage by this method. For example, there are no parts liable to be injured by the action of the sewage or of grit upon them, and the working parts are few and not likely to get out of order. The sewage inlet and outlet valves are in excess of the full area of the delivery pipe, and a free passage is given for the carrying away of all solids which drop direct into the delivery passage sloping towards the outlet, and are thus removed by the first flush of liquid from the container. Previous screening of the sewage is thus unnecessary, an advantage over pumping plants where periodical cleansing of screens and sump wells is essential. MUNICIPAL AND SANITARY ENGINEERING. (Daniel Adamson & Co.) ELE Electricity. -— Introduction and Defini- tion — Components of Electricity — Electric Lighting — Flame Arc Lamps — Incandescent Lamps — The Electricity Works —Systems of Charging for Electricity—Electricity Meters— Transforming Stations and Apparatus—tElectric Motors.—No useful purpose would be served by endeavouring in this article to define and explain the term electricity in the sense in which it is used by the physicist. As used by the engineer, electricity has come to denote a form of energy. The independent . use of the word in these two senses - rarely leads to misunderstanding. , The ’ physicist in his ‘electronic theory of matter” states that the atoms of matter themselves are made up of “ electrons ’” (hypothetical concentrated units of negative electricity); each aggregation of electrons being. sur- rounded by:a sphere of positive elec- tricity, and that, consequently, matter, in its last analysis, is identical with electricity, and consists of nothing else. While the physicist appears to regard this profound alleged knowledge with considerable satisfaction, it is evidently of very little practical use to the engineer or to the layman, who have for many years considered electricity to be something which, consumed in sufficient quantities, serves to provide light and heat, and to propel tramcars and railway trains, and to drive machinery in workshops and factories. Light, heat, and work are well known to be forms of energy. It is furthermore well known that energy may be converted from one form into another. To the engineer and layman, electricity is also a form of energy. At present, the engineer deals with electricity as something which can be bought and sold in definite quantities, and his purposes are sufficiently served, therefore, by simply regarding electricity as a form of energy. Components oF Execrriciry.—Electricity may be sub-divided into three components: (1) Pressure, (2) Current, (8) Time. 149 ELE In engineering calculations the units in which these components are expressed are— The unit of pressure = the volt. The unit of current = the ampere. The unit of time = (usually) the hour. Electricity is used commercially in one or other of two forms: I. Continuous electricity. Il. Alternating electricity. In the first of these, the direction of the current is constant, whereas in the second the current alternates in direction many times per second. A detailed consideration of the theory of these two forms of electricity cannot be undertaken in this article, but the appro- priate use for each form will be set forth in a later section of it. The following explanations of terms, although they should be taken as applying strictly only to continuous electricity, are in most instances substantially true of alternating electricity. Any quantity of electricity is made up of the product of the three components, pressure, current, and time. The unit of electricity is the kilowatt hour, sometimes called the Board of Trade unit, or merely the unit. It is pre- ferable to employ the term kilowatt hour (kw. hr.).1 A quantity of electricity in kilo- watt hours is equal to 1,000 times the product of the pressure in volts, the current in amperes and the time in hours. In other words: Kilowatt hours = 1,000 x volts xX amperes x hours. The above is the equation for the quantity of energy. Power is the rate of expenditure or trans- formation of energy. Consequently power is expressed in kilowatt hours per hour, i.e., in kilowatts. The power equation is thus obtained by dividing both sides by the time in hours. We thus have for the power equation : Kilowatts = 1,000 x volts X amperes X hours Hours z.e., kilowatts = 1,000 x volts ® O's mes | gam | 266 |B gas2/ “eg | eRe 285 | Pao | gsm OssaoM| gas a Mom oes | aS | ses | so888| “sn | “a8 a) 2,7 Sane SHE tS| od poaos ag 828 | 6.7% |Ssaeeyt|] 3s 8 Bud A Osa | O8 Bae on Oa cada 1 147 76 223 1:68 5:87 2 294 76 370 2°78 9°78 3 440 76 516 3°87 13°50 These 400 c.p. lamps differ slightly in form from the 50 ¢.p. lamps, in that they are fitted with Edison screw caps instead of bayonet fittings. The reason for this modi- fication is that the manufacturers find the “Edison screw cap” more suitable for running on heavy currents than the ordinary bayonet holder. When comparing the running costs of these lamps with the equivalent running cost of the flame arc lamps, one must keep in mind that the candle-power of the are lamp is considerably reduced by deposits on the inner globe, and this loss amounts, as stated before, to some 20 to 30°/,. In order, therefore, to maintain the apparent advantage in effici- ency of the flame are over the metal lamps, the globes of the arc lamp must be constantly cleaned—an item which will increase the cost of maintenance. On the other hand there is no diminution of light in the metal lamps, as the globes remain clear and the candle-power is maintained practically constant through- out their life. Moreover the life of the metal, lamps taken above are conservative values, and it is very probable that 1,500 hours would be more in accordance with the facts. The field of interior illumination by elec- tricity is now almost exclusively filled by the metal lamp. Data for the costs of 400 c.p. and 50 ¢.p. sizes have already been given. For interior illumination, however, 153 ELE the great majority of lamps are nowadays some 25 ¢.p. each. The present market price of these lamps is about 8s. per lamp as against the price of 4s. per lamp of a year ago. The near future will doubtless witness further material reductions in the price of metal lamps. The first cost is of less consequence the higher the price paid for electricity. Thus taking at 1,000 hours the life of a 25 c.p. metal lamp, and its consump- tion at 1°3 watts per c.p., the total outlay per lamp per 1,000 hours of actual burning, for ENCYCLOPADIA OF ELE times called the Generating Station, sometimes the Central Station, and sometimes, and prefer- ably, the Electricity Works. If the area to be supplied is very limited in extent and in the immediate neighbourhood of the Electricity Works, it may be economical to employ sets in which continuous electricity is generated. Almost all modern Electricity Works are, how- ever, equipped with electric generators supply- ing polyphase alternating electricity. This alternating electricity is transmitted at high pressure to suitably located sub-stations, where Fic. 2.—General Arrangement of Power Station and Sub-station. various prices of electricity, works out as follows :— oy 4 wet bl ga om os Ot a ag ‘ay 82 aS Bp a2 ge ae 54 Sen on a3 1d. 3-0 2-70 57 0:07 2d. 3-0 5-40 84 0°10 8d. 3-0 8-10 11-1 0:18 4d. 3-0 10-8 138 0-17 5d. 3-0 135 16°5 0:20 Tae Evecrriciry Worxs.—The building and apparatus where a portion of the energy of the coal is transformed into electricity is some- by means of motor generators, it is trans- formed into continuous electricity and dis- tributed to the consumers in this form. This arrangement is indicated diagrammatically in Fig. 2. The coal is brought to the electricity works by canal or rail. In the illustration, the coal is indicated as being transferred from a canal boat to a conveyer, by which it is deposited in large hoppers at the top of the boiler-room. In large works these hoppers often have capacity for 5,000 tons or more. The coal next passes through shoots from the hoppers to the auto- matic stokers under the boilers, sometimes passing through weighing devices interposed just before the coal reaches the automatic stokers. These stokers are adjustable, and 154 ELE deposit the coal uniformly over the grate, and in the correct quantity. The correct adjust- ment of the supply of air is no less important, and is attained by the assistance of CO, recorders, which should constitute part of the equipment of all Electricity Works. The boilers should be of some one of the several excellent water-tube types which are now avail- able. These are much more compact, and are in other respects more satisfactory than the fire-tube types formerly employed. Even with the most compact boilers, however, the boiler- room necessarily extends over a considerable area. The largest boiler which may at present be considered as thoroughly standard, and obtainable from any one of several reliable manufacturers, has a normal evaporative capacity for raising 15 tons of steam per hour “from and at” 100° C., and can, when forced, supply at the rate of over 20 tons per hour for short periods. The superheating tubes are generally incorporated in the boiler, and may be considered asacomponent. Sucha boiler’s normal capacity, when supplying steam at 13 atmospheres and with 50° C. of superheat, which are conditions which represent approved practice, and when the feed-water temperature is 50° C., is only 12°5 tons of steam per hour, since this quantity is equivalent to 15 tons “from and at” 100° C. The outputs of Electricity Works are best expressed in millions of units (i.¢., of kilowatt hours) per year. These outputs range from one million units per year for the Electricity Works of a small town, up to 100 million units and more per annum for Electricity Works in large cities. A Works of the latter size would require, as an average, some 100 tons of steam per hour and for peak loads this would usually rise to over 200 tons per hour. Consequently, in order to have sufficient spare plant, at least 20 of the above described boilers would be required. These would be arranged in groups of four, and each group would supply steam to a steam turbine of some 8,000 h.p. capacity. There would be five of these steam turbines, and each would drive a 6,000 kw. polyphase MUNICIPAL AND SANITARY ENGINEERING. ELE alternator. All this apparatus would prefer- ably be arranged in five distinct groups, as this gives additional certainty of absolutely uninterrupted supply. Each of these groups also comprises a surface condenser. Outside of the station are located cooling towers. The switch gear may be located either at one side of the engine-room or in a separate 7 An a a — ad E a a = : ; u @ \— hw ‘ow = D =A aM Re [a — —_ — — oo Tannen oO = — J —_ qa A AR oO ; — st Med F A — Boilers. D — Switchboard Gallery. B — Turbo-Alternators. E — Chimneys. Cc — Exciters, F — Cooling Tower. Fic. 3.—General Arrangement of Electricity Works. building. In modern plants the switch gear is controlled by relays from an operating desk. By this means the massive gear for high pressure and large amounts of power may be perfectly controlled by the suitable manipulation of the low-pressure relay circuits. The general arrangement of the Electricity Works is indicated diagrammatically in Fig. 3. It would exceed the limits of this article to 155 ELE enter upon the discussion of all the machinery required in an electricity works. Considerable interest, however, naturally arises in regard to the significance to be attached to the rating ascribed to the electricity generators. The capacity stated on the name-plate of the set is of little use in judging its capacity. Although generating plant is always sold to some sort of a specification, there is, as yet, no widely acknowledged standard basis of rating as regards, for instance, temperature rise and overload. Thus we are not learning much when we are informed that the aggregate rated capacity of the generating sets in- stalled in any particular Works is so many kilowatts. It has consequently come about that little or no useful knowledge is imparted when it is stated that the capital cost of an Electricity Works is £25 per kilowatt of plant installed. It is rarely stated whether by the kilowatts capacity is meant the aggregate capacity of the plant installed or only the lesser capacity arrived at after deducting the portion to be considered as a reserve. There are also the alternatives that the kilowatts capacity may be intended to mean either the average power or the maximum power delivered from the Works. A suitable groundwork on which to prepare a specification for the generating sets is that, on the basis of the rating assigned to them, they shall be capable of dealing with a 25 % overload for 1 hour, and with a 50 % over- load for 5 minutes without detriment to any part of the steam-electric set, and that when continuously operated at the rated output, no accessible part of the electric generator shall sustain a temperature rise, as thermometri- cally determined, of more than 40° C. above the temperature of the engine-room in the immediate neighbourhood of the generating set. There are very many other matters, such as the steam consumption, the mechanical construction, insulation, pressure regulation, uniformity of angular rotation, &c., which must be carefully stipulated in the detailed specification, but for the purposes of the ENCYCLOPAIDIA OF ELE broad outlines appropriate to this article, a discussion of these details would be out of place. The load factor is the ratio of the average power delivered from the works during the entire 8,760 hours in the year, to the maxi- mum power delivered at any time during the year. For a miscellaneous load made up of lighting, power, and tramways, the load factor will usually be not less than 25% nor more than 40%. Under favourable conditions, when a considerable percentage of the power is required for certain electro-chemical or thermal processes, such as the manufacture of calcium carbide or aluminium, the resultant load factor at the outgoing cables from the Electricity Works may be even 60% or more, though large miscellaneous undertakings with a load factor of even as much as 50% are still very exceptional. On the basis of these heating and overload requirements, an Electricity Works will, according to the magnitude of its output, require to comprise electricity generating sets of the following aggregate rated capacity :— Aggregate Rated Capacity in kw. of Gene- rating Sets Installed, for following Load fr Hopakelvine per Year Factors: 0°60 0°40 0°30 1-00 276 407 528 500 1,820 1,900 2,470 20°0 5,070 7,500 9,790 100- 24,400 | 84,000 | 45,200 In the following table are given representa- tive values for the total cost of such Electricity Works when built in accordance with best modern practice. | Total Cost of Electricity Supply Stations, Rated Output of Station in £, for following Load Factors: in Megakelvins per Year. 0°60 0°40 0°30 1:00 10,400 | 12,500 | 13,850 5-00 33,700 | 46,750 | 54,250 20-0 95,200 | 136,000 | 175,000 100: 364,000 | 505,000 | 636,000 156 ELE In addition to the capital outlay for the Electricity Works, there is the capital outlay for the conductors by which the electricity is conveyed to the consumer and for all the works, such as subways or towers, required in the construction of this transmission line. Usually also there will be small intermediate stations, termed sub-stations, in which motor generators are installed, and where the elec- tricity which has been transmitted at the high pressure required in the interests of low outlay for conductors, is transformed into electricity at the low pressure desired by the consumer. The costs of the system between the Electricity Works and the con- sumer’s premises vary widely according to the distance, the number and distribution of the consumers, the amount of electricity required by the consumers individually and collectively, the extent to which the times during which the various consumers’ require- ments for electricity overlap with one another, and on several other conditions. In general, these costs will aggregate from one-half of the cost of the electricity works up to, and some times even in excess of, the cost of the Elec- tricity Works. The aggregate of the capital and depre- ciation costs of the Electricity Works and of the distribution system, which may be termed the capital costs, taken together with the operating costs, lead to a cost per unit delivered at the consumer’s premises, which, averaged for all the consumers, may, with coal at 10s. per ton, and with a load factor of 35%, so far as concerns the general order of magnitude, be taken as requiring the following average price per unit :— Annual Output from Electricity Works Average Price in Pence in Units C i Pa Hours per Unit. 5,000,000 1:3 10,000,000 1-0 20,000,000 0°70 50,000,000 0°60 100,000,000 0°55 MUNICIPAL AND SANITARY ENGINEERING. ELE Estimates indicating lower average prices are sometimes seen, and the results are, from their very nature, greatly dependent upon very many special circumstances of each case, such as the terms on which capital may be obtained, facilities for obtaining ample and cool condensing water at a low price, accessi- bility to rail or water-ways as affecting not only the price of fuel but also the price of machinery as delivered on the site, wages, intelligence and disposition of employees, enterprise and knowledge on the part of the management ; nature, extent, and geographical distribution of the industries in the region, and on various other conditions. It should not be concluded that all con- sumers will pay this average price. On the contrary, an equitable distribution of the charges allocates to certain consumers a price of two or three times the average price, while the supply to other consumers is profitable, even at half or less of the average price. The equitable price to any particular con- sumer will be less— 1. The less the distance to which his elec- tricity must be transmitted. 2. The greater the number of consumers who can be supplied over the same conducting system. 3. The less the extent to which the consumer’s load overlaps the load of other consumers. 4. The greater the amount he consumes per annum. 5. The greater the annual load purchased from the Electricity Works by the consumers collectively. 6. The higher aggregate load. 7. The higher the load factor of the consumer’s own load. Many other conditions must also be taken into account. Thus, if the consumer requires electricity in the same form and at the same pressure as that at the outgoing cables from the Electricity Works, he will pay a much lower price than if he requires the electricity the load factor of this 157 ELE transformed in pressure or in kind, or in both respects. Systems oF CuarGinG ror HELEcTRiciry.— There are numerous methods whereby con- Fic. 4.—Section of Typical Meter. sumers are charged, but the following methods are the more common ones :— (1.) Flat rate. This method requires the consumer to pay a constant price per unit, irrespective of his load factor. For private lighting this rate generally lies between 8d. and 6d. per unit, and for power the limits are generally of the order of 1d. and 2d. per unit. (2.) Fixed minimum consumption rate. This method requires the consumer to pay a certain sum each year irrespective of his load, in addition to a certain price per unit for each unit consumed. This system is generally used for private light- ing, when there is only one customer, or perhaps a few, being supplied over a long and otherwise ‘‘dead”’ main. It is ENCYCLOPADIA OF ELE" number of 8 c.p. lamps, or the equivalent thereof, wired. (3.) Maximum demand rate. This is some- times called the ‘ Wright system,” or “Brighton system.” This rate charges a high price (generally 7d. or 8d.) per unit for a consumption equivalent to the use of the maximum demand for a certain time (generally 1 hour per day), and a low price (generally between 2d. and 4d.) per unit for any energy consumed beyond this amount. In this system a “maximum demand indi- cator”’ is introduced into the consumer’s circuit. For an example, suppose the con- sumer’s quarterly (say 90 days) consumption is 1,500 units, and the indicator shows a maximum demand of 10 kilowatts, there will be 10 x 90 = 900 units to be charged at the high rate (7d. or 8d.), and only 1,500 — 900 = 600 units to be charged at the low rate (2d. to 4d.). (4.) Sliding scale rate. The customer is required to pay a net flat rate for the first 1,000 units (or other quantity) consumed per quarter. For each successive 1,000 units an increasing discount is made from the flat rate up to a certain total consumption, a fairly representative method, however, of charging for electricity used for power purposes. This system is very similar to the ‘“‘Manchester system” introduced by Dr. Hopkinson. The price charged under this system was made to depend upon a fixed rental plus a proportional charge for energy, the fixed rental being determined by the Fic. 5.—Diagram showing Wiring of the ‘‘ Adnil”’ One-meter System for Lighting and Power Circuits. after which the price per unit remains constant. Execrriciry Mrtsers.—It is not sufficient for a consumer of electricity to be acquainted only with the current and pressure which he 158 . ELE may be using, but he must also be able to ascertain the total energy delivered to him, irrespective of the current and pressure at any particular time. An instrument capable of measuring this energy is termed an “electricity meter.” A rough classification of electricity meters is afforded by the nature of the circuit on which they are intended to be employed. Thus there are those that can be employed on 1. Continuous electricity circuits only ; 2. Alternating electricity circuits only ; 3. Both continuous and alternating elec- tricity circuits. They may again be classed as 1. Motor meters, 2. Clock meters, and 3. Electrolytic meters. All three of these types are extensively used. Practically all modern meters are of the watt hour type, frequently called integrating or recording watt meters. These register the use of electricity in watt hours by - means of dials and pointers. Sometimes these dials are arranged to read directly in units (1,000 watt hours), and parts and multiples of units. Hach dial is ‘divided into ten divisions, and one revolution of the pointer of any dial is equal to one division of the dial of next greater value. The dials are most con- veniently and ‘accurately read in the order beginning with that having the lowest capacity, and in recording the reading, the result should be written from right to left. In Fig. 6 are given several dials which will serve as an illustration in reading. In this case the reading is 8839°5 Board of Trade units. The accuracy of meters generally lies between 1 and 2 °/, slow or fast. Three per cent. either side should be con- sidered the maximum allowable. A type of electricity meter which has come extensively into use, especially with small consumers, is the “ prepayment meter.” With this meter the consumer cannot possibly use more light than he pays for, and since he has to pay for the light before he obtains it, he does not incur any liabilities in this respect. MUNICIPAL AND SANITARY ENGINEERING. ELE TRANSFORMING STATIONS AND APPARATUS.— The electricity, when it is sent out from the Electricity Works, is usually of a pressure unsuitably high for the consumer’s purposes. Very often also, the consumer’s electrical apparatus requires to be supplied with elec- tricity of some other commercial variety than that in which it is sent out from the Electricity Works. The commercial names for the lead- ing forms of electricity are I. Continuous electricity, and II. Alternating electricity. This second form may again be sub-divided into Ila. Polyphase electricity, and IIb. Single phase electricity. It is in the form Ila, i.e. polyphase elec- tricity, that the energy is usually sent out from the Electricity Works. As sent out from Board of Trade Units /000 /00 10 ) 14nib per Division oO 1 oO 9 8 2 8 7 > 7; 5 4 5% 199 2 34.2 Fic. 6.—Arrangement of Dials on an Electricity Meter. the Works the electricity is of high pressure. Ti the consumer requires his electricity in this same form but at lower pressure, the change is effected by interposing a so-called stationary transformer. Such a piece of apparatus is, in principle, a laminated iron structure on which are wound two coils, one of which, termed the primary, is connected to the high pressure circuit, the other, termed the secondary, being connected to the low pressure circuit, 2.e. to the circuit on the consumer’s premises. Stationary transformers also suffice for obtain- ing a single phase supply from a polyphase circuit. Thus, when it is required to simply 159 ELE change the pressure of alternating electricity, a stationary transformer suffices. In this type of apparatus the transformation is effected at an efficiency of some 90 to 98 °/,, accord- ing to the size, periodicity, and pressures. Very often, however, the required trans- formation is from the high pressure polyphase electricity supplied from the Electricity Works, into low pressure continuous electricity; in fact, in the majority of cases, the low pressure circuits, whether for lighting or for power, are designed for continuous electricity. To effect a transformation of energy from any form of alternating electricity into con- tinuous electricity, rotating apparatus is required. The transformation is usually effected on a large scale in apparatus located in so-called sub-stations. The most suitable apparatus for the purpose is a motor generator. The motor receives the electricity to be trans- formed and converts it into mechanical energy, which serves to drive the electric generator in which it again becomes transformed into elec- trical energy. This electrical energy is in the continuous form and of the pressure required by the consumer. The transformation is, in the customary sizes, effected with an efficiency of some 85 to 90 °/.. There is a device termed a rotary converter which is often put forward for such work. It is, however, as regards adjustability and convenience of operation, distinctly inferior to the motor generator. It has slightly higher efficiency, and is also cheaper, but its superiority in these respects is more than offset by its inferior operating characteristics. The same verdict applies to the so-called motor converter which is a compromise between the motor generator and the rotary converter. Exectric Morors.—The most suitable type of electric motor can, in any particular case, only be determined upon by careful considera- tion of the work required of it. The two chief classes are 1. Continuous motors. 2. Alternating motors. 1. Continuous Morors.—Where a variable speed is required, continuous motors are pre- ENCYCLOPADIA OF ELE ferable, as any desired range of speed may be provided by suitably designed continuous motors. Exceedingly fine speed adjustments may also be obtained with these motors. Continuous motors may be divided into two broad classes : a. Series wound motors. b. Shunt wound motors. Series wound motors are usually employed for work where a high starting torque is desired, and where the motors are started and stopped at frequent intervals. They are almost invariably employed for tramcars and for electric propulsion in general. Series motors are not suitable where constant speed is desired at varying loads, since the speed of the motor decreases greatly with increasing load. Shunt motors should be supplied for cases where it is desired to obtain constant speed independently of load variations. This speed can be altered to any one of a wide range of values by simple adjustment of the excitation. After the excitation has been once adjusted, the speed remains constant for all loads until the excitation is readjusted for some other desired speed. This process is termed “ speed variation by shunt control.” 2. Aurernatinc Motors.—These are usually of the polyphase type and have the character- istic that, except for types of complicated construction, they can only be run efficiently at some one particular speed. This restricts their use to a certain extent, but for industrial processes it constitutes a valuable property. The most hardy form of polyphase motor is that commonly called a squirrel-cage motor, for the reason that the conducting system carried by the rotating member bears some resemblance to a squirrel-cage. In this type of motor there are no moving contacts, and consequently there is a minimum of likelihood of anything getting out of order. On the other hand, this type of motor has but slight starting torque, or when arranged for develop- ing any considerable amount of starting torque it is necessary to consume, during the process of starting, a very large current. The 160 ELE motor is so hardy as to be absolutely unharmed by these large but temporary currents. On the other hand, these currents interfere with the maintenance of good pressure regulation on the supply mains, and are thus harmful where lights are supplied from the same circuits. If the supply mains are liberally designed, there should be no objection to the use of squirrel-cage motors of not over 5 h.p. capacity, even when required to develop, at starting, one-third of their full load torque. Much larger squirrel-cage motors may also be permitted, provided they may be started up without load. When high starting torque with only moderate current consumption is required, polyphase motors of the slip ring type should be employed instead of squirrel- cage motors. With these slip ring alter- nating motors, equally good starting torque may be obtained as with continuous motors. With the slip ring type it is also prac- ticable, by the use of an external rheostat, to obtain any desired speed, but only at very low efficiency. There is another class of alternating motor termed the single phase motor. When a vari- able speed motor is required on premises where the supply is alternating electricity, a single phase commutator motor should be employed. For work where the speed may vary with the load, such motors are available up to several hundred h.p. capacity, but the types of single phase commutator motor suitable for con- stant speed with varying load, are only satisfactory in. very small sizes. All single phase motors are very large and expensive for their output, and they have relatively low efficiency as compared with continuous motors and polyphase alternating motors. Series wound single phase commutator motors have for several years been employed for traction, but with indifferent results. The chief drawback is that the equipment is far heavier and more expensive than the equivalent equipment with continuous motors. Hi, Mi. H, M.S. MUNICIPAL AND SANITARY ENGINEERING. ELE Electrolysis, Purification by.—Purifi- cation of water or sewage by direct electrolysis has been a failure in practice, mainly because a great part of the liquid passed nearly or quite unaltered between the electrodes. In an indirect process, the Hermite, sea water is electrolysed and added to sewage or used for flushing. The fluid acted in most cases as a solution of hypochlorous acid (see ‘‘ Chloride of Lime”), and its standard strength was 0:05 % of available chlorine. A cause of failure was that the solid lumps in raw sewage were so difficult of penetration. By the electro- lysis of brine containing 2% or 3% of NaCl, Woolf prepared ‘ Electrozone,’’ which was employed on the effluent at Maidenhead, but afterwards abandoned; it was later used with hygienic success at Havana, Cuba. Difficulties have been the expenditure of power in pro- portion to the result and the rapid spoiling of the solutions. A stronger liquid is now manufactured from brine by the “ Oxy- chlorides ”” Company in a special electrolyser which claims several economic advantages, while by certain additions the properties of the fluid are made more lasting. Its use is still being tried at the Guildford Sewage Works, and has recently been examined there by the writer, and also by the Sewage Commission. Raw sewages from this and other places, and effluents from septic tanks and primary, secondary, and tertiary filters, were treated with the solution under varying conditions to ascertain its efficiency as dealing with putre- factive and pathogenic organisms and with suspended matter which might cause sub- sequent trouble. The experiments showed, in common with the results of other investigators, that the germicidal power of these solutions was exerted almost immediately, and was greater than the chemical measure of their ‘available chlorine’? content, but that the latter was very rapidly reduced by organic matters present, whereas it was advisable for a small margin to be left for a slightly longer continued action, in which the active chlorine would disappear. For efficiency the chlorous solution is therefore applied quantitatively, 161 M ELE and for economy the organic matter should be previously reduced by ordinary sewage treatment, the electrolysed solution being used as a “finisher.” In the strong raw sewage at Guildford the total organisms were reduced by 3 parts per 100,000 of available chlorine from several millions to 50,000, by 5 parts to 20, and by 7 parts to 10 per c.c. With 3°7 parts available chlorine the reduction was: coli organisms from over one million to none found in 1 «.c.; enteritidis spores from over 1,000 to less than 10; total organisms from 28 millions to 240 pere.c. Average weaker sewages gave similar results with less of the solution, and within limits a longer period of treatment algo allowed of a lower available chlorine. The sludge was less, and when spread on land remained sweeter than with ordinary chemical treatment. It was found that in these pol- luted liquids about 60% of the available chlorine was almost at once taken up by the organic matters, while the remainder acted immedi- ately on the bacteria and more slowly on the resistant impurities. In septic tank liquors with 24 to 44 parts of available chlorine and 1 to 4 hours contact, an original content of 24 to 44 million total organisms, 100,000 to a mil- lion coli, and 10 to 1,000 enteritidis spores per c.c., became 20 to 600 total, with coli and enteritidis absent from 1, and in most cases from 5 c.c., while the incubation and dissolved oxygen tests were also rendered satisfactory. With good effluents sterility, except as regards a few organisms of the hay- bacillus type, which are useful in the further breaking down of organic matter, was ensured by 5 parts per 100,000 of available chlorine, and removal of colt and enteritidis by 0°5 or even 0°25 part, in 2 to 4 hours. Mixing and proper time are attained by running through a con- duit with baffle plates or cascades ; the effluent at the outfall should show a faint blue tint with iodide of potassium and starch. The solution also proved effective against the growth of alge and fungi in waters, and in the treatment of a tap water for conferva the only chemical alteration was an increase of the chlorine from 2°1 to 2°4 parts Cl per ENCYCLOPAEDIA OF EST 100,000 and a decrease of the ‘‘ oxygen con- sumed.” The Royal Commission on Sewage found at Guildford that a small quantity of the liquid rendered septic tank effluents in- offensive, and that “a dose of oxychloride more than sufficient to remove smell and kill coli did not prejudice the purifying ability of filters.” The above results as to conditions for practical sterilisation have been since confirmed by Phelps and Carpenter at the Massachusetts Station,! who consider that electrolytic chlorine is cheaper and probably more efficient than chloride of lime, and by Kellerman and others for the U.S. Depart- ment of Agriculture.? (See also ‘‘ Ozonz, PurIFIcaTION OF WATER BY.’’) 5. R. Enteric Fever.—(Sce “ TypHor Fever.’’) Estimating (General Engineering).— The methods by which the cost of engineering work may be arrived at vary somewhat with the class of the job, and also with the purpose of the estimate. If, for instance, a municipal engineer wishes to count the cost of a pro- posed undertaking, which, if proceeded with, will be executed by a contractor, he will chiefly be concerned with the price to be paid, not with the actual cost of the work to the contractor or manufacturer. If, on the other hand, the work is to be carried out by his own staff, he will require to ascertain the probable cost of production. In the first case the engineer will be in the position of a buyer, and will, therefore, acquaint himself with the market values of the various classes of material and workmanship contained in his scheme. Supposing, however, that he intends to carry out the work himself, he is then somewhat in the position of a contractor, except that he will not be embarrassed with the difficult question of profit. The latter depends upon the nature of the work, the state of trade, competition, the reputation of the contractor, and other factors. To properly 1 « Techn. Quarterly,” 1906. ° Bulletin 115, Oct., 1907. 162 EST weigh such considerations requires a know- ledge of, and a talent for, business, that can only be gained by experience, coupled with an aptitude which is more or less a gift. From what has been said it will be evident that two principles are involved in an engineering estimate—the technical and the commercial. The technical work consists in calculating the quantity and frequently the weight of the material, and estimating the amount of labour required, whilst the pricing of the material and labour, and the addition of a proper sum for working expenses, contingencies, and profit, constitute the commercial element. The materials employed by engineers are numerous and varied, but the methods used to determine their extent are much the same in all cases, and consist in the practical appli- cation of the rules of mensuration. With some materials, such as metals, a further calculation is made to ascertain their weight, whilst with others this is unnecessary, as their price is based upon the cubical con- tents and sometimes their superficial area. Obviously, many articles will be purchased in a finished state. The estimation of work- manship is far more difficult and needs experience and judgment. Cost sheets of similar jobs, when available, should always be studied, but the information derived therefrom must be applied with discretion, as the con- ditions may not be the same, especially after a lapse of time. Certain articles of manu- facture, castings and forgings for instance, are so regularly and repeatedly produced that a rate, varying with the class of the work, can be charged, which will cover both material and workmanship. In this case it is, of course, only necessary to calculate the weight of the article—whether itis produced on the premises or bought outside. The number of foremen, shop labourers, and others indirectly engaged upon the work, bears a fairly constant relation to the number of craftsmen, so that, except in special jobs requiring extra supervision or assistance, their wages are not directly charged, but added in the form of a percen- tage, usually upon the skilled labour. Two 163 MUNICIPAL AND SANITARY ENGINEERING. EST systems of pricing materials and workmanship are in vogue; the simpler and more usual plan is to charge them at rates which will cover working expenses and include profit, the resulting estimate representing the probable cost to the buyer. The other system is to rate the material at its actual cost to the manu- facturer, and to debit each item of workman- ship with the wages that it is estimated, will be paid, plus a percentage to cover working expenses. In this way, the probable actual cost to the manufacturer or contractor is arrived at, leaving him free to add a sum for contingencies if the work is of a nature to require it, and whatever amount of profit he may desire, or consider advisable. This is certainly a more exact method than the other, and has many advantages; for one thing it enables a close comparison to be made between the estimated and the actual cost of the work. The question of working expenses is a most important one, as in some branches of engineering, ¢.g.,a machine shop, they amount to as much, or even more, than the wages paid to the skilled men. Working or indirect expenses may be said to consist of those items which it is not practicable to charge directly to the customers, such as rent, rates, fuel, wages of unskilled labour, supervision and management, interest on capital, repairs, insurance, and the many other expenses incurred in carrying on the work of an estab- lishment. They may be arrived at by dividing the total expenditure over a given period under three heads, viz., materials charged to jobs, wages ditto, the remainder representing indirect expenses. The ratio that the last will bear to the direct expenditure will vary with the nature of the work carried on, and therefore will not be the same for each department; further, it will alter from time to time, according to the state of trade. The percentage representing indirect expenses might be applied to material, wages, or both. As wages are not liable to such fluctuations as material, and for the reason that many items of indirect expenditure will vary with the number of skilled workmen employed, a uM 2 FER percentage based upon the wages of the latter will generally bear a more constant relation than one upon material, and is in consequence usually to be preferred. ‘This point is, how- ever, largely decided by the nature of the business. As previously mentioned, some departments are more expensive to run than others; to arrive at a correct distribution involves a careful division of the aggregate expenses into those which are special to each department and common toall. If the special expenses are allotted to the departments incurring them, and the common expenses are spread over the departments in proportion to the skilled wages paid in each, a practically correct distribution should be effected. E. L. B. Ferozone, or magnetic ferrous carbon (see ‘‘ INrERNATIONAL Process or SEWAGE PuriFication’”).—This material is obtained from the same mineral that forms the basis of “ polarite”’ (see ‘‘ Potarire’’), but is treated in a different way. Ferozone is rich in ferrous iron, and alum, calcium, sulphate of magnesia, and rustless magnetic oxide of iron are amongst its constituents. The object of the “ferozone”’ is to act as a precipitant and to assist in the disinfection and deodorisation of the sewage and sludge. Ferrometer.—(See ‘“Conprr’s SuLpHatE or Iron Process.”) Filtering Head.—(See “ Fiurrarion.”) Filters, Domestic.—Filters may be used in domestic practice for removing visible suspended matter, for arresting microscopic organisms such as bacteria, and for modifying the chemical composition of the water itself. From the sanitary standpoint the effect of a filter on the chemical composition of a natural water is of no practical importance. Apart from injurious metals, such as lead, and from excessive quantities of such salts as calcium carbonate, on which filtration exerts only a trifling effect, it is questionable whether any ENCYCLOPADIA OF FIL chemical constituents even of polluted waters in the quantities in which they can occur naturally have any physiological effect at all. There is certainly no evidence whatever that water which has been subjected to such chemical modification as can be produced by a filter is in any respect more wholesome or less dangerous than the same water before it has undergone such chemical treatment. Few domestic filters do more than remove suspended matter. They generally allow the passage of bacteria through the filter-mass into the fil- trate. Ifa water which has been infected even slightly and temporarily is passed through such a filter, some of the infective bacteria will be arrested in the favourable breeding ground provided in the filter pores, and may multiply there for very long periods, causing enormous increase in the extent of infection of any further water which may pass through it, or polluting dangerously a fresh supply of water which before filtration may be quite pure. Accordingly the ordinary chemical filter, whether of carbon (animal or vegetable charcoal, plain, “‘ silicated,” or “‘manganous ”’), sponge, felt, iron (spongy or magnetic), or equivalent materials must be condemned as able to produce grave danger and wholly incapable of affording any real protection to health. When used for the removal of visible suspended matter any suspicious water passed through them must be treated so as to destroy or remove any disease bacteria which it may contain. The removal of bacteria from water by filters depends on some surface action which is not thoroughly understood. It is not merely a straining such as occurs in the removal of visible suspended matter, for bacteria will be arrested in pores much larger than themselves. Bacteria so arrested may find their way ultimately into the filtered water if the conditions are such as to allow this. This passage of bacteria through the pores is not caused by mere pressure of water, and is probably due to the growth of the bacteria in the pores of the filter under the influence of substances favourable to their development. The extent to which this 164 FIL growth occurs depends on the nature of the bacteria. Those which are normal inhabit- ants of water, and, therefore, develop at low temperatures upon substances such as are contained in water, will grow through the pores of a filter, when bacteria which cause disease in man and grow normally at higher temperatures and upon media not found in water may fail to penetrate. Of bacterial filters the Pasteur (Chamberland) is the best known. Laboratory evidence has shown that it arrests any pathogenic bacteria contained in drinking water, and, what is still more MUNICIPAL AND SANITARY ENGINEERING. FIL applied direct to the main, the filtrate being collected in a suitable reservoir. The filter is thus kept constantly charged and omissions to fill it avoided. A filter should be chosen of larger initial output than what will be actually drunk, as there is some decrease in output through use, the extent varying with the nature (not necessarily with the bac- teriological quality) of the water. W. P. Filter-Presses for. Sewage Sludge.— Of the various methods for dealing with sewage sludge, that of forming it under = a ‘“‘Dehne” Sludge Press, by Harzer & Co. important, the filter has been used widely under conditions permitting accurate record of the effect on waterborne disease. Other forms of filter devised for bacterial filtration are the Berkefeld in infusorial earth, the Mallié, and the Doulton. No considerable practical experience is available in regard to the last two. The Berkefeld was the filter supplied to the British troops in the South African war, and experience gained in that campaign, con- firmed by a subsequent investigation in the laboratories of Netley Hospital, showed that, contrary to what had sometimes been hoped, it could not give the required protection without precautions and tests that are im- possible in domestic use and even in general institutional practice. Wherever possible a filter should be of the “‘ pressure” type and pressure into cakes is among the best. For this purpose filter-presses are used, by which means the greater part of the superabundant moisture isremoved. Agood typeof filter-press consists of a number of strong corrugated iron plates placed vertically, each pierced with a hole in the centre, and having planed margins raised somewhat above the levels of the corrugations. These plates are covered on both sides with filter-cloth, which is fixed around the centre holes. When the plates are tightened one against the other a hollow space is:found between each two plates owing to the raised margins. The end plate is not pierced, and the packing of the filter-cloth makes the spaces quite water-tight even under pressure. The liquid to be filtered is forced through the hole in the first plate, filling the 165 FIL hollow spaces one after the other, and driving the air out by way of an air-valve which is closed as soon as the liquid is seen to rise. As the pressure is continued, the liquid is forced through the filter-cloth, leaving all solid matter in the hollow spaces between the plates. After having passed through the cloth the clear liquid runs down the corruga- tions, and finds exit through a channel to a trough outside the plates. When the accumulated solids have filled all the hollow spaces (about two-thirds of the space of the whole press), the shutting arrangement is loosened, the plates separated, and the cakes of solids allowed to drop out. These sludge presses can be made with any desired number of plates and the flanges keeping the plates apart can be made of such depth as to provide pressed cakes from 1 in. in thick- ness upwards. The amount of moisture retained and the character of the effluent depend partly on the nature of the filter-cloth and partly on the pressure used, supplemented by any drying process adopted. The drying can be carried on while the cakes are in the press, before it is opened, by passing either hot air or steam through the cakes by an arrangement of channels, which ensures every part of the cake being thoroughly treated. The cakes thus obtained are quickly made and can be easily handled. The process is as uearly as possible automatic, and is cheap. Filter-presses of this description are in use at the Oldham Sewage Works, where Dr. J. Grossmann’s system of extraction of fatty acids from the sludge, and the utilisation of the solid residue as a fertiliser in the form of a dry sterilised odourless powder, containing a high percentage of nitrogen, is being carried out. Filtration (of water, through sand.)— Filter Beds—Sand Washing—Refilling Beds after Skimming—Length of Service.—Abso- lutely pure water, as understood by the chemical formula H,O, does not occur in nature, and, without aération, is an un- palatable liquid, not beneficial to the human ENCYCLOPAEDIA OF FIL system. The terms ‘‘pure” and “impure,” as ordinarily employed, are therefore of relative significance, and simply indicate that a water is either fit or unfit for human consumption. Some form of purification is necessary with the great majority of waters available for public use, as all are liable to contain impuri- ties both in suspension and in solution, consisting of organic as well as inorganic matters. Themeans adopted for purifying the water supply should be of such a character as to render the water perfectly fit for drinking without previous domestic filtration or boiling. Upland surface water often contains animal and vegetable impurities, and these sometimes cause great troubleby growths and obstructions in mains or pipe-lines, as, for example, arose in the conveyance of the Vyrnwy water from North Walesinto Liverpool. Gathering grounds may also be polluted with peat, iron, or even with animal excrement. But it is with river and low-lying lake supplies that the greatest measure of risk lies, such, for instance, as - obtains in the ease of the rivers Thames and Lea, from which a very large part of the London supply is derived. In all such cases an efficient system of purification, as carried out by the Metropolitan Water Board, is an absolute necessity. Springs afford a safer supply, but their gathering grounds require constant supervision, as surface waters may at times gain direct access to.the water by fissures. Underground or deep-well waters are frequently of a high degree of organic purity, but are oftentimes’ highly charged with mineral impurities in suspension or solution, such ag iron, salt, lime, &c., which require removal or reduction by appropriate means before the water can be utilised for public supply. Attention must be directed to the biological purity of the water as well as to its chemical characteristics, and, since pathogenic impurity may escape both bacteriological and chemical analysis, efficient filtration is the only remain- ing barrier tending to safeguard the con- sumer. But even the most careful filtration 166 FIL cannot always be regarded as an absolute safeguard, hence itis usually wiser to abandon a polluted source of supply whenever an initially pure water is available at reasonable cost. Fintration.—The greatest dangers in a public supply is that the water should become a vehicle for the dissemination of diseases such as typhoid and cholera, and the con- nection between sudden outbreaks of this description and the water supply may be best studied from the official reports of inquiries into the epidemics occurring at Worthing (1893), Maidstone (1897), and Lincoln (1905); also at Hamburg and Altona in 1892. In the latter case the practical advantage of sand filtration was proved to be very marked, for, whilst cholera was rampant in dis- tricts supplied with Hamburg unfiltered river water, the population drinking the Altona water, subjected to careful sand filtration, was comparatively free, Enor- mous reductions in the per- centage of bacteria are brought about by sedimenta- tion followed by sand filtration. Sedimentation affords one of the most important natural means of purification, and is carried out ‘ upon a large scale in connection with the supply of river water to London, notably at the large settling and storage reservoirs of the East London Waterworks adjoin- ing the Lea at Walthamstow and at the new reservoirs constructed for the purpose of ‘taking in Thames water when the river is high, as recently completed at Staines. Simple sedimentation, if the water be allowed to stand long enough, removes nearly all the suspended impurities, and carries down a large proportion of bacterial life contained in the water, some 50°/, of the latter being removed by 12 days’ storage. Purification by this process is, however, slow, and the necessary tanks and reservoirs occupy a large MUNICIPAL AND SANITARY ENGINEERING. FIL amount of space and are costly, but, where efficient sedimentation is carried out and the water subsequently passed through sand filters in the best condition, the number of microbes in the filtrate is found to be reduced by as much as from 97 to 99°/,. Some of the principal factors affecting the reduction of bacteria in a water supply are: (a) the length of time for sedimentation given to the raw unfiltered water ; (b), the fineness of sand and thickness of bed through which it is filtered ; (c) the rate of filtration through the sand bed ; (d) the cleansing of the bed, the renewal of sand, and the general care and watchfulness of the attendants in carrying on the process. Fitter Brps.—The most general method 4; Asphaite on Concrete Fic. 1.—Section of Sand-Filter Bed, showing arrangement of Brick Under-drains and Graduated Layers of Filtering Materials. of purification in England, where large quantities of water have to be dealt with, is that of slow filtration through sand. The various filtration works for the supply of London with water from the Thames and Lea are among the largest and most efficient works of the kind in the world. A “filter bed” is formed by constructing a large shallow tank or reservoir, about 8 ft. deep, usually by excavating partly in the ground and part embanking, and building the walls of brickwork or concrete made water tight with a rendering of cement mortar or a lining of bituminous sheeting overlaid with 42 in. brickwork, or.with concrete. The floor of the filter is given a longitudinal slope towards the outlet, and a cross slope to the 167 FIL centre, so that the water draining through the sand may run to a common outlet. In filling in the materials into the filter bed, the object to be kept in view is to secure an open porous under-layer, and to this end the first material laid in is of the nature of large stones or sea-beach having a large longi- tudinal open-jointed collecting drain running through the centre of the floor of the bed with small laterals or branch collecting pipes cross- ing the bed at intervals of from 3 ft. to 6 ft. The means of collection from the bottom of the bed should be as uniform as possible, so as to secure an equal rate of filtration through- out. One method (Fig. 1) is to form the collecting channels with a 8-in. layer of bricks laid on an asphalte bottom, and overlaid Fig. 2.—Section of Outlet Chamber to Filter, showing Regulation of Water Head. with another course of bricks placed close together to form a roof over the channels, to carry the gravel and sand which is then laid in. The bricks so used should be of a good, hard, durable quality, not liable to pulverise and break down, otherwise settlements will be caused in the sand, the underdrains become blocked, and unequal filtration or leakage will take place through the sand. The filters should contain a layer not less than about 2 ft. thick of good, sharp, clean sand, consisting as near as possible of pure silica. It is necessary that means should be pro- vided for the regulation of the rate of filtration and the measurement of the supply to each filter, so that the proper amount of ‘‘ head ” of water may be maintained on the sand. The depth of water on the bed is generally ENCYCLOPADIA OF FIL put at about 2 ft., and the rate of filtration should not exceed from 4 in. to 6 in. vertical drop per hour—equivalent to from 18°75 gallons to 287125 gallons per square yard of surface per hour. A rate of about 2 gallons per square foot per houris generally allowedin thiscountry, but a good deal will depend upon the condition of the water. When a filter has been drawn down it should be partly refilled from below with filtered water until the sand is covered, and for this purpose advantage may often- times be taken of the “‘ head” available from an adjoining filter. The unfiltered water may then be delivered into the filter, and the surface of the sand will not be disturbed. With the same object in view, means should also be provided at the inlet to break the flow of the incoming water by providing a water cushion for the water to fall upon and pass thence quietly on to the filter. The surface of a sand filter requires cleaning at intervals varying from about 10 days to 4 or 5 weeks, according to the quality of the water. This is done by skimming off about 4 in. to 4 in. of the surface of the sand with wide flat shovels, placing the same in heaps on the filter for removal to a sand-washing floor. The sand so removed is not usually immediately replaced, but re- mains until a number of such skimmings have reduced the total thickness on the beds to from 12 in. to 18 in. The thick- - ness igs then made up to the original level with the washed sand, which is well mixed with that already on the filter bed. Some- times the top layer of sand remaining on the bed after the last skimming is removed before putting on the clean sand, and afterwards put on the top of the latter layer. The first water from a filter after cleaning will not, as a rule, be satisfactory for use, unless the filter has been refilled from below, and is therefore frequently run to waste. This arises mainly from the fact that the bulk of the work of filtration is done in the thin film of sand on the surface of the filter, which, after a very few days’ use, becomes coated with a fine 168 FIL deposit of mud, and a gelatinous vegetable growth sets in, thus forming a coating which proves to be by far the most efficient part of the filter. Once formed, the surface film should not be broken until the filter requires cleaning. To avoid disturbance of the filtering layers of sand, it is necessary to provide for the free passage of air to and from the bottom of the filter by means of air pipes in the side walls of the filter. The roofing over of filters is not often done in this country, although there are advantages to be derived therefrom in the prevention of frost, and the exclusion of direct sunlight, which gives rise to the evolution of gas from the top layer of sand, and causes patches of the surface film to rise and float on the water, thus leaving bare places on the filter through which the water filters more rapidly than on the adjoining surfaces. ‘The area of filters required for any given popu- lation may readily be calculated from the permissible rate of filtration already named, allowing a supply at the rate of from 25 to 30 gallons per head, and adding to the area so arrived at an additional area of about one- fourth of that quantity. This additional unit of surface is required so that any cor- responding section of the total area may be thrown out of use for cleansing purposes without interrupting the continuance of the supply. For a supply of 1,000,000 gallons per day an area of at least 2,800 sq. yds. of beds would be required, filtering at the rate of 450 gallons per square yard per 24 hours, on the assumption that this rate of filtration could be regularly maintained. As the filters become “ ripe,” however, the rate of filtration decreases, and the quality of the effluent increases. Sand filtration does not, of course, entirely prevent the passage of bacteria through the sand, and attempts have been made to produce a perfect artificial filter, so that the passage of bacteria and their spores may be entirely prevented by passing the water under pressure through materials having capillary passages sufficiently fine to attain this object. Filters of this type are MUNICIPAL AND SANITARY ENGINEERING. FIL the Pasteur-Chamberland filter, using biscuit porcelain as a filtering medium, and the Berkefeld filter, in which baked infusorial earth is employed. If properly attended to and frequently sterilised these both give satis- factory results for small domestic filtration purposes. A public water supply, however, should be of such a quality as will render domestic filtration quite unnecessary, as it rarely happens that domestic filtration is carried out with sufficient care and attention to yield much advantage to the householder, and in many instances the so-called filtration becomes positively harmful. Efforts have been made by means of the surface film upon sand to increase the power of sand and other granular materials to arrest bacteria when passing through the pores of such substances at a. greater speed than is ordinarily permissible for successful filtration. This has been done by adding coagulants, such as alum, to the water to be filtered. The effect is to quickly produce a gelatinous substance between the particles of the filtering material. The sand used for filters should be as nearly as possible pure silica, and be quite clean and sharp. The grade of the sand- grains may be between ‘005 in. diameter and ‘Ol in., or say ‘008 in. on the average. Fine grade sands give better effluents than coarse, but the filters naturally choke more readily and call for more frequent cleansing. Tf, on the other hand, the sand should be too coarse, the impurities penetrate more deeply into the bed, and so entail the removal of a thicker coating at each cleansing. It is often a difficult matter to procure a suitable sand in the locality of filter beds, in which circum- stances it becomes necessary to import material from a distance. The present writer has obtained large supplies of suitable sand from Hayle, on the coast of Cornwall. This may be placed in the beds without washing, provided the effluent for the first day or two is run to waste. The sand layer upon the bed may be from 2 ft. to 3 ft. in thickness, to allow a number of skimmings before renewal 169 FIL with new sand, or with the old sand removed, the same having first been washed. Sanp Wasuine.—Where plenty of good and suitable sand is readily obtainable, it may not prove economical to wash the sand skimmed off, but it is not often that the purchase of new sand is found to be the cheaper course. Several different types of sand washing plant are in use, such, for example, as that of Hunter & Goodman, as supplied to several of the London waterworks, and Walker’s, used at Reading. The main object is to secure thorough cleansing of the sand skimmed from the bed with the expenditure of a minimum of labour and water in carrying out the process. In many cases it is necessary to cleanse the dirty washwater from the sand washing pro- cess, and the writer has for many years used settling-tanks, followed by shallow filters, containing about 18 in. of boiler pan - ash, which proves very effective in rendering the water fit for disposal into a water course. Sand washing may cost from 1s. to 2s. 6d. per cubic yard, according to circumstances. The “filtering head,” or the difference of top water level within the bed and that in the “outlet chamber,” determines the rate of filtration, and some suitable means should be provided for regulating the work being done. Special appliances for this purpose are supplied by makers of waterworks apparatus, but all such arrangements should be as simple in design as possible, and involve a minimum of attention. The arrangement illustrated in Fig. 2 has been found to be simple in workjng, and to meet all requirements. The adjustment of the sluice valve A. regulates the quantity of water passing over the gauge at B., and the amount or depth of water going over the gauge is recorded at the ground surface by means of a float C. The valve D. admits of the draining down of the entire filter bed if required. Reriuuing Beps arrer Sximuine.—lIt is a good plan, after cleansing a filter bed, to refil the same with filtered water to the height of about 1 ft, if possible, from the bottom upwards, so as to avoid entrapping air in the 170 ENCYCLOPADIA OF FIL interstices of the sand, and also to avoid disturbance of the surface of the bed by the inflow of water from the top. Refilling from below is readily done where the beds are arranged at different levels, as, by a proper adjustment of the inlet and outlet valves, water from the high level beds may be made to head back into those at a lower level. Lenernh oF Service or Fitters.—The quality of the water dealt with is the principal factor in determining the length of time a sand filter can be run without skimming. In dealing with river waters and others con- taining a good deal of suspended matter, and much microscopic animal and vegetable life, the period of service of the filter will be greatly increased by preliminary storage and sedi- mentation. The London filters run for 80 to 40 days, according to the condition of the water and the amount of previous sedimentation which has taken place. At Berlin and Hamburg the usual period of run before scraping is about 40 days. Filtering operations are oftentimes much interfered with by animal and vegetable growths upon the beds, which, in certain seasons of the year, are sometimes so prolific as to choke the surface in a few days. When the filter is drained down for cleansing, these surface accumulations can often be rolled up off the surface of the sand like a carpet, leaving the clean surface of sand underneath. The writer has experienced much trouble in this connec- tion from an abnormal development of the diatom asterionella occurring in a mixed supply of underground water and spring water, the mineral constituents of the former favouring the rapid development of the growth when exposed to warmth and sunlight in open reservoirs or filters. Keeping the under- ground water separate, and treating it in mechanical filters, effectually removed the trouble from the open storage reservoir and sand filter beds. Binding materials, such as alum, lime, or sulphate of alumina, are sometimes added to the water to be filtered, with the object of increas- ing the power of the sand to arrest bacteria, ay FIN &c., in passing through the filter. The effect of the coagulant is to produce a glutinous sub- stance upon the filtering media, which acts much in the same way as the film of mud and vegetable growth which forms on the surface of the bed after a few days’ use. Coagulants are often added to raw turbid waters, especially in America, to hasten the deposition of fine suspended matter previous to filtration. Cost or Sanp F'1LTers.—This depends largely upon local conditions, the position and accessibility of the site, and facilities for obtaining suitable materials. Under average conditions uncovered sand filters may be expected to cost from £10,000 to £12,000 per acre to construct, and covered filters (seldom used in this country) about £15,000, exclusive of sedimentation basins and other extraneous works. The working cost of sand filters is also very variable. In London the cost ranges from 3s. to 4s. 9d. per million gallons filtered, including labour, sand washing, and all expenses of cleansing. In smaller works the cost would be proportionately higher. : W. H. M. Fine Beds.— (See “‘ Szewace Drisposau.”) Fire Stations and Appliances.—The site to be selected for a fire station should, if it does not stand alone, form the corner of a block. Ready egress and ingress are essential features to be aimed at, and it is desirable that the ingress should lead to a rear court- yard direct, and not through the engine-house proper; a back entrance to the engine-house admitting the engines direct from the court- yard. Owing to the rapid development of the automobile fire appliances, it is now first of all necessary to decide, before planning a station, whether the appliances are to be horsed or automobile. Unless there be some very cogent reason to the contrary, there should be no difficulty in deciding in favour of the automobile. In the latter case examina- tion pits are necessary under the engine MUNICIPAL AND SANITARY ENGINEERING. FIR stands, and drip pits 6 in. deep let in the flooring to receive the oil drippings from the engine. In the case of a steam motor engine a shaft connected with a chimney to the roof. over the funnel of the fire engine boiler is required to carry off the smoke from the oil fuel when the engine is lighted up on starting out. Where the appliances are to be horsed, the stables should be in the immediate rear of the engine, with the doors leading from each stall opening outwards to-admit of each horse being trained to run up to its allotted position under harness suspended above the pole of the engine. Steamers, Horsep.—For residential districts the capacity of a steam fire engine should not be less than 350 gallons per minute, delivered through a 1 in. nozzle. For manufacturing districts the pumping capacity of an engine should not be less than 450 gallons per minute, delivered through a 14 in. nozzle. The requirements of a district should govern the number and capacity of pumping fire engines. Unless the water supply for the district is such as to dispense with the necessity of a pumping engine, the engines should be of sufficient capacity to deliver the required number of 1 in. jets, which size alone can be considered as being the minimum diameter of efficient fire jets. Pumping Eneines, Avutomosrte.—Most people will consider that the steam- engine for an emergency service such as the fire service is the most reliable under all condi- tions. The uncertainties of the petrol engine as a power for an emergency engine, such as a fire engine, are such as to preclude absolute reliability (which in this case is an essential factor) being obtained where only one engine is available. On the other hand, where an absolutely reliable engine is always in reserve, the petrol pumping engine is decidedly an acquisition to the efticiency of a fire brigade. There is an important factor to be considered in deciding as between a petrol and a steam mechanically propelled pumping fire engine. The former stands practically ready to move 171 FIR out on the starting of the engine. In the case of a steam propelled engine it is necessary to have a sufficient head of steam in the boiler to enable it to be started in a given number of seconds. That is to say in brigades where the arrangements do not permit of an immediate turn out on receipt of a “call,” it is only necessary to keep a head of steam so regulated that the maximum pressure will be reached during the time which will elapse STORE ROOM RECREATION ROOM | DUTY Room ENGINE ROOM oS °o 70 20 30 40 se Feer — GRouno froor Pran — Fic. 1.—District Fire Station, London Road, Edinburgh. before the men are able to assemble at the fire station to proceed to the fire. If two minutes are required 20 lbs. of steam will suffice, if one minute is required 60 lbs. will suffice, if the engine is to be available for immediate turn out a minimum pressure of 80 lbs. is required. There are one or two different methods of heating the boiler of the steam motor-engine. The simplest is by inserting a gas ring burner in the fire box. This, however, is the most ENCYCLOPEDIA OF FIR expensive, for to maintain a head of 60 lbs. of steam will cost about £1 per week. An alternative to the foregoing is to raise steam in a stationary slow combustion boiler to the required head, and connect the latter to the fire engine boiler by flow and return pipes, by means of which the steam is maintained in the fire engine. From the point of view of cost of main- tenance at the fire station, the petrol engine is the more economical, but petrol being so much more costly than the paraffin oil used as fuel for the steam engine, the over-all maintenance is almost equally balanced between both types of engines. Host Tenper.—The utility of this class of machine consists of the quantity of gear and number of men carried upon it, Whether horsed or mechanically driven, a useful hose tender should carry from 1,200 to 1,800 ft. of hose, 4 stand pipes, 8 branch pipes, nozzles, breechings, hand- pumps, lines, scaling and hook ladders, jumping sheet, lamps, &c. Horsep Escaps.— A machine having almost the same carrying capacity as a hose tender, carrying in addition a fire escape of an average height of 50 ft. which is secured in position by an easily detachable mechanical device. CuemicaL Eneine.—The chemical engine, or chemical cylinder, as constructed in this country, is an addition to a hose tender or horsed escape in the form of one or two cylinders of from 30 to 60 gallons capacity which are charged by gas generated by a mixture of bicarbonate of soda and nitric acid. Another, and latterly more largely adopted method of supplying gas power to discharge the water from the large cylinders, is to carry compressed air in high pressure cylinders which are connected up to the water cylinders and controlled by valves. The advantage of the compressed air over the chemically produced gas pressure is that as soon as the water cylinder has been discharged on the fire, the latter may be refilled and the compressed air cylinder is again available for 172 FIR immediate use. A 60-gallon cylinder will discharge an effective jet of water of } in. to 7s in. diameter at high pressure to a distance of 40 ft. for eight minutes. TurnrasLe Lapper.—These machines are built from 60 ft. to 85 ft. in length, and consist of three or four telescopic section ladders. They are built on a mechanically revolving base on a low platform, and may be obtained with either hand power or mechanical extend- WASHING. to s ° to ao so 40 so —— Grouno Fi00r Plan Fic. 2.—District Motor Fire Station, Stockbridge, Edinburgh. ing gear. The latter is an ingenious engine, which derives its power from compressed air or gas, in cylinders carried on the machine. Four such cylinders are usually carried, and will raise the ladder to its extreme height, an average of several times. These ladders are indispensable to fire brigades in districts where the buildings ure above the average height, as they are readily available either for saving life or for use as a water tower. MUNICIPAL AND SANITARY ENGINEERING. 60 FEET FIS Nozzues.—Theré are various forms of nozzles now in use; the most useful nozzles for fires requiring one or two deliveries being those controlled by a shut-off valve on the branch-pipe known as the “London” nozzle, -which is provided with one nozzle outlet. Another, and more effective nozzle is the “‘ Multiplex,” which has the alternative of: three sizes of nozzle, viz., 4 in., * in., and #in., and a shut-off. This is a useful nozzle, as it provides one of four alter- natives which may be obtained without shutting off the water. Shut-off nozzles should only be used on gravitation pressures. Steamers and other pump- ing engines should use the “ Multiplex ” “Steamer” nozzle which has three sizes: ? in., $ in., and 1 in., without a shut-off. A. P. Fish Life in Streams.—The well- known fact that fish are greatly affected by the condition of streams has led to the proposal of a “fish test’ for effluents, namely, that their quality should be such that fish live healthily in them. Such a definition involves necessarily the absence of poisons and the presence of dissolved oxygen. But while an effluent that kills fish is obviously unhealthy, it does not follow that one where fish will live is therefore a good one. Fresh water species are gross feeders, and are often seen in large numbers at. the mouths of sewers, where fecal matter is visibly floating, being attracted by the insects, crustacea, and fragments of food. They are, in fact, more affected by muddy water and by chemicals from factories than by excreta, which some actually feed on. Perch and trout can live in water holding 8 or 4 c.c. of oxygen in solution out of the average of 7 c.c. per litre, but are soon asphyxiated when only 1:7 cc. is present. They are not injured by car- bonic acid till 10 to 15°, by volume is reached. Fish often die at once when placed in an effluent from chemical precipitation 173 FIS with lime and ferrous sulphate, on account of deficiency of dissolved oxygen. Fish as a rule prefer clear streams, and only enter muddy water for food and for breeding purposes. Heavy sediments act injuriously by covering the bed and closing up resting places, and in spawning grounds by interfering with the ova and cutting off the light that is necessary for normal develop- ment. Butit is pointed out that as salmon traverse the long muddy reaches of the Usk, the Humber, and the upper Severn, the mud and silt of these rivers cannot be inimical to grown fish, or at all events to salmon. A chemical investigation of the sediment in rivers is of great importance. In one case the mud for over 400 yds. below a works dis- charge was impregnated with naphthalene products, and when disturbed was poisonous to river life, and the writer found the deposit below a paper mill to contain gypsum, chalk, and various pigments, and that below a copper works, to contain this metal; the fish in both were injuriously affected. The effluent from lead mines is similar. In another river where the fish had died, he observed the sediment to be black from ferrous sulphide: the water contained much ferrous iron in solution, which had robbed it of dissolved oxygen,and had modified the aquatic vegetation to anaérobic and semi-aérobic kinds causing offensive odours. Sharp quartz particles and coal washings may cause injury to the eyes, gills, or even the skin of fish, which are some- times “smothered,” through mechanical clogging of the gills by a discharge of sludge when a mill-dam is opened, and in certain cases by storm water. The same effect has occurred from the abundant growth of “distillery fungus,” leptomitus lacteus, where “burnt ” ale, spent lees, and general waste are sent into streams. In America, great destruction of fisheries has been occasioned by the discharge of sawdust. In these cases also, deficient aération is at work, since all crude effluents, heavily loaded with organic matter, such as the above, and those from starch factories, tanneries, &c., deprive the ENCYCLOPADIA OF FLO liquid of free oxygen, hence the chemical figures of dissolved oxygen, and oxygen con- sumed, should be continually watched in relation to their amounts in the river and the volumes of the two waters mixing. As dis- tinguished from fungus growths, green aquatic vegetation renews the dissolved oxygen, and when not too dense gives a shelter to fish, and, by their feeding on it, is hindered from overgrowth. In certain cases the pollution of estuaries and shores has also done damage to sea fish. At low temperatures, while the solubility of oxygen in water is greater, the amount required to support fish life has been shown to be much less; therefore it is in the summer that special regard must be given to the oxygen content of streams. Other factors, such as disturbance, injury to spawning grounds, and obstructions to access, require consideration, and an increase of the number of birds that feed on fish may render the latter scarcer. Under conditions of proper dilution and aération, the discharge of sewage or of sewage effluents, is beneficial to fish, since it nourishes crustacea, such as shrimps, and other small life which then form the fishes food. But from polluted rivers it has been shown that the colon bacillus is taken up by fish and multiplies rapidly in their intestinal tract, while its absence was noted in fish from unpolluted waters, and it seems likely that typhoid and other pathogenic organisms may be carried by fish migration. For further details on the subject see the reports of the Royal Commissions on Salmon Fisheries, 1902, and on Sewage Disposal, 1908, Appendix VI. 8. R. Flash Point.—(See “Om Ewnernzs.”) Floating Arms.—Floating arms are em- ployed to draw off the supernatant liquid from precipitation and sedimentation tanks without disturbing the sludge which has been deposited in them. ‘They are also used to empty water- filters. The arm consists of a trunk, generally of iron, and rectangular in section, pivoted at its lower end on the outgoing pipe, and 174 FLO having at its upper end, which is open, a float, so placed as to hold the mouth of the trunk just below the water level. When the tank is full, the arm is steeply inclined, but, as the liquid is drawn off, it gradually falls, until it rests in a nearly horizontal position on the floor, the level of the mouth meanwhile keeping pace with that of the surface of the liquid. A.J. M. Flow in Pipes and Conduits.—Laws of Fluid Friction — Hydraulic Gradients — Hydraulic Mean Depth — Velocity in Pipes — Formule — Futility of Close Calculations — Discharge —- Head for Velocity — Velocity in Sewers. — The velocity of flow in a pipe or conduit depends upon the relation between two opposing forces—the frictional resistances within the pipe, and the power available for overcoming them. Although for practical purposes it is convenient to regard the velocity as being uniform all over the cross-section of the flow, this is very far from being the case. The layer of fluid in contact with the sides is retarded by friction, and moves very slowly: the centre of the stream is subject to no such impedance, and the velocity here is much above the average. This consideration seems to point to the existence of a number of concentric cylinders of fluid, each sliding within the other at a rate which gradually increases as they approach the centre. The actual state of affairs is much more complex. In all but the smallest pipes the contents move in a series of eddies, more or less irregular, but having a general tendency to roll like wheels along the side. A large part of the power to which the motion is due is thus expended in overcoming the viscosity of the fluid. Laws or Fiuip Friction.—Fluid friction is subject to the following laws: (1) The resistance due to friction is not affected by differences in pressure; that is to say, the friction in a water-main at a given velocity is the same whether the water is merely running freely without pressure, or is subject to a MUNICIPAL AND SANITARY ENGINEERING. FLO pressure of several hundred pounds to the square inch. The same formule and tables therefore hold good irrespective of the pressure in the pipes. (2) The frictional resistance is proportional to the area of the wetted surface. (8) At very low velocities the frictional resistance is directly proportional to the speed ; but when the velocity is over 6 in. per second the resistance increases approximately as the square of the speed. (4) The frictional resistance is governed by the nature of the surface of the conduit. It was at one time believed that the former was independent of the latter, the fluid being supposed to slide along a thin film held in contact with the surface of the conduit. Subsequent experi- ments have shown that this is not the case, and that the nature of the material of a pipe Fie. 1. or conduit exercises a marked effect on the rate of flow in it. The force which causes the flow in a pipe is usually that of gravity, and is measured by the fall, or the loss of pressure or “head” in a given length of pipe. In some cases it is convenient to express the power expended in overcoming friction as so many pounds per square inch; but in dealing with water-mains or sewers it is more usual (in this country at any rate) to speak of the virtual inclination, or “‘ gradient,”’ of the flow. Thus a pipe 1,000 ft. long, which conveys water from one reservoir to another having its level 10 ft. lower, is said to work under a head of 10 ft., or at a gradient of 1 in 100 (= 10in 1,000). In America this would be called a grade of 1 %, or 52°8 ft. per mile. Hypravtic Grapient.—The gradient on which the flow in a pipe depends is not necessarily that at which the pipe itself is laid, but is the “ hydraulic gradient,” that is to say the slope from the water level at the source to that at the point of discharge; or, if the water 175 FLO is delivered under pressure, to the level to which it would rise in a vertical pipe erected at that point (see Fig. 1). Inter- mediate changes in the inclination of the pipe do not affect the flow, provided that no part of it rises to a height of more than 34 ft. above the hydraulic gradient. It is not desirable, however, that any part of the pipe should rise above the gradient line, as the consequent reduction in pressure is apt to lead to the disengagement of dissolved air, which would accumulate at the upward bends and obstruct the flow. Similar accumulations are apt to take place at all high points, even be- low the line of the hydraulic gradient. Suitable automatic valves should, therefore, be placed at all summits, to prevent the accumulation of air. In the case of a “rising main,” the hydraulic gradient will start from the point to ee Ke -------- CIRCUMFERENCE Fig. 2. which the water would rise in a vertical pipe carried up from the pump. The power which maintains the flow in a conduit is equal to the weight of the fluid multiplied by the fall, or loss of head. The resistance to the flow depends on its velocity and on the area of the surface with which the fluid is in contact. The circumference of a circle is shorter than the sides of a square of equal area. ‘The frictional resistance in a round conduit will therefore be less than that in a square one, having the same cross- sectional area, and the former will have a higher velocity than the latter with the same loss of head. For a like reason the velocity in a large pipe will be greater than that in a small one. Hypraviic Mean Deptu.—lf the cireum- ference of a pipe were straightened out, as in Fig. 2, to form one side of a rectangle having the same area as the pipe, the depth ENCYCLOPADIA OF FLO of this rectangle would be equal to one- quarter the diameter of the pipe. This depth is called the “hydraulic mean depth” (h.m.d.)—sometimes, less appropriately, the “hydraulic radius.’ The hydraulic mean depth of any cross-section may be obtained by dividing the area of flow by the ‘ wetted perimeter,” and the velocity in any such cross- section will be equal to that in the circular pipe having the same h.m.d. and hydraulic gradient. Tables of pipe velocities may there- fore be used to obtain the rate of flow in conduits of any form. Vevoctry In Pires Runnine Partiy Futt.— The h.m.d. and velocity in a pipe, such as a sewer, running half full are equal to those in the same pipe running full bore; and with depths greater than half the diameter the rate of flow will be even higher. ‘The maximum velocity (1°14 times that in the full pipe) occurs when the depth of flow is about four-fifths of the diameter, and the maximum discharge (1°08 times that of the full pipe) with a depth of fifteen-sixteenths of the diameter. On the other hand, with depths less than half the diameter the velocity is less than that of the full sewer. Fig. 3 shows the proportional velocities and discharges for a pipe running partly full, those for the full pipe being taken as unity. Formutz.—Within the limits of ordinary practice the rate of flow was formerly believed to be proportional to the square root of the product of the hydraulic mean depth and the hydraulic gradient, and the older formule were constructed on this basis. The first regular formula was that introduced by Chezy, and was as follows:— v=c Vrs, v being the velocity in feet per second, 7 the hm.d. in feet, s the slope, or fall divided by the length, and ¢ a constant to be determined by experiment. Different values for this con- stant have been obtained by various investiga- tors. Hytelwein fixed it at about 95, and his formula — v = 95 Vrs —was widely used down to the latter part of the last century. The rates of flow given by this and similar formule are found to be too high in the 176 FLO case of small pipes, and too low in that of large ones, the velocity as a matter of fact increasing faster than the square root of the hydraulic mean depth. This fact is taken account of in the formule now in use, in some of which also the constant increases with the gradient as well as with the h.m.d. The arrangement of some of these formule has in course of time been varied from that adopted by their authors, the symbols in particular having been changed by different writers on the subject. In the present article, 120 110 ms a 5 * 90 as Q S 7a Qs o i 60 8 Q 50 ~~ ~ aX 40 Se 5 3 30 an = 20 3 10 eo Oo 10 20 “30 ‘40 Proportional Depth MUNICIPAL AND SANITARY ENGINEERING. FLO Ganguillet and Kutter’s : 41-6 + ie i oe .= Vrs. 00281 n 1 + (416 ) = + + F a n being a coefficient for roughness, varying from 0009 for well-planed timber to 0°050 ‘for torrential streams encumbered with detritus. For pipes of cast-iron or stone-ware n lies between 0°010 and 0°013. For ordinary use Darcy’s formula is simpli- 420 /00 Pipe Full “80 °30 ‘50 ‘60 “70 100 Fia. 3. for the sake of clearness, the same symbols have been used throughout. Among the better known of the more recent formule are the following :— 2g ds Weisbach’s: v = + —____ < o1age 4. Obie Vv in which g = acceleration due to gravity = 32°2 and d = diameter of pipe in feet = 4r. 29 rs Darcy’s: v= uENEEEY aNT=Ys7;Y a7 x/ 0087285 (1 at BaO6G? 3;— Neville’s: v = 140 V rs — 11 rs. M.S8.E. fied by the substitution for the denominator of his fraction of a multiplier c, which ranges from 65 for 3 in. pipes to 118°3 for very large ones, the formula thus taking the same form as Chezy’s, viz, v= ¢ Vrs. Kutter’s formula is far too complicated for ordinary use, and several simplifications of it have been*-pro- posed which give substantially the same results. One of the most convenient of these is that devised by the late Mr. Santo Crimp and Mr. Bruges, and used by them in the preparation of their admirable “Tables and Diagrams” of velocity and discharge. This formula, in which the cube root of the square the hydraulic mean depth is 177 N FLO substituted for the square root of the latter, is as follows: v = 124 Vr Ws. The close agreement between the results of this formula and those obtained from Kutter’s, and their very wide divergence from those yielded by some of the older formula, will be seen from Fig. 4, which shows the gradient required according to the various formule to give a velocity of 8 ft. per second in pipes of different diameters. These formule, and the tables which have been worked out from them, 36 33 30 27 24 2/ 18 Diameter in Inches 8 / IN /00 200 Gradient ENCYCLOPADIA OF 600 FLO deviations in the diameter of a pipe of moderate size may easily affect its carrying capacity to the extent of several cubic feet per minute, while, as Messrs. Crimp and Bruges point out in the preface to their tables, the variations due to the smoothness or roughness of the pipes may range up to 20 % The effects of corrosion or incrustation will often be still more serious, water-mains having been known to lose more than half their capacity from these causes. e3 rg 800 /000 1200 Fie. 4. hold good, not only for water and sewage, but for liquids and gases of all kinds. Jt would, however, be inconvenient in practice to have to calculate the pressure of a gas in terms of the height of a column ofitself. The pressures of steam and compressed air are therefore expressed in pounds per square inch, and low pressures, such as those of lighting gas, in inches of water. Furimity oF Ciosz CaLcuLations.—One sometimes sees the carrying capacity of a pipe worked out to many places of decimals. Such minuteness of calculation is quite useless, as it presupposes a degree of accuracy which neither the formula nor the pipes employed are capable of attaining. The allowed Discuarce.—The discharge is arrived at by multiplying the cross-sectional area of the stream by the velocity: thus @ = a v, where Q = cubic feet per second, a = cross-sectional aréa in square feet, and v = velocity in feet per second. In circular pipes running full Q = Tv r Where the discharge is given in cubic feet per minute, it can readily be converted into gallons per day by multiplying by 9,000. A convenient mode of arriving at the approximate discharge in gallons per minute direct from the velo- city is to multiply the velocity in yards per minute by the square of the diameter in inches, and divide by 10. The results dv, d being the diameter in feet. 178 MUNICIPAL AND SANITARY ENGINEERING. FLO FLO thus obtained are about 2% short of the true ones. velocity in question can never be attained in the length of the sewer. Liuits oF Veuocity.—lIt has been said that the velocity in a water-main should be between 2 and 44 ft. per second ; and occasionally 3 ft. The following tables, which are worked out from Crimp and Bruges’ formula, cover most of the cases met with in ordinary practice :— "SHILIOOINA NAAID BOL CaUINdAY SLINGIAVAY 990T 796 8F8 | .9E G10 | 606T| GOST] 969T) OBST) EFT 8L8T GLET 99TT rsh aon FOOT | SIST| Sart| 9ST} Le 8SIT 690T 086 T68 G08 a Bd @iFT| 66eT| GSst| GSsT| STL} FOTT} TeOT L96 788 ors 98h 899 ue a e6IL|__SSTL|_ FLO |__FIOL|__ 796 S68 gg8 GhL QTL 9S9 969 L&g “ 6r6 G68 88 108 PGh LOL 099 sT9 g9g 8Tg TLY GP LLS a GGL 989 o¢9 sT9 LLG Trg cog 697 S&P L6E T98 SCS 686 a ogg 0S LLY ISP OP 868 TLS StS SIs 666 G9G 686 GIG a 89s Oss 1gé STs 6G 9LG 896 684 Kad G0G FST 99T LPT jn 9&6 VGG GIG 006 68T LLY GOT sgt Tht OST SIT 90T | 3-6 | ut POT GST LPT 68T T&T 83I SIT o on oa hee a Mea ee S&T 96T 6IT SIT 90T | ¥-66 | 8-26 T-98 . : . ; ae Ho a : 46 |0-68 |8-88 |9-8L | 8-64 1-89 8-29 9-L¢ VG ; u £08. eon a 6:89 L-F9___|-1.09 1-99 1:29 I-87 L-tP 1-07 T-9¢ L-6s_ | 6:89 |0-9¢ |0-8g | T-0S TLb |Gbh | GIP $-88 6-98 P-G8 F-63 G-96 | 9-8 Ee 6-0F |6-88 |8-98 |8-FS L-G§ | L08 | 9-86 ae ne ya Ra ee ta ie . . 9-23 |G3S [0-16 |L6E | ¥-8T . . : ; ‘ 4 Let OT §-81 Gol | 8-IT O-TT |8-OT | 29-6 78-8 OT-8 98-L 89-9 | 68-9 u8 ‘aqnuto rad qoog orqng : edreyostq, 9 & sc | bag | + | ts fe | te | g % ¥% ¥% 3 “wed ‘puooes rad yoo, : AqIO0TOA, ‘SHILIDOTHA NUAIO HLIM SHOUVHOSIC, Boy BHeDPOHO DY Woe | © & Beer setae ite | ogg | ¢¢9 | sr | ¢98 | B66 | PITT | G8ET | 9LOT | 690 | 6T9G |. o aaa 3 ang ae 197 9T¢ | 8g | 99 | 294 | G88] LEOT | SSSI | GEFT GPST | GES | .8E z 2 3 az 5 oe $ g 6z2 | P9e | 907 | Sor | ETS | P89 | TL9| 8LL| S16 | 9SOT | FIST | SZOT $904 | .08 38 5-3 ocx € 2 | 98% | LTE | Soe | G6 | OFF | SOG | 89 |_929 P6l_| PF6_| SFLL| TIFT | S8LT | LZ 2,8 ee See 2 op Tse | Fer | S6F | SLE} 8L9 | L08 | 9L6 | GOST | SZST | uF Sea onBae we’ os PPG | OLZ | LOE | SEE hast | Te 4 . 23 2 Ey £02 | 922 | agz | 28% | BTS | S9e | ATP | FBP | 89S | 949 | LTS 600T “ 7 a my f oS, g9t | F8T | G0w | 08% | 092 | 96a | OFE | FES | ZF | OSE [G99 | Te OFOT | wBT eo | co ¢ a2 § Ost | SFI | T9T | IST | FO |_GES_| 99S | 608 | BIE TgP_| G6G_| FF9_ | STS_|_/ST a 23 ae 38 a 2 0 ; 16 | LOL | OL | PST | TST | GAT | SET | 622 | 69% ozg | see | 8Lb | G09 | .T 2g SSs3q 2 2 1 a3 92 |F8 |#6 | GOL| GIT | Set | Sgt] OST | ITZ | Tes | POs GLE | GLP | OL oo8 ar g q 5 99 |e, |18 | 16 | OL] ATT | Sel | 9ST} e8T | STS | 79s |) 9E | GIP 8 eres So 8 986 6L6 SSS 8 ie SHAS mH HH © 9¢ |e9 lon |82 |88 | OOT| SIT] PET] LST | 98T | 986 ‘ rane > oP os 8 Lp | %9_|89_|¢9_|F4_| *8_| 96_| GIL) Ist QST_| 68T_|_8Z__|_966_" |_uh oe og 2 g 3 2. Bs & se ler |2p |e¢ [09 |89 |8L | T6 | LOL | LVI | PST | O6T Or | 9 =a Ss a's 9a'5 a2 og lee lig lap jap | eo [eo | TL | 8 | OOT | Tet | GPT gst |. a oF 88 3 a8 zz |\¢oz [82 |e |se¢ jor |9F | 8S jo [FL | 06 | TIT OFT | WF aes >to HS 3 $ | 13 |Te |og [er log [19 Gh 196 =“ 3682344 og ct | LT [6 [Te | ¥6 geese 40% UL T + qUOTpBIH Zea © aS* ees F a. A & EB S 2 eM $ wlelel |e fe | te 8 %& % ¥ @ | “wed Sega nats? o “puooes aed qaa,q : £9190] A, Hos i gi Sa. 8> Sh HEC HOSS mains the head needed for these purposes may per second is mentioned as the limit which ought not to be exceeded. generally be disregarded, but with a short, The question of steep sewer that required to generate the tabled velocity will often be so great that the velocity is not, however, one to be settled by 179 n2 FLO any hard and fast rule, as the best rate to adopt is different in nearly every case. For a rising main, for instance, there is a certain size at which the interest on the cost of the onr Cea re of a Oi > me 3 N & 19 6D Oy aS pa re > 5 = ong H roo 8 EE a al oO na N ° erk 3g eo eS qo = 3 2 coos < DOS = 4 : 3 tO fH 19 1o tow iG OS AB ane a8 oon 5.8 FD a) nm wn oO oD o s 4 sH CO a, COON oe 0 DF A oO g‘a ons ae CO Beast wn oe a0. wk aS aren a Er o wat 19 OD A oOn® NOS oO q = Ort H wn moo fn BSS a 3 ‘8 osa 2 awe a ats e wss es s ono 9g * . . a = a 2 aa S oa 5 Aa oF mies a bat ES a O° 94 Qao'o Os a mo Oe eA pipe, plus the annual expense of pumping, is a minimum. With a smaller pipe the saving in initial cost is more than wiped out by the increased expense of pumping; while with a larger one the saving in pumping will not ENCYCLOPEDIA OF FLO suffice to pay the interest on the additional cost of the pipe. Vetocity in Sewers.— With sewers another set of considerations comes into play, namely, the necessity for maintaining such velocities in them as will prevent the formation of deposits. Du Buat and others have made careful observations of the speed required to keep various substances in motion, and to shift them again when they come to rest. Based on these observations, certain rules have been laid down as to the rates of flow which should be maintained in sewers and drains. For 4-in. and 6-in. pipes a velocity of 3 ft. per second is desirable, and for 9-in. and 12-in. sewers 24 ft.; while for still larger diameters 2 ft. per second is regarded as sufficient. For this reason, and because of their greater hydraulic mean depths, large sewers may be laid with gradients very much flatter than are permissible with smaller pipes. From this fact a tendency has arisen, in cases where fall is scanty, to employ larger sewers than are called for by the flow, for the sake of the flatter gradients at which it is assumed that they may be laid. The advantage thus sought is wholly illusory, since the actual velocity in a sewer at any gradient depends, not on the size of the pipe, but on the h.m.d. of the stream flowing in it; and, for any given flow, the larger the pipe, the less, as a rule, will be the h.m.d., and consequently the less the velocity. In arriving at the velocity, therefore, the depth of flow must be taken into account. Messrs. Crimp and Bruges’ tables, already referred to, include one giving the proportional h.m.d., velocity, and discharge, for depths of flow corresponding to every 735 of the diameter. To take a concrete example: a 4-in. pipe at a gradient of 1 in 160, running half full, will carry 4°9 cu. ft. per minute (44,100 gallons per day) with a velocity of 1:87 ft. per second. In larger pipes, laid at the same gradient, the depth and velocity will be as follows :— 6" pipe, depth 13”, velocity 1°82 ft. per sec. oF ” ” 13”, ” 1°75 ” ” 12" ” ” 14", ” 1°68 ” ” 180 FLO A 12-in. sewer would not infrequently be used in such a case, and a 4-in. pipe at a gradient of 1 in 160 would be regarded as out of the question ; yet the larger pipe would give a velocity only nine-tenths of that which would be attained in the smaller one. The rate of flow in a sewer is in fact governed by its gradient and by the quantity of sewage flow- ing in it, and only to a much less extent by its diameter ; and, so far as the velocity is affected by the latter, itis almost invariably greater in a small pive than in a larger one. For various reasons, such as the necessity for providing for storm-water or for a future increase of population, a sewer has often to be made much larger than would suffice for the ordinary dry weather flow; and instances are by no means uncommon in which the depth of flow does not ordinarily exceed one- tenth of the diameter. In such a case the velocity will be only two-fifths of that of the full pipe, and, unless the gradient is excep- tionally steep, will be far short of what has generally been supposed to be necessary. With flows at the rate of 1,800 gallons per day or under, and gradients flatter than 1 in 20, 14 ft. per second is the highest velocity which can be attained, and this only in a 4-in. pipe; and a 12-in. sewer at 1 in 100 will have a rate of flow of 2 ft. per second only when carrying 46,000 gallons per day or more. There are thousands of sewers all over the country in which the flow is utterly inadequate to maintain the velocities which are generally regarded as essential, and which, nevertheless, give perfectly satisfactory results. This apparent discrepancy between the indications obtained by experiment and the results of practical experience is due to a variety of causes, among which may be men- tioned the local increase of velocity which takes place wherever the waterway is narrowed by an obstruction, and which either moves the latter bodily onward or breaks it away piecemeal. Irregularities in the laying of the pipes, and the intrusion of the jointing material into them, play a much greater part in check- MUNICIPAL AND SANITARY ENGINEERING. FLU ing the flow in a sewer and in causing deposits than any reasonable flatness of the gradient. The velocity along the invert of a sewer is stated by Mr. Baldwin Latham to be 3% of the mean velocity. Wherever there is any doubt as to the self-cleansing properties of a sewer, flushing should be resorted to. In most pipe sewers the flow, especially near the head of the sewer, is liable to fall for hours at a time below the minimum which can be depended on to prevent deposit. It will, therefore, be prudent to provide means for flushing in every case. (See “ FLusHING.”) Maximum VeEtociry In Srewers.—In large sewers, where the depth of flow is considerable, and large quantities of grit are apt to be present, it is usual to limit the velocity to about 4 ft. per second, to avoid excessive scour on the invert. In pipe sewers 6 ft. per second has been mentioned as a maximum: in practice such a speed would only be exceeded on very steep gradients, and with flows much larger than are ordinarily met with. Steep gradients, have also been objected to on the ground that, owing to the consequent shallowness of the flow, solid matter is apt to be left stranded in the pipe. Flows which are insufficient to keep a steep sewer clear cannot, however, be relied on to maintain a self- cleansing velocity in a flat one. A. J. M. Flushing Cisterns.—(See “Waste Pre- VENTERS.” Flushing Drains and Sewers.— Wherever possible drains and sewers should -- be self-cleansing. This depends partly on their gradients, but chiefly on the amount of care which is taken in laying the pipes and making the joints. For 4-in. and 6-in. drains 8 ft. per second is regarded as a self- cleansing velocity; for 9-in. and 12-in. sewers 2% ft. per second will suffice; and for larger diameters velocities as low as 2 ft. per second may be used. Where these velocities are not obtained with the ordinary flow flushing should be resorted to. Even when the velocity is sufficient to prevent any actual obstruction, 181 FLU flushing is still desirable for the removal of the accretions which take place on the sides of the sewer. It is especially necessary where the flow is small, as in the upper lengths of a sewer, or in districts not yet fully built up. In certain cases the provision of means for ample and frequent flushing will admit of the use of gradients of exceptional flatness. Rainwater is practically useless for flushing purposes, the rainfall being far too uncertain to be depended on. Its admission to the sewers, moreover, necessitates the use of larger pipes than would otherwise be necessary, with a consequently sluggish flow. So far as the drains from houses and public institutions are concerned, the provision of special means for flushing can generally be obviated by placing a bath waste at the head of each principal drain. In sewers also the discharge from an ejector or rising main will often serve to flush a long sewer. Where no such means are available a penstock or valve is sometimes placed in the sewer to head up‘ the sewage for flushing purposes. This plan is objectionable on account of the deposits which take place behind the penstock when the sewage is thus kept stagnant, and, for pipe sewers at any rate, proper flush tanks should be provided. These may be filled with sewage if there is fall enough from the feeding sewer into the one to be flushed, but clean water is preferable. Where the water is obtained from the mains the connections should be trapped, to prevent the return of air from the sewers. The size of the flush tank will depend on the size and gradient of the sewer, the following being the capacities usually employed :— For a 9-in. sewer . 800 to 400 gallons j¢ Lr Ss » + 400,, 600 ,, ay LD 43 » » 600 ,, 800 ,, i LBS 5 » +» 800 ,, 1,000 _,, and so on The discharge from a flush tank may be effected by hand, but should generally be automatic. For house drains tipping buckets may be used, but where the quantity to be discharged exceeds 100 gallons, a siphon will berequired. There are many forms of siphon ENCYCLOPEDIA OF FOO on the market, all belonging to one or two types. In one, when the tank is full, the water falls over a lip, creating a vacuum in the descending leg. In the other, the air is held back by a deep seal, so that the water in the tank ponds up over the siphon until it stands high enough to force the air through the seal, when the siphon at once discharges full bore. A good siphon will start with a drop-by-drop supply. A.J. M. Flushing Tanks.—Tanks or cisterns con- structed to automatically discharge a certain quantity of water at stated intervals for the purpose of flushing drains or certain sanitary fittings, such as urinals, &c. The discharge of the water is brought about by either a tipper or a siphon, fixed in the tank. The timing of the discharges is arranged by the regulation of the tap through which the tank is filled, or by a clock making electric contact at certain hours and thereby releasing the water. (See also ‘‘ Wastr PREVENTERS.’’) Footpaths, Construction of. — General Requirements and Width— Foundation for Foot- ways — Construction — Forms of Footpaths — Materials. GENERAL REQUIREMENTS AND WiptH.—To ensure satisfaction with any class of footpath, care must be exercised in the choice of materials. They should be durable, ensure perfect comfort and safety to the pedestrian, be smooth and tough but not slippery, of fine texture and uniform quality throughout, and they should wear evenly and not flake, must not absorb an abnormal quantity of water, but dry quickly after rain, should be pleasant in colour and appearance and allow of easy cleansing. As regards the width of footways, the Local Government Board model bye-laws on new streets suggest that each footpath shall be not less than one-sixth the entire width of the street. In several large provincial towns and London boroughs special regula- tions are in force, and the following which govern the widths of footpaths in all new 182 FOO streets in the metropolitan borough of Wands- worth will be of use. ‘In all roads about to be formed 40 (forty) feet in width, each footpath to be made 8 feet wide. In all roads about to be formed 45 feet or 50 feet in width, each footpath to be made 9 feet wide.” As a general rule, roads 54 ft. wide have footpaths 10 ft. 6 ins. wide, and roadways 60 ft. wide have footpaths 12 ft. wide. Founpations ror Foorways.— These are usually of three kinds :— 1. Concrete. 2. Ashes or gravel. 3. Hardcore. Concrete foundations should be used for asphalte pavements and under brick paving. The depth varies from 3 in. to 4 in., but a greater depth should be given if the footway is liable to be broken up for main or service pipes of any kind. Ashes or gravel foundations are used under flag pavements and sometimes under brick pavements. The material should be clean and dry and have a thickness of 4 in. to 6 in. Hardcore foundations should be provided under all other pavements, especially tar- macadam and granite paving. The depth varies from 4 in. to 6 in., and in cases where soft clay is found an extra depth should be allowed. A system adopted for the founda- tion under flag paving in a South London borough is as follows :— The ground is excavated, where necessary, to a depth of 84 in. The bottom layer is composed of 8 in. of good clean stone or brick hardcore thoroughly rolled and consolli- dated. On the top of the hardcore a layer of ashes 8 in. in depth is provided, thoroughly rolled and watered. On the top of the layer of ashes artificial stone paving is laid, having a mortar bed 3 in. inthickness. This method has given very satisfactory results. Construction.—All footways should be laid with a cross-fall from the back of the footpath to the kerb in towns, &c., and from the kerb to the back of the footpath in the case of country roads. The following extract from MUNICIPAL AND SANITARY ENGINEERING. FOO the model bye-laws of the Local Government Board on new streets gives useful informa- tion :—‘‘ He shall construct each footway in such street so as to slope or fall towards the kerb or outer edge at the rate of one half of an inch for every foot in width, if the footway be not paved, flagged or asphalted; and at the rate of not less than a quarter of an inch and not more than one half of an inch in every foot in width if the footway be paved, flagged or asphalted.” The Municipal Engineers’ Specification gives the following cross-falls :— 4 in. per foot of width for asphalte. , » flags (natural and artificial). z» ue ie », concrete in situ. », tar matrix. 2, i: . { 7 cement matrix. » bricks, macadam. The cross-fall should be allowed in the foundation, the material being laid of uniform thickness. The kerb should be laid first on concrete 6 in. in depth, and show a channel, as suggested by the model bye-laws of the Local Government Board, not less than 8 in. in the shallowest part and not more than 7 in. in the deepest part. It has been found in times of heavy rains that the gully gratings get choked with dead leaves, and much water passes beyond the gully. To prevent this, overflows should be cut in the kerb over each gully about 1 ft. 9 in. to 2 ft. in length. Where carriage entrances occur in the foot- path it is usual to construct them in either of the following ways :— 1. The kerb is dropped to within an inch of the channel for the width of the carriage entrances, and the materials (either granite setts, cubes, or blue bricks, &c.) are laid butting against the paving material of the footway. 2. No kerb is laid in front of the carriage entrance, but the paving material is laid up to the channel. Instead of the setts, &c., butting against the flags of the footpath, a return edge kerb 6 in. in width is laid from 188 FOO the outer kerb to the forecourt fence or wall. In each case the carriage entrance is laid at the same level as the remainder of the foot- way, except near the edge where it com- mences to dip to meet the channel. The footway kerb on each side of the carriage entrance is bullnosed. Forms or Footratus.—There are two forms of footpaths, 1. Macadam. 2. Paved. 1. Macapam.—The first is used for country roads and villages, but is not to be recom- mended. The disadvantages are many :— (a) The material becomes loose with traffic ; (b) the paths are muddy in wet weather and very dusty in dry weather; (c) they are uneven on the surface, and require constant repairs. This class of footpath is certainly an advance on the bare earth, and is con- structed by laying a covering of gravel, engine ashes, or other similar material about 3 or 4 in. deep on the top of the earth, it being then well watered and rolled to a solid formation. 2. Pavep Foorways.—There are a great many materials used in this form of pave- ment, among them being :— Natural stone flags. Artificial stone flags. Concrete of various kinds. Tar paving. Bricks. Asphalte. Various combinations of the above. Marerrats.—1. Naturat Stons.—There are many quarries from which natural stone may be obtained, but are too numerous to mention in detail in this article. Yorkshire stone is largely used, and is very tough in fibre and wears well if properly selected. Natural stone flags should not be less than 23 in. in thickness, and should be bedded and jointed with cement mortar. The price of the stone varies in different districts from 5s. to 8s. 6d. per super- ficial yard, including the foundation. The price in London for 2 in. thick ranges from 4s. 8d. to 5s. 8d. per superficial yard, and when laid, from 5s. 8d. to 6s. 8d. per superficial yard. ENCYCLOPADIA OF FOO ArtiriciaL Stone.—The patent stone flags on the market are too numerous to mention, and only a few will be touched upon. Each stone should be laid to break the joint 6 in. A few makes are Victoria, Aberdeen Adamant, Croft, Imperial, Excelsior, Atlas, Nonslip (hard York) stone. The advantages of this class of paving are: Less cost, even surface, durability, square edges, regular sizes; and the disadvantages are: Tendency to become slippery in wet weather and under the heat of the sun, liable to easily break if bedded unevenly, somewhat dazzling in the sun, when lifted by a pick for repairs are liable to chip. The cost differs considerably, but, as a guide, varies from 4s. 6d. to 6s. 6d. per super. yard laid. The cost at the works is as follows :— Victoria 2 in. . 8s. 6d. per yard super. 2 24 in. . 4s. 6d. ” ” 2 Nonslip (hard York) 2 in. gy OS OO). Sa: Say ” Imperial 2in. .58.9d. ,, 5, ” ConcrETE IN situ Pavine.—These pavements are generally composed of granite chippings and Portland cement, in the proportion of 4 of chippings to 1 of cement for the bottom layer, and 1 of chippings to 1 of cement for the top layer, having a total depth of about 1} in. to 2 in. When laid in long lengths this paving cracks very considerably, and wood screeds should be laid down dividing the paving into bays about 4 ft. to 6 ft. in length and the full width of the footpath. Alternate bays are laid and allowed to set before the intermediate bays are filled in. To give a better foothold, these are either grooved or indented by rolling with a grooved or spiked hand-roller. They are difficult to repair, can only be laid after the frosty season, and take considerable time to execute, but, on the other hand, have few joints. Several firms make a speciality of this class of paving, laying it at a fixed price per square yard, and guarantee to maintain it for certain periods of time, and for this reason the work is best left to them to execute. 184 FOO Tar Pavine.—This paving is composed of a bottom layer of tarred granite chippings about lin. in diameter rolled down to a thickness of 2 in. This coat is then left open to traffic for a period of about a week. The surface is then swept, and the top layer, con- sisting of tarred chippings about } in. to 2 in. in diameter, is then laid and rolled to a thickness of about 1 in. This is then covered with crushed shell and sand. The cost works out at about 2s. 6d. per superficial yard. Bricxs.—These are largely used as paving materials, and form very durable surfaces. They are laid on a bed of concrete, varying from 3 in. to 4 in. in thickness in hori- zontal or diagonal rows. A very effective form of paving is obtained by having a centre portion about 4 ft. wide laid in red bricks and the margins on either side laid with Kentish rag spalls about 4 in. deep, all laid. on concrete. The cost of this works out at about 9s. per yard super., including foundation, using red sand bricks. AspHALTE.—This form of pavement is laid in exactly the same manner as for roadways, the price being the same. It is slippery and dangerous in wet and hot weather. The foundations for the above pavements have been dealt with in the first part of the article. . F. L. and R. H. B. Footways.—(See ‘‘ Roaps anp Srreets.”’) Forced and Induced Draught.— Mechanical draught, whether “forced” or “induced,” enables a higher temperature to be obtained in a furnace, and therefore increases its capacity. It also permits the use of inferior fuels. Several systems of forced draught are in use; one consists of a closed stokehold into which air is forced by means of a fan; thus a greater quantity passes through the furnace than would obtain with natural draught. Under this system the stoker of necessity works in a pressure above that of the atmosphere, and the compartment MUNICIPAL AND SANITARY ENGINEERING. FRE can only be entered or left through an air lock. Another plan (Howden’s) is to use a closed ashpit and aspecial fire-door, to both of which air, previously heated, is conveyed, the supply to the ashpit being at a lower pressure than that to the fire-door. The act of opening the fire-door automatically shuts off the supply. In Meldrum’s well-known system the ordinary firing arrangements are retained, but the ashpit is closed. Two bell-mouthed pipes project into the space below the firebars, and in each pipe there is a steam jet, the blast from which forms an air injector and so pro- motes combustion. This system can be applied to any kind of boiler or the furnace of a refuse-destructor. The simplest example of induced draught (other than that due to a chimney) is that in use in locomotive and portable engine-boilers —in this case the exhaust steam is discharged into the base of the chimney—the orifice of . the blast pipe being usually placed just above the top row of tubes. Mechanically induced draught is effected by employing a suction fan to draw the waste gases from the flue and discharge them into the smoke stack. Other advantages of mechanical draught are that the chimney need only be high enough to disperse the waste products and to fulfil loeal requirements. It also admits of regulation, automatically or otherwise, to very varying demands, and is independent vf climatic conditions. Both systems have their advocates. The choice, however, depends partly on local circumstances. (See “ Boruers, Curmneys.”) E. L. B. French Drains are trenches or grooves filled with rubble, stone, chalk, or large gravel to allow water to pass away freely. At the back of a retaining wall in a wet soil French drains are put in vertically at intervals of about 10 ft., with a weep hole about 3 in. diameter through the wall at the foot of each drain, to carry off the water and prevent an increase of thrust by hydrostatic 185 FRO pressure at the back of the wall. In draining land by this means the trenches, about 2 ft. deep, have inclined sides with the bottom filled in with rubble, chalk, or gravel, and covered with straw or brushwood to prevent choking; the soil is then returned to fill the remainder of the depth, say a foot, and lightly rammed to consolidate it. Frost.—Errecr on Warer Pipes anD Sanitary Firrines.—Water at a tempera- ture of 82° F., or freezing point, congeals and forms into a solid mass known as ice. At the moment of so doing it expands at great force. It is this action which causes frost-burst in water pipes that have not been properly protected, although the effects are not, as a rule, noticed until the advent of a thaw. Various materials resist frost-burst to different degrees. Lead pipes offer small resistance, but will frequently expand or bulge out sufficiently to prevent fracture. Cast-iron pipes, although stronger, are readily split from end to end. Wrought- iron pipes resist fracture better than either of the foregoing, but are also frequently split. Hot-water pipes exposed to frost suffer no less than cold-water pipes, and the effect may be much more serious, as the blockage of the pipes by ice may lead to boiler explosions, either by causing excessive steam pressure, or by the sudden admission of cold water to an overheated boiler. Similarly, explosions may be caused by frozen expansion pipes which are gradually blocked by ice formed from condensation in the pipes. The prevention of frost in water pipes lies’ in protecting the pipes against frost by placing them in frost-proof positions or by encasing them in non-conductive materials where ex- posed. Wrapping the pipes in several layers of brown paper pasted down will frequently suffice. Other suitable materials for protection are sawdust, cork chips, hair felt, plaster of Paris, asbestos, slag wool and boiler com- positions. The effect of frost on ‘sanitary fittings is less serious than on water pipes, leading merely to the temporary disuse of the ENCYCLOPADIA OF FUE fittings affected. In most cases the trouble is caused by leaking taps, the water from which freezes in the waste pipes and gradually blocks them. W.M. Fuel.—Combustion is a rapid chemical combination accompanied by the evolution of heat and usually light. The chief supporter of combustion is the oxygen contained in the air, and all bodies which burn in air burn with greater brilliancy in oxygen gas. The quantity of air required for the complete combustion of different fuels varies, but should in each case be correctly apportioned. Insufficient air prevents complete combustion and produces smoke, but an excess of air causes waste of heat as it needlessly lowers the temperature of the flue gases. If the composition of a fuel is known the heat evolved by its combustion can be cal- culated. The fuels mostly used are those substances containing large proportions of carbon and hydrogen, such as coal, charcoal, coke, peat and wood, and the liquid and gaseous fuels, the most important of which are the mineral oils and coal gas. The comparative value of the principal fuels in British thermal units is as follows :— Evaporative ges * Fuel. Power from | thermal | ‘Garton 212° F. Units. Value.- Carbon ws 15:0 14,500 1:00 Charcoal (wood) 12°4 12,000 83 Coke (average) 6 13°5 13,000 83 Welsh Coal (average) 15°3 14,800 1:02 Petroleum (average 20°7 20,000 1:38 Coal Gas (average 21-7 21,000 1°45 The ordinary comparative power of Welsh steam coal from 100° F. of feed-water is from 10 to 11 lbs. of water per lb. of coal. In the choice of a coal for pumping purposes the principal point to consider is the selection of that class which, upon the average of a series of tests, evaporates a given quantity of water from a given temperature at the lowest cost. From the steam user’s point of view this consideration practically embraces the 1&6 FUE whole matter and will determine his decision. A careful commercial test of the various coals that may be under consideration should be made by evaporating a certain known quantity of water in the same boiler by each of the different fuels in turn, taking special care that all the influencing conditions of the test are similar in every case, so that all may be on the same basis as near as practicable. If the fires be not drawn between each test, they should at least be in the same condition as near as possible, the feed-water should be of the same temperature, or proper allowance made, the quantity passed into the boiler should be accurately weighed and the water- level left the same at finish as it stood at the start of the test; the total coal used must also be weighed, and the percentage of ash ascer- tained. It is also important to note any variation of draught in each case, to observe the amount of smoke produced, differences in stoking, and the nature and amount of the clinker and ash. From such a test it will oftentimes be found that the cheapest coal is by no means the most economical to use. In the coal-mining districts of the Midlands and North of England, and at places where the cost of freightage is light, itis often found economical to use a low class of fuel which may be had at the pits’ mouth for a few shillings per ton, but in the South-East of England, where the cost of carriage from the mining districts is heavy, it is as a rule more economical to use the best class of fuel than to pay the heavy carriage rates on a low class material, a large percentage of which will result in ashes. This question of high-class versus low-class fuels is one of great practical importance, and is worthy of the careful consideration of every engineer in the light of the special circumstances of his own case. Of oil-fuels, a large quantity of that now available in this country comes from the newly opened Beaumont field in Texas. It will evaporate about 15 lbs. of water per pound, has aspecific gravity of 925 at 60° F., a flash point of 185° F. (Abel test), and ignites at 200° F. Its average calorific value MUNICIPAL AND SANITARY ENGINEERING. GAS is 19,500 British thermal units. Texas and Roumanian cheap oils are now largely used in oil-engines for motive power purposes, in loco- motives, and also in stationary boilers. Gas.—Gas Supply—Manufacture—Distribu- tion — Public Street Lighting — Domestic and Trade Uses—Water Gas. Gas Suprry.—The supply of gas in the United Kingdom is a business carried on as a virtual monopoly, and, in the case of all large undertakings, also under the protection of private Acts of Parliament. There is never an expressed guarantee against competition ; but this is implied by the law and rests upon the necessities of the business and the consideration of public convenience, as there cannot advan- tageously be two sets of gas mains in different ownership in the same street. Some small country gas companies have no special Act, and therefore depend upon maintaining a good understanding with the highway authority, without which they could not lay a main or touch a pipe already buried underneath a public road. Private and public gas Acts give this power, requiring. in return certain con- ditions of the undertakers as regards limitation of profits, sliding scale of selling price and dividends, quality of the gas, and obligation to supply on demand. Gas property is freehold. It is not usual to grant local authorities power to purchase gas undertakings without the consent of the proprietors; although this is sometimes done on proof of expediency being given. The opportunity of obtaining pur- chasing power ordinarily arises when the company promotes a Bill for fresh and additional powers, such as are calculated to enhance the value of the undertaking. Muni- cipal gas committees succeed to all compatible powers and obligations of the gas company. The general English law of gas supply is contained in the following statutes: The Lighting and Watching Act, 1883; Gasworks Clauses Act, 1847; Towns Improvement Clauses Act, 1847; Sale of Gas Acts, 1859-60; Gas and Water Facilities Act, 1870, Amend- ment Act, 1873; Gasworks Clauses Act, 1871; 187 GAS Public Health Act, 1875; Conspiracy and Protection of Property Act, 1875; Public Works Loans Act, 1875; Burghs Gas Supply (Scotland) Act, 1876; Public Health (Ireland) Act, 1878; and Amendments Acts. Manvracrure.—The town gas distributed in the United Kingdom is chiefly composed of the ‘gaseous distillate from bituminous coal, carbonised in closed fire-clay retorts at a tem- perature of 1,800°—2,000° F. For economical reasons this coal gas is in many places supple- mented with a proportion of carburetted or “blue” water gas (see article, ““ Warer Gas”’). In good working, about 11,500 cu. ft. of gas should be made from a ton of good coal, the choice of which depends upon geographical and transportation considerations. Townson or near the eastern and southern seaboard, including London, use chiefly the strongly- coking coals of Northumberland and Dur- ham; with occasional or partial supplies of railway-borne coals from Yorkshire, Derby- shire, Nottinghamshire or North Wales. The quality of gas is expressed in terms of the luminous intensity, in the equivalent number of standard sperm candles of ‘six to the pound, of a flame burning at the rate of 5 cu. ft. per hour, as measured by the photometer under statutory conditions. The gas of the Metropolis and the South of England generally, as well as abroad, wherever the Durham gas coal goes, is rated at from 14 to 16 candle- power. The tendency is in favour of a still lower figure, because this manner of stating the ‘“ quality’’ of town gas is obsolete and does not correspond with modern uses of the commodity. What is classified as 14-candle gas yields on the same basis of consumption, with the incandescent (Auer, or Welsbach) “mantle,” 100 candle-light. Gas of higher vandle-power with the luminous flame, does not yield a proportionally better light by the incandescent system. Other saleable products of the distillation of coal for gas-making are coke, tar, and ammoniacal liquor. Sometimes cyanogen salts are also recovered. The gas being the _ principal product, which must be made in ENCYCLOPAEDIA OF GAS quantity to supply the daily demand, the other products of manufacture are classified as “residuals,” or by-products, the market value of which goes to reduce the prime cost of the gas in the holder. The crude gas as it comes from the retorts is laden with the vapours of tar and ammoniacal liquor, which condense in due course, and is charged with the gaseous impurities, sulphuretted hydrogen, ammonia, and carbonic acid. The first is removable by means of oxide of iron or slaked lime; the second by washing with water, with recovery of the ammonia; the third is often left in but is otherwise removable by slaked lime. When oxide‘ of iron is used to absorb the sulphuretted hydrogen, the sulphur is re- covered in saleable form. Some sulphur impurity, in other forms than the offensive sulphuretted hydrogen, always remains in coal gas, the quantity ranging from 20 to 50 grains in 100 cu. ft., according to the nature of the coal and the temperature of carbonisation. This sulphur is supposed to exist partly in undetected organic forms without chemical affinity, and consequently irremovable by chemical treatment, and partly (in the case of gas made at a high temperature) as bisul- phide of carbon. In whatever forms the sulphur may exist in gas, it burns to sul- phurous acid. After purification, and being measured, for administrative reasons, gas is stored in sheet-iron holders over water. Ample storage capacity is a great aid to economy in working. The gas-holders should always be of a capacity equal to one day’s (24 hours) maximum output. Disrrizution.—The weight of the holder gives the pressure at which the gas is sent out for distribution through the town mains and house services. This weight is lifted, on the manufacturing side, by mechanically driven “‘exhausters”—so called because they draw off the gas from the retorts, and force it onwards through the purifying apparatus into the holders. The pressure of the holders, on the outlet side, is regulated by ‘‘governors.” These control the town supply according to the demand, irrespective of any varying 188 GAS pressure exerted by the holders, which differ in capacity and weight. Sometimes the weight of the holder is insufficient to give the required pressure, when the difficulty can be met by the use ofa “ booster’ fan. Registering pressure indicators should be kept to show the amount of the initial pressure at the works outlet mains, and also at critical localities in the district ofsupply. The law requires gas mains and services to be kept constantly charged under pressure (Gasworks Clauses Act, 1871, clause 11; Burghs Gas Supply (Scotland) Act, 1876, clause 56). This pressure is not to be less than will balance the weight of a column of water, from midnight to sunset, six-tenths of an inch high, and eight-tenths of an inch high from sunset to midnight. Such’a mini- mum pressure was sufficient at the date of the passing of the Acts, when the sole use of gas was for lighting by means of flat flame or Argand luminous flame burners, which were low pressure appliances, working most satis- factorily at five-tenths pressure. It is in- adequate now, when the greater part of gas sold is used for fuel purposes, and by means of incandescent lighting burners, all of which require a pressure of not less than fifteen-tenths at the point of ignition. There- fore the minimum permissible pressure of gas in the street mains night and day should be not less than twenty-tenths, or 2 in. of water; and this pressure should be available all over the district of supply, irrespective of repair operations, &c. Trunk gas mains may be of cast-iron or steel, jointed by means of spigots and sockets, with rope-yarn and lead, or with turned and bored joints. If of steel they may be welded, or of drawn tube. Mains in roadways should be 2 ft. 6 in. deep to the top of the sockets, and are most con- veniently laid about 3 ft. from the kerb. Gas mains must not be laid nearer to a water main than 4 ft., and must cross such mains, if necessary, at a right angle (Lighting and Watching Act, 1833). It is the modern prac- tice to supply houses in streets from ‘service mains,” laid at a depth of 12 in. underneath each side pavement, for convenience of access. MUNICIPAL AND SANITARY ENGINEERING. GAS. No main less than 4 in. in diameter should be put underground. In a few large cities street subways for gas and water mains, electric cables, &c., exist under new thorough- fares, but their construction is not generally favoured for old roads. Mains must have a fall of ;4, to siphon traps for condensed water. House services are usually of iron, with a few exceptions in favour of lead pipe. A good quality of steam piping, painted, should be used. Gas mains are best tapped on the side, and the service pipe should never be smaller than 1 in. for ordinary frontage lengths. It must be laid with a fall towards. the main. Owners or occupiers of any premises situate within 25 yards from a main are entitled to a supply of gas, on paying for all service piping beyond the first 30 ft., and entering into a written contract if required (Gasworks Clauses Act, 1871, clause 11 et seq.). The supply must be by meter, if required by the undertakers, who must provide the meter (on demand) according to the Sale of Gas Act, 1860. The register of such meter is prima facie evidence of the quantity of gas. consumed, subject to appeal to two justices. Payment for gas may in certain circumstances. be demanded in advance, or security may be required. Such security, if in cash deposited, is not an advance payment. Interest is payable on cash deposits. The supply of prepayment meters, stoves, and gas fittings is not compulsory. The amount of gas bills, including meter hire, is recoverable by sum- mary process before justices. Private Acts usually provide against gas stoves, &c., being taken under distress for rent; and also limit. the period of error for defective meters to the current, or preceding quarter. Pusuic Srreer Licutinc.—The supply of gas to public lamps is compulsory on demand at a price settled by agreement when not specified by the special Act. It is usually taken on the basis of the lowest price charged to any private consumer for lighting. The posts, lanterns, and burners are usually the property of the consumer, whether a public authority or any person requiring a street, 189 GAS lamp. Lighting, cleaning, and repairing are ordinarily contracted for with the gas company at intervals of 3 or 5 years. Painting is separate. A schedule of hours of lighting and extinguishing, based on local time, forms part of the contract. ‘* Moonlight schedules” are only favoured for rural districts. The exten- sion of compulsory services to public street lamps is for 50 yards from an existing main. (A main is a pipe supplying two or more con- sumers.) The supply of gas to public lamps may be on the average meter system, with a meter to every 10 or 12 lamps, but since incandescent lighting has been in vogue this system has generally been abandoned as a needless expense. Street lamps may have governors fixed to them at the expense of either party (Gas Works Clauses Act, 1871, clauses 24 to 27). Anti-vibrators are usually required for incandescent street lamps in busy thoroughfares to economise mantles. Ordi- nary old-fashioned street lamp-posts and lanterns cannot be satisfactorily converted to the incandescent lighting principle, for which strong, steady posts and wind-proof lanterns are necessary. The capital cost of new posts, lamps, &c., is recouped by the annual saving in gas consumed, which is only 34 to 4 cu. ft. per hour with Welsbach “C”’ or Kern No. 4 burners, or Sugg’s or Bray’s equiva- lents, as compared with 5 cu. ft. per hour with the old flat flames. With an average yearly lighting period of 4,000 hours the differ- ence quickly mounts up. There is a partial set-off in the cost of mantles, of which from 5 to 12 yearly, or more in roads with heavy traffic may be required. This com- parison sets no value on the increased brilliancy of incandescent lighting, which is represented by the proportion 80 to 12 in direct candle- power intensity. A lamp-renewal fund should be maintained by every local gas authority so as to enable the fixtures to be kept up to date. Nothing gives a worse impression than to see an insufficient number of street lamps, ill-kept lanterns, and poor mantle maintenance. Posts in rural roads may be spaced 80 yards apart, and more thickly according to the density of ENCYCLOPEDIA OF GAS the traffic. Streets over 50 ft. wide between frontages should have double burners, of which one could be extinguished at midnight. Wide boulevards, open places and squares, the processional approaches to public buildings, docks, and large railway stations, are best lighted by high-pressure gas.in powerful units. The extra cost of gas compression for this purpose .is about 1d. per 1,000 cu. ft., and its efficiency is doubled or trebled according to the system adopted. Parliament Square, Parliament Street, and other centres of metro- politan traffic are always kept up to the latest style of good street lighting. There are several mechanical devices available for the simul- taneous lighting and extinguishing of public street lamps, some driven by clockwork, others by pneumatic’ pressure of the gas itself. Domestic anp TrapE Uses.—About 50 °/, of the gas sold in towns is consumed for domestic fuel purposes, chiefly cooking and warming of rooms. It is also fast coming into use for heating water circulators in substitu- tion for kitchener boilers. Discounts up to 25 °/, on the normal price, according to quantity, are usually allowed for gas consumed as fuel for trade and industrial purposes, and for gas engines. It is claimed that the cheapest electric light for large business pre- mises is provided by means of private gas power. The consumption of town gas to generate a unit of electricity on the pre- mises is about 30 cu. ft. High temperature furnaces for glass melting, enamelling, or steel brazing and tempering are economically worked with high pressure gas. Water Gas (CarBuRETTED) is largely manu- factured in British towns, especially where the gas coal supply is railway borne, to sup- plement the bulk coal-gas output. Its com- parative cost to the latter in the holder differs in different localities, and therefore it is not everywhere equally favoured. This also largely depends upon the current price of the oil used in the manufacture. Apart from the bare fact of the works cost of this kind of gas, its in- cidental and consequential recommendations are considerable. It can be installed at a very 190 GAS important saving of capital, which is a great advantage where increased producing power is required for a heavily-capitalised undertaking. It can be held as a stand-by with far less cost and trouble than reserve coal-gas plant. Itis a check upon labour difficulties. When coke is a drug in the market it provides a profitable outlet for the surplus of this residual, and this feature alone in many places justifies the manufacture. Carburetted water gas is not often sent out in this country in a larger pro- portion than 50°/, of the total, and less than this is the general practice. It is pro- duced by first raising a bed of incandescent coke in a cupola to a high temperature by a blast of air, which is called ‘the blow,” and then passing steam into the glowing mass until its temperature is again lowered, which is called ‘‘the run,” and so on alternately. The “ water gas’ resulting from the action of the coke upon the steam is called “ blue water gas,” and in some systems this product is added directly to the coal gas before purifica- tion. From 10 to 15 °/, of “blue” Water gas, which is non-luminous, but has a high flame temperature, can be added to common coal gas without detriment to the incandescent lighting or the fuel value of the latter. If more water gas is required to be admixed with the coal gas for town distribution it is necessary to ‘“‘carburet”’ it—that is, impart to it luminosity and calorific. power—by an addition of petroleum oil gas or of some hydrocarbon spirit vapour. In the process of carburetted water gas manufacture the oil is injected into the cupola system and gasified in the current of hot water gas. Where “blue” water gas is added to the coal gas, the mixture can be carburetted afterwards by passing it over or through a vessel containing benzol or petroleum spirit. Blue water gas costs to manufacture about one-third the cost of coal gas; the carburetting brings it up to about the same works cost as coal gas of the same illuminating power. W. H. Y. W. Gas Burners.— Modern gas lighting is prac- tically confined to the various patterns and MUNICIPAL AND SANITARY ENGINEERING. GAS sizes of incandescent mantle burners, of which the original, and still the largest in use, is the Welsbach Incandescent Gas Light Company’s “C” type of burner (Fig. 1). Since the expiration of the master patent, the British market has been flooded with cheap and flimsy makes of this burner, but the genuine are marked ‘‘aur’’. These burners take to pieces easily for cleaning, which is a great advantage, as atmospheric dust is the chief source of trouble with all mantle burners. They have no provision for regulating the gas or air supply according to the pressure of the gas, and therefore are only satisfactory when the gas inlet nipple is suited to the quality of the gas supply (because a burner made for 14-candle gas will not properly burn 20-candle gas), and also where the pressure is maintained between thirteen-tenths and twenty-tenths. Where higher pressures prevail, and also where a varying proportion of carburetted water gas may be supplied, some form of gas regulator ‘(as the “ Pond”’ or the ‘‘ Nico’) is desirable, and the fixed primary air holes should be con- trolled by a thin brass adjustable shutter. These “C?”’ size burners are the standard for all makes of mantles. They consume from 34 to 4 cu. ft. of gas per hour, according to the pressure, and yield a light intensity equal in the horizontal direction to that of 60 to 75 candles. As the distribution of their light is mostly horizontal, or upwards, these burners require top reflectors for downward lighting. A valuable improved pattern of upright burner of the type is the ‘“‘ Bray” (Fig. 2) which has several good features, including gas and air adjustment. It is well suited for church or theatre lighting, as it bears turning down without lighting back. Messrs. W. Sugg & Co. also make a variety of upright burners, in a series of sizes, for public street lamps. The most efficient form of upright incandescent burner is the “ Kern” (Fig. 3) which yields 20 °/, more light than the ‘‘C” burner from the same quantity of gas, but is rather more severe upon mantles. It does not requireachimney. No. 4 “Kerns,” giving 100 candle-power, are much used for 191 GAS ENCYCLOPEDIA OF GAS 192 GAS public street lamps. They should be governed down to twenty-tenths pressure, for which pur- pose Carpenter’s (South Metropolitan) governor is the best. An excellent pattern of storm-proof lantern, with antivibrator fitting, is shown in Fig. 4. This is suitable for all public street lighting on the ordinary scale, for everything short of very wide, first-class thoroughfares. InvertED Burners.—Lately incandescent burners of the inverted, or semi-inverted type have seriously challenged the superiority of upright burners, being of at least equal effi- ciency as illuminants for the quantity of gas consumed, and having a better form of light distribution. Fig. 5 shows a strong pattern of Inverted lamp, the “ Bland,” with protected glass and top reflector for workshop use. Fig. 6 is a ‘ Nico Intense” lamp of the New Inverted Gas Lamp Company, which yields a light of 65 to 70 candle-power for an hourly consumption of 24 to 2% cu. ft. of gas. In it the supply of air to the flame is heated, and the outer globe has no bottom orifice. Fig. 7 is a ‘* Vesta Veritas’ burner, of Messrs. Falk, Stadelmann & Co., based upon the same prin- ciple and yielding similar results. The inner glass is plainly shown. A useful form of inverted burner is shown in Fig. 8, which re- presents the adjustable lamp of Messrs. G. Bray & Co. This can either be fixed upon an ordinary gas bracket, or pendant arm, in which case the gas and air inlets are upright, and the burner tube only is bent over into the in- verted position, or, as shown by the dotted lines, it can be used quite inverted. This fitting is very convenient for shops, and gives little trouble in adjustment. The inverted form of burner is also adapted in several patterns to outdoor and public street lamps. A windproof lantern arrangement of Messrs. Falk, Stadelmann & Co. for a single mantle is shown in Fig. 9, and a “ Vesta Veritas’ grouped burner lamp is shown in Fig. 10. These lamps are much favoured for outside shop lighting, as the light is very bright, quite steady, and directed wholly downwards without any shadow. A serviceable lamp of the same type, made M.S.E. MUNICIPAL AND SANITARY ENGINEERING. GAS by the Welsbach Company, is shown in Fig. 11. Hico Pressure Gas Burners.—When a more brilliant source of light is desired than the ordinary incandescent mantle can afford, the effect is producible by artificial intensi- fication of the combustion, which means burn- ing more gas in less space, thus raising the mantle temperature. The simplest way of doing this is by increasing the chimney draught of, say, a large ‘‘Welsbach Kern” burner (Fig. 12). The convenience of these ** self-intensified ” lamps is that they are quite independent and self-sufficing. The illustra- tion is of a 800-candle-power burner for indoor use, as in the lighting of a warehouse, covered goods yard, &c. For outdoor use a Scott- Snell lantern produces the same effect by mechanical action maintained by the heat of combustion. The most trustworthy means of heightening the brilliancy of incandescent gas light is pressure-increasing mechanism of a positive kind which is applicable to both indoor and outdoor lighting, public or private. There are systems in which the air, or the air and gas supply, are put under higher pressures than the normal, but in general only the gas is so treated. The simplest apparatus of the kind, and highly efficient, is the water-power system of Messrs. James Keith, Blackman & Co. (Fig. 18). The compressor, which occupies little room, can be set up wherever there is a water supply under pressure, and it produces a brilliant mantle action under a gas pressure of 9 in. of water. A useful series of upright and inverted burners is available for this treat- ment, which costs no more than ld. per 1,000 cu. ft. of gas passed through the apparatus, while the intensity of the light is increased to 30 candles per cubic foot con- sumed per hour. Another system achieving the same objects is that of Messrs. Sugg & Co., who employ hot air or gas engine power for the purpose, and raise the gas pressure to about 17 in. of water. Triple mantle lanterns so illuminated constitute lighting units of 1,000 candle-power. Another system, the Sale- 193 0 GAS ENCYCLOPADIA OF GAS i } fl | mi A i aN : 4 , . i. A a re \ 7 y) | a Fic. 10. 194 GAS Onslow, supplies upright mantles with gas at 54 in. pressure. The most brilliant gas light of the period is that produced by the inverted system of Fig. 13. Messrs. James Keith, Blackman & Co., worked at a gas pressure of 54 in. of water (4 in. of mercury). The compressor is driven by electric power (Fig. 14). The effi- ciency of the mantles is about 60 candle-power per cubic foot of gas consumed in the lanterns - such as are shown in Fig. 15. The whole equipment is substantially constructed, and the lanterns are durable. A peculiarity of this system is that the mantles are put on in the Fie. 14. soft condition, and shape themselves as the flame is turned on. Various sizes of lamps can be used on the same supply. The light is suitable for large factories, railway yards, wharves, and the most important main city thoroughfares. W. H. Y. W. Gas and Electric Light Testing.—The testing of gas is generally confined for practical purposes to the estimation of the illuminative 195 MUNICIPAL AND SANITARY ENGINEERING. GAS value when burnt under defined conditions ; to the determination of its heating power and the pressure of the gas in the service. For- merly the quantity of sulphur present in the gas either in the form of sulphuretted hydrogen and other sulphur compounds was considered of importance, but recent legislation has omitted for all practical purposes any restric- tion on these in the metropolis, and for many years past they have rarely been considered in connection with the supply to the provinces. In the case of the electric light the essential features of the test are the intensity of light yielded and the current required, expressed in terms of volts and amperes or “ Board of Trade units.” The measurement of the light in both cases involves the same photometrical procedure, and is based upon the natural law that the intensity of the light emitted by a given radiant diminishes in inverse ratio to the square of the distance. The following example will illustrate this :— When it is desired to compare a light with a standard light, a candle for instance, if a translucent paper having a spot of grease in the centre is held between the two lights it is clear that if it is too close to one radiant the light will be too bright on the side of the paper nearest to it, and the light will shine brightly through the greased portion. If the paper is then carried over to the opposed radiant the effect will be trans- posed, but in its passage from one to the other it will be seen that at some point between them the illumination of each side of the paper will be equal and the grease spot will all but entirely disappear in consequence of the reflected and transmitted light being equal on either side. This neutral point hav- ing been found, it is clear that the actual intensities are equal at the given distance from the respective lights. Simple calculation then gives the relative intensities thus: If the distance of the one light be 26 in. from the neutral point and that of the other 2 44 in., then a = 2°86, so that the greater light 02 GAS of the two is 2°86 times that of the weaker. If the latter be known to be, say, equal to 8 candles, i.c., a low-power incandescent electric light, the actual intensity of the greater will be 2°86 X 8 = 22°88 candles. In England the standards of comparison generally em- ployed are either the Parliamentary standard sperm candle, consuming spermaceti at the rate of 126 grains per hour, the sperm con- sumption being ascertained by weight and the intensity of the light, presumed to vary with the rate of consumption, which must not exceed 126 grains per hour nor fall below 114. In the metropolis the standard employed at the gas-testing stations is that known as Harcourt’s 10-candle pentane lamp, which consumes the vapour of pentane (obtained from light petroleum spirit) carried forward to the burner by a current of air. When the flame is at the regulated height the intensity is taken to be equal to 10 standard candles, and no further calculation is needed in that respect. Many alternative standards have been proposed, but beyond certain calibrated electric incandescent lamps used for temporary purposes either of the foregoing are generally employed. The instruments known as photometers are of many divergent patterns, but the essentials comprise simply supports for the two lumin- ous radiants to be compared and the com- parison screen which may be either Bunsen’s greased disc above described, or its alternative, the star disc of Leeson, consisting of a thick piece of paper with a perforation in the shape of a star, covered on either side with a thin paper, thus giving opaque surfaces with a translucent centre. This is best for comparing coloured lights of different character. The principle of Rumford’s shadow photometer—in which the comparison is made by noting the depth of shadow cast by two vertical rods illuminated by the respective lights, which are moved nearer to or further from the rods until the shadows are of equal depth, or, more truly speaking, the illuminated surfaces are of equal brightness—is employed in the table photometer used in the official testings. The ENCYCLOPADIA OF GAS accessory apparatus necessary for festing the illuminating power of coal gas consists in uw” meter for measuring the rate of consumption,, which is generally 5 cu. ft. per hour, a clock’ with stop action to denote time intervals, a governor to control the steady flow of gas to the testing burner, and a pressure gauge to test the pressures in the different parts of the apparatus. The most complete ‘ bar” photo- meter comprising the whole of these neces- saries is that known as the “‘ Tooley-Street pattern,” which gives the steadiest flame to the gas and candles by reason of the freedom from sideand top draughts. This was developed as the results of experiments by the writer at the time when the late Professor Tyndal was one of the Gas Referees, the principle involved being the attainment of a large volume of air moving at a slow intensity in a steady upward direction, with the result that an ample supply of air was carried to the burners and the products of combustion freely and steadily removed without top or side draughts. The candles are carried during the test in a suitable balance, and the quantity of sperm consumed weighed with the candles in situ, as great risk is incurred if they are touched, by reason of spilling some of the melted sperm, or otherwise disarranging the rate of con- sumption. If required, any other standard of comparison may be employed in this photo- meter, and in the case of testing powerful gas or electric lights these may be placed on suit- able supports in a line with the photometer bar, the side of the casing surrounding the gas burner being removed, and the usual scale on the bar being neglected, the respective distances being measured as above indicated ; or a special scale may be engraved on the bar, the usual one being for lights 60 in. apart, the readings in that case being made direct instead of having to be calculated as made. It is unnecessary here to enter into details of the method of computing the rate of consumption of the gas and candles, as tables are generally provided with the instruments. An important branch of this work is that introduced by the writer in 1885 under the 196 GAS term, ‘“‘ Radial Photometry,” which denoted the estimation of rays in all directions emitted from a light source. According to the then usual practice only the horizontal rays were taken account of, but the introduction of the inverted and other burners rendered it neces- sary to estimate in particular those rays falling at varying angles from the horizontal to the perpendicular. For this purpose the radial photometer was made by Messrs. Sugg & Co. to the writer’s design. The support for the illuminant is attached to and shown in front of the raised disc, which slides up and down in its stand. The disc of paper, greased or stained as required, is held in the clamp in front of the lower disc on the right-hand support. Fixed rigidly to the sup- porting block is the horizontal bar on which slides the comparison standard light. As the inclined bar is moved by any alteration in the position of either block, the taller of the two upright supports slides sideways on the base board, thus always maintaining the full distance of the light from the disc—the arrangements being such that the light may either be directly above the disc or below it— the moving bar indicating and controlling the direction of the rays. methods have been proposed, but this is the most complete instrument for the work and is extremely easy to manipulate, even with lanterns of many hundred candle - power intensity. A convenient portable instrument was de- signed by Mr. Trotter, and described by him in a paper read before the Institute of Civil Engineers in 1892. It was designed for estimating the intensity of street lighting. A small standardised electric lamp was fitted at one end of a box. The light from this was received on a reflecting screen of Bristol board mounted on an axis through its upper edge. Above this a simple cardboard screen with a star-shaped hole cut in it was fixed in a hori- zontal position, so that the observer when looking down on the box would see the reflect- ing screen through the star-shaped opening. ‘The method of observation consisted in MUNICIPAL AND SANITARY ENGINEERING. Many alternative: GAS inclining the reflecting screen at different angles, this motion being given by a fine chain wound on a snail cam. A convex lens was used in certain cases to increase the available light from the electric lamp. The results of the tests of illuminative value are controlled by the quantity of gas con- sumed in the case of that illuminant, or the strength of the current in the case of electricity. In the case of gas it is not the pressure which is the governing factor, but the chemical or illuminating constituents, or even more im- portant in certain respects, the heating quality, and hence it is that tests for the calorific value of the gas seem likely to displace to a great extent those for mere illuminating value. In the case of electricity the equivalent factor is the voltage, a given volume or amperes being assumed, and the tolerance shown by public authorities to the electrical industry by neglect to establish a severe system of tests and punishments for default in supply, as in the case of gas, has gone not a little way to encourage the growth of the newcomer in the field of luminous energy. For instance, a few percentages different in the photometrical value of gas makes but little difference, but may be punished with heavy and irritating penalties. On the other hand, what happens if the voltage of a supply drops? From tests made by the writer it was found that a 16- candle-power lamp was found to give 15-03 when the current indicated 99°38 volts; but at 96 volts the luminous intensity fell to 10°9 candles, or 27°38, and when it fell to 90 volts the loss of candle-power was exactly 50 per cent. It is therefore clear that the necessity for maintained voltage is of the greatest importance, and too much stress cannot be laid upon it, especially when it is considered that this difference in voltage makes practically little on the quarterly account which is based on the Board of Trade unit, i.e. quantity = amperes, multiplied by intensity = volts. Thus 1,000 amperes x 1 volt = 1,000 = 1 B.T.U., or 10 amperes X 100 volts = 1 B.T.U., which latter might represent the above case, when a drop of 10 volts out of 100 would mean, with 197 GAS the sample amperes, 900, or a reduction of 10 °/, on the bill for a 50°/, reduction of light. . It is impossible within the compass of the present article to discuss the questions of Calorimetry ; Illuminating Effect, i.e., suitable distance of a light from a surface to be illu- minated ; Illuminating Value, 2.c., intensity of the light which would be required at a foot distance to produce the effect of the given light at its given distance, and other similar points. These should be studied in the text- books devoted to Public Lighting, &c. The following comparison of cost of illumina- tion by various methods will be of interest. It is abstracted from the writer’s work on “ Public Lighting.” Electricity at 4d. per B.T.U. Coal gas at 3s. per 1,000 cu. ft. Cost of producing Cost of each Light. per hour, , Candles of Light during one hour. Electricity : Pence. Pence. Are Lamp _... .. 450 ¢.p. 2°2 1:0 35 Frosted Globe * 40 1:0 ” Opal ” 67 10 Incandescent Lamp .. 160 ,, 12°5 0-2 Nernst Lamp .. 65°0 ,, 6:2 0-4 Coal Gas: Flat Flame Burners... 13°0 ,, 13°8 0:18 Argand i 16:0 ,, 11:2 0:18 Welsbach Mautle 600 ,, 21 0:13 Intensified oS . 800°0 ,, 12 0°36 Petroleum : Kitson’s Incandescent 1000:0 ,, 0°8 0°80 Flat Flame .. = 95 4, 9°5 0:09 W. J. Dz Gas Engines.—Heat engines are classified either as internal or external-combustion engines. In the external-combustion engine, heat is generated in a furnace and transmitted through the metal sides of a vessel containing a working fluid, as in the case of the ordinary steam boiler. The water so contained forms the medium by which part of the heat given out by the fuel is transformed into another form of energy and thence passed on for use ENCYCLOPHDIA OF GAS in the steam-engine. In the internal-combus- tion engine the heat-producing materials are, at the outset, introduced into the working cylinder uncombined, and there develop the whole of the heat due to combustion, and finally, after having done work in the cylinder, are ejected from it as waste products of combustion. The internal-combustion engine, in thus having the whole heat gene- rated within the cylinder, possesses an impor- tant advantage from a thermo-dynamic point of view, seeing that, in external-combustion engines, from 25 to 30 % or more of the total heat produced is lost in the flue gases by radiation and other causes. It has to be borne in mind, however, that the temperature of the cylinder of an _ internal-combustion engine, of which gas and oil-engines are the best examples, must, for practical reasons, be constantly kept below a certain limit by cooling by means of a water-jacket, and this operation involves a waste even in excess of the chimney waste above-named. Notwith- standing the fact that some 50% of the total heat generated in the gas-engine cylinder is lost by the water-jacket in this way, experience shows that a higher thermo-dynamic efficiency can be realised in practice in internal-combus- tion engines than has yet been obtainable in even the best examples of the external-com- bustion type. With the view of testing the comparative efficiency of large gas-engines worked with Dowson gas and of a good steam- eng ie and boiler, Professor Witz, of Lille, carried out experiments which yielded , the following thermo-dynamic efficiencies! :— Per cent. Steam boiler 68 to 76 Gas-producer ... 70°6 Steam-engine ... 9°7 Gas-engine be 18°0 Steam-engine and boiler 70 Gas-engine and producer 12:7 Dowson gas, obtained from a producer worked with anthracite and coke was used with a 112 I.H.P. single cylinder gas-engine, 1 « Proc. Inst. C. E.,” vol. cix. 198 GAS and the total consumption of fuel was 1°349 lb. per brake horse-power per hour. The steam- engine under trial was a simple jacketed con- densing-engine, with steam at 75 lbs. per square inch generated in a boiler with economiser, and a coal consumption of 2°4 to 2°7 lbs. per brake horse-power hour. Even when a gas-producer is used, the internal-combustion engine shows a considerable efficiency over the steam-engine, and where, as in the case of an oil-engine, the fuel is introduced directly into the cylinder without any external losses, the thermo- dynamic efficiency of the internal-combustion engine will show a still more favourable com- parison with the steam-engine and boiler. In large sized steam-engines higher efficiencies than that assumed above are readily obtain- able, but, at the same time, the internal- combustion engine, comparatively speaking, is in its early stages, and further important improvements may be confidently anticipated. The commercial history of the gas-engine dates from 1876, when Dr. Otto introduced the well-known Otto-Crossley engine now 80 widely used, and applied the cycle of operations originally suggested by Beau de Rochas in 1862. Since 1876, the development of the gas-engine has been more in the improvement of details of construction, increased efficiency, and the use of higher compressions, than in the introduction of any entirely new type of engine. The original Otto gas-engine is a thing of the past, but the present general uniformity in design of gas-engines( is a strong indication that the “Otto cycle” is best suited to the commercial gas-engine, although there may be considerable variety in other details. The Otto cycle engines are explosion engines in which the combustible gaseous mixture is compressed previous to the explosion. The “cycle” consists of five operations, viz. :— Outstroke, charges the cylinder with gas First and air mixture at atmospheric pressure. revolution | Instroke, compresses the charge into a combustion space. Dead centre, the charge explodes. MUNICIPAL AND SANITARY ENGINEERING. GAS Outstroke (caused by the explosion), ex- Second pansion of the gases. revolution | Instroke (due to action of fly-wheel), expul- sion of the burnt gases from the cylinder. An impulse to the piston is thus only given every two revolutions (i.c. four strokes) of the engine, so that a very heavy fly-wheel is necessary to maintain a constant speed. In the Otto-Crossley engine, the cylinder, which acts alternately as a motor and a pump, is open-ended and horizontal, and in it works a long trunk piston, the front of which carries the cross-head pin. The cylinder is much longer than the stroke and the piston thus leaves a space, known as the ‘combustion space,’ in which the charge is first compressed on the inward stroke as above-named and then burned. Inagas or oil-enginea large amount of stored energy is needed to carry the piston through the negative portion of the cycle as set out above, and for that purpose a large fly-wheel and heavy crank shaft are provided. The valves are four in number—the charge inlet valve, gas inlet valve, igniting valve, and exhaust valve—and are all of the conical seated lift type. The igniting or timing valve determines the time of the explosion. One of the latest improvements in the Crossley engines is due to the introduction of a “scavenging ” arrangement by which the exhaust gases remaining in the clearance space are drawn away at the end of the stroke. Self-starters have become necessary with the introduction of large-sized gas engines, as the starting of these would present considerable difficulty by simply pulling the fly-wheels round as in the smaller engines. Various methods are employed by different makers, but the general idea is to store up a small amount of energy in a separate vessel for the purpose of giving, when re-starting, the first impulse to the piston. In the Westinghouse double-acting engines of large size an auto- matic compressed air starter is supplied, in which air is stored during the previous run, or is separately compressed and is turned into one cylinder of the engine—the valve functions of which have been altered—until 199 “G GAS explosion takes place in the others, when the air is cut off from the starting cylinder, which then resumes its normal functions. Some makers adopt the method of filling the cylin- der with gas and then open a connection to a compressed air vessel from which sufficient air under pressure is allowed to flow until a rich explosive mixture is formed at a consider- able pressure, which, upon ignition, gives an effective starting impulse. An important practical point to be taken into consideration when adopting large size gas-engines is the avoidance of nuisance caused by their running. This may arise from the noise or smell of the exhaust or from air or ground vibration. The noise from the exhaust may be deadened by conducting it into a “ silencing chamber,” or pit placed underground containing large pebbles or stones from which an outlet pipe gives relief into the open air. Internal air vibration is often caused by the displacement of a large trunk piston setting up rapid pulsa- tions of air which may be transmitted through- out the passages and other rooms of a large building if such directly communicate with the engine-room. Ground vibration is often set up by the running of large engines, also vibration not only to-the walls of the building in which the machinery is situated, but also to those of adjoining properties. Such vibration may be transmitted considerable distances through the ground or communicated to the walls direct where the foundations of the engine abut thereon. Where a material nuisance is alleged to be caused in this way to neighbouring properties, the prevention of “such vibrations is often a problem of consider- able difficulty. An alteration of the speed of running has in some cases reduced the trouble, possibly due to the altered period of vibration. If such period happens to coincide with that of the building itself, the resulting vibration is likely to become more pronounced. Another remedy applicable in some cases is the bolting down of the engine upon a yielding and springy bed, such as thick cocoanut matting or similar material, sandwiched between two iron plates, the whole being securely held ENCYCLOPADIA OF GAS together by strong foundation bolts. In a gas or oil-engine the water-jacket surrounding the working cylinder is required to perform the important function of conveying away the excess of heat due to combustion in the cylinder which cannot under present con- ditions be converted into useful work. By this means the temperature of the cylinder is kept within suitable limits without which lubrication would be impossible. The heat absorbed by the jacket-water amounts to from 80 to 50 % of the total generated by the combustion of the gases in the cylinder. The circulation of the water takes place in an annular space, of from # in. to 2 in., cast around the cylinder, at the underside of which the cool circulating water enters and from the top of which the heated water flows away to the circulating water storage tanks, or as may be arranged. The maximum temperature of the circulating water should not exceed 150°F’., and, with water of 60° at the inlet, the quantity required to keep the cylinder cool will be from 44 to 5 gallons per I.H.P. hour. The circulation is generally arranged through circulating tanks having a capacity of from 20 to 30 gallons per I.H.P. The jacket pipes will be from 1 in. to 2 in. diameter for engines up to about 20 I.H.P., and from 2 in. to 8 in. for inlet with 24 in. to 34 in. for the outlet in the case of larger engines. Sometimes several circulating tanks are arranged in series, the pipe connections being arranged so that the water is drawn from the bottom of one tank to the top of the next in the order of the circulation. In order that the consumption and working of each engine may be indepen- dently checked, a separate gas-meter should be ’ provided for each ; it should be placed outside the engine-room in an atmosphere of normal temperature as an increase of temperature means an increase in the volume of gas for the same weight. A flexible gas-bag or bags should be provided between the meter and the engine, in order to reduce the effect of fluctuations of pressure in the mains. The ignition of the explosive mixture within the cylinder of a gas- engine without permitting escape of gas has 200 GAS been a detail of some difficulty in the design of the engine. It is accomplished in various ways. In “ flame-ignition” a portion ofburning gas is carried through a small aperture in the slide when just closing. If the aperture becomes carbon coated, as often happens, missfires are occasioned. In “tube-ignition” a cast-iron tube is maintained at white heat by a Bunsen burner, and when the timing- valve opens, the charge, being partly com- pressed into an ignition chamber in communi- cation with the tube, then ignites. ‘Electric ignition” is accomplished by causing an electric spark or shower of sparks to take place in the cylinder or in a chamber brought into communication therewith. Gas Furts.—The fuels most commonly used in gas engines are ordinary town coal gas, Dowson-Mond, or other cheap classes of power or generator gas. In the larger engines, notwithstanding the improvements made in economy of gas consumption, the price of ordinary town gas supply is usually too high to permit of its use to advantage except when working intermittently. In these cireum- stances, and where the ordinary gas is not available, a ‘‘ gas-producer” plant may be in- stalled to generate a non-illuminating gas cost- ing (including all charges, depreciation, wages, &c.) from 24d. to 4d. per 1,000 cu. ft., accord- ing to the size of the plant. These gases are poor in calorific value as compared with coal- gas, and proportionately greater volumes are required to evolve the same amount of heat. The calorific value of 1 cu, ft. of coal gas at atmospheric pressure and 82° F. is from 600 to 650 British thermal units, whilst that of a producer-gas varies from 145 to 165 thermal units per cubic foot. From 4 to 5 volumes of the producer-gas are there- fore required to give out the same amount of heat as one volume of coal-gas, and the cost per 1,000 cu. ft. must be multiplied by this figure before comparison with coal-gas. Not- withstanding this, the producer-gas shows a large saving, which, with coal gas at 8s. per 1,000 cu. ft., may vary from 30 to 60 °%/, according to the size of the plant. MUNICIPAL AND SANITARY ENGINEERING. GAS The process of manufacture of Dowson gas, now so extensively used, consists in injecting a mixture of superheated steam and air through incandescent coke or anthracite and collecting the resulting gas. There is no external fire as with ordinary gas retorts, and the production is automatically regulated from the gas-holder without the employment of skilled labour to work the apparatus. Its heating value is equivalent to about 150 British thermal units per cubic foot, and the quantity of air required for its complete com- bustion is only from 1 to 14 volumes to 1 volume of the gas. The capacity of an engine cylinder is, therefore, suitable for either coal or Dowson gas, the gas and air valves being adjusted to admit more gas and lessair. The products of combustion of Dowson gas must be expelled from the cylinder or their presence will cause the fresh charge to miss fire. This is done by what is called the, “scavenger stroke” or its equivalent. The average fuel consumption for a gas-engine driven by Dow- son gas varies from about 1 lb. per I.H.P. for the larger engines to 13 lb. per H.P. for the smaller sizes. In engines fed from the town gas supply the guaranteed consump- tion is now usually from 15 to 20 cu. ft. per I.H.P. per hour, according to the size of the engine and quality of the gas. Tzstine Gas-Eineines.—The testing of a gas-engine is, in many respects, very similar to a steam-engine, but there are important distinctions to be kept in view. Indicator diagrams cannot ‘be entirely relied upon, though if carefully taken they are useful for practical purposes. The brake horse power of a gas-engine should always be taken as the measure of its duty in preference to the indi- cated. Very stiff springs must be used in the indicator (from 745 to 345) so that only the compression, explosion and expansion curves are clearly given by the diagram obtained. Besides the indicator diagrams taken during a trial, it will be necessary to note the brake readings of the spring balance and load on brake, the speed of the engine and number of explosions per minute, also the quantity of 201 GAS gas used in cubic feet with its temperature and pressure, as well as the weight of the jacket-water and its inlet and outlet tempera- tures. The reading of the barometer and, if possible, the temperature of the exhaust are also noted. W. H. M. Gas Water-Liquor Purification.—The impurities washed away during the process ENCYCLOPADIA OF GAS ammonia is valuable as a fertilizer. It is recovered by boiling this liquor (adding lime at an intermediate stage for the decomposition of combined ammonia) and usually absorbing the evolved gases in sulphuric acid. From 100 tons of coal there will be obtained one ton of sulphate of ammonia value about £12. The costs, consisting of acid, lime, coke, labour, bagging, and wear and tear, amount —Plan — I{ Ammonia Waste Liquor Purification Plant (Radcliffe’s Patents). of purifying gas are principally ammonia, sulphuretted hydrogen, carbonic acid and cyanogen compounds. Phenols and cresols are also present in this ammoniacal liquid through cooling of the hot gas. The to £3 15s. Od., thus leaving a profit per 100 tons of coal (equal to 1,000,000 cubic feet of gas) of £85s.0d. From one ton of sulphate of ammonia there is produced about 2,500 gallons of a waste liqour containing free lime, 202 GAS hyposulphite, sulphate, carbonate, cyanide and sulpho-cyanide of lime, and phenols and cresols. Itis antiseptic, and has an oxygen absorption test of between 400 and 600. Its common destination is the sewers. Since the development of the bacterial processes for the purification of sewage many local authori- ties have been obliged to exercise their powers and prohibit its discharge, because with this material present, the difficulties and expense of the problem of sewage purification is vastly increased. On the other hand gas under- takings have to face a considerable loss of revenue. While most large gas undertakings work up their liquor as above described, smaller concerns sell their product as liquor to a chemical works. In the locality of these chemical works the problem is still further increased in difficulty. A process has been introduced by J. Radcliffe, of East Barnet, for the purification of this ammonia effluent, and is now working at a number of gasworks. With the ammonia gas produced by boiling as described also are evolved carbon dioxide and sulphuretted hydrogen, and upon absorption of the ammonia by acid these gases remain, and are employed for the purification of the waste liquor. The liquor enters the plant at A. The solids are removed in B, the clear liquor is pumped from C to D and passes to E. The waste gases from the liquor heater of the sulphate plant enter by E and leave at the top, passing to the condenser of the sulphate plant, the working of which is in no way interfered with. The lime is pre- cipitated and phenoloids decomposed. About three volumes of air are mixed with the waste gases employed by means of the injector shown, a separate air pipe leading to the section above E. and passes toG. A large volume of air is injected at H, leaving at I, carrying away phenoloids and other liberated impurities. A condensate containing these accumulates at J, and thence is led to a fire K. Cyanogen com- pounds are more completely removed if neces- sary by replacing L with a tank for settling out carbonate of lime, and introducing a small MUNICIPAL AND SANITARY ENGINEERING. The liquor re-enters at F GAU amount of vitriol continously at I’. The liquor passes to settling tank M and filter tanks N. The bacterial effect of the purified effluent was determined with sewage effluent, adding various amounts as below to sewage, incuba- ting five hours at 32° C. (by O. Hehner). “Sewage without addition, bacteria per c.c., 2,419,000; sewage plus 4 °/, effluent bacteria per c.c., 2,837,000 ; sewage plus 6°/, effluent bacteria per c.c., 2,475,000; sewage plus 8 °/, effluent bacteria per e.c., 8,211,000; sewage plus 12 °/, effluent bacteria per c.c., 3,846,000. “Up to 12°/, the liquid has not only not anti- septic action on bacteria but greatly stimulates their growth and development.” These plants have been successfully working for years in works which have been compelled to cease working their ammonia recovery plant. The cost for labour and material are nothing and the outlay small. Gauging Streams, &c.—The simplest way of ascertaining the flow of a small stream is to catch the water in a vessel of known capacity and to make a careful note of the time taken to fill it. Several trials should be made in order to establish a mean. Sucha method is, necessarily, only applicable to very small supplies. For measuring larger volumes of water, gauging with a weir is the most reliable system. The weir is formed by damming the stream with a plank and allowing 208 GAU the water to flow freely over a rectangular notch cut in the same (see Figs. 1 & 2). The width of the notch should not exceed two-thirds that of the stream and its depth must be sufficient to pass all the water that is to be measured. The edges of the notch should be bevelled, as shown, and any leakage at the sides or bottom of the plank prevented by the use of puddled clay. The depth of water flowing over the sill should not be more than a quarter of the total depth on the up-stream side, and the dam should be high enough to form a reservoir through which there is no perceptible current. The bottom of the notch must be set truly horizontal by means of a spirit level. Fie. 2. A gauging stake is then driven in until its top is exactly level with the sill of the notch ; this stake should be placed in the still water well away from the depression that occurs in the vicinity of the overfall, so that the true depth of the flowing section may be measured. A thin rule should be used with its edge in the direction of the current. The quantity of water passing over the weir may be calculated with sufficient accuracy for all practical pur- poses by the following formula :— Q= 481 L. V7 18 @ = Discharge over notch in cubic feet per minute. L = Length of notch in feet. h = Height of water above top of stake in inches. A weir with a V-shaped notch is easier to ENCYCLOPADIA OF GAU construct, and, as the breadth of the over- flow bears a constant proportion to the height, is preferable to a level notch when the volume of water is sufficiently small to permit its employment. The notch must be an exact right angle, with its (inverted) apex level with the top of the stake. The edges should be bevelled on the outfall side and the weir formed in the same manner as for the rectan- gular notch. The discharge may be calculated by the following formula :— D=1978VV h. D = Discharge in gallons per minute. h = Height of water above top of stake in inches. If the stream is too wide, or its banks are unsuited to the use of a weir, a fairly reliable estimate of the flow may be arrived at if the average cross-sectional area of the stream and the velocity of the water are known. The velocity of the water may be ascertained by observing the mean time that a float (such as a bottle sunk to the cork) occupies in travel- ling between two points—say 100 feet apart. Several experiments should be made in the most uniform section of the stream that can be found, and the float should be cast into the water well above the starting point. Owing to the friction of the sides and bottom of the channel the velocity of the water will not be uniform ; the actual quantity passed will be less than that indicated by the float, by an amount which depends upon the material of which the channel is composed and, to some extent, its shape. The formula may be stated thus :— _ DBL = ee > q = Flow in cubic feet per second. D = Average depth of wetted channel in feet. B = Average breadth of ditto. L = Distance traversed by fioat in feet. T = Average time, in seconds, taken by float from point to point. 204. GEL K = Co-efficient = ‘65 for rocky stream beds. ='70 for small earthen channels. ‘80 for large ditto. °85 for smooth conduits. The results by this method are only approxi- mate, and it should not be resorted to when others are admissible. The mean velocity of a stream can be more reliably determined by taking observations at various points with a current meter. This usually consists of a small screw propeller driven by the water and combined with a revolution counter, the relation between the revolutions of the screw and the velocity of the current being established by drawing it through still water at various speeds. When it exists,and permits a free discharge to the water, a sluice affords a very convenient method of obtaining the volume of a stream. The gate must be opened until it exactly passes all the water coming down the stream. The breadth and height of the opening and the depth from the surface of the water to the centre of the orifice must then be carefully measured. The discharge may be found thus :— gq = 8025 AK.V H q=Quantity of water in cubic feet per second. A = Area of orifice in square feet. K = Coefficient = °62 for a sluice without side walls. = '96 for a sluice with walls in a line with the opening. H = Head = surface of water to centre of orifice in feet. For cylindrical extensions, of the same diameter as the orifice, but with a length rang- ing from twice to sixty times the diameter, K varies from °82 to °62. E. L. B. Gel, a term introduced by Graham to denote the gelatinous result of the coagulation of Colloidal Matters (gq. v.). MUNICIPAL AND ‘SANITARY ENGINEERING. GER “Germs” of Disease.—Numerous dis- eases are now known to be due to the presence in the system of very minute forms of animal and vegetable life, popularly spoken of as “germs.” Many of the specific infectious diseases, of which Professor Osler, in his “Principles and Practice of Medicine,” enumerates twenty-five, are known to be due to bacteria, and it is probable that all of them are due to similar organisms. Proof is at present wanting in many cases, and in some it may ultimately be found that the ‘‘ germ” is an animal rather than a vegetable parasite. Thus malarial fever was for long considered to be an infectious disease allied to typhoid fever, but recent researches have proved that the specific organism is a sporozoa, and that human beings are infected by the bite of cer- tain mosquitoes, in the bodies of which the microscopic animal undergoes one stage of its singular development. Bacteria are parasitic fungi, and it is believed that some may be so small as to be beyond the limit of visibility under the highest possible magnifying power of the microscope. Even with the highest available power they appear like single cells, ranging in form from a sphere to a short cylindrical rod. According to their forms they are usually divided into three groups. Cells, spherical or nearly so—Coccii cells, rod-shaped and straight or but slightly curved—Bacilli cells, elongated and twisted or forming spiral threads— Spirilla. Erysipelas, pneumonia (certain forms of), gonorrheea, Malta fever and cerebrospinal meningitis are the chief diseases known to be due to cocci, anthrax, plague, typhoid fever, dysentery (certain forms of), influenza, diph- theria, tetanus, tuberculosis, leprosy and glanders are due to bacilli, while the germ of cholera is a spirillum. Many of these bacteria can be made to vary enormously in virulency by different methods of cultivation, and when introduced into the system they may or may not cause disease. (Vide ‘ Zymoric Diseaszs.”) The mere presence of these germs is not sufficient to account for their effect, and 205 GOU in the majority of cases there is no doubt that these effects are due to specific poisons, “toxins,” which the germs produce during their growth. They may enter the system through abrasions of the skin or internal mucous membrane, through the lung tissue, or through the alimentary canal. hey may multiply upon the surface of the tonsils and by their growth destroy the tissue beneath and so gain access to the system. The effects produced vary considerably, as will at once be realised by comparing the history of a person suffering, for example, from typhoid fever due to the typhoid bacillus with that of one suffer- ing from phthisis due to the bacillus of tuber- culosis. Many of these germs are capable of being grown outside the human body on suitable media. Most of them are easily destroyed by a temperature of 80° C., but a few, such as the bacillus of tetanus and of anthrax, will withstand a temperature of 100° C. for a short time. These latter are spore-bearing bacilli. The majority are non- spore bearing and multiply by simple fission. Those producing spores only do so under certain circumstances, and these spores are much more resistant than the bacilli, and may survive under conditions which rapidly prove fatal to the bacilli themselves. (See “ Zymoric DisEases ’’ and “ Bacrerta.’’) J.C. T. Goux Tub System.—This is one of the conservancy methods of dealing with the Absorbent lining of A sawdust, shavings etc Goux. collection of human excreta, and has been in use at Halifax for many years. The principle ENCYCLOPADIA OF GUL involves the lining of the tub or pail with some absorbent material with the object of securing dryness, retarding decomposition, and preventing nuisance. The size and class of pail is shown in the accompanying figure, and, by the employment of the mould, also illustrated, absorbent materials such as saw- dust, shavings, shoddy, stable litter, leaves, or other like substances, are compressed into the form of a lining some 6 in. in thick- ness, into which the excreta is received. When the pails are received for collection the upper portion of the lining is broken up and scattered over the contents with the object of rendering the same as free from odour as possible. Grease Traps.—Surface traps or gullies designed to prevent also the passage of grease Grease Trap. from scullery sinks into drains. These traps are usually provided with a dipped inlet and outlet and offer a large water area for the cooling of the grease. Frequently they are supplied with a bucket or tray which when lifted out of the trap removes the solidified grease from it. Grease traps are liable to give rise to nuisance and are best avoided if possible. Gullies, or Surface Traps.— These are traps placed on the inlet end of drains provided for the re- ception of rain and waste Their use is to prevent the issue of water. drain air at those points. The sanitary forms 206 HEA of these traps are of siphon shape, and that illustrated is typical of them all. They vary mostly as regards the form of inlet, and are available with or without branches for the reception of waste pipes, &c. Some are provided with flushing rims, that being a convenient method = of connecting a flushing = tank to drains. In selecting Gully. gullies, preference should be given to those which provide a sufficient seal with a minimum quantity of water, and which have a good base, as the latter will greatly facilitate proper fixing. Rain-water and waste-water pipes may be arranged to discharge into the gullies either above or under the gratings of the traps, but should in all cases do so above the water level. mH i|! Head (pressure, loss of ).—Water, or other liquids, when flowing through pipes encounter a resistance due to friction and, to a slight extent, the viscosity of their particles. The pressure required to overcome this resistance and to propel the liquid through the pipe, is conveniently expressed in the terms of the head or height of the liquid that would correspond with that pressure. The friction of water in pipes increases nearly as the square of its velocity and directly as the length of the pipe; but it is inversely proportional to the hydraulic mean radius of the same (i.e., the cross-sectional area divided by the circumference). Any alteration in the direction of the flow by bends or, more, particularly elbows, increases friction, and the latter should always be avoided if possible. Sudden contractions or enlargements are also undesirable, in that they create eddies. The condition of the interior surface of the pipe is likewise an important factor, the friction in encrusted pipes being about twice that in perfectly clean, smooth pipes, added to which there is a further loss by reduction of area. The loss of head MUNICIPAL AND SANITARY ENGINEERING. HEA in clean cast-iron coated pipes may be found as follows: : Vo a= K? xX 25D" H = Head in feet. V = Velocity of water in feet per second. D = Diameter of pipe in feet. I = Length of pipe in feet. kK = A co-efficient depending upon the size of the pipe, which varies as follows :— Diam. of pipe infeet .. 25 *5 °75 1:0 1:25 15 1:75 2-0 Value of K.. 70 86 97 106 118 118 121 123 Diam. of pipe in feet .. 25 3:0 3:5 40 Value of K.. 127 181 185 188 Similarly V will be equal to K / 2 x a The discharge in cubic feet per second will obviously be equal to the sectional area of the pipe in feet multiplied by V. (See “row or Water In Pipes” and “ Hypravzic Memoranpa.”) E. L. B. Heat, Utilisation of.—(See “Dezsrruc- TORS.” Heating. — Open Fires Hot Water and Steam Heating — Hot Water lLow-Pressure Systems—Two-pipe Method—One-pipe System — Hot-water Boilers — Selection of Boilers — Radiating Surfaces for Ordinary and Horti- cultural Buildings—High Pressure or Perkins System — Heating Water by Steam — Steam Heating — Low Pressure — Vacuum Systems — Ventilation and Heating—Air Warming-stoves.— Ideally the warming of rooms and buildings is to raise and maintain the air and surfaces at an even and agreeable temperature through- out, with a minimum of fuel and attention, and withont adding impurities to the air, creating draughts, or unduly robbing the air of its invigorating properties and humidity. Oren Fires possess a cheerful appearance. Bodily warmth may be quickly absorbed, ventilation is assisted, and the fire is available for domestic purposes. On the other hand, there is considerable disproportion of heat emitted to fuel consumed; much dirt and 207 HEA labour is involved, and the room, especially if large, is not equably warmed. Although open fires provide perhaps the most healthy means of warming rooms, their use in towns adds seriously to the pollution of the atmosphere. Hor Warer anp Steam Herarinc.—A more equable temperature may be maintained with a considerable saving of fuel by warming the house or building with hot water or steam. Hot-Water Low-pressure Systems.—In low-pressure systems an open pipe is carried above the supply cistern, the pressure being thereby limited to the head of water. A boiler is placed below the rooms to be warmed, and one or more pipes—flow and return pipes —carried along or returned in the direction in which heat is to be emitted. ‘‘ Flow” pipes leave the top of boiler and ascend, permitting convection currents to rise therein, whilst “return” pipes descend, the water therein returning by gravitation to the boiler, entering it near the bottom to ensure circulation throughout. The system should, as far as possible, be arranged to obtain the maximum vertical, as opposed to horizontal piping, the 70 OTHER WORK. Fic.1.—One-pipe Steam System. size of mains and branches proportioned to the radiating surface required, and a boiler of ample proportions provided. Low-pressure ENCYCLOPADIA OF HEA hot-water heating may be sub-divided as follows :— Two-Prrzr Mernopv.—Flow and return pipes are carried along side by side, the branches to Fic. 2.—Two-pipe Hot-water System. the different floors and radiators being taken off the flow and return pipes. Objections to this method are, (a) two pipes must be run to every part of the premises to be heated ; (b) radiators being connected to both flow and return, short circuiting may result. One-Pire System.—This system has for its principle the running of one or more large circuit mains. Each main leaves the top of the boiler and rises as vertically as possible to its highest point, returning to the boiler by way of the radiators. Branches and flow and return connections are taken from the return main—in some cases a few may be taken from the flow—the same as if directly off the boiler; flow connections from top of main and return connections from side of main furthest from boiler. As single mains are used they require to be larger than with the two-pipe system; the volume of water to be carried is, however, practically the same. Advantages of the “ one- pipe system” are, short-circuiting is impos- sible, and generally the constructional cost is lower. 208 HEA A modification of the “ one-pipe system,” known as the “overhead or drop system,” is largely adopted in buildings possessing similarly planned floors. The main pipe is ‘carried direct to the top floor or attic above, distributing branches being here taken off and “dropped” to return to the boiler. Radiators are connected to the “drop” pipes, the feed at the top and return at bottom. No air cocks are required, but an expansion cistern or tank through which the whole MUNICIPAL AND SANITARY ENGINEERING. ec HEA calculated by multiplying the heat emission per square foot of radiating surface by the total area of radiators, mains and branches. The heat emission in B.T.U. of hot- water radiators and pipes varies from about 200 to 150 per hour with the temperature of the air about them at 60° F. A reliable estimate of boiler power required may be >» —_— to Other system is vented is required Work above the highest part of mnain. With this system a more rapid circulation is "to Other Work obtained, and smaller pipes may be used. | Hot-watEr Borners.—The 2 success of any hot-water | apparatus is dependent upon the boiler. The amount of radiating surface, in- cluding mains and branches, should be ascertained, and a boiler of ample proportions provided. Uniform rating | of boilers is much needed. A common basis is to allow 1 sq. ft. of boiler surface to to {Im im 35 ft. of 4-in. pipe. j ratio is reduced to 1 ft. to 25 ft. by at least one maker. Regard should, however, be had to the fact that the efficiency of boiler surface a Return from Other Work ee Saws Return from Other Work ex) varies with its position rela- tive to the fire. A better method is to list the boiler capacity in B.T.U. per hour. This should be based on an apparatus working under normal con- ditions. The practical test in all cases is the fuel consumption and heat transmission when banked to last a specified time. As the boiler- capacity should always be at least equal to the radiator emission required to properly warm the various rooms, &c., the capacity may be M.S.E. Fig. 3.—Hot Water Overhead or Drop System. .obtained by multiplying the total area of radiators, uncovered mains and branches |by 180, the result giving the required capacity in B.T.U. per hour. SeLEcTION oF Borters.—Brick-set boilers are now giving way to “independent” types. These are compact, occupy less space, and are more easily examined and repaired. Cast-iron sectional boilers are largely used. They 209 P HEA possess many advantages, and, with proper care, should last longer than wrought-iron, but are somewhat more complicated, and the thickness of the castings are not always uniform throughout. In a well-designed type of this class a large heating surface is exposed to the fire and hot gases. The grate area is well-proportioned, and the front well fitted for draught regulation. These boilers are fairly economical in fuel. ' Rapratine Surrace Requirep.—This may be estimated by either of the following methods : (1) By calculating the heat in B.T.U. required to raise the temperature of air contained in and passing through the apartment, plus the heat lost through the several materials, walls, windows, &e., enclosing the room (in most cases exposed surfaces only need be considered), and dividing the sum of the whole by the B.T.U. emitted per square foot of radiating surface, which for radiators and low pressure hot water, to maintain a temperature of 60° F., may be taken as 160°. Owing to leakage of air through ill-fitting doors, windows, &c., two to three air changes per hour should be allowed. The following table gives the coefficient in B.T.U. to raise the temperature of air, also the heat transmission through walls, &c. The calculation is in B.T.U. per hour for 1° difference in temperature of air, and also on the two sides of the walls, &e. Heat Lossss. Coefficient. Air ss ae .. leu.ft. .. °019B.T.U. 44 in. Brick wall . Llsq.ft. .. 15 9 9 *5 59 ies Wi 55 .. "BS 9 14.sC««,, 25 dope. 8S as ee 227 9 18° 55 43 sar EH ‘a an 28 - Single windows Ske ABR 55 .. 1:03 - Double a5 oe aye 3 .. ‘48 i Single skylights ie 8 5 sep LT = Double __,, ag 2 fs ae, 25 ae Corrugated iron roofs.. .. 35 .. 217 3 Ceilings close to roof .. .. <5 .. "B2 a 53 with good air space Soe 9 ah a we “LS 55 Floors (12 in. concrete and wood) .. .. 5 ay NT ms » (woodon joists) .. ,, Geo MOB 45 Doors 13 in. thick oo: ke ‘i .. "45 ‘3 To ascertain the loss in B.T.U. per hour from any room or building, multiply the air ENCYCLOPHDIA OF HEA coefficient in table by the cubic capacity and the air changes, and by the difference between the required internal and the external tem- perature. To this must be added the sum of the products of the different surfaces multi- plied by their respective coefficients and by the difference between the external and in- ternal temperature. Dividing the total by 160 gives square feet of radiating surface required to maintain a temperature of 60° inside when 30° outside. Or (2), a simplified formula may, in ordinary cases, be used. The formula by W. Jones, based on a lifelong experience, is easy of application :— For Orpinary Buiupines (not horticul- tural).—To obtain 60° inside when 30° out- side, and water 170° G ,W Cc S=@ 71 137 120% 160" S = Ft. super radiation required for the stated temperature. G = Ft. super glass. W = Ft. super exposed wall. C = Cubic capacity. 120 for rooms under 5,000 cu. ft. capacity. x | 140 5 5,000 to 25,000 ,, bs 150 3 25,000 to 100,000 ,, ee 160 5 over 100,000 56 3 The above rule assumes the loss through doors, walls, and windows to be from two to three changes of air per hour. If more air changes are required, add cubic capacity + 300 for each additional change. For Horticuttrurat Buinpines.—The fol- lowing rule by W. Jones gives the feet sup. radiating surface required for the same tem- peratures as in last :— G,W,c¢c ae MI a) A table of coefficients for use with other temperatures is given in “Heating by Hot Water,” by W. Jones. Norule or combination of rules will be applicable to every case; e.g. an increased amount of radiating surface will be required in the case of rooms or buildings exposed to severe weather. 210 HEA Hich Pressure orn Psrxins System.—- This system has been in use upwards of 60 years; its use, however, is not nearly so extensive as the low pressure system. It con- sists of a series of very strong wrought-iron tubes—similar to hydraulic tubes—usually of “ Z in, bore, screwed together with right and left hand threads. One of the ends of the tube to be drawn together is tapered, inside and out, to a conical edge, the other end being trued to a flat face. Powerful tongs are required to draw the tubes together, the actual joint being made by forcing the coned edge into the flat face of the opposite pipe. The boiler is coiled of the same description and size of tube, the number of coils being proportioned to the quantity ‘of radiating surface. At the highest point of the apparatus is fixed an air vessel or expansion pipe, the capacity of which must be carefully proportioned to the quantity of water contained in the | apparatus. Water is pumped into the apparatus from a point near the boiler until it reaches an overflow placed at the bottom of the-expansion pipe. The overflow is then plugged, the apparatus being hermetically sealed. It is afterwards tested to a pressure up to 8,000 lbs. per sq. in. Owing to the apparatus being sealed, the water may attain a temperature of 800°. to 600°, being, of course, accompanied by high pressure; and the expanded water compresses the air in the expansion pipe. Considerable experience and special appliances are re- quired to properly erect this system; but although the apparatus may appear to be highly dangerous, it is not so in fact, as any defect manifests itself at the boiler and puts the fire out. Advantages claimed for this system are: The temperature of the water is Automatic Valve 211 MUNICIPAL AND SANITARY ENGINEERING. Steam Control kag. Fig. 4 HEA quickly raised. It may be used to assist ventilation (in this case it should be filled with anti-freezing liquid). The pipes are smaller and neater in appearance. The system is suitable for large buildings that are well ventilated. The disadvantages are: Repairs necessitate the calling in of a specialist, pre- Tube Return .—Vertical Steam Calorifier with Indented Tube. ferably the erecting firm. The high tempera- ture of the pipes often produces unpleasant smells, due to the burning of organic matters present in the air. Pipes must be kept well away from woodwork. The system is specially suitable for high temperatures such as are required for laundry purposes, &c. Heating Water sy Stram.—Where a steam supply is available the building may be p22 HEA warmed by water heated by contact with steam-heated surfaces, or by allowing steam to pass direct into the water. Warming by steam-heated surfaces is accomplished by steam-heaters, or ‘‘calorifiers,” generally cylindrical in form, which takes the place of the hot water boiler, connections being simi- larly made thereto. Inside the calorifier there is usually a coil or series of tubes through which the steam passes, warming the water in contact with the outside of the tubes. The condensed steam is or should be ultimately returned to the boiler. “a COLD SUPPLY Fic. 5.—One-Pipe Steam Gravity System. The power of steam-heaters or calorifiers varies with the temperature of steam and with the form of tube and general construction ; 1 ft. super of steam-heated tube is usually much more effective than an equal amount of hot water boiler surface. Heating by the injection of steam is accomplished by means of an “‘injector;”’ the issuing steam warms the water and impels the same along its course. There is an amount of water added to the apparatus equal to the steam condensed, which must be allowed to overflow, and then returned to the boiler-house for use in the boiler. These systems are very suitable for large institutions with a central heating plant or boiler-house. ENCYCLOPADIA OF HEA Steam Heatinc.—Steam is extensively used for warming public buildings, schools, factories, &e., and is undoubtedly superior to hot water for warming in conjunction with ventilation, as, for example, in the plenum systems. It may be economically employed where steam is generated for other purposes, exhaust steam being frequently and advantageously utilised. Where a steam supply is not available and the building is of limited dimensions, as for residential purposes, hot water possesses many advantages and will doubtless continue in favour in this country. Generally speaking, a steam system requires a skilled atten- dant—a matter of importance in small buildings where the caretaker is expected to attend to the apparatus. Moreover, repairs are, if anything, more costly, and the temperature of the steam (unless under vacuum systems) is not easy of manipulation. For large buildings, how- ever, steam possesses many advantages. Steam in condensing gives up its latent heat—approximately 966 B.T.U. per pound, which quantity of heat is dissipated by the pipes of radiators before the steam is entirely condensed. The latent heat is for practical purposes the same for all pres- sures, and no useful purpose is served by working at high pressure; in fact, the reverse is the case, owing to the higher temperature of the pipes, &c., burning up organic matter in the air, causing un- pleasant smells, and also robbing the air of humidity. In a properly erected steam- heating system, the steam should be carried to the radiators with a minimum of con- densation and be there dissipated. The water of condensation should be properly drained without interfering with the flow of steam, and be directly or ultimately returned to the boiler. Adequate provision should be made for the escape or removal of air from the apparatus. The system should be free from noise, and the steam generated and maintained with a minimum of fuel and attention. Low-pressuRE—ONnE-Pipr Gravity SysteM.— 212 HEA MUNICIPAL AND SANI One or more large circuit mains are used, the highest point being practically directly over the boiler; from here the main descends until it returns to the boiler, entering below the water-line. Single connections are taken off the main to supply radiators. As the water returns to the boiler by gravitation, little attention is required, especially when a good form of automatic damper is fitted, to control the temperature of steam by draught regulation. A little water is periodically added to the boiler to replace any slight escape of steam. This is the cheapest system to erect, and when properly executed is entirely satisfactory. TARY ENGINEERING. HEA the admission of only the maximum amount of steam that the radiator will condense when the controlling valve is full open. As the supply of steam is reduced, so will a propor- tionate amount of radiator surface be in use. A boiler is placed in a cellar or pit, a tank being placed about two metres above the ordinary water-line of boiler. Two pipes connect the tank to the boiler, one being taken from the bottom of tank and connected to bottom of boiler to ensure a return of con- densed water; the other pipe—the “safety pipe ”’—connects the tank to the boiler at a point situated a few inches below the normal water-line. This pipe projects into the tank AI, sll, NS ZL 24 eae Pa ane ote ----} Water Line - --}- a eee meee SN Fic. 6.—Two-Pipe System, Low Pressure Steam. Low-pressurE—Two-Pier System with WET Return.—The highest point is practically directly over the boiler; from here it gradually falls until the last radiator is passed, when the main at once drops below the water-line of boiler, returning to the boiler at that level. Two connections are required to radiators, the inlet from steam main, the outlet through which condensed water flows being taken direct to the return pipe, the end being sub- merged. Care should be taken that con- nections between two or more returns are made below the water-line of boiler. This system is more costly to install, but is held by many to be more silent than the “ one-pipe.”’ Open-Pirz System.—This system is largely used in France, but is not common in this country. It has for its principle of operation to allow sufficient capacity beneath its end for water to return to the boiler. An open pipe is taken from the top of the tank and carried beneath the fire bars. The main steam pipe leaves the top of the boiler whence it gradually descends as in previous systems; the end, however, terminates in a siphon, the height. of which should provide a water column equal to the maximum boiler pressure. The end of the siphon is carried along, gradually falling until it enters the safety tank above the level of water therein. Return pipes from radiators are connected to the return pipe from the siphon and the ends of radiators are open to the atmosphere, the water of condensation being returned to the boiler vid the safety tank. Advantages of this system are: (a), that small pipes may be used to supply 213 HEA radiators ; (b), the supply of steam, and con- sequently the temperature of the apartment, may be regulated; (c), its free discharge of air; (d), its noiselessness and low steam pres- sure. The use of an automatic damper regu- lator is indispensable. Vacuum Systems.—Vacuum systems may be used with live or exhaust steam. These systems have for their principle the removal of air from the apparatus, and the creation of a partial vacuum which permits the steam to more freely enter and flow to all parts of the i Cy ENCYCLOPEDIA OF HEA valve, which automatically opens when the apparatus is cold, but closes when in contact with steam, thus preventing the passing of steam to the condensed water pipes and mains. Fig. 8 shows a small installation having only one radiator (2) and one coil (3), which may be termed the essential components of a vacuum system of any size. This small apparatus is supposed to be supplied either by live steam from the boiler on the right, or by exhaust steam from the engine on the left, since either or both together can be used in a \r Hk e -p--4 RETURN I ~~" SAFETY TANK ¥ AIR PIPE > SAFETY PIPE WATER LINE~ 4 — — “I a} RETURN J Fic. 7.—Open-Pipe System, Low Pressure Steam. system. The whole of the latent heat of the steam is given off in the radiator, and the steam temperature may beregulated. One of the most popular systems is that patented by Warren Webster & Co., of America, the licensees in this country being the Atmo- spheric Steam Heating Co., Ltd. A brief description is as follows :—A pressure-reducing valve is fitted to reduce the pressure of steam entering the system to about 4 lb. per square inch. A vacuum pump is fitted to the end of the condensation main to extract both the air and the water of condensation. On the outlet of radiators is fitted a thermostatic vacuum system. The live steam would first pass through a reducing valve (6) and a main valve (10), and the exhaust steam through a grease separator (7) and main valve (9), before reaching the rising pipe supplying the radiation. On each unit of radiation there would be an automatic valve (5) on the outlet, and a hand control valve (4) on the inlet, as well as a similar automatic valve (8) to drain the main and riser, and so keep the apparatus clear of water. From the automatic valves (5 and 8), small pipes would be taken into the main return or condense main, at the end of which is placed the vacuum pump (1). In 21+ HEA the working of such an apparatus the vacuum pump would be first started, and would ex- haust the air from all mains, radiators, &c., through the automatic valves, so that when steam was admitted a partial vacuum (average not more than 10 in.) would everywhere pre- vail, and the only work required of the steam would be that of imparting its heat to the heating surfaces by condensation. Under these circumstances it is clear that a very quick circulation of the steam to the furthest limits of the apparatus is’ attained. The function of the automatic valves is important ; ENGINE MUNICIPAL AND SANITARY ENGINEERING. HEA the future. In fact, it may be said that vacuum systems and rapid circulation hot water (low pressure), are now generally favoured by heating engineers. VENTILATION AND Heatinc.—The heating and ventilation of rooms or buildings should always be considered in combination. Where a room is warmed by hot water or steam, ventilation may be obtained or supplemented by the use of ventilating radiators, the air passing through a grating in the wall behind the radiator, being warmed. by contact there- with. Another method, but which is open to C3 BOILER Fic. 8.—Vacuum System. they prevent “‘ short circuiting” of the steam ‘into the vacuum maintained return main, which itself would tend to destroy the vacuum, and so secure that no steam shall be wasted. Where exhaust steam is available for use, a back pressure valve (11) on the exhaust pipe is required to seal the apparatus. This is generally adjusted to open at 4 1b. pressure. Gauges (12) are set up to indicate the pressures in the steam and return mains respec- tively. Among the advantages of a vacuum system may be mentioned : perfect circu- lation, absence of noise, controllability of temperature, economy in working and: main- tenance. The system has recently been installed in many important public buildings, and will undoubtedly be extensively used in objection on the score of cleanliness, is the ‘placing of a heating battery under the floor, encased in sheet iron; air passes through a grating, and is warmed by the heating battery, thence passing into the room. In plenum systems itis usual to warm the air at a point near the fan, the air being either forced or drawn through the battery of heating pipes. A much larger quantity of heating surface is required with systems designed to aid or be used in connection with ventilation. (See ‘¢ VENTILATION.’’) Warmine By Hor Arr Furnaces orn Caort- F1ERS.—The hot air furnace generally takes the form of a cast-iron stove, with its back corrugated or arranged with a number of fins or gills. The stove is placed below the 215 HEA rooms and generally set in brickwork. The air to be warmed is conveyed in pipes to the furnace and heated by passing over the corrugated surface or gills, being afterwards conveyed to the different rooms by means of pipes or ducts. As this system brings in rap ENCYCLOPEDIA OF HEA system are: (a) low cost of construction ; (b) as fresh warm air is introduced, ventilation is necessary, and (c) the floor space of the room is not interfered with. On the other hand, the fuel consumption is excessive, and the temperature of the furnace frequently | To Expansion, Tank Z Exparrsion Pipe Flow Gottle. pias Flow. 1 Mainy Return Boiler Altitude| Gauge | '~/¢ Water Supply Te IT Siphon Bottlé fr —— Fic. 9.—‘‘ Beck” Rapid Circulation Hot Water Apparatus. warm air, it is necessary to provide a suffi- ciency of suitable outlets. The system is difficult to install in existing buildings owing to the size of ducts compared with hot-water or steam pipes, necessitating much cutting away. The advantages claimed for the burns and dries the air. The stove is apt to be burnt through and permit sulphur fumes and probably overheated air or gases to enter the ducts and set fire to the building. It cannot be easily installed in existing buildings. In every case air should be drawn from an 216 HEA unpolluted source, the heating chamber and ducts should be occasionally cleansed, and the air humidified when possible, and adequate exhaust ventilation provided. Arr Warmine Stoves.—These stoves are very suitable for many buildings, and are extensively used for hospitals. A good deserip- tion of such a stove is that manufactured by Messrs. Shorland. The “ Galton” air warm- ing stove is also well known. In all such heating appliances the air is drawn from outside and warmed by contact with the exterior of the stove, afterwards passing into the room—the cheerful appearance of the fire not being interfered with. THe “ Bscx ’’ Rapip Crrcvtation Hor Water Apparatus.—This simple but inge- nious apparatus (Fig. 9) is primarily based on the recognised fact that ebullition, or the pro- duction of steam bubbles in an ascending flow pipe may have the effect of causing a con- siderable acceleration of the circulation, provided that suitable means are employed to regulate the ebullition, which unchecked causes shocks and noise. From an ordinary hot water boiler an ascending main flow-pipe is taken up into a pocket or bottle, from the lower part of which the circuit pipes are taken, while from the upper part a pipe is led first down through a deep siphon and then directly up to the expansion tank. In operation the steam bubbles, being lighter than the water, reach the upper part of the pocket, where they accumulate in quantity sufficient to cause a displacement of the water in the siphon towards the expansion tank. This displacement is taken advantage of to actuate a diaphragm or other form of regulator, which, through a suitable arrangement of pulleys and chain, acts upon the ashpit and smoke-pipe dampers—checking the fire and stopping the production of further steam bubbles. As soon as the temperature by this means has diminished, the steam condenses, causing a reverse displacement, which, through the regulator, acts on the fire to render it again more active. The effect of the arrangement described is to prevent the MUNICIPAL AND SANITARY ENGINEERING. HOR steam bubbles passing into the heating cir- cuits at all, while taking advantage of their presence to cause a considerable acceleration of the water in the circuit pipes, and the practical result on the hot water apparatus is avery considerable reduction of the sizes of all the circuit pipes, and of all the radiation. —(See also “ Hor-Watser Suprry”’.) W. F. Hermetically Sealed.—A vessel, tube, or other enclosure is said to be ‘ hermetically sealed” when it is closed completely against the passage of air, gas, or other fluid by fusing the extremity or opening of such vessel. The term is sometimes less correctly applied to any air-tight closure, and is also commonly used in connection with sanitary fittings, traps, pipe-joints, &c., which are proof against the passage of sewer gases. “Hermite Process” or Szwacs Punrirt- cation. This system was installed for the purpose of disinfecting the sewage in a main line of intercepting sewers in Ipswich by Messrs. Patterson & Cooper, Engineers, Westminster. A deodorising and antiseptic fluid was pro- duced by electricity from sea water, or from a solution of magnesium and sodium chlorides. This fluid was put into the drains or applied to the flushing of w.c.’s, much in the same way as in ‘‘ Conder’s process ”’ (see ‘‘ ConDER’s SuL- PHATE OF Iron Process’). In Ipswich the antiseptic fluid was admitted at the head of the main sewer, and the organic constituents in the sewage were oxidised thereby; but the process was discontinued about the year 1905. Horse-Power.—The indicated horse-power of an engine is readily calculated from the indicator diagram (see ‘‘ Inpicator’”’), and for this purpose the mean effective pressure per square inch within the cylinder must be found. This is done in practice by dividing the diagram into ten parts by equidistant vertical lines, then scaling off the pressures from the diagram at the middle of each division within the enclosed curve, and finding 217 HOR the average by dividing the aggregate of the pressures so scaled by ten. Having found the mean pressure acting on the piston through- out its stroke, the following rule may then be applied to find the horse-power, viz.: Multiply the area of the piston in square inches by the mean pressure per square inch, and by the piston speed in feet per minute; then divide the product by 33,000 ft. lbs. per minute (the equivalent of one horse-power per minute), and the quotient is the required indicated horse-power. This rule is usually put in the form of a formula, thus :— : _ PLAN . : Indicated horse-power = 33,000" in which P = the mean pressure on the piston in lbs. per square inch. L = length of stroke in feet. A = the area of the piston in square inches. N = the number of strokes per minute. The “ brake,” ‘‘actual,” or “ effective” horse- power of an engine is the measured horse- power given off from the crank-shaft of the engine ; or, may be described as the net effective horse-power available for external work, and as shown by the friction brake. It is the ‘‘ indicated horse-power ” as given by the above scale, less the power required to drive the engine itself, which latter may vary from 10 to 25 per cent. according to the type and sizeof the engine. The “mechanical efficiency” of anengine is the ratio of the brake to the indicated horse - power, — thus mechanical efficiency :— ___ Brake horse-power ~~ Indicated horse-power" The term ‘‘ nominal’? horse-power, though gradually becoming obsolete, is still used in England to express certain proportions of cylinder, but has no generally recognised value as a standard of measurement. The use of the term is now largely discarded owing to its having gradually receded so far below the actual horse-power, but it is found convenient for rating purposes to have a rule for estimat- ing the power of an engine from its general dimensions. The nominal horse-power may be ENCYCLOPEDIA OF HOT taken at about one-sixth the indicated horse- power. Hot Water Supply.—General Systems— Tank — Cylinder — Combined Systems — Boilers and Incrustations—Steam Calorifiers—Mixing Valves—Hot Water Calorifiers—Hot Water Gas Geysers—Gas Boilers—Materials—Boiler Explo- sions.—A hot-water supply apparatus, to be con- sidered satisfactory, should yield an adequate supply of hot water at all taps within a short time of the lighting of the fire—say, one hour. In addition, the fuel consumption should be moderate ; provision made for shutting down and emptying the apparatus for the execution of repairs, cleaning out of boiler, &c.; the heat conserved by placing the pipes and storage vessels in warm positions, or by covering the same; and a reliable form of safety valve should be fitted to the boiler. Moreover, the size of the boiler and pipes, together with the storage vessel, should be properly proportioned. As it is seldom neces- sary to draw water off continuously, some means of storing the heated water is usually provided; closed storage vessels of a rect- angular (tank) or circular (cylinder) form being mostly used, and connected to the boiler by “flow” and ‘‘return”’ pipes. The manner of connecting pipes to and from the storage vessel, and the position occupied by the latter varies, constituting what are known as different systems. There are, however, certain principles and essential details common to all systems: (a) The boiler must be placed below the storage vessel. (6) Boiler must be connected to storage vessel by two pipes, viz. : Flow pipe, the lower end of which leaves the top of boiler, the other end terminating in the vessel about one-third the height of same from the top. Return pipe. The lower end terminates near bottom of boiler; the other end at bottom of storage vessel. These pipes must be given a rise towards the storage vessel ofat least 1 in. in 10 ft. 218 HOT (c) The cold water feed is connected either to the return pipe, boiler, or to the bottom of storage vessel, preferably the latter. It should be of ample diameter to ensure water entering the apparatus as fast as it is withdrawn, and a stopcock of the fullway type fitted thereon. The pipe should be connected in such a manner that convection currents cannot rise and set up “local circulation’ therein; a simple method being to form a dip before the same enters the apparatus. It is a good plan to place a tee-piece or other fitting on the end of the supply pipe in storage vessel to spread the incoming water over the bottom of same,’ that the water may not readily push its way up to and mingle with the hottest water at top of storage vessel; at the same time the incoming water is prevented from taking a direct course to those pipes from which water is being drawn. (d) An open pipe, or, as it is generally termed, ‘‘ expansion or exhaust pipe,” usually 4 in. to 1 in. diameter, is taken off the top of storage vessel, whence it rises, ter- minating a short distance above the level of water in supply cistern. This pipe permits air to automatically pass out of the apparatus, and also prevents a ‘“swelling-back” of water (much in excess of the actual expansion) into the supply cistern ; the pipe also prevents, should the stopcock on supply be inadvertently closed, the apparatus being sealed and sub- jected to increased pressure. The end may be either just carried above and turned down to discharge into supply cistern, or may pass through a roof. The former is the most usual, and is generally satisfactory. Should the boiler, however, be of a powerful descrip- tion, an ejection of steam and water may take place, filling the roof space with steam, and also heating the water in supply cistern. Should the pipe be taken through the roof, that portion containing water should, if possible, be kept inside to prevent freezing ; failing this it should be well protected. The term “ expansion pipe” is hardly a good one; water upon being heated expands about sy of its volume from 40° to 212° F., or boiling MUNICIPAL AND SANITARY ENGINEERING. HOT point; the increase due to expansion is gradually pushed through the supply pipe into the supply cistern, the capacity of which, measured above the water line when cold, should therefore be at least equal to # the volume of water contained in the whole apparatus. (e) Arrangement for Emptying : An empty- ing cock, with a loose key, to be used only in EXPANSION | TUBE QM —— SECTION OF JOINT Fic. 1.—High Pressure System. case of repairs—should be provided at the lowest part of the apparatus. (f) Safety Valve: A good form of safety valve—preferably of the dead-weight type— should be connected direct to the boiler, and be periodically tested by lifting the spindle to ensure the valve is not stuck fast or choked. (g) Draw-off Connections: Hot water 219 HOT should—especially in the case of lavatory basins—be obtained immediately the tap is opened. As water will not circulate in single branch pipes, the length should be reduced as much as possible, either by carrying the main pipes in the direction of the fittings to be supplied, or by running branch circuits. The connection of branch circuits to main pipes and storage vessels is important, and itis as well to point out, that when a tap t——OF4J el Fic. 2.—Tank System. is opened on any pipe, water rushes to such tap from every possible source, hence, from the two ends of circuit branches; these branches should, therefore, terminate only where the hottest water is available. Systems.—Tanx Systems.—A tank—usually rectangular—is placed above the highest draw- off tap and connected to the boiler by flow and return pipes; an open pipe is taken off top of tank and the cold water supply brought in at bottom of same, all as heretofore detailed. Draw-off connections are taken 220 ENCYCLOPADIA OF HOT from the flow pipe, or from a specially provided pipe connected to the tank at about the same level as the end of flow pipe therein. Connections are sometimes taken off the expansion pipe, which is a satisfactory arrangement, providing an out- flow of water can be maintained; this, of course, depends upon the rate at which cold water enters the apparatus. Objections sometimes urged against the “tank system ” are:(a) The placing of the storage vessel at some distance from boiler necessitates long flow and return pipes with consequent friction and loss of heat from the surfaces thereof. (b) The tank is frequently placed in a cold position. (c) When draw-off connections are taken from the main flow pipe, the tank may be emptied during failure of the water supply; the water in boiler may then evaporate and the boiler be burned and leak. An advantage of the tank system is that the placing of storage vessel above the taps ensures a good outflow of water to the highest taps, the water gravitating thereto until the water in tank is lowered to the level of the particular pipe supplying the tap. Should the draw-off tap, however, be on the main flow pipe, water will afterwards pass to the tap vid the return pipe, being, of course, much colder. From what has already been stated with reference to ‘‘draw-off connections” a tap placed on the flow-pipe must always result in the issuing water being drawn from both the flow and return, although, owing to the force of gravitation and generally lesser friction, the bulk would be from the flow pipe so long as the upper end is immersed; hence, the arrangement is generally satisfactory. Cytinper System. — A storage vessel— generally of cylindrical form to withstand the greater hydraulic pressure—is placed néar to and just above the level of boiler, short flow and return pipes only being required. The open or expansion pipe is taken off top of cylinder and should travel in the direction of draw-off taps, which are then connected thereto, the pipe ultimately terminating above HOT the supply cistern as previously explained. To ensure the issue of the hottest water immediately a tap is opened, the water should circulate past the various taps, which may be done by returning the expansion pipe—after the last branch is passed—to the cylinder, connecting to the same about 6 in. from top, thus ensuring the hottest water only reaching the taps. The foregoing would be termed a “ secondary circulation.” The cold water supply is connected to the &) br Fie. 3.—Cylinder System. bottom of cylinder and should be capable of ensuring a continuous flow of water at the taps. An emptying cock is also imperative. The advantages claimed for the cylinder system are: (a) Short flow and return pipes between boiler and storage vessel, ensuring a quicker transference of heated water and reducing risk of freezing. (b) As draw-off connections spring from the top of storage vessel the latter cannot be MUNICIPAL AND SANITARY ENGINEERING. HOT thereby emptied should the water supply fail. (c) Cylinder is generally placed in a warmer position. A fault often met with is a poor out- flow of water to fittings placed just under the cold-water cistern, this being due in the first place to the low head of water, and secondly, to the water having to travel down to the cylinder and thence push, as it were, the hot water before it until the top is reached ; i PL Fic. 4.—Cylinder System with Secondary Circulation. hence in this respect the tank possesses an advantage. Compinep Systems.—A combination of the foregoing systems has the advantages of both and the disadvantages of neither. This may be described as a cylinder system with secondary circulation, supplemented by a tank placed above the highest draw-off tap and connected to the cylinder system by dis- connecting the highest part of the secondary system 221 HOT circulation and carrying the same up to and connecting to the bottom of tank, an open pipe being taken from top of tank. Draw-off connections may be taken from either the secondary flow or return; other return pipes may be taken from the bottom of tank to supply taps, and should be ultimately connected to cylinder near the top. The secondary flow pipe may stand up a short —s Ir T 100 GALS. 3 &' “150 GALS |: are 9) eC 2® ENCYCLOP.EDIA OF HOT fire being made to suffice for cooking, hot water supply, and for warming the kitchen. More fuel, however, is required for cooking, &e., owing to a large quantity of heat being absorbed by the hot water apparatus; a further quantity is also lost by passing or escaping up the chimney, although this may be reduced by fixing a suitable but, at the same time, more expensive type of boiler. The efficiency COILIN LINEN CUPBOARD Fic. 5.—Combined System. distance inside the tank, but a return pipe must leave the bottom to ensure through circulation. The combined capacity of the two storage vessels is not increased beyond that of other systems, and it is desirable to make the upper vessel about, two-fifths of the required storage. Borers. — The most usual medium of obtaining a supply of hot water is by a boiler placed at the back of the kitchen range, one of range boilers is proportional to the area presented to the fire; for this reason “boot boilers” yield larger quantities of hot water by absorbing more flue heat than ordinary “bath boilers.” The proportioning of boilers and storage vessels is very important, and although no hard and fast rule can be laid down, it is generally preferable to use small rather than large storage vessels, quicker results being obtainable. For ordinary 222 HOT work the following proportions are satis- factory :— | aun | ee | ares | Saeeet Inches, Gallons.’ | Inches. Saddle 25 , 2 or 8 9 Boot 30 1 8 or 4 11 Saddle 30 1 53 11 Boot 40 1k 4or5 12 Saddle 35 4 a 12 Boot 45 <5 3 14 Saddle 40 “3 a 14 Boot 50 59 5 or 6 INDEPENDENT Borters.—The most economi- eal arrangement for heating water is by means of independent boilers. These boilers are circular in form and connected in a similar manner to range boilers. The fire may be banked to last several hours, and practically any fuel may be burned therein. They are eminently suited for large houses, hotels and the like, in fact, wherever hot water in fairly large quantities is required at all times of the day. Borzers anp Incrustation.—Water con- taining lime in solution (temporary hard water) is apt to cause much trouble and expense by furring of the boiler and pipes. Heating such water to a temperature approaching boiling point removes the tem- porary hardness by expelling carbonic acid from the soluble calcic bicarbonate, and causing precipitation of the insoluble calcic carbonate, producing fur, which, unless removed from time to time, prevents the passage of heat to the water within the boiler, eventually causing destruction of the same by burning of the plates. The extent of fur formation depends upon: (a) the amount of lime in solution; (0) the quantity of fresh water passed through the boiler; and (c) the temperature of the latter; a variation in any one of which will bring about different results. All boilers used for temporary hard . water should be provided with means of access and of a form to enable the interior to be freed from fur; hence, coil boilers and the like are quite unsuited for such purposes. MUNICIPAL AND SANITARY ENGINEERING. HOT Srzam Catortriers on Huaters.—Where a steam supply is available the same may be usefully employed in warming water for domestic or supply purposes. These calori- fiers may be powerful enough to heat the water as it passes through, or where the demand is large and intermittent a storage vessel may be coupled up to the same or a storage form of calorifier used instead. The connections to calorifiers and storage vessels, Fic. 6.—High Pressure Boiler and Coil for Indirect Supply. and the arrangement of cold supply, expan- sion pipe, &c., is similar to the ordinary hot water apparatus. The efficiency of calorifiers, depends upon their form, the arrangement of tubes within, and the steam pressure. An automatic steam control valve to govern the temperature of water and prevent waste of steam is a desirable feature. A very efficient form of tube for use in calorifiers is an indented type (Row’s patent) as may be seen from the following. “Relative heating value 223 HOT of 1 sq. ft. of indented heating surface at various steam pressures (Row) ” :— Steam in lbs. per sq. in. 5 10 15 20 25 30 40 Gallons of water raised from 50° to 180° F. in 1 hour 35 42 56 62 80 93 108 An allowance should be made for scaling up when hard water is used. Mixine Vatves. — Water is sometimes heated by the intermixing of steam and water Fic, 7.—Section of Twin Boiler (Jones & Attwood’s Patent). in a valve as the water issues. These valves may be regulated to give water at any pre- determined temperature. An objection some- times urged against this arrangement is that a failure of the steam supply would enable steam to issue should the valve be opened, They certainly offer a convenient and cheap means of obtaining hot water, but where taps are scattered it would probably be more economical to use calorifiers. The use of live ENCYCLOPADIA OF HOT steam also entails the addition of fresh water to the boiler. Hot Water Catoririers.—Where water contains much lime in solution it may be preferable to heat the same by “indirect methods,” i.e., by means of a boiler connected to a coil or closed vessel placed inside a storage vessel, the water therein being heated by contact with the coi! or closed vessel. The advantage of such an arrangement is that incrustation is avoided as the water in the boiler and coil, &c., is unchanged, whilst the water in the storage vessel is not heated to a temperature high enough to expel carbonic acid and cause fur formation. The primary heating apparatus may consist of an ordinary independent boiler with a coil or other arrangement connected thereto, or may be of a “high pressure’ description. Obviously more heating surface will be required in the storage vessel than in the boiler; the surface of coil or heater in the vessel should be about five times the heating surface allowed in the boiler. Hor Water Gas Gerysers.—Hot water geysers are extensively used for supplying hot water for baths and lavatories, especially in flats, bungalows, and houses not possessing a hot water apparatus ; they are also frequently fixed where a warm bath is required at an early hour. Geysers are generally constructed of copper—tinned inside—and possess a large heating surface over which the water flows, a continuous supply being furnished so long as gas is burning. The temperature of the issuing water will depend upon the rate at which the same passes through the geyser, the gas consumption remaining the same. In a good type of geyser, the gas should not have access to the water; an automatic valve to ensure that gas can only be burned whilst water is in or passing through. the same should be fitted, and a flue pipe, not subject to “ blow-down”’ provided ; in fact, no geyser should be fitted without such a flue. A warm bath should, with gas at 3s. per 1,000 cu. ft., be obtained for about 1d. Gas Borters.—Gas boilers are frequently 224 HOT used in place of and also to supplement range boilers. They are useful where a continuous supply is not required. When used to supplement an existing system the boiler is connected to the flow and return thereof by branch pipes. A flue is re- quired with these boilers; a thermostatic valve to automatically lower the gas when the water has reached a predetermined temperature is a useful accessory. Materiats.—For temporary hard water, wrought iron galvanized is the most suitable material for pipes and storage vessels, the boiler being usually uncoated. Owing to the action of most soft waters on un- coated iron causing discoloration. or in the case of galvanized pipes, &c., dissolving the zinc coating, cop- per is to be preferred. The tubes should be thick enough for screwing and gun-metal fittings used through- out. It is often advisable to tin the threads and afterwards sweat the joints together. Copper pipes may be easily bent in the ordinary MUNICIPAL AND SANITARY ENGINEERING. HOT application of heat the temperature is raised, and expansion of the contained water being prevented, an enormous pressure is created, which ultimately bursts the boiler. As an example of the enormous stored energy under these circumstances, 1 cu. ft. of water heated to exert 60 lbs. pressure per square inch amounts We EE TT te ay ree ut CEE Une iat ~~ Hits eed 1 rp Sout Wy a [yaeyt pea el manner, unless sharp bends are required or the pipe is of a large diameter, when it may be filled with sand, resin or lead to prevent flatten- ing. Pipe clips should be used and built into the wall to support and permit movement of the pipes ; where passing through walls, floors, &c., metal sleeve pieces should be pro- vided. Borer Expiosions.—Although the ordinary domestic boiler is of small dimensions, an explosion may be wrought with serious, if not fatal, consequences. The cause of domestic boiler explosions is frequently misunderstood. It may be stated that these explosions are invariably caused by a stoppage of the cir- culation pipes, and not through the entry of water into an empty red-hot boiler. A com- plete stoppage of the circulation pipes her- metically seals the water in the boiler; upon the M.S.E. Fic. 8.—Hot Water Calorifier for Indirect Hot Water Supply. to about 800,000 foot pounds, or 3850 times as much as an equal volume of steam at the same temperature. By far the largest number of explosions are due to pipes being choked with ice; it is seldom that an explosion is due to fur owing to the accumulation being gradual, and when nearly stopped a loud thumping noise gives ample warning. It will be at once obvious that the placing of stop- cocks on flow and return pipes, especially in the absence of a safety-valve, is a dangerous 225 Q HOT proceeding. It is popularly supposed that the entry of water into a red-hot boiler will burst the same, and is, in fact, the cause of Fig. 9.—Horizontal Steam Water or Calorifier (Storage Pattern). explosion. In the first place, some time would elapse before the whole of the water in the boiler was evaporated and further, should the water ma Fic. 10.—Steam Heater with Coil. suddenly enter a red-hot boiler, the steam generated would force the water back until the steam pressure was released. It is possible that the boiler may be fractured, but nothing in the nature of a serious ex- plosion would result. Very few people would, the writer believes, keep a fire in a range fitted with a boiler when no water was obtainable at the taps; in fact, the absence of water is usually taken as an indication that something is wrong. With circulation pipes choked with ice, however, WATER SUPPLY. ENCYCLOPEDIA OF HOW no such warning is given; hence the import- ance of placing the pipes in warm positions or keeping the water warm. ‘The writer knows of no instance where a domestic boiler explosion has occurred when a safety valve has been fitted direct to the boiler. There are several other proprietary systems of ‘accelerated hot-water circulation.” The advantages claimed for such systems are that smaller pipes may be used and the pipes run at any desired level; in many cases the boiler may be placed above the lowest radiators, an obvious advantage in many instances. Amongst such systems in successful operation may be mentioned ‘The Pulsial system of heating by low pressure hot water,’ erected by Messrs. Werner, Pfleiderer & Perkins, Ltd., Kingsway, London, W.C.; ‘“ Barker’s Cable system of vacuum hot-water heating,” erected by J. F. Phillips & Son, Old Queen St., West- minster; ‘*The Reck system,” designed by Captain Reck, of Copenhagen. In the fore- going systems, steam at, or about, atmo- spheric pressure is generated in the boiler. Another system is to install a motor or steam- driven pump on the circulation pipes near the boiler, hot water being pumped through the apparatus. W.F. House Refuse.—(See “ Rerusr Drsposat.’’) ‘“Howatson Process” or Szwace Purt- FIcaTIoN.—This system has been tried at STEAM SUPPLY. STEAM “TRAP - TO RADIATORS. ee eS CHECK VALV E, =— CONDENSE MAIN Fic. 11.—Arrangement of Steam Calorifiers for Warming of Hot Water Supply. 226 HYD Middelkerke, Wenduyne, Haeren, and else- where. It has also been satisfactorily applied to the purification of drinking water at Ostend, Haeren, and other places. Peroxide of chlorine is used as a sterilising agent, and this is obtained by the decomposition of chlorate of potash by sulphuric acid. The organic matter in the sewage is rapidly oxidised by the soluble gas thus produced, and a high degree of purification is obtainable. Hydraulic Gradient.—(See “ Firow in Pires aNpD: Conpuits.’’) Hydraulic Mean Depth.—(See “ Firow IN Pregs anp Conpuvuits.’’) Hydrolytic Tank.—tThe first tank of this type was installed at Hampton-on- Thames in 1903. The novel design and the special mode of operation implied so complete a departure from the usual methods of construc- tion and of practice that more than ordinary thought and time were devoted to its con- sideration. The principles of its action are as follows :— (1) The rapid separation of the main volume (80 to 90%) of the liquid from the remaining part of the sewage. (2) The exclusion of this proportion from any contact with the resulting sludge, from the presence of the generated gases, and from any but the shortest tank operation. (8) The concentration of the suspended impurities in the smaller volume (10 to 20%) of the sewage. (4) The continuous removal of this volume from the sedimentation chambers by its down- ward displacement into a separate chamber, where the suspended matters are deposited. (5) The correction of the periodical outflow of suspended matter, the result of the gaseous disturbances, by the re-deposition and removal of these solids in an additional chamber. (6) ‘lhe limitation of the hostile forces of sedimentation and gaseous eruptions to separate chambers. (7) The submission of the whole of the 227 MUNICIPAL AND SANITARY ENGINEERING. HYD sewage to the attracting influence of self- cleansing surfaces, in order to abstract as large a proportion of the finer suspended and colloidal solids as possible. (8) The prevention of any undue accumula- tion of scum and of sludge by periodically withdrawing the excess; and (9) The continued maintenance of the working capacities of the several chambers. The following description, together with the drawings of the Hampton tank, will demonstrate how these principles are carried out. The sewage having passed through a 4 in. mesh screen enters one of two detritus tanks. These have a capacity of 38,000 gallons each, or one-eightieth of the present daily flow of sewage, and are worked alter- nately, the sewage being diverted from one to the other every fortnight. The sludge is removed from the full tank by means of a valved opening, through which it passes to the sludge manhole. In this way nearly one- half of the total quantity of sludge is removed from the sewage. The sewage leaving the detritus tank enters the centre of a transverse channel, which conveys it into the sedimenta- tion chambers of the hydrolytic tank by delivering it behind submerged walls. The tank is divided by light walls into three com- partments, the centre one of which is the reduction chamber, the outer two being the sedimentation chambers. The only means of liquid communication between these com- partments are the narrow openings at the bottom of the sedimentation chambers. At the end of the tank is a weir divided into three portions, one for each chamber; the relative widths of these divisions govern the outflow of sewage from the several chambers and determine the proportional quantity which flows through each. The side weirs (sedi- mentation) have a width of 7 ft. each, or a combined width of 14 ft., and the central (reduction) weir has a width of 2 ft. The total width of 16 ft. is, therefore, apportioned so as to permit of 87°57 of the sewage passing along the sedimentation chambers and over their weirs, whilst ensuring that Q 2 ENCYCLOPADIA OF HYD HYD “aoydueyy ‘spag Fo suorpeg yyrm ‘yuey, oysjorpsFy Jo uvpqg—| “oT UFTZS 10 F795 ee ee ae sre all AAALAC (HU f “SHURA MANRPHRNNANRN TO ONNREON nH i + SDAIN NR zany MNO Sy meen “Sd ppl alfa a) Eliminators “S$Gad AUVILYAL MAN 40 SNOILIES RUTLOOLO RB ai SOIFI| AYVANOITS snow bust . j \ opener es wees e=ONVT OL INION (ee on vs =e (OULVTNIA ATIVOINYH ITH) >>> YNVL DLATOUTAH >%. T t T t t — .. F T 1334 Obl 02! ool 08 09 Ov 02 O OF ogt3ag “LIFTS 10 FIV 228 HYD MUNICIPAL AND 12°5°% of that liquid shall pass out of the bottoms of them into the reduction chamber and over its weir. The entire volume of sewage enters the sedimentation chambers. Of this volume 87°5'/ travels along a prac- tically level plane, while the lighter and heavier particles describe upward and down- ward curves, the length of the curve being proportioned to the weight of the particle and to the velocity of the flow. The lighter par- ticles rise to the surface, and are retained there by the submerged walls at the end of the chamber. The heavier particles in falling have their curve shortened by the descending volume (12°5'/) of the liquid which passes out of the bottom of the sedimentation cham- bers into the reduction chamber; in other, words, the natural downward displacement of the particles are accelerated by the down- ward flow of one-eighth of the entire volume of sewage, by which means the deposit is carried into the reduction chamber. The slower rate of flow in this chamber permits the solids to descend into the lower part of the chamber, and prevents so large a quantity of the deposited matters from being carried out of the tank during periods of agitation caused by the gases generated. The forma- tion of gases is, with almost negligible excep- tions, limited to the reduction chamber. The rising gases in the reduction chamber are separated by the sloping walls from the depositing solids in the sedimentation cham- bers, and thus the confusion in operation which would otherwise ensue is obviated. The part of the chamber below the openings at the bottom of the sedimentary chambers is for the reception of sludge; it is designed to hold the sludge contained in 40 days’ average flow of sewage. In actual work, however, it holds double this quantity. Along the floor at intervals valves are fixed, through which 3,000 gallons of sludge are removed from the tank about once a fortnight into the sludge manhole. Floating solids on the surface of the liquid in the sedimentary chambers, and those floated in the reduction chamber, are occasionally, when unduly SANITARY ENGINEERING. HYD accumulating, raked over into the empty detritus tank. The sewage flowing over the weirs enters a channel which leads to the four hydrolysing chambers, which are arranged a & | Bz Oo TF | ow 2 | So a o | ON ea eo) ee 3 gs 8 z 3 b) 2 2 || . | & g ee ae 2 | 3g eo) ioe = | ££ | © @ az | 32 sot 2 | = & | & = © = a 3 sh sae se S 5 | & & s Ee | o -& ie 5 3 <4 Pe nm o € Bi stood a = c 3S oO © es = a oO n os 2s o ¢ £23 ot || | = 39 nN N 5 3 5 | 2 @ EY mo OD “Ez S & o | a | @ z a| ¢ 22 | 2 = ae 9 2 | X g Rn 42 e | & 5s | $ 5 |} 6 = |e A | 3 ha 4 S| » & | & a F | gs 5 of ql pop ££ | @& oO - i 6s o | »e 2 | @ 3s S | cB El o in sequence. The liquid is conducted to the bottom of each chamber and passes upwards through the material to the surface, where it flows over a weir and descends to the lower part of thenextchamber. After the operation 229 HYD OF ENCYCLOP.EDIA HYD ‘s[Iujoqy Jo suorqoag puv ue ‘wavy, oyApoapAE—'z “ory RD SEES. NG FM -- 38 .6- i enn OS “9 iH OFLVTNDIY -9 '6-- 0,9-- >he--— 230 HYD has been repeated in the four chambers the liquid enters the channel which conducts it to the contact beds. Tank and channels are mechanically ventilated, and the withdrawn gases are purified before being discharged into the atmosphere. The sludge is conveyed into trenches in the land and is almost imme- diately covered over with earth. Five years’ uninterrupted experience has demonstrated the practical value of the hydrolytic tank as a highly efficient means of removing the sus- pended matters from sewage, for collecting the sludge, and for admitting of the maximum withdrawal of these matters during the con- tinuous work of the tank. 8. H.C. Hydraulic Memoranda.—The following brief hydraulic notes and memoranda will be found convenient for reference by readers of this work and for engineering calculations generally :— Water, HquivaLents, &c. One Imperial gallon = 2777463 cu. in. = ‘16 cu. ft. = 10°00 lbs. avoirdupois at 62° F. ” ” » = 4546 litres. One United States gallon = 231 cu. in. ” ” ” » = 833111 lbs. One cubic foot of water = 6°23 imperial gallons. 7480519 United States gallons. 62°28 lbs. 55606 cwt. 0278 ton: 28°3116 litres. oF a 3 0283 cu. metre. One cubic inch of water = 252°286 grains. ‘3 b » = 03604 lb. One pound of water = ‘10 Imperial gallon. i .s » = 27°74 cu. in. One ton of water = 224 Imperial gallons. One litre of water = ‘22 Imperial gallon. One cubic metre of water = 220 Imperial gallons. MUNICIPAL AND SANITARY ENGINEERING. HYD One cubic metre of water = 1 ton (approxi- mately). One kilo. of water = 2°2046 lbs. Pressure, Hap, &c. Head in feet x °43835 = pressure in lbs. per square inch. *841 = pressure in lbs. per circular inch. Head in feet X 62°425 = pressure in lbs. per square foot. Pressure in lbs. per squareinch x 2°306 = Head in feet. Pressure in lbs. per square foot x ‘016 = Head in feet. r A pressure of 1 lb. per square inch =‘column of water 2°31219 ft. high. A column of water 1 ft. high = a pressure of 4325 lbs. per square inch. Head in feet x Piers, Discoarce, &c. Gallons contained per foot run of pipe = (dia- meter in inches) ? x 084. Lbs. per foot run of pipe = inches) ? x 84. Doubling the diameter of a pipe increases its capacity four times. Discharge varies as the square root of the “ head.” Cubie feet of water per minute x 9,000 = gallons per 24 hours. The friction of liquids in pipes increases as the square of the velocity. (diameter in RaInFAuL. Average rainfall for England is usually taken at 30 in. per annum. One inch of rain over 100 sq. ft. of surface yields 52 gallons. One inch of rain over an acre of surface = 100 tons of water (approximately). One inch of rain over an acre of surface = 8,630 cu. ft. of water. One inch of rain over an acre of surface = 22,650 gallons. Rainfall in inches X 52 = gallons per squar foot. 231 HYD Rainfall in inches x 2,828,200 = cubic feet per square mile. Rainfall in inches x 143 = millions of gallons per square mile. Evaporation.—The annual amount of evapo- ration is very variable according to cireum- stances. On land surfaces in this country it varies from 8 in. to 20in. On large water surfaces at Lea Bridge it was found to be about 21 in. per annum, but, in many cases, the amount of evaporation from large water areas 1s equal to the rainfall. Horss-powEr.—The horse-power required to raise a given quantity of water in gallons to a given height is found as follows :—Multiply the water to be raised in gallons per minute by 10 and by the height the water has to be raised in feet, and divide the product by 33,000. To the net horse-power thus obtained must be added an allowance to cover friction and “slip,” according to the necessities of the case. An addition of at least one-third is usually made. Another rule is as follows :— Actual horse-power = ‘0023 H Q. Where Q=quantity of water raised per minute in cubic feet. Where H = height in feet. Contents of wells or cylinders in gallons per foot of depth or length:—Diameter in feet squared X 4°9 (approximate). Eaquivatent Prezs.—To find how many pipes of smaller diameter are required to discharge the same quantity as one large pipe :— $s ; : VD? Number of pipes required = |=, Vv p° Where D = diameter of large pipe in inches. Where p = diameter of small pipe in inches. Distripurion oF Warer.—In determining sizes of distributing mains a main room should be provided capable of yielding the maximum discharge with an expenditure of head in over- coming friction not exceeding 25 /of the available statical head. For moderately large pipes 3 ft. per second is generally regarded as a suitable rate of flow. The maximum ENCYCLOPAEDIA OF HYD rate of draught upon water mains may be from two to two-and-a-half times the average consumption during the 24 hours. The maximum statical head upon water mains should not exceed 200 ft., or about 86 lbs. per square inch; and for an effective supply should not, if possible, be less than 100 ft. It is more advantageous to have ample main room than to rely upon excessive statical head as, upon occasions of heavy draught, the “head” will be rapidly absorbed in overcoming frictional resistance in the mains. Turning valves on and off too suddenly leads to concussion and “hammer,” and may burst a main. Hydraulic Ram.—The hydraulic ram is a machine which is largely used for the pur- pose of raising water to a height considerably above the top of the “ fall” or head available as motive power. In other words, the appa- ratus utilises the momentum of a stream of water falling through a small height in order to lift a portion of that water to a greater height. Thus 100 gallons of water falling through 10 ft. would raise 10 gallons to a height of 80 ft., or, 100 gallons falling 5 ft. would raise 1 gallon to an elevation of some 300 ft. The mechanism of the hydraulic ram is designed to take advantage of the “ ramming ’”’ force, or momentum of the flow of water in a pipe when suddenly arrested. The outline diagram (Fig. 1) illustrates the general arrangement of the different parts of a system for raising water by means of a hydraulic ram. The water from the source of supply flows down a “ drive-pipe’”’ of considerable length, and with the requisite ‘fall’? to work the ram; when the water approaches its maximum velocity at the ram its flow is suddenly and automatically checked, the momentum thus producing a rise of pressure within the ram which closes the “waste outlet valve’? and forces a part of the water through the “delivery valve” into the “air vessel” and “delivery main.” ‘The height to which the water is thus delivered depends upon the amount of fall available. 232 HYD Under ordinary circumstances it may be said that the hydraulic ram returns about 50% of the natural effect, or, in other words, the quantity of water raised multiplied by the height of the delivery above the ram will be about 50% of the quantity of water working the ram multiplied by the “ fall,’ in the same unit of time. It is very generally estimated that one-seventh of the water can be raised to about four times the head of supply, or one- fourteenth eight times, or one twenty-eighth sixteen times, thus giving a useful effect of about 57%. Various improvements have been introduced during recent years by ram makers in regard to economy of drive water and other matters, and in the Bailey’s Decceur’s hydraulic ram one-third of the drive water is forced to two-and-a-half times the height of fall, one-sixth to five times the fall, or one-tenth to eight times the fall, giving a return of about 83 % of the natural effect. In determining the size of ram suited to any particular case, it will be necessary to ascertain the fall in feet available from the source of supply to the site of the ram, the height to which the water is to be raised, the horizontal distance from the source of supply to the place of delivery, and the quantity of water required to be lifted per hour or day. If the source of supply is limited, then the flow should be accurately gauged to ascertain the yield in gallons per minute. An approximate idea of the quantity of water which should be available at the source of supply for the purpose of working small and medium-sized rams may be gained from the fact that for every gallon raised some 8 to 12 gallons must pass through the ram. Larger sizes raising water to high elevations with comparatively low falls consume, pro- portionately, more water in working. The quantity of driving water required to work a ram will depend, therefore, upon the amount of working fall available, the height to which the water is to be raised, and the quantity of water to be raised. Under suitable conditions rams can be worked with less than 1 gallon of water per minute. The diameter of the MUNICIPAL AND SANITARY ENGINEERING. Ta HYD fall or injection pipe in hydraulic rams is very generally about twice that of the delivery or rising main. The length of the supply pipe may be made from five times to ten times the height of the “fall.” Any working fall from about 18 in. up to 100 ft. will work a ram, but the greater the fall obtained up to about one-third of the total height the water has to be raised above the ram, the more economical will be the result, i.e, the ram will cost less to raise a given quantity and less driving water will be required. Where a dam carinot be formed across a stream, the requisite fall may be got by carrying the driving water the requisite distance down the stream by means of stoneware pipes running nearly level until the necessary fall is gained, but where the driving water is plentiful a small working fall will suffice with a more powerful ram, and High Level or Cistern "Diagram showing arrangement of Hydraulic Ram. may be found cheaper than obtaining a greater fall and using a small ram. Rams will force to a distance of several miles, some firms guaranteeing as much as 10 miles; and, with a sufficient driving water and working fall will force to any height up to 1,000ft. As one instance of a high lift may be cited that of a pair of Blake’s rams worked by impure stream water, with a fall of only 9 ft., raising 4,500 gallons of spring water per day to a height of 719 ft. above the rams (i.e., about eighty times the height of the working fall), and to a distance of 1,223 yards for the supply of a large horse stud farm. The height to force is calculated from the level of the ram or bottom of the working fall. The usefulness of hydraulic rams has been very greatly extended by the introduction of those forms in which the water for the motive power is obtained from one 233 HYD source, and that raised for use from another. This is accomplished by the introduction of a cylinder and piston, with the necessary valves, between the working-barrel or main pipe of the ram and the delivery pipe. A hydraulic ram should be simple and strong in design, as, when fixed, very little attention is usually given, the apparatus frequently being left for months at a time. The air chamber should be of tested strength, all joints faced, and all valves, such as delivery, beat, and snifting valves, should be made of gun metal. The apparatus is a very useful and economical one in some circumstances, will work even when flooded with water, and requires no lubrication or packing and very little attention. The action of the hydraulic ram is some- what violent and noisy, and the wear and tear necessarily considerable. These objections are largely overcome by the hydraulic pressure pump, by means of which a large quantity of water under a small head, flowing slowly through a supply pipe, is made to steadily raise a portion of the water to a higher level. The apparatus consists generally of a large piston working vertically in a cylinder sur- mounted by a small upper cylinder, in which works a hollow plunger delivering into an air vessel from which the delivery pipe, or rising main, is taken off in the same manner as in the case of the hydraulic ram. Where duplicate cylinders are provided the apparatus can be made to deliver water steadily and continuously. Hydrogel.— (See “ Cottorpan Matvers.’’) Hydro - Pneumatic “¢ KJECTOR.”’) Systems. — (See Hydrosal.— (See ‘‘ Cotzorat Marrers.’’) Hydrostatic Head.—The pressure due to the weight of liquids, when they are confined, is proportional to the height of the column, and is equally exerted in all directions. Any ENCYCLOPEDIA OF HYG vessel which contains a liquid has, therefore, to sustain upon each point a pressure, the intensity of which will vary according to the height or head of the liquid above that point, but which will, otherwise, be quite indepen- dent of the shape of the vessel. As an instance, suppose a closed tank with a pipe projecting vertically from its top and that both are filled with water; the intensity of the pressure upon the hottom of the tank will be proportional to the height of the tank plus that of the pipe. Again, suppose this arrange- ment inverted, with the end of the pipe closed; the pressure per square inch or per square foot, as the case may be, will, at the bottom of the pipe, be precisely as it was at the bottom of the tank when in its former posi- tion. The large “body” of water in the tank does not, as so many people suppose, make any difference whatever to the intensity. From this it foilows that the pressure per square inch, for example, will be equal to the head in inches multiplied by the weight of a cubic inch of the liquid—the same, of course, applies to any other unit of measurement. (See article on ‘‘ Hypravuic Mrmoranpa.’’) E. L. B. Hygiene and Public Health. — Defini- tion—Preventive Medicine—Sanitary Code and Administration — Medical Officer of Health —aActs of Parliament — Bye-Laws. — Hygiene is defined as the science which teaches us how to keep the body in health; but it would be more exact to define it as embracing the application to this end of a whole group of sciences which throw light on the growth, development, and vital activities of man. It aims at rendering growth more perfect, life more vigorous, decay less rapid, and death more remote. The principles involved and the scope of the field of study necessarily embrace every circumstance which affects, for good or evil, man’s physical’ wel- fare; or in other words all those factors, personal and environmental, that determine perfect health. It is not possible here to fully enunciate those principles; the object and 234 HYG scope of hygiene and public health can only be broadly defined. The importance of the subject from the standpoints both of the individual and the State, cannot well be exaggerated, for it seeks to promote that physical health which determines in such large measure the happiness and productive- ness of the individual. The value of the observance of the laws of hygiene are, from the communal standpoint, largely economic ; nothing, for instance, is so costly as disease, and just as the employer of labour gains, both in the quantity and quality of work performed, by paying due regard to the sanitary environ- ment of his workers, so does the State reap a material benefit by promoting wise public health legislation, that physical efficiency which, while promoting moral and mental health, also increases that vigour and productiveness of the community which determine national prosperity. Seeing, then, that it is a prime matter of State concern that the public health should be conserved, and recognising that the individual is often ignorant or helpless in these respects, the State has sought to pro- mote the general health by public health legislation and to provide the necessary machinery to give it effect. Preventive Mepicine.—Hygiene is essen- tially preventive medicine, but it also embraces matters which are beyond the province of medicine. A convenient subdivision of this great subject may be made into (1) General and personal hygiené; (2) Special hygiene ; (3) Public health. General hygiene embraces those external or environmental conditions of locality, site, dwelling, air, water-supply, soil, refuse and sewage disposal, &c., which determine healthy life ; while measures which relate more particularly to the individual’s person, and are so largely dependent upon individual habits and initiative for their observance, are included in the sphere of personal hygiene. Thus bathing, washing, clothing, food and diet, exercise, &c., are matters of personal hygiene. Special hygiene embraces the hygiene of special circumstances, as, for instance, school hygiene, industrial MUNICIPAL AND SANITARY ENGINEERING. HYG hygiene, military, naval, and tropical hygiene. Public health in the sense of State hygiene may be taken to embrace the legal pro- visions and the administrative measures which are designed to protect the health interest of the community, such as the pre- vention of the spread of infectious disease, the prevention of unwholesome conditions in the community, the protection of the public water and food supply, and generally the removal of nuisances which, by favouring the prevalence of disease, may act as foci of infec- tion to the community. Much remarkable testimony is forthcoming to the benefits which have accrued from the application of the laws of hygiene; as, for instance, the great reduc- tion in sickness and mortality among sailors in our navy, among the soldiers in our army, among the prisoners in our gaols, and the occupants of our hospitals, factories, work- shops, &c.; and the effect of the growth of public health legislation and administration and of an increasing realisation by the people of the importance of the demands of sanita- tion, is shown by the reduced death-rate from all causes and from certain special diseases (more particularly certain communicable dis- eases) ; while the increase in the mean duration of life of all classes is no less noteworthy. If it is conceded that the observation of the laws of hygiene leads to the survival of some who would otherwise have succumbed as the result of the law of the survival of the fittest, then it must be conceded also that preventable disease does not kill only; too often it maims or enfeebles; so that in a substantial—per- haps in a very large—proportion of cases it subtracts the patients whom it may ulti- mately spare from the sum of the vigorous and adds them to the sum of the relatively inefficient. Sanrrary CoDE AND ADMINISTRATION.—It may be said that no other country possésses a sanitary code and administration so complete as that of Great Britain. The provision for public health administration in this country includes the Local Government Board (a central authority directly under Government), 235 HYG county councils, borough councils, urban and rural sanitary authorities, and their respective staffs of officials. The Local Government Board is charged with some measure of con- trol and supervision of Poor Law and Public Health Administration (including vaccination) throughout the country. For these purposes a large staff of skilled advisers and inspectors has been appointed, and a National Vaccine Establishment for the supply of vaccine-lymph is maintained. The more important powers and duties of the Local Government Board may be summarised as follows: To issue regulations and instructions with reference to the prevention and suppression of epidemic disease ; to inspect vaccination; to regulate the borrowing powers of local authorities, by inquiring into projects of sanitary improve- ment relative to housing of the poor, sewage disposal, water-supply, hospitals, &c., when the projects involve the raising of a loan for their undertaking; to revise and approve local sanitary bye-laws; to sanction or veto the appointment of local sanitary officials, when the State pays a moiety of the salaries of such officers. The Home Office deals with the conditions of labour in factories and work- shops, &c., and possesses a staff of inspectors charged with many duties under the provi- sions of the Factory and Workshops Acts, &c., and the Orders issued from time to time. County councils supervise generally the sanitary administration throughout the county, and may report a defaulting sanitary authority to the Local Government Board. They are also given certain administrative powers in reference to public health matters ; they are, for instance, charged with the administration of several important public health measures, namely, the Rivers Pollution Prevention Act, the Education Act, the Mid- wives Act, the Isolation Hospitals Act, the Contagious Diseases Animals Acts, 1878 to 1886. ‘The several sanitary areas comprised within the county are constituted either boroughs, urban or rural sanitary districts; and the borough or district councils are charged with the local administration of the ENCYCLOP.EDIA OF HYG bulk of public health legislation. To assist in the satisfactory performance of these duties a clerk, a medical officer of health, a surveyor, and one or more sanitary inspectors are appointed to serve each local authority. Mepican OrriceR oF MHeatra. — The duties of the medical officer of health, as defined by the Local Government Board, require that he shall inform himself respect- ing all influences which may injuriously affect the public health in his district, and advise the sanitary authority thereon ; that he shall investigate, report and advise upon outbreaks of contagious, infectious, or epidemic disease, and give immediate information to the Local Government Board and county council of any outbreak of dangerous infectious disease ; that he shall deal with unsound food, offensive trades, &c., and shall furnish an annual report ; subject to the instructions of the sanitary authority he shall direct or super- intend the work of the sanitary inspector. The duties of a sanitary inspector relate to the inspection of nuisances, of offensive trades, food, &e.; the procuring of samples under the Sale of Foods and Drugs Acts, and the taking of measures, under the direction of the medical officer of health, for prevent- ing the spread of dangerous infectious disease. Acts or Paruiament.—The chief Acts of Parliament which have reference to the public health embrace measures to guard the health interests ofall classes of the community, from the cradle to the grave. Indeed the practical realisation of the true scope of preventive medicine is one of interesting evolution. Preventive medicine at first took cognizance of little else than dangerous infectious disease and prescribed certain measures of precaution almost exclusively when these diseases reached epidemic proportions. Then followed the adoption of measures directed towards ensur- ing .an improved sanitary environment for the people. These mainly related to the drainage arrangements and water supply; in fact, at first they went little further, and it is only comparatively recently that the 236 HYG fuller needs of hygienic environment began to receive the attention their importance demands. Personal hygiene remained rela- tively neglected for what were conceived to be the superior claims of sanitary environ- ment; but when the broader horizon of preventive medicine was illumined by a truer conception of its scope and demands, it was recognised that the personal and social cir- cumstances of the community were at the root of the main difficulties with which pre- ventive medicine had to contend. The fact is now generally appreciated that the hygienic well-being of the community will be deter- mined more by education and training, developing individual desire and initiative, than by legal enactment. While therefore we possess in several Public Health Acts the power which enables administrative bodies to provide the sanitary environment of the individual, whether at home or in the workshop or factory, legal measures have more recently appeared upon the statute book which mainly concern themselves with the personal demands of hygiene. It is only possible here to schedule the more important legal enactments which are embraced in the public health legislation of this country. They are as follows: The Public Health Acts of England and Wales, London, Scotland, and Ireland—including certain Public Health Amendment Acts, the more recent of which is the Amendment Act of 1907. These Acts contain provisions dealing with conditions which are nuisances or injurious to health, offensive trades, water supply, house drainage, sewerage and sewage disposal, scavenging and cleansing, houses let in lodgings, common lodging-houses, under- ground rooms, unsound food, slaughter-houses, dangerous infectious diseases, and disinfection. The Local Government Acts, 1888, 1894. The Midwives Act, 1902. The Births and Deaths Registration Act, 1874. The Notification of Births Act, 1907. The Infant Life Protection Act, 1897. MUNICIPAL AND SANITARY ENGINEERING. HYG The Education (Administrative Provisions) Act, 1907. The Employment of Children Act, 1903. The Provision for Meals for Children Attend- ing Public Elementary Schools Act, 1906. The Prevention of Cruelty to Children Act, 1894. The Children’s Act, 1908. The Shop Hours’ Acts, 1886, 1892, 1904. The Factories and Workshops Acts, 1891, 1895, 1907. The Alkali, etc., Works Regulation Act, 1881, 1892. The White Phosphorous Matches Prohibi- tion Act, 1908. The Housing of the Working Classes Acts, 1890, 1900, 1908. The Customs and Inland Revenue Act, 1890, 1903. The Open Spaces Acts, 1887, 1890. The Infectious Disease Notification Acts, 1889 and 1899. The Infectious Diseases Prevention Act, 1890. The Isolation Hospitals Act, 1898. The Vaccination Acts, 1867, 1871, 1898, 1907. The Cleansing of Persons Act, 1897. The Aliens Act, 1905. The Inebriates Act, 1898. The Public Health (Interments) Act, 1879. The Burial Acts, 1854, 1855, 1857. The Cremation Act, 1902. The Public Health Water Act, 1878. The Rivers Pollution Prevention Acts, 1876, 1898. The Canal Boats Acts, 1877, 1884. The Sale of Foods and Drugs Acts, 1875 to 1899. The Sale of Horseflesh Act, 1889. The Margarine Act, 1887. The Butter and Margarine Act, 1907. The Public Health (Regulations as to Food) Act, 1907. In addition there are in force many orders, bye-laws and regulations which are authorised by Acts of Parliament. The more important orders are the Dairies, Cowsheds and Milkshops 237 INC Orders of the Local Government Board, 1885, 1899, and several orders issued by the Home Office relating to factories and work- shops. Among the regulations issued by the Local Government Board special mention should be made of those designed to prevent the importation of cholera, yellow fever, and plague into these islands, and those relating to canal boats, and to the importation of unsound food and foreign meat; while among the regulations which local sanitary authorities are empowered to make, those relating to dairies, cowsheds, and milkshops, and the removal to and the detention in hospital of infectious patients removed from ships and vessels, are of special importance. Bysr-Laws.—Subject to the approval of the Local Government Board many bye-laws are authorised to be made by local sanitary authorities, and to assist those bodies in framing such bye-laws the Board has issued a series of model bye-laws. Bye-laws may be made dealing with houses let in lodgings, offensive trades, common lodging houses, new buildings, slaughter-houses, cleansing and scavenging, the prevention of certain nuis- ances, mortuaries, &c. Finally, the public health legislation of this country includes many local improvement Acts which only relate to the particular dis- trict for which the special powers have been sought and obtained. These Acts are now numerous, and they constitute an important addition to the sanitary legislation of the country. As instances of such Acts, the London County Councils General Power Acts and the Sheffield Corporation Act, 1908, for the compulsory notification of consumption in that city, may be cited. H.R. K. Incandescent Lamps.—(See ‘“ Exscrri- city’? and “ Gas.”’) Indicator.—The Expansive Use of Steam— Condensing.—All good class modern steam pumping machinery must be designed and worked with a careful regard to fuel economy, and smallness of steam con- ENCYCLOPAEDIA OF IND sumption of the engines. To this end the tendency for many years has been towards the employment of high-pressure steam, used expansively in either two, three, or four stage compound engines (more commonly spoken of as compound, triple, and quadruple engines respectively), the use of high-duty valve gears, and many other improvements having for their common object the produc- tion of the largest possible amount of work from any given weight of steam passing through the cylinders. At works using large quantities of steam power, as in the case of water or sewage pumping stations, where the coal bill necessarily becomes a considerable item in the annual expenditure, it is therefore of primary importance that the engineer should be well acquainted with the best avail- able means of frequently and fully investigating the behaviour of the steam in the cylinders of the various engines that may be under his charge. Any neglect to systematically perform such investigations may, even in a station of medium size, easily involve the waste of con- siderable sums annually in fuel for the want of a knowledge of the efficiency of the per- formance of each individual engine. The need for some convenient means of thus investigating the work of his engines was first realised by James Watt, who introduced the “‘steam-engine indicator,’ an instrument for the purpose of describing a diagram, the area of which has a definite relation to the amount of work done upon the piston by the steam in the cylinder. It will not be necessary to here describe the indicator in detail, but it may briefly be stated to consist of a small cylinder communicating with the engine cylinder, and fitted with a small piston, which the varying steam pressure drives upward against the resistance of a spring of a stiffness suited to the pressure. A lever, connected with the piston-rod of the indicator, imparts motion to a pencil, which traces the diagram on a card wrapped round a vertical drum, which is turned backwards and forwards by means of a string connected with the piston-rod of the engine. The figure thus drawn by the 238 IND indicator shows the varying pressure acting upon the piston of the engine at every point of the stroke; the mean pressure is thence readily ascertained, and the power of the engine calculated. The indicator diagram also affords invaluable information as to the interaction of the steam and cylinder walls, and enables defects in the design, setting, and working of the valves for the admission and exhaust of steam into and out of the cylinder to be detected and remedied, and the economy of the engine thus improved. By the teachings of the diagram of work performed the advan- tages of the expansive use of steam, com- pounding and condensing, can alone be fully appreciated. A theoretical indicator-diagram of work upon the piston in a condensing engine, with early “cut-off” of steam, is shown in Fig. 1, and serves to illustrate the advantage of expanding steam in a single cylinder instead of using full pressure to the end of the stroke. It will be seen that full steam is used during a small portion only (A &) of the stroke of the piston, the remainder being completed by: the pres- sure of the expanding steam; that the pressures gradually fall as the end of the stroke is approached, as roughly repre- sented by the hyperboliccurve D H. The area of the diagram is a measure of the work done, and the portion B C D E represents that performed by the “full steam” without con- densation, H D H J that done by expansion without condensation, and dA BJ G@ that resulting from the use of the condenser. It is thus seen that by “condensing,” by the use of high-pressure steam and expansive working, great economy is obtainable by the introduc- tion of an earlier ‘‘ cut-off,” and a higher ratio of expansion, thus using at each stroke a less weight of live steam. In all modern economical steam plants of any considerable size, the tendency is towards the use of high- -pressure steam and high ratios of expansion in the cylinders. For this purpose a compound engine having two, three, or even four cylinders, becomes neces- f<- Initial Steam Pressure ---- > MUNICIPAL AND SANITARY ENGINEERING. t 1 ' t I &! eee tS a l | \ ee 1 4 IND sary. Theoretically, there is no difference in the expansive power of steam of given initial and terminal pressure, whether effected in one or two cylinders, provided the compound cylinders are correctly proportioned. The single-cylinder engine has considerable theo- retical advantage over the compound engine, but, practically, the advantage lies decidedly with the compound principle. This arises from the circumstance that although very high rates of expansion are theoretically possible in the single-cylinder, the practical economical limits are soon reached, because high ratios of expansion involve high initial pressures and ful Steam _D_- Point of Cut-off | | I 10 Cut-off | | x Stroke 4 | I St ee | pe ene Felease H Be -— dy Fic. 1.—Theoretical Indicator Diagram—Condensing Engine. great differences of temperature between live and exhaust steam. When the live steam enters a relatively cold cylinder a considerable initial condensation takes place, thereby largely neutralising the advantage of a high expansion ratio. This difficulty is met by permitting the steam to successively expand in either one, two, three, or even four cylinders, according to the initial pressure of the steam used, and the ratio of expansion adopted. We thus have what are known as ‘the single, compound, triple, and quadruple forms of engines respectively, and it is in thus dim- inishing the effects of initial condensation with high expansion ratios that the main advantage of “ compounding” lies. Thereis, however, a further advantage in that the multiple cylinder engine lends itself to the equal division of the work between two or 239 IND three cranks set at angles of 90° or 120° with each other, thus giving a more equable turning effect, and avoiding dead centres. In the distribution of the steam between two or three cylinders, each piston should give to its crank as near as possible an equal amount of work, and there should also be an approximately equal fall of temperature in the different cylinders. From what has been said it will be gathered that a high initial pressure is necessary in order to get the full advantages to be derived from the use of steam in the compound and triple-cylinder engine. For compound engines a pressure of from 90 lbs. to 120 lbs. per square inch is required, and, where a steam pressure of 150 lbs. is availabie, triple expansion engines Full Stearn SS < Point of Cut off lodmission Line Point of Admission Point of Compression x Exhaust =a Atmospheric N Fre. 2.—Actual Indicator Diagram—Non-condensing 3 Engine. will be more economical than compound. Higher pressures still are necessary for the quadruple expansion engine, but these are seldom used for municipal purposes. The actual indicator diagram, as taken from the steam engine, differs considerably from the theoretical diagram given in Fig. 1, and may be considered under two heads, viz., those from non-condensing engines and those from condensing engines. From the study of the diagram from any given engine, much useful information may be obtained in addition to the power of the cylinders indicated by carefully observing the nature of the deviations from the theoretical diagram. The diagram shown in Fig. 2 is from a non-condensing engine, that is, one which exhausts directly into the atmosphere. It will be noticed that from the pointof admission the steam pressure at once rises, and is well maintained to the point of cut-off, where a slight ‘“ wire-draw- ENCYCLOPAEDIA OF IND ing ” of the steam is indicated by the rounded corner of the diagram. The absence of any such wire-drawing in a diagram points to the efficiency of the valve gear. From the point of cut-off the steam works expansively through the remainder of the stroke till the “ release ” of the exhaust steam occurs at the point indi- cated. The exhaust line of the diagram falls to the atmospheric line through the exhausting of the steam being well carried out without back-pressure, and a small amount of ‘‘ com- pression”? takes place on the return of the piston before the admission of a fresh supply of live steam to the cylinder. A larger amount of compression than that shown would advantageously tend to decrease the amount of initial condensation in the cylinder, and to produce smoother working in the engine. A practical indicator diagram from a condensing engine (that is one which exhausts into a vacuum) is given in Fig. 3, which fully explains the functions of the different parts of such a diagram. Fol- lowing the diagram round from the point of admission of the steam (JM) the following cycle of operations occurs at each stroke. Upon the admission of live steam the “clearance’’ space is first filled, and the pressure in the cylinder then rises to £, whereupon the piston moves forward under full steam to the point of cut-off. From this point the forward stroke is completed by the expansive force of the steam to the point of release. Upon the release opening to exhaust the pressure at once falls to J, and the piston returns because the vapour pressure in the condenser cannot be wholly removed, thus showing a certain amount of “ back- pressure,” as in the diagram. The exhaust ports being fully open on the return of the piston from J to K, a horizontal line is drawn till the point of compression is reached and the remaining steam is compressed to A/, the point of admission. Here it meets the incoming live steam due to the advance opening or “lead” of the valves immediately before the commencement of a new stroke, and the steam pressure again rises to point Z. In practice, 240 IND there are many variations in form from this diagram, and it is by observing these differ- ences from time to time that defects in the working of an engine are detected. For example, if the “ full-steam ” line falls in the manner shown by the dotted line E F G, it indicates ‘ wire-drawing” at the point of cut- off on account of narrow steam ports, insuffi- ciency of valve opening, or throttling, and the steam is thus prevented from following up the piston at full pressure. The common slide valve, actuated by an ordinary eccentric, owing to the slowness with which it closes the port, always produces a certain amount of wire-drawing. To obtain a perfect cut-off the valve must open quickly, MUNICIPAL AND SANITARY ENGINEERING. IND Cushioning is partly effected by giving the slide valve the requisite amount of ‘ lead,” that is, allowing it to open the steam port before the piston arrives at the end of the stroke. Want of lead on the valve, causing late admission of the steam, shows itself upon the diagram by a rounded corner such as C to D, or if very marked by a sloping admission line as from A to B owing to the piston having travelled through a part of the stroke before full pressure is upon it. In addition to the admission of steam before the end of the stroke, it will be observed from the diagram that its release on the other side of the piston also takes place before the end of the stroke. remain open till the point of eut- = ¥7-7-~7~-1-- Pili Steams 2 Potek CLG? off, and then close quickly. There FFF Te eeu 8 eee te i . _ Not 1 | are several special valve devices Pee eg : ea 1S designed to meet these conditions, oe 5 of which the Corliss valve gears, s gee 1 which are very perfect in their & & % action, are perhaps the best , & oe ! 3 Nd ' known, and have the merit of § 3 § cs aoe ee een spheric Pressure(/4-7/b3 ee producing a very sharply defined i § | LAE Pt eT Aelesion it Seca ; ae I | {pinta Cenpression diagram. A moderate amount of 4 dod ose (lec a nha Em ‘ 3 g 5 sel Fe Ses Ne Back Pi “compression” is shown in the -t-----bedae= = one ; ara ire In Cor Si diagram from K to M. This is a el sii : : Absolute Vacuum or Zero Line ' brought about by closing the be+------- Stroke ------------ — exhaust port a little before the piston has completed its stroke, thus compressing the steam still remaining in the cylinder into the clearance spaces. The extent of compression, or “cushioning,” which may be advantageously employed depends mainly upon the speed of the engine. A large amount of cushioning is required in high-speed engines to arrest the momentum of the rapidly moving parts, but in engines with a slow piston speed a moderate compression will be sufficient to ensure smooth running. In engines having great piston speed and high ratio of expansion the exhaust steam may be compressed up to the initial pressure of the steam, in which case the cylinder becomes heated to the initial tempera- ture, and the condensation of the fresh live steam upon entry is thereby greatly reduced. M.S.E. M fo K = Compression Fig. 3.—Actual Indicator Diagram—Condensing Engine. This prevents excessive back pressure, and has the effect of rounding that end of the diagram as shown. If the steam were carried to the end of the stroke before opening to exhaust the diagram would approximate to the form shown by the line H J indicating excessive and wasteful back pressure. A leaky piston produces a diagram with a loop enclosing minus effective pressure—the pressures on each side of the piston tending to equalise, and initial condensation is shown by the sudden falling off of the pressure and corresponding fall of the expansion curve from the point of cut-off. This and re. evaporation may be detected by drawing the hyperbolic expansion curve. By the same means the 241 R IND effect of a leaky slide valve upon the diagram would be revealed as it would raise the expan- sion curve at the expense of live steam. Excessive compression would produce an effect upon the diagram similar to that shown by the dotted line V P # (Fig. 3). An indicator with too light a spring or too heavy a piston pro- duces a shaky diagram having a wavy outline. Reference has been made above to the hyper- bolic expansion curve, and it may be convenient here to observe that steam is nota perfect gas capable of expanding in strict accordance with Boyle’s law, nor is the curve of its expan- sion strictly represented by a hyperbola. The expansion line, however, of a good diagram approximates to the hyperbolic curve so closely that it is used as a convenient datum for purposes of comparison. Its application in this connection frequently enables defects in the diagram, and consequently in the action of the steam valves, to be detected which might otherwise have escaped observa- tion. On the left hand side of the diagram (Fig. 1) will be noted a space marked *‘clearance,”’ and to which further reference must be made. The piston of an engine in practice does not, at the end of its stroke, come quite close up to the end of the cylinder. The small space thus left between piston and cover is necessary to allow for the wear of the journals and affords room for any condensed steam or priming which may occur. In addition to this there is also the volume of the steam ports between the valve faces and the cylinder. The spaces are collectively known as the clearance of the cylinder, and have an important bearing upon the expansion of the steam and the economy of the engine as they have to be filled with steam when ‘‘admission’”’ occurs. Clearance, therefore, influences the thermodynamic efficiency of the engine mainly by altering the consump- tion of steam per stroke. Neglecting clearance, the ratio of expansion of steam in a cylinder, is equal to the volume of the cylinder divided by the volume to the point of cut-off, but if clearance be taken into account the true ratio of expansion is much less. Thus, referring ENCYCLOPADIA OF INT back to Fig. 1, if P NV represents the volume swept through by the piston up to the point of release, K P the volume of the clearance, and P § the volume swept through during admission or to cut-off, then the apparent ratio of expansion is P N/P 8, whereas the real ex- pansion is(K P+P N)/(KP+PS). The losses arising from clearance cannot in practice be avoided altogether, but may be considerably reduced by the ‘‘ compression” of a portion of the steam on the return stroke as already explained. W. H. M. Infectious Diseases.—(See ‘ Zymoric Diseaszs.’’) Intake.—In water supply the “intake ” is the source or point on the banks of a river or lake at which the supply is derived, and from which it is conveyed to the waterworks pumping station for subsidence and filtra- tion. The site for the “ intake works” should be chosen with great care. At the point selected there should be no tendency for the river to deposit silt or débris of any kind, and for this reason a convex bank or straight reach, with suitable training works where necessary, is preferable. The intake chamber should be situate below the dry-weather level of the river, so as to exclude floating matter, but above the bed of the river to prevent silt and deposit gaining access. The inlet should always be protected by means of a grating to prevent any large objects entering. The intermediate position, or level, of the intake as above enables water to be drawn off in cold climates between the floating ice and the ground or anchor ice. Suitable means for flushing out the intake chamber should also be provided. There are two intakes to the East London Waterworks on the river Lea—one at Ponder’s End and the other just below the Ordnance Factory at Enfield. Another intake connected with these works is situate on the Thames just above the Sunbury Weir at Wheatley’s Ait. It is of paramount importance that all water intakes from rivers should be as high up the stream as practicable, 242 ies ei aciien INT above sewer-outfalls or other discharges con- tributing to the pollution of the water. Intercepting Sewer.— (See “Srwsracz.”’) Interceptor.—A bent pipe so formed that while liquids are permitted to flow through it, air is prohibited. (See ‘“ DisconnecTING Traps.”’) International Process of Sewage Puri- fication.—This system of sewage purification employs a magnetic precipitant and deodorizer called ‘“ ferozone,” and the liquid is afterwards filtered through a “polarite” filter. The sewage of Mangotsfield is treated by the International Company’s process with Candy upward flow precipitation tanks, and the effluent has been very favourably reported upon. (See “ Pouarrre” and “ Ferozons.’’) Inverted Siphons.—(Sce “ Srrxons.’’) Irrigation, Broad.—(See “Srwace D1s- POSAL.’”’) Isolation Hospitals.—Acts of Parliament —Provision of Isolation Hospitals— Local Govern- ment Board Requirements as to Wards—Porter’s Lodge and Receiving Blocks —- Administrative Buildings — Ward Pavilions — Laundry— Mor- tuary — Protection Against Fire — Telephonic Installation—Cost of Hospitals—Local authori- ties first obtained powers to build or otherwise arrange for hospitals to deal with infectious disease by the passing of the Sanitary Act of 1866. These powers were increased by the Public Health Act, 1875, and the Isolation Hospitals Act, 1893. In 1883 the Epidemic and other Diseases Prevention Act was brought into force as an amendment to the Public Health Act (England), 1875. It pro- vides for the prevention of any threatened pestilence, such as epidemic, endemic, or in- tectious disease, and makes regulations for the speedy interment or other disposal of the dead ; house - to- house visitation; provision of medical and hospital accommodation ; and also provides for the cleansing, ventilation, 243 MUNICIPAL AND SANITARY ENGINEERING. ISO disinfection, and the guarding against the spread of disease. The Infectious Disease (Prevention) Act, 1890, in addition to other matters, enables local authorities to make free provision from time to time for tempo- rary shelters, or house accommodation, with the necessary attendants, for the members of any family in which an infectious disease has appeared, who have been compelled to leave their dwelling for the purpose of enabling such building to be disinfected by the local authority. The Isolation Hospitals Act, 1893, was promoted to enable county councils to establish hospitals for the recep- tion of patients suffering from infectious disease. This Act does not extend to the ad- ministrative county of London, or to any county borough, or, without the consent of the council for the borough, to any berough containing, according to the census for the time being in force, a population of 10,000 persons or upwards, or to any borough con- taining a less population, without the like consent, unless the Local Government Board by order direct that the Act shall apply to such borough. Under this Act the council of every county may, on such application being made to them and proof adduced, provide or cause to be provided a hospital for the reception of patients suffering from infectious diseases. An application to a county council for the establishment of an isolation hospital may be made by any one or more of the authorities having jurisdiction in the county, or any part of the county. Such an application may be made in pursuance of a resolution passed at a meeting of any authority by a majority of the members assembled thereat, and voting in a manner in which votes are required by law to be given at a meeting of the authority. An application for the establishment of an isolation hospital may also be made by any number of ratepayers not less than 25. Such application shall be made by petition, and shall state the district for which the isola- tion hospital is required, and the reasons which the petitioners adduce for its estab- lishment. In 1899 an Act was passed to R 2 ISO extend the Infectious Disease (Notification) Act to districts in which it has not hitherto been adopted. It extends to and takes effect in every urban, rural, and port sanitary district. This Act provides that the head of the family, or the nearest relative of the patient resident in the building, must give immediate notice (in ease of infectious disease) to the Medical Officer of Health; that the medical practi- tioner attending the patient, on finding a case of infectious disease, must notify to the Medical Officer of Health for the district the name of the patient, the situation of the house, and the infectious disease from which the patient is suffering. The Isolation Hospitals Act, 1901, which is an amendment of the Isolation Hospitals Act, 1893, provides that any local authority (including a joint board) within the meaning of the Public Health Act, 1875, which has provided under this Act, or any local Act, a hospital for the reception of the sick, may, with the sanction of the Local Government Board, and with the consent of the council, transfer it to the council of the county within which the hospital or any part of the district of the authority is situate. Any hospital transferred under this section shall be appropriated to a district formed under the Isolation Hospitals Act, 1898, and may be adopted as an isolation hospital; and any hospital so appropriated shall be treated as if it had been originally established under the Act for the district. Any expenses in- curred by a county council in or incidental to the transfer of any hospital under this Act shall be defrayed as structural expenses in- curred by a hospital committee within the meaning of section 17 of the principal Act. Provision oF Isonation Hosprrats.—Hos- pital accommodation for infectious and con- tagious diseases is required more particularly in towns than in rural districts; still some provision should be made for the most isolated villages. The best arrangement for small populations is by the provision of a hospital accessible from several villages. Such a building could be planned with accommoda- tion for four or more cases of infectious disease, ENCYCLOPEDIA OF ISO and be well isolated. In towns wards should be placed in one or more pavilions, with space enough for the erection of other blocks, temporary or permanent. In all hospitals there must be a division between the hospitals coming within the category of so-called fever hospitals. They may be divided into two classes: those of the sanatoria type, pure and simple, and those of the hospital type. In all cases it is necessary that small-pox cases should be separated from scarlet-fever and diphtheria patients. In the case of infectious hospitals the ratio is about twenty beds for a population of 25,000. In twenty-seven im- portant towns, having a population of nearly 4,500,000, there are twenty infectious beds to each 29,000 persons. At the present time London has about 10,216 beds in the hospitals of the Metropolitan Asylums Board. Some authorities advocate accommodation for infectious cases in the proportion of ten beds per 10,000 of population, with arrangements to admit of three different infections in both sexes. Itis well to provide an average number of two or three simultaneous infections, and this should be supplanted by temporary arrangements in case of necessity. When authorities contemplate the erection of a hospital for small-pox it may be laid down, with a view to lessening the risk of infection, that the erection of the hospital should not be on a site where it would have within a quarter of a mile of it as a centre either a hospital, whether for infectious disease or not, or a workhouse, or any similar establishment, or a population of 150 to 200 persons; or upon any site where it would have within half a mile of it as a centre a population of 500 to 600 persons, whether in one or more institutions or in dwelling-houses. It should be understood that even when the above con- ditions are strictly fulfilled, there may be circumstances under which the erection of a small-pox hospital should not be contemplated. Cases in which there is any considerable collection of inhabitants just beyond the half- mile zone should always call for special con- sideration. The site of a hospital should, if 244 ISO possible, be in the open country, and so maintain a maximum amount of purity of air being breathed by the patients. Pre- suming that the situation is unfettered, except by hygienic requirements, the qualities of a site more favourable to an isolation hospital is a clean, porous, and dry soil, with free circulation of air round it. Locan Government Boarp’s REQuIREMENTS as To Warps.—The Local Government Board, in their memorandum of requirements and suggestions relating to the provision for infectious disease cases, state that ‘any building intended to contain infected persons or things should be placed at least at a dis- tance of 40 ft. from the boundary of the site.” The following minimum amount of space per patient should be provided in wards for infectious cases :— 12 ft. 144 sq. ft. 2,000 cu. ft. In designing isolation hospitals it will be found that if the above amount of floor area is to be adhered to, then the requisite cubic space can only be obtained by adopting a height of some 14 ft.. As this height is some- what excessive in other than wards of great length, it is desirable that a height of, say, 12 ft. or 18 ft. should be adopted, and the floor space be correspondingly increased. The following table gives the requisite space, and at the same time provides a ward more suited for supervision :— Wall space, per bed. Floor space Cubic space Wall space, per bed. 12 ft. Height of ward 13 ft. Floor space 156 sq. it. Cubic do. 2,028 cu. ft. Porrer’s Loner anp Recrivine Buocxs.— The entrance to a fever hospital should be so situated as to allow for the separate admission and discharge of patients, and also for the delivery of stores and for tradesmen to trans- act their business without coming in contact with the infected parts of the hospital. In the case of small isolation hospitals one entrance should suffice for all purposes. In MUNICIPAL AND SANITARY ENGINEERING. ISO the case of large hospitals, however, it is desirable that the porter’s lodge should be so situated as to allow of the provision of two entrances, one for infected to enter, and with a carriage drive direct to the hospital build- ings, and another for non-infected, with a roadway leading to the administrative build- ings. The porter’s lodge usually comprises an office and waiting-room, sitting-room, kitchen, and the usual out-offices on the ground floor, with at least two bedrooms and a bath-room on the first floor. In some cases the rooms for receiving and discharging patients are provided in connection with this building. When this provision is provided in a distinct block, the receiving apartment should comprise a room for the medical officer to examine the patient, patients’ clothes store, and bath-room. The discharge block should comprise an undressing room, where the patient is relieved of the hospital clothing and then bathed. Adjoining the undressing- room, and dividing the discharge room, should be placed a bath-room, in order that the patient, after bathing, may receive his own clothes and pass into the discharge-room, which should also act as a waiting-room for relatives or friends of the patient. In some hospitals two receiving and discharge blocks are provided, one for scarlet fever, the other for diphtheria and enteric fever. ADMINISTRATIVE Burtpines.—The admini- strative buildings should provide accommoda- tion for medical and nursing staff, stores, cooking, &c. In small isolation hospitals provision is made for matron’s quarters, nurses’ sitting- and mess-room, medical officer’s room, dispensary, mending-room, stores, and the necessary sleeping accommodation for the staff. In large hospitals the medical super- intendent is provided with a residence separated from the other buildings. The kitchen and stores should be placed centrally to allow of easy distribution of food and stores. The matron’s department, which comprises linen stores, needle-room, and the like apartments, should also be placed in the central administrative block. In the case of 245 ISO small isolation hospitals the nurses’ depart- ments will also be provided in the adminis- trative building. When, however, there is a large staff of nurses, as in the case of large hospitals, they are housed in a separate and distinct building. When a nurses’ home is provided it should contain mess-rooms, general sitting-room or common room, reading- room, and bedrooms. ‘The bedrooms should measure 13 ft. by 8 ft. 6 in., or 12 ft. by 9 ft. The whole of the rooms should be heated by radiators ; fireplaces should not be provided in the bedrooms, as they are rarely used. Provision should be made for at least one sick-room for use as occasion may require. Water-closets, lavatories, slop-sinks, and baths should be provided on each floor in proportion to the number of beds. Suitable provision should be made in large hospitals for medical students undertaking a course of studies. In this case a well-lighted and ventilated lecture-room should be provided in connection with the administrative build- ings. When provision is made for housing students, they should be accommodated in a block quite distinct from the other buildings. Warp Pavitions.— In considering the number of beds apportioned to each disease, it should be borne in mind that scarlet fever demands almost a half of the total bed accommodation. As scarlet fever is, in the large majority of cases, an acute disease Juring the first one or two weeks only, and seeing that it is generally admitted to be most desirable to separate these cases from convalescents, the best arrangement is to have two separate blocks—a small one for acute cases and a large one for convalescents. The small pavilion should have a couple of one- or two-bed wards for the isolation of delirious and noisy cases. The separation wards should be provided with separate and distinct water- closet and slop-sink. The walls and ceilings of all wards should be finished with a plaster or cement face, and be painted or varnished. The angles made by the walls with each other and with the ceiling should be finished with quadrant shaving the concave surface to the ENCYCLOPADIA OF ISO ward. The whole of the ceilings should be quite plain, free from all projections, angles, or cornices which accumulate dust. The floors of all wards should be constructed of such material as will be capable of being easily cleaned. Wood as a material for floors in wards is far from satisfactory, being full of joints, which frequently open and become receptacles for impurities. ‘The best material for floors is terrazzo, or one of the many jointless floors now in general use. The latter are preferable, being much warmer. The windows, where the cost will allow of it, should be double-glazed to prevent the loss of heat and to maintain an even temperature in the ward. They should have an area of not less than 1 ft. of glass for every 70 cu. ft. of ward space. A window should be arranged between each pair of beds, and it is advisable to place a window in each corner of the ward, between the end wall and the last bed. The windows should be divided into two parts, of which the upper part is made to fall in and form a hopper ventilator, glazed hoppers being fixed on each side; the lower portion being formed as double-hung sashes. The doors in the wards should be so arranged as to facilitate nursing, and be large enough to allow the passage through of the sick on movable stretchers. The doors should afford an opening of from 8 ft. 8 in. to4 ft. The construction of all doors in wards should be such as to present as few projections or places for the accumulation of dust as possible. The upper part of entrance doors to wards should be glazed. The ward adjuncts for water- closets, slop and scalding sinks should be separated from the wards by intervening lobbies, having windows at each side. It is advisable to fix in each of these lobbies a radiator capable of raising the temperature to a higher degree than that of the ward,'so that the air is drawn from the ward into the lobby instead of vice versé. In the disconnecting lobby between the wards and water-closet and slop-sink two openings should be formed in the external walls, one for the reception of soiled linen (which can be drawn through by 246 ISO the attendant on to a trolley outside), and a smaller opening in which stools can be kept for inspection. It is necessary to fix a tightly- fitting internal iron door to each of these openings. A nurses’ duty room should be provided in connection with each large ward ; it should lead direct from the corridor and be so situated as to overlook both the principal and the separation wards. It should contain a@ gas cooking-stove, dresser, washing and rinsing sink, andasmall cupboard. Provision should also be made in each pavilion of a water-closet, lavatory, and a robing-room for the use of the staff. It is advisable to pro- vide open fireplaces in all wards in addition to the heating by hot-water pipes and radiators. In the case of large wards down draught stoves should be provided, fixed in the centre of the wards. Suitable provision should also be made for the admission of fresh air and the extraction of vitiated air. (See ‘ VEn- TILATION.”” Tue Launpry.—The laundry, which is one of the most important departments of an isolation hospital, should be so situated as to allow of the receiving and dispatch of linen without any undue distance being traversed. This building should, however, be well removed from the ward pavilions and the adminis- trative buildings. The laundry should con- tain two departments, one for the staff and the other for the patients’ washing. Adjoining the patients’ washhouse provision should be made of a foul-washhouse for receiving and steeping articles soiled by excreta. It should be fitted with tanks classified for scarlet fever, enteric fever, diphtheria and isolated cases. The laundry proper should comprise a wash- house, drying apartment, ironing rooms and receiving and delivery rooms. Provision is necessary for disinfecting all clothing of the patients, bedding, &c., from the wards. The disinfecting chamber should adjoin the laundry and be fitted with a steam disinfector. The disinfecting apartment com- prises two chambers, one for receiving the infected clothing and the other for receiving the clothes after they have passed through MUNICIPAL AND SANITARY ENGINEERING. ISO There should be no com- (See the disinfector. munication between the two chambers. “ LAUNDRIES.”’) It is also necessary to make provision for the destruction of all refuse, which frequently consists of mattresses and bedding on which patients have been lying, bandages, portions of food, ordinary sweepings, and solid and liquid excrement. This building is best placed so as to adjoin the laundry. Morrvary.—LEvery hospital should be pro- vided with a mortuary, which should have facilities for isolating bodies for the purpose of viewing and identification. The mortuary should comprise a room fitted with slabs for the reception of dead bodies, visitors’ waiting- room, and viewing closet. A post-mortem room should adjoin the mortuary and have a north light. This room should be well lighted and ventilated and furnished with sinks, lava- tory, anatomical table, and glass shelves for the storage of bottles. The whole ofthe walls should be faced with glazed bricks or glazed tiles, and the floor covered with terrazzo paving. Prorsctrion against Firnzr.— Where buildings are of two or more storeys in height they should be provided with external fire-escape staircases for use in cases of emergency. Suitable provision of fire appliances is also necessary to protect the buildings against fire, and the most ready means should always be at hand with which to attack a fire at its out- break. Fire hydrants fitted with hose and hand pipes should be fixed in every building, and, in addition, fire buckets should be ue vided as an extra precaution. TrLepHonic Instratuation.—A system of electric intercommunication should be pro- vided between every part of an institution, either by means of telephones or bells. Tele- phonic communication between each of the ward pavilions and the administrative buildings is also necessary for cases of emer- gency. A bell-call should also be provided from the medical superintendent’s and the matron’s office to the porter’s lodge and the nurses’ home; also from the stores, laundry 247 ISO and porter’s lodge; a signal code in reference to the supply of steam, outbreak of fire, or other call, being previously arranged. Cost or Hosprraus.—The cost of erecting bay Hr Discharge Pipe for_EFffiluent3 Discharge Pipe For Gas & Fat thr: Long Le of Sich Pe & Outlet Manhole Effluent Chamber Connection ni Kt Deposit Chamber Kessel Separator. hospitals for infectious disease has been found to vary considerably. The average cost of the Metropolitan Asylums Board’s Hospitals, which provide accommodation for some 500 beds in each institution, is about £450 per bed. The cost of isolation hospitals in the provinces is found to be from £500 down to £272 per bed; as an example Baguley, ENCYCLOPEDIA OF KES Cheshire, cost £512 per bed; Burnley £486; Coventry £3083 ; Liverpool £4563, while the Bridlington isolation hospital cost only £272 per bed. A.C. F. “Ives” Tank. — The “Tves” upward-flow self- acting continuous precipi- tating tank of the Universal Sewage Purification Co. was introduced by Mr. Ives in 1894 and 1895, and has been installed by several authorities. It is somewhat complicated in design, is circular in plan, and in- cludes arrangements for aération. As a preliminary preparation, the centrifugal reduction of the coarser solids by whirling them against bafflers is employed, by which they are broken up and brought into suspen- sion for subsequent chemical treatment. The precipitant used in connection with this tank is Spence’s alumino- WY ferric in the form of slabs of suitable size, and the tank effluent is passed over land, or through coke or ash filter beds. Short Leg of Siphon Inlet Manhole Kessel Separator.— This is a_ boiler-shaped apparatus first introduced in Germany with the object of the economical removal of suspended matters from sewage. It consists of an elongated vertical cylinder having an inverted cone-shaped bottom and a domed top as illustrated in the figure. The vessel is erected on iron or brick supports over the line of sewer, and the flow of sewage is siphoned through the cylinder at such a rate as will permit of the deposition of solids, the liquid portion being discharged 248 KES with a loss of head of about 8 in. only in the level of the sewer. From the figure it will be seen that the inlet or short-leg of the siphon takes its sewage from a small manhole and discharges within the vessel at a point verti- cally over a central deposit pipe into which the coarser solids are deflected. As indicated by the arrows, the sewage liquid rises and enters @ narrow annular slot around an internal inverted-cone, the lower portion of which connects with a discharge or effluent pipe (forming the long-leg of the siphon) which, passing downwards through the lower part of the Kessel, terminates by means of a trapped end in a second manhole. The end of the long-leg is made about 8 in. lower than the level of the inlet or short-leg so as to ensure the necessary siphonic action upon which the motion of the sewage through the Kessel depends. Needless to say the whole apparatus must be made and kept perfectly air-tight throughout, and accumulations of air from the sewage or elsewhere in the top of the vessel would interfere with its proper action. A further pipe is also provided from the apex of the cone, as shown in the illustra- tion, for the discharge of gas and fat. To start siphonic action through the Kessel it is necessary, as in the case of any other siphon, to first fill the apparatus with water and then simultaneously open the valves on the legs. The size of Kessel for any given case depends greatly upon the nature of the sewage, but the capacity must be large enough to give a sufficiently slow speed of flow to permit of the deposition of the solids. A cylinder 8 ft. in diameter will deal with from 2,000 to 4,000 gallons per hour, and one of 380 ft. diameter from 25,000 to 50,000 gallons per hour. For physical reasons the height of the vessel must not exceed the limit of the atmospheric pressure as compared with the specific gravity of the sewage, or say, from 27 to 30 ft. It is stated that with ordinary domestic sewage about 70 °/, of the solids in suspension are removed. The Kessel is not at present in use in this MUNICIPAL AND SANITARY ENGINEERING. LAT country, but there are a number of such plants at work in Germany and others in course of erection. The design of a Kessel to meet any particular case naturally depends upon the class of sewage to be dealt with and the rate at which its suspended solids are found to precipitate, but, broadly speaking, it is claimed equally thorough precipitation of solids can be secured in either the Kessel or in the “ Com- min-Separator”’ (sce “ Commin-Smparator”’) at half the cost of septic or ordinary sedimentation tanks. Lateral Water Filtration.—A combina- tion of the lateral and downward flow of water through filter beds has been adopted in order to secure rapidity of action and economy of construction and maintenance. ‘This principle is embodied in the McGregor system, which has been introduced in Canada. Round a sunken circular pure water reservoir a number of concentric filter beds are built, each ring from the centre outwards being stepped on a higher level, the base of the outer ring being on a level with the top of the inner bed. The number of the concentric rings, their width and depth, and the composition of the bed may be varied according to the amount of water required, the quality of the water and the degree of purity to be arrived at.. The bases of the beds have a slight inward slope, and at the base of the inner walls are open- ings—protected with metal screens fitting in iron gratings. The inner bed has, in addition to these screens, duplex wire strainers, through which the filtered water flows into the reser- voir. The beds are divided into sections by means of partition walls, so that one or more sections can be put out of action for cleansing or repairs without interrupting filtration. The crude water is sprinkled over the top, and outer, bed, and flows downwards and sideways, from bed to bed. The stresses on such beds are very slight and evenly dis- tributed. Armoured concrete may be used for their construction, and the reservoirs and beds may be protected from the action of sun and frost by a roof. 249 LAU Laundries.—These establishments fall into two main divisions: (1) those equipped for hand labour ; (2) those wherein machinery is driven by mechanical power. Each of these divisions is, for purposes of consideration, divided into four classes :— («) Private laundries. (b) Trading laundries. (c) Baths and wash-houses laundries. (d) Public institutions laundries. (1) Hanp Launprties are found chiefly in connection with private houses and certain descriptions of public institutions, such as schools, workhouses, lunatic asylums. For some years the tendency has been for the genuine trading hand laundry to disappear, and the new Factory and Workshop Act, 1907— amending the Factory and Workshop Act, 1901 (referred to as “the Principal Act’’)—has hastened this desirable consummation. The sanitary requirements in hand laundries neces- sitate the provisionof good ventilation, lighting, drainage, and an adequate supply of fairly soft water. (See ‘‘ Water Sorrrentne.”) There should be at least two rooms ; the wash-house and the ironing and packing room. A drying closet may be built into one corner of the ironing room, or the iron heating stove may be screened off so as to form a drying closet ; but in such an establishment a built-in brick closet is best. This should bein two divisions each of them having a door. Between the divisions there should be a kind of cell to contain an iron heating stove, and there should be direct communication between this heating chamber and the closet by means of hot air flues, provided with dampers. The heat can then be directed into or shut off from one or both of the divisions as desired. In this way it is possible to economise heat, and, at the same time, afford workers the necessary protection from radiation. When one section of the closet is being loaded, or unloaded, heat is shut off and the door opened. In large establishments it may be necessary to provide more heat than that produced by the above method. This can be obtained by placing a small furnace beneath the closet, ENCYCLOPAIDIA OF LAU or by providing hot air or steam radiators. The floors should be impermeable, and for the wash-house, concrete, floated with good cement, is best, as it is easy with this material to arrange for a slight inclination towards a gutter, placed centrally or against the lateral walls, and communicating with a trapped drain. The plant usually consists of steeping tanks and washing troughs. These should be either of hard wood or salt-glazed stoneware. Rotary washing-machines and hydro-extrac- tors are now made for driving by hand-power (see below). (2) Powzr Launpries are equipped with machines which are generally worked by steam-engines, although gas-engines and hydraulic and electric motors are also used. (a) Private Lavnprizs should contain not less than two rooms, (1) wash-house, fitted with washing troughs, steam-driven washing- machines, wringer or hydro-extractors ; (2) ironing and packing room. This last may be fitted with strong tables for hand ironing, or with ironing machines. A good plan is to place the drying closet between the two rooms, with a door opening into each, so that the wet linen may be inserted from the wash- house side, and when dry may be removed by the other door. The floor of the wash-house must be smooth and impermeable. In small laundries, induced draught will be sufficient for ventilation; there should be inlet grids with air-filtering boxes near the ground, and outlet grids, preferably communicating with vaned cowls in the roof. The latter should be near the chimney stack, as the heat thus gained will become the accelerator of circula- tion of air. (b) Trapine Launprres.— An essential point in all large laundries is that the estab- lishment should be planned so that the soiled linen enters at one door, and after being counted and sorted, passes on to be steeped, washed, rinsed, dried, starched, ironed, and packed, and so out at another door. We must, therefore, have not less than four main rooms, preferably on the ground floor, with engine and boiler-house attached, and ample sanitary 250 LAU accommodation near, but having no direct communication with any of the working rooms. The first room is the receiving department, where the linen is counted and sorted, table, bed, body, and kitchen articles forming different heaps to be treated separ- ately. This room being the most exposed to contamination should be fitted as plainly as possible to facilitate cleansing. The wash- house should come next, and communicate either by means of a corridor, or a trap-door in the partition wall, with the receiving department. The wash-house must be well lighted, either by means of sky-lights or windows placed rather high up. The walls must be smooth, white-washed at the upper part, but having a dado 6 ft. high, painted in oil colour. ‘The floor should be of concrete with a coating of cement, and given a slight inclination towards a draining gutter, placed either down the middle of the room or against the walls, such gutters being protected by iron grids, and connected with trapped drains. In order to economise power, the heavy rotary washing machines and hydro- extractors should be placed as near the ironing room partition as possible, as this will simplify the planning of the shafting for transmission of power, reduce its extent, and lessen the length of belting. It is a good plan to run both washing.and ironing machines from one main shafting, as this not only economises material and power, but the pulling from right to left tends to equalise the strain and so con- duces to smooth running. Against the opposite wall there should be large steeping tanks of either galvanized iron or salt-glazed stoneware, and washing troughs of hard wood or stoneware. Tanks and troughs should be fitted with cold and hot water (or steam) service pipes and taps, and large waste valves. The wastes of tanks and troughs, and also of all machines, should discharge through a free opening over the drain, not directly into it; by this means the: dangers of siphonage (of water or gases) are prevented, and stoppages arising from articles being dropped through are avoided. MUNICIPAL AND SANITARY ENGINEERING. LAU On reaching the wash-house, all very soiled linen (body, bed, and kitchen chiefly) is steeped in the tanks. If the fouling is of an organic nature (blood or excreta), cold or luke- warm water, with a very little soda should be used to soften, but prevent coagulation. After steeping, the articles are generally treated by hand in the washing troughs to remove stains, and are then passed on to the washing machines. There are a large variety of wash- ing machines, but those most commonly used are of the rotary type, and consist of an outer stationary cylinder and an inner revol- ving cage. Both cylinder and cage are provided with doors, and may be made of wood or metal, or the cylinder may be of metal, and the cage of wood, or vice versd. The outer casing should be fairly solid, and fitted with hot and cold water taps, steam valve, water gauge, large outlet or waste valve, and fast and loose pulleys for the trans- mission of power, with starting and stopping gear. The cage is made either of rods placed close together, or of perforated sections, so as to admit water freely. The rods or the sections may be so arranged as to present an internal corrugated surface, or ‘‘rubbers’”’ may be provided. In many cases, a series of metal tubes or a rounded slat of hard wood, are placed like a mid-feather to act as lifters. When the linen is packed in these cages, the doors are closed, hot water is admitted and dissolved soap and soda added through a hopper. The water may be brought to the boil by admitting steam. The machine is then set in motion by bringing the driving belt from the fast to the loose pulley. Then the cage revolves, rolling over the linen, carry- ing it half up the revolving circle, and allowing it to fall back into the soap suds; meanwhile a rain of soapy water falls through the perforations. In many machines, this action is increased by providing horizontal bands of metal or wood on the outer periphery of the cylinder, which act like cups, lifting the water which descends through the perfora- tions. Were the cage to revolve only in one direction, the linen would not be properly 251 LAU cleansed, as it would soon be formed into a tight ball, so the revolution of the cage is automatically reversed at every five or six revolutions. The cleansing action of such machines consists of a series of motions, combining rubbing, rolling, and squeezing, mean while forcing the water through the fabric. Without stopping the machine, the soapy water can be emptied by opening the waste valve; then hot water can be admitted for the first rinse, followed by rinses in warm, and finally in cold water. After this, blueing fluid may be introduced. Handling is thus reduced to a minimum, and all operations made as automatic as possible. After washing and rinsing, the linen may be passed through wringers or placed in hydro-extractors. ‘he hydro-extractor consists of a strong outer casing and an inner perforated basket, which is made to revolve in an upright position. The wet linen is packed in the basket, which is then set in motion and driven at a high speed (from 800 to 1,500 revolutions per minute), the centrifugal force expelling the water, which, escaping through the perfora- tions, is drained off. From the wringers or hydro-extractors the linen may be either starched (by hand or machinery), or may pass direct to the drying closets. These may con- sist of rooms heated by means of waste gases from stoves, or by steam passing through radiator coils, or the room may be fitted with a series of draw-out horses on which the linen is hung. If an ordinary drying room is used, it should be in duplicate, as the closet has to be cooled down before the attendant enters to hang upor remove the linen. From the drying closets the articles pass on to the ironing room. Here small articles and finery are ironed by hand, but most of the linen handled is dealt with on elaborate machinery. Bed and table linen is generally treated on large machines of the ‘‘ Decoudun ” or multi- ple roller types. The ‘‘ Vecoudun” machine consists of a concave steam chest, forming on the top a polished metal bed, on which a large hollow roller, covered with flannel, and sheeting rests. Steam is admitted into ENCYCLOPEDIA OF LAU the bed at a high pressure, and consequently a& pressure-gauge and safety-valve necessary. ‘Ihe linen is placed on the lip of the bed and the revolving roller guides it gently through, drying and polishing it us it goes. ‘lwo or more passages are necessary. In the multiple roller machines, the steam heated bed has two, three, or more depres- sions, in which flannel covered rollers revolve. In such machines the heating surface is larger and the action more rapid. A large variety of more or less complicated machines ure now made for ironing shirts and collars and cuffs, for goffering, and so on. T'rom the ironing room the linen passes to the despatch depart- ment, where it is inspected, checked, and packed. It will be seen that », well ordered laundry offers considerable safeguards to health, as the linen is handled as little as possible, the soiled being kept away from the clean ; it is, moreover, subjected to the action of soap and steam. ‘The ventilation of such an establishment must be efficient, and this can rarely be attained by any ‘natural ” system of inlets and outlets, even if the out- lets be heated. Mechanical propulsion or extraction is necessary. ‘I'his is usually accomplished by means of fans placed high up in the walls or the roof, in wn opening communicating with the interior and exterior of the building. ‘These fans may be placed so that they extract vitiated air and steam from all departments. In large establish- ments where the extraction is considerable, it may be necessary to regulate the introduction of fresh air, which is usually drawn into a cleansing and warming chamber by means of a suction fan, and then blown through air conduits, provided with regulator inlet grids in each room. (c) Laundries attached to public baths and wash-houses (q.v.) are now often elaborately fitted up. (d) Posie Inscrrurion Launpris should be planned on the same principle as trading establishments, to secure a regular circuit, the clean linen being kept apart from the soiled, once it has left the wash-house. HO 252 LAU Whenever possible all departments should be on the ground floor, whether in a separate building with top-lights, or, as is often done, in the basement. special attention must be paid to ventilation, and artificial lighting becomes necessary. Unless the laundry is at some distance from the institution, the corridors near dormitories may be connected with the receiving room by means of shutes, so that the soiled linen can be removed to the laundry rapidly without difficulty. Such shutes must be smooth and impermeable to permit of periodical flushings, and provided at the corridor end with tight- fitting doors. Linen from infectious diseases wards is placed in galvanized iron bins containing some disinfecting fluid, and is then removed to the wash-house. After steeping for a prescribed number of hours, the linen is removed and washed separately. After the first soap wash (or breakdown), the second soap suds are boiled during the process of washing by means of the admission of steam under pressure. The liquid from the disinfecting bins and the washing machines used for infected linen, or linen soiled with blood and excreta, should be run into a special steam-tight tank, built beneath the floor, and boiled for some minutes by the admission of steam, then allowed to cool before being discharged into the sewer. The washing machines for this class of laundry are usually of a heavy type with strong doors, as much “steam is used, both to facilitate cleaning and as a bactericide. Foul rotary-washing machines are made to deal with soiled body and bed linen. This machine consists of a single cylinder, of heavy metal, hung hori- zontally in bearings supported by standards. A casing of splash-boards is provided, partly enclosing the lower section of the cylinder. ‘The cylinder has a steam-tight door, and also a large orifice protected by a grid and a screw- down cap. The foul linen having been placed in the machine, the door is fastened close and the cap unscrewed ; then cold water is admitted and the machine set in motion. Plenty of water must be used to soften and MUNICIPAL AND SANITARY ENGINEERING. Only in the latter case’ LAV remove dirt, which is carried away by the rush of water as the cylinder revolves. After a few minutes hot and cold water is run together, then the machine is stopped, the cap screwed down, and soap and water admitted, the regular processes of washing, boiling, and rinsing being pursued. Such machines, like the ordinary rotaries used for treating infected linen, should have two-way waste cocks, so that the water may be dis- charged either into the disinfecting tank or direct into the sewer. In institution laundries the wash-house and drying closets are rela- tively of more importance than the ironing room, thus differing from a trading establish- ment. In school, workhouse, and asylum laundries, where inmates often take a share in the work, special precautions must be observed in fencing machines and providing safety guards, protecting all working parts. Lavatory Basins.—Now almost exclu- sively made of white glazed earthenware. There are three types: (a) Tip-up lavatories ; (6) plug basins; and (¢) “‘Rivulet” basins. In the first-named the basins are emptied by tipping their contents into containers below them, to which the waste pipes are fixed. Although convenient in hotels and other public places where the basins are in constant demand and rapid emptying therefore desir- able, they can hardly be regarded as sanitary in view of the large soiling surfaces exposed. Plug basins, which are the most frequently used, are made as self-contained fittings, or may be fixed under marble, slate, or other slabs. In selecting them particular attention should be paid to the waste pipes and over- flows. In hidden standing overflows in which the water contained by the basin is in contact with that in the overflow, and in basins in which water enters through the waste pipes, there is great risk of carrying infection from one user to the next. The spread of skin disease, there is reason to think, is greatly due to these types of appliances, which are frequently to be found in public places. Rivulet basins are useful 253 LEA in hospitals, schools, kc. They are basins in which a depression is substituted for the bowl, water flowing constantly through it. Although very sanitary, the hands being washed in running water, they tend to waste water, and can only be made use of in special circumstances. All basins should be fixed free of all enclosure. Lead.—The chief ore of lead is galena, or sulphide of lead, which has a crystalline form and striking lead-like lustre. It is smelted and run into half-round troughs to form pigs weighing 1 cwt.each. Sheet lead is generally made by casting a thick block weighing from 4 to 6 tons and passing it under metal rollers ead Ne Cylinder Press for making Lead Pipes. until it is reduced to the thickness required, when it is called milled lead. ‘he sheets are from 24 ft. to 86 ft. long, and 5 ft. to 8 ft. wide, the finished thickness varying from aj in. to 7 In. thick, but they are generally known by the weight in pounds per foot super., say, 3 lbs. to 10 lbs. In roof work the lead for aprons, flashings, and soakers is 4 Ibs. or 5 lbs.; for hips and ridges, 5 lbs. to 7 lbs.; for gutters and flats, or any place liable to be walked upon, 6 lbs. to 8 Ibs. ; for soil pipes, 7 lbs. or 8 lbs.; for lining sinks, 6 lbs. to 8 lbs. The weight in pounds per foot super. multiplied by 0°017 will give the thickness in decimals of an inch. For example, 8 Ibs. lead is 07186 in. thick, or a trifle over din. Lead pipes are made ina hydraulic press, the principle of which is shown inthe figure. Molten lead, from which ENCYCLOP.EDIA OF LEA the scum has been removed, is contained in a steel cylinder having a rod standing up in the centre equal in diameter to the inside of the pipe. s:| 3 338 |'! Ee Dae @alo a | |eas SO )o & ' monn Ore wo 6 > D> wn oO Sill |B 22 | | | S8S |38)/s ee HON it |. 52 2 Ss oO li iit [ti oaKs a tO 2 Ra a a “level”? note book. After entering, each read- ing should be taken over again asa check. The staff is then carefully turned round to face point C, the level shifted and set up between C and D, and “‘ back” and “ fore” sights again taken and duly booked; the process is repeated 256 LEV through the series. In ordinary work “ inter- mediate” readings are taken, to do which the staff only is shifted; thus, ifthe distance from A to C was not more than, say, 250 t., one might read from the level to B and again to C; in this case B would be an intermediate sight. A specimen of the bookings, with suppositious figures, is here given. By starting at a given “datum” point and working back again to it, the accuracy of the levels may be checked ; or, if the line be started on a Government “bench”? mark (a broad arrow) ascertained from an ordnance survey sheet, and finished on another, a check is afforded ; this has been assumed above, where it will be seen that the total fall (6°69 — 1:09) agrees with the difference in level of the bench marks. Darum Linz.—All levels are estimated with reference to a horizontal line, such as the ordnance ‘“‘datum” (in Great Britain, the mean level of the sea at Liverpool), or any other altitude that may be convenient. In the above case of supposed levelling, point A is obviously 142°20 ft. above ordnance datum. To plot a line of levels, or “section,” on paper, the datum is first drawn and the horizontal distances marked off to a convenient scale; the vertical lines are then erected from these points and the reduced levels are pricked thereon (for convenience of measurement a large scale is here adopted). The points are connected by a line which represents the surface of the ground. Levelling may also be performed with the theodolite. (See “Surveyine, GENERAL PRIN- CIPLES OF.” Altitude may also be approximately deter- mined by means of an aneroid barometer which indicates difference of level by registering the variation in atmospheric pressure. The well-known principle that the boiling point of water varies with the atmospheric pressure, and therefore the altitude, is made use of in an instrument known as the “‘Hypsometer,” which consists of a small boiler heated by a spirit lamp and fitted with a M.S.E. MUNICIPAL AND SANITARY ENGINEERING. LIG thermometer. This apparatus is sometimes employed as a check to the aneroid. BH, D, B, Liernur Process of Sewage Removal and Disposal.—The Liernur process pro- vides for the pneumatic removal and disposal by evaporation of the sewage of towns. The area to be drained is divided into districts, each provided with a “district reservoir,” from which the sewage is pneumatically extracted and conveyed through 84-in. and 4-in. iron pipes to a receiving reservoir at the central station by means of a vacuum pump maintaining a vacuum not exceeding half an atmosphere. The system is in use at Trouville, where, it is stated, the sewage is stored in a covered tank for about a week, mixed with sulphuric acid for the purpose of fixing the ammonia, heated in tubular boilers to 126° C., evaporated to a semi-solid state, and then reduced in a rotary chamber to a dry powder, the value of which is put at from £7 to £8. The process is worked by the Liernur Company at Trouville at an average annual charge of 16s. per house. The system was first applied at Amsterdam in 1871, and has been introduced at Leyden, Riga, and other places, including, more recently, Stansted in Essex. Lighting.—(See ‘“ Acurynenz,” “ Enec- TRIcITy,’’ and ‘‘ Gas.’’) Lightning-Conductors.—Lightning is the sudden dissipation of electrical energy which has been stored between a thunder-cloud and the earth, or between one cloud and another, with a considerable difference of potential. It makes its own path, and forces its way through obstacles without regard to their electrical resistance. The function of a lightning-conductor is not so much to furnish a path for the flashes of lightning when they occur, as to dissipate the electrical energy as fast as it is generated, and thus prevent it from accumulating in dangerous quantities. With this in view a conductor should terminate 257 8 LIG in a series of points to which the electricity may be attracted. The falling drops in a shower of rain also help to dissipate accumu- lations of electricity. Where a great difference of potential exists between two clouds, culminating in an electrical discharge from one to the other, the charge in the lower cloud is liable to over- flow suddenly to the earth, causing the so- called ‘‘B flash,’ against which lightning- rods afford little or no protection. It used to be considered that each lightning-rod formed the centre of a ‘‘ protected cone,” having a diameter at its base equal to the height of the rod, or even greater. Sir Oliver Lodge, nowever, is of opinion that there is no space near a rod which can be definitely styled an area of protection. A single rod does not afford adequate protection even for a chimney shaft, and a building can only be rendered absolutely safe from lightning by enclosing it in a network of wires like a birdcage. For practical purposes a reasonable degree of safety may be secured by placing two or more rods in suitable positions, and joining them by a horizontal conductor, to which any exposed metal-work and all prominently projecting parts of the building should be connected. From an electrical point of view iron is preferable to copper as a material for lightning-rods, the high conductivity of the latter being positively objectionable. Owing, however, to the rapidity with which iron oxidises, copper should be used for rods placed in inaccessible positions. A main conductor of iron should be built up of stout galvanized wire, and should weigh not less than 2% lbs. per foot. A copper rod may consist either of tape or rope, and should weigh not less than 6 oz. per foot. For subsidiary conductors smaller sections may be used. All joints should be as perfect as possible, both electrically and mechanically. The rods should not be insulated from the building, but should be secured by metal holdfasts. They should be arranged as far as possible in straight lines, sharp bends being highly dangerous. The foot of each rod should ENCYCLOP.EDIA OF LIM have a good earth connection in permanently damp soil. This may take the form either of a metal plate not less than 3 ft. square, or of a spike driven deep into the ground. All metal stove pipes should be connected to earth, as should also the columns of a steel-frame building. Cases of damage to a modern steel-frame structure are practically unknown. The question of hghtning-conductors was investigated by the ‘‘Lightning-Rod Con- ference”’ (1878—1881), and again by the “Lightning Research Committee’ (1901— 1905), who formulated a set of rules for guidance in the protection of buildings. A. J. M. Lime and Sulphate of Iron (Treatment of Sewage).—For the disposal of the Metro- politan sewage at Barking and Crossness, lime and sulphate of iron have been used as precipitants in tanks on the continuous flow principle for many years. Four grains of lime to one of sulphate of iron per gallon of sewage are the proportions used. An excess of lime is detrimental to the effluent as a portion of the suspended matters are rendered soluble thereby. (See ‘‘ Lonpon Marty DratnaGe.’’) Lime Process (Treatment of Sewage). — Following the employment of Clark’s process for treating water supplies, lime has been largely used as a precipitant for sewage, either alone or in conjunction with other materials. The purest lime, such as from the upper chalk or limestones of Derbyshire, should be used. It is added to the sewage in a perfectly caustic state in the proportion of 12 grains per gallon after a preliminary screening of the sewage. For the best results the lime should be in solution, and to this end it is first slaked with water and ground in a mortar mill or lime mixer to a finely divided or creamy condition. It is then thoroughly incorporated with the sewage by means of mechanical agitators, and the mixture allowed to settle for an hour, or longer if possible. Where 258 LIM the quantity of sewage is large, however, the precipitating tanks are worked on the continuous principle. The resulting sludge, which is considerable in quantity, is periodically swept out of the tanks into sludge wells, and from thence pumped, gravitated, or otherwise conveyed to sludge lagoons to dry more or less, so that it may be employed as manure on land, or disposed of according to local circumstances. Sometimes it is pumped direct on to land, and steam-ploughed in, which is the most satisfactory method, as otherwise putrefaction soon sets in and gives rise to nuisance. Where no more economical means are available, it becomes necessary to reduce the bulk of the sludge by pressing out the water in sludge presses, but this costs about 2s. per ton of pressed sludge cake. The cost of the lime process is about 8d. per head of the population perannum. The method is in use at Wolverhampton,» Willesden, Bury, Leyton, and many other places. The resulting effluent is alkaline, and a secondary decom- position sets in when discharged into rivers ; the effluent is also destructive to fish life. Lime. — Pure lime consists of a com- bination of the gas oxygen with the metal calcium forming an oxide of calcium, but neither calcium nor lime occurs in a natural state. The various limes of commerce are obtained by burning limestone, marble, chalk, or other substances, consisting chiefly of car- bonate of lime, the carbon dioxide and moisture being driven off by the heat, causing a loss of weight of about one-half. There are various forms of lime, but the commonest are chalk lime, grey lime, and lias lime. Cua Lime is known as a fat or rich lime because it will bear the admixture of a large quantity of sand. When freshly burnt in the form of lump lime it will absorb a large quantity of water, disengage great heat, and swell into a bulky powder of hydrate of lime: this is the process of slaking. When mixed with sand and more water it is used for plastering, but not for mortar. It sets slowly by the evaporation of moisture, and hardens more slowly by the re-absorption of carbon dioxide 259 MUNICIPAL AND SANITARY ENGINEERING. LIM from the air. It will not set in a damp situation, and is unsuitable for mortar, as it has so little ultimate strength. Grey Lis, or stone lime, obtained by burning limestone or the lower chalk, is a “poor ”’ lime, that is, it will not bear much sand added, owing to the greater proportion of inert matter contained, say 10°/, to 80°/,, but itis a slightly hydraulic lime, because some of the impurity is clay, which gives it, when burnt, the property of setting in a damp situation. This lime slakes more sluggishly and with less disengagement of heat, but 1t sets more quickly and attains greater ultimate strength and hardness. It is used for mortar, say one part lime to two or three parts sand, but should not be used for plastering owing to the tendency to “ blow” from the delayed slaking of certain hard burnt particles. Lias Livnis produced by burning the lime- stone from the lyas beds at Lyme Regis, Rugby, Bath, Aberthaw, &c. Owing to a large proportion of clay in its composition the lime produced is generally very hydraulic, and will even set under water. It takes a long time to slake, and should be ground either immediately after burning or while being made into mortar in a mortar mill. It makes good concrete in substitution for Portland cement, and is largely used for mortar for engineering works. It sets quicker than other varieties of lime and is much stronger. Hypratep Lims.—Lime in its dry hydrated form, or slaked with just sufficient water for the purpose, is now becoming a marketable product in America. The advantages of hydrated lime are summed up as follows :— ‘Since if exists as a delicate white powder, and comes into commerce in sacks, it is more easy to handle and can be more accurately measured than the lump product. The method of handling this material re- sembles that of cement, and it requires no ageing after being mixed with water. Further, it does not deteriorate rapidly, and can be stored for a long time in any dry place without undergoing material changes, thus 8 2 LOC doing away with the loss of lime due to spoiling and the danger of fire from the quick-lime coming in contact with water.” Hike Local Government Board Require- ments: Cemeteries.—The requirements of the Local Government Board in regard to cemeteries from the sanitary standpoint can best be ascertained by reference to a memo- randum issued by the Board dated December 18th, 1880. This memorandum begins by pointing out that the Public Health (Inter- ments) Act, 1879, provides for an extension of the powers of Sanitary Authorities under the Public Health Act, 1875, so as to include the acquisition, construction, and maintenance of “a place for the interment of the dead, in the Act of 1879 called a Cemetery.” It then goes on to say that in cases where the Sanitary Authority propose to defray the cost of estab- lishing a cemetery by means of a loan the sanction of the Local Government Board becomes necessary (Public Health Act, 1875, s. 233). Among the points considered by the Board in each particular case, before granting their sanction to a loan for the purpose of a cemetery, the question as to whether the proposed site is suitable or unobjectionable from a sanitary point of view will find a place. The dangers to public health which will be considered are set forth as being the con- tamination (1) of air, and (2) of drinking- water; and the memorandum then proceeds to set forth the view taken by the Board as to the hygienic principles to be observed in the establishment of a cemetery. The memoran- dum above referred to should be read in conjunction with a circular of the Local Government Board dated August 19th, 1879, explanatory of the provisions of the Public Health (Interments) Act, 1879, and also a memorandum dated July, 1908, covering a set of model bye-laws with respect to the manage- ment of a cemetery. The Board also supply a form of queries to be filled up and of infor- mation to be furnished in connection with applications by Burial Authorities relative to ENCYCLOPEDIA OF LOC the provision of new burial grounds. The form sets out in detail the various documents which must be forwarded in addition to the answers to the questions specified. The Board in loan applications require, inter alia, particulars in Form K, No. 2, as to existing indebtedness and assessable value of the dis- trict ; and the periods allowable for repayment of loans are 60 years for purchase of free- hold land, 30 years for erection of buildings, and 20 years for other work. The memo- randum of July, 1908, sets out, inter alia, the requirements of the Board in regard to space, which will vary (as it is pointed out) according to the death-rate of the district. Taking average numbers in a_ stationary population of 1,000, there would be 19 deaths per annum, of which 7 would be under 12 years of age. This, on the basis of 4 sq. yds. for an adult and 2 for a child, would mean that 62 sq. yds.-of ground is specified as a yearly requirement. These are the sizes recommended for grave spaces (i.e., of the plots of ground each to contain one grave), into which the cemetery is to be divided. On the basis of paths occupying one-sixth of the available space, in one acre 4,033 sq. yds. would be available for grave spaces; and this, assuming a single interment in each grave, means that an acre of-ground will serve a population of 1,000 for 65 years. Other details are set out somewhat voluminously, indicating diverse usages according to the nature of the soil, but these can best be understood by studying the memorandum itself. W.M.F. Local Government Board Require- ments: Hospitals.—The control of the Local Government Board exercisable over local authorities in regard to hospitals arises in several ways, but chiefly through the usual medium of application for the borrowing of money by the local authority which can be pro- vided for by section 69 of the Local Govern- ment Act, 1888, so far as County Councils are concerned, and by sections 233 and 284 of the Public Health Act, 1875, so far as other 260 LOC authorities (extra metropolitan) are concerned, whilst London itself has its own Public Health Act, which deals with the subject. In regard to these applications, in addition to the usual particulars as to cost, plans, &c., the Local Government Board generally requires provision to be made for the repayment of any loans sanctioned by them for hospital purposes within the following periods :— Land purchase (freehold) 60 years. Buildings (permanent) ; . 80. ,, Heating apparatus L : x 80 .; Floating hospital 2 ; e BOD | Furniture. . A : . 10 ~=,, Ambulances and vans . : 10 _—=*», The Local Government Board has from time to time issued memoranda on the subject, and the most important.of these is one dated May, 1902 (which can be obtained from the Government printers). It provides a great deal of useful and suggestive information as to some points which may be taken to be practically the requirements of the Local Government Board in regard to these hos- pitals. It has reference to isolation hospital accommodation, and it professes to be issued with a view to indicating to local authorities, more especially to those of districts of small or moderate size, the importance of providing hospital accommodation for the isolation of infectious cases and the means by which they may most advantageously make such provi- sion. The principles it sets forth are said to be those which should be kept in view by all local authorities who propose to provide kos- pitals for their district by means of loans sanctioned by the Local Government Board. The memorandum goes on to deal with the subject of the area to be served and the size of the hospital in proportion to the population of the district; it further deals with the choice of a site and the erection of hospital buildings, and it includes plans of different types of ward-blocks, with especial reference to small-pox hospitals. This memorandum gives in the most accessible form the require- ments of the Local Government Board as to hospital schemes. It should be stated that in MUNICIPAL AND SANITARY ENGINEERING. LOC this memorandum it is pointed out that the Local Government Board do not as a rule sanction loans for the erection of iron hos- pitals or any hospital buildings of a temporary character, except under special circumstances. With regard to cost of hospital schemes, some observations are made in the annual report of the Local Government Board for the year 1904—5. This is what the Board say :—‘‘ In connection with the borrowing of money by local authorities for hospital purposes, we have found that in many cases expenditure— sometimes of large amounts—has been in- curred in excess of the loan sanctioned by us in respect of the scheme. In some instances this has resulted from under-estimating the cost; in others it has transpired that the arrangements which we approved in connec- tion with the proposal for the original loan have been extended or otherwise varied with- out our consent. ..... It is important that ratepayers should know the probable cost of a proposed scheme before it is decided upon, und we trust that local authorities will do their best to see that the estimates which accompany their proposals are as accurate and as complete as they can be made No material alteration should be made without our consent in the plans of works in respect of which we have sanctioned the borrowing of money. In some cases we have found that departures from hospital plans provided by us have involved expenditure which we could only regard as needless or extravagant; we have in these cases declined to allow the additional expense to be defrayed out of loan monies.” The memorandum of May, 1902, referred to above gives specific details in regard to accommodation. Thus, in the ward-blocks each bed should have at least 12 lin. ft. of wall space, 144 sq. ft. of floor space, and 2,000 cu. ft. of air space; in calculating the latter, any height of wards above 18 ft. should not be taken into account. All inner surfaces (of walls, floor, &c.) to be non-dust-harbouring. Ventilation to be by windows on opposite sides, constructed with double-hung sashes 261 LOC and hopper fanlight falling inward with side cheeks. Area of windows proportioned as 1 sq. ft. to every 70 cu. ft. of ward space. Windows to face south-east and north-west respectively. Closets and slop-sinks to be placed in annexes separated from the wards by cross-ventilated lobbies. Instructions are also given as to other buildings. At least 40 ft. must be left between any building which is to contain infected persons or things and any other buildings. The drains of each block must be trapped from the common drain and ventilated separately by an inlet just above the trap and by ventilating shafts at their highest points. Three most excellent plans, setting forth all these and numerous other details, accompany the memorandum. There has also been published, under date of March, 1908, an appendix to this memoran- dum, containing a fourth plan for an obser- vation block. In this provision is made for 1,440 cu. ft. of air-space per bed in lieu of 2,000 in view of other improvements in construction. W.M. F. Local Government Board Require- ments: Loans. — The principal bodies concerned in the raising of loans for sanitary purposes are, (1) county councils, (2) municipal corporations, (3) urban and rural district councils, and (4) parish councils. In addition to these principal bodies, lesser public or semi-public bodies, such as burial boards and port sanitary authorities, are also invested with borrowing powers, subject to the control of the Local Government Board. The raising of loans and their repayment is subject in part to statutory provisions and in part to departmental control. Thus, the Local Government Act, 1888, by which county councils were created, sets out the purposes for which and the conditions under which a county council may borrow money; similarly, the Municipal Corporations Act, 1882 (amended by the Local Government Act, 1888), provides for borrowing by town councils, whilst the Public Health Act, 1875, and subsequent amending Acts provide for the loan necessities ENCYCLOPEDIA OF LOC of urban and rural district councils. Parish councils derive their borrowing powers from the Local Government Act, 1894; and the other authorities named, from the Burial Acts and other measures particularly affecting their existence. Loans may be raised only with the con- currence of the Local Government Board into whose hands the revisionary powers formerly exercised by the Treasury and all recently constituted new powers have been placed. There are three methods in which loans can be raised, i.e., (1) by the issue of stock, (2) by mortgage, and (8) by borrowing from the Public Works Loan Commissioners. The issue of stock by local bodies is provided for mainly by the Local Government Act, 1888, and by the Public Health Acts Amendment Act, 1890. Under both these Acts the Local Government Board are authorised to issue regulations, and such have been issued, and are in operation, under dates 1891, 1897, and 1901, and appear under the two headings of County Stock Regulations and Stock Regula- tions respectively. They deal with the issue of stock in every detail, and should be consulted whenever particulars are required. As regards mortgages, these are governed by the Commissioners Clauses Act, 1847, and have reference: to the security which the persons termed Commissioners entrusted with powers to carry out authorised works may give for the loans they obtain. The provisions of this Act have been incor- porated into many local Acts, and also Acts (like the Burial Acts) which apply generally. In regard to loans obtained from the Public Works Loan Commissioners, who are a body brought into existence by the Public Works Loans Act of 1875, it may be said that the schedule to that Act specifies the purposes for which the Commissioners are empowered to lend money, and to this list of purposes from time to time additions are made in and by Acts of Parliament passed for new objects or to expand existing objects of national importance. Thus, the Commis- sloners may lend money to local authorities 262 LOC whose districts do not exceed in rateable value individually £200,000, for such purposes as the provision of allotments, the carrying on of education (elementary and higher), the purposes of the Public Health Acts, and the provision of small dwellings for the working classes. The rules under which the Com- missioners lend money include stipulations that the works or undertakings shall be entirely new, and that the power of borrowing which is being exercised shall not have been so exercised before. Money required for the purpose of repaying an old loan cannot be obtained from the Commissioners; and repay- ment is generally specified under an annual system extending for a period not exceeding 30 years. (For powers to borrow for specific purposes, see the various articles under separate headings). W.M.F. Local Government Board Require- ments: Mortuaries.—In dealing with appli- cations for loans by local authorities for the purpose of providing mortuaries, the Local Government Board gives some assistance. They have provided a set of model bye-laws under section 141 of the. Public Health Act, 1875. This set is numbered XV. Mortuaries, dated 1896, and copies (price 2d.) can be purchased from the Government printers. To these model bye-laws is appended a memoran- dum dated 25th July, 1882, with observations by the Local Government Board as to the extent to which local authorities ought to avail themselves of their power to make proper provision for dealing with dead bodies which come under their care, and including suggestions as to the erection of mortuary buildings, and their general management. Sanitary authorities when desirous of raising loans for such purposes must obtain the sanction of the Local Government Board, and that sanction may be taken to depend upon the adoption of the suggestions contained in the Memorandum of 1882, beyond which the most important consideration is that of drainage, and in regard to this the Board should first be consulted. Thirty years is the MUNICIPAL AND SANITARY ENGINEERING. LOC usual period allowed for repayment of loans for buildings of this class outside the Metro- polis. It should be observed that outside the Metropolis local authorities have no statutory power to provide buildings in which to hold coroners’ inquests, but are in a position to grant the use of portions of existing buildings for that purpose. The requirements (or ‘ suggestions”’) of the Board as to site and structure of mor- tuaries are given in the Memorandum XV. referred to above. Buildings should be con- cealed from public view ; external architecture to ‘“‘serve to convey the impression of due respect for the dead.” Every chamber in- tended for the reception of corpses to be on the ground floor ; in addition a-waiting-room for visitors and for the use of mourners assembling, a caretaker’s house, and a shed or outhouse for the keeping of shells and other appliances. The mortuary chamber to have a ceiling, or, if open to the roof, a double roof to be put in with a space of 8 in. between each covering. Louvres or air-gratings for ventilation under the eaves. Windows on the north side; if necessary elsewhere, to be fitted with external louvre blinds. Cement floors preferable. Water to be laid on with a tap in the chamber. Shelves and tables preferably to be made of slate slabs, and to be placed so that their upper surfaces may be from 24 to 3 ft. above the floor. Two chambers to be provided—one being for infectious cases, and this should be placed as far as possible away from the other. The entrance to each chamber to be direct, without any intervening passage. These principles are very clearly set out in the plan which accompanies the memorandum. W.M. F. Local Government Board Require- ments: Sewage and Sewage Disposal.— When a local authority is proposing to inaugu- rate some scheme of sewerage or of sewage dis- posal which will involve the borrowing of money under the provisions of sections 2833 to 235 of the Public Health Act, 1875, the sanction of the Local Government Board must be obtained, 263 LOC and in order to obtain that sanction the scheme which the local authority is proposing to adopt must be submitted in detail for the approval of the Local Government Board. If, however, such a scheme does not involve the borrowing of money, it will not be necessary to seek any such approval, though, of course, the general powers of intervention by the Board remain. The Local Government Board do not favour any particular scheme, but leave it to the local authority to consult their own engineers and formulate such a scheme as appears to them to be suited to the requirements of their own particular district. Such schemes natur- ally vary considerably, but as there is no fixed scheme, and as there are no specific plans recommended for adoption by the Local Government Board, it is only necessary that the scheme propounded and submitted should conform to certain general requirements. The scheme, whatever it may be, must be definitely adopted and approved by the local authority before it is submitted to the Local Government Board. The general requirements of the Board fall practically under three headings : 1. Requirements as to the period fixed for repayment of the proposed loan. 2. Certain undefined suggestions made from time to time in the annual. reports and the published correspondence of the Local Government Board. 3. Certain definite requirements set out in the form of estimate (K. No. 29). As to Periops or Repayuent. — The fol- lowing is taken from the Report of the Select Committee on Repayment of Loans (1902) as being a list of the periods usually allowed by the Local Government Board for the repayment of loans sanctioned for sewage purposes :— Land Purchase 60 years. Sewers and surface water drains and such ordinary works as tanks, filters, &e. 30 years. Sewage Lifts 30 years. Ejectors 15 years. Polarite 10 years. Sludge Presses 10 years. Farming Stock 5 to 10 years. ENCYCLOPEDIA OF LOC For general observations on this topic see Local Government Board Report, 1906-7. INDEFINITE SUGGESTIONS AMOUNTING MORE oR Less To RequirEMeNnts.—These are both varied and numerous, and they inelude such general principles as concern estimated costs, employment of engineers, the adoption of competitive schemes, and the management or supervision of sewage-disposal works. In regard to the last-named, the Board favour the retention by local authorities of this manage- mentin their own hands (but see Local Govern- ment Board Annual Report for 1902-3, where special reference is made to the need for skilled supervision). In dealing with applica- tions to sanction loans for sewerage purposes, the Local Government Board require not only full and complete details and plans, but also a variety of miscellaneous information as to rateable value of the district where the loan is to be repaid from, and satisfactory proof of all necessary consents having been obtained, together with details of existing works pro- posed to be superseded, in respect of which there may be a portion of an earlier loan still outstanding. Derinire REQuIREMENTS.—These are mostly set out in the form of estimate (K. No. 29), but not entirely so. They may be expressed, however, in the following classification! :— I. Sewers.—(a) In the case of brick sewers, radiated bricks to be used when obtainable. (b) Side junctions for house drains to be inserted in brick sewers at the time of con- struction. Junction pipes to be provided on all pipe sewers. (c) Main sewers as far as practicable to be laid at such depth and with such gradients as to afford means for draining the cellars and basements of houses. (d) Sewers laid under roadways to have at least 4 ft. of cover between the top of the pipes and the surface of the horse-road; but when this is impracticable the pipes to have 1 Extracted from Wood and Johnson’s ‘‘ Encyclo- pedia of Local Government Board Requirements,” Vol. II., Part 57, where the details are very fully set out. 264 LOC a 6-in. coating of concrete. This latter requirement applies also where the pipes are laid in the roadways at a depth exceeding 15 ft. Where they are laid under fields there is to be at least 8 ft. of cover. (e) Sewers to be laid in straight lines with manholes at all changes of direction or gradient, and no two manholes to be more than 100 yards apart. (f) All manholes and underground cham- bers in roadways to be of sufficient strength to carry the heaviest traction engine or other traffic likely to pass over them. (g) All joints to be of cement and not clay. (hk) Efficient ventilation to be provided. (i) Adequate measures to be adopted for preventing the infiltration of sub-soil and surface water into the sewers. (7) A storm overflow to be constructed in such a way as not to come into operation until the ordinary dry weather flow of sewage has been diluted with five times its volume of storm water. Il. Machinery.— All pumping machinery to be provided in duplicate. lil. Sewage Disposal.—The requirements of the Local Government Board here depend upon whether the scheme submitted to them is one which involves the discharge of sewage matter into non-tidal rivers. If it does it must include proper provision for the purifi- cation of the sewage upon an adequate area of land, in addition to any preliminary treatment it may undergo, and this will be insisted upon unless it can be shown that land suitable for the purpose cannot be obtained. With regard to the area required, this will vary in different eases, and will depend not only upon the quality of the sewage, but also upon the nature of the land available, and further, upon the details of the preliminary process suggested. Where, however, it is only proposed to deal with domestic sewage and land is available, the Local Government Board require as a minimum the following proportions of area per population :— Broad irrigation (without any previous treatment) one acre of land to every 150 265 MUNICIPAL AND SANITARY ENGINEERING. LOC persons of the population of the area to he drained. Irrigation after bacterial process, one acre to every 1,000 persons, or one acre to every 30,000 gallons of drainage. Other methods, one acre to every 1,000 or 2,000 persons according to the system pro- posed to be adopted. Where it is intended to construct bacteria beds for sewage treatment, the following requirements are also specified :— (a) The beds must be large enough to deal with twice or three times the dry weather flow of sewage according as the district may or may not have a separate surface water drainage system. (b) Where the beds are to be worked on the contact principle and the sewage is to be finally treated on land, one, i.e., single con- tact, will suffice. The working capacity of the beds will be taken at one-third of the capacity of the tanks after the filterimg material has been put in, and there must not be more than three fillings in 24 hours. (c) Where the filters are to be worked on a percolating principle and land treatment is provided, the maximum rate of filtration must not exceed 56 gallons per square yard per foot in depth of filtering material per day. (d) Where land treatment is impossible the cubic contents of the filtering matter in either case must be double what is indicated under (b) and (c). (e) Provision must be made, in addition to what has already been provided for the dry weather flow, for dealing with up to at least six times its volume by providing extra land or by passing it through storm water filters capable of admitting a continual rate of filtration not exceeding 500 gallons per square yard per day. (f) Where septic tanks are to be provided, their capacity should not be less than the ordinary daily dry weather flow of sewage to the outfall. Special requirements have to be considered in regard to applications by local authorities to the Local Government Board for sanction LOC to loans under section 32 of the Public Health Act, 1875, for the construction of works out- side the district of the local authority. In a ease of this kind it is usual for the Local Government Board not to make an inquiry until the time has expired during which objections may be lodged in order to avoid the unnecessary expense of having a further inquiry later on. In urgent cases, however, and if there is not much likelihood of objec- tions being made, the Local Government Board will, on application, arrange for an inquiry to be held without waiting for the usual time to expire. This inquiry having been held, the period of objection must be allowed to expire and the matter can then be dealt with immediately. A copy of the statu- tory declaration required, also copies of the newspapers containing the necessary adver- tisements, should be forwarded. If no objection has been made, the fact should be stated; but if any objection has been made, a resolution must be passed and a copy of it be forwarded requesting the Local Govern- ment Board to appoint an inspector to make further inquiry and report. W.M. F. Local Government Board Require- ments: Water Supply.—Under the pro- visions of the Public Health Act, 1875, certain local authorities are empowered to construct and maintain waterworks and take over and lease or hire waterworks and to contract with any person or persons for water supplies; but if they wish to purchase any waterworks or any right to take over or convey water, either within or without their district, they must obtain the sanction of the Local Government Board. In fact, it comes to this, that when a local authority wishes to raise money for the purpose of providing a water supply, the Local Government Board will have to be consulted, and then there are certain require- ments which will have to be complied with. The Local Government Board do not specify what these requirements are, although they supply an official form of estimate (K. No. 20), in which the local authority should set forth ENCYCLOPEDIA OF LOC iull details of the estimated cost of the scheme. It is understood that although they do not publish any special information, nor do they issue any plans for the guidance of the local authorities, or do anything else to furnish in a succinct form the particular requirements to be met, they do have regard to various matters which they deal with on general lines. Their requirements may be brought practically under two headings :-— (1.) As to the financial aspect of the pro- posed scheme ; and (2.) As to the practicability or sufficiency of the proposed supply. (1.) Of course the Board go very fully into the financial aspects of the matter, and apart from the provisions of the Public Health Act, 1875, and the Public Health (Water) Act, 1878, with regard to the incidence of expenses, they consider carefully the whole subject of cost in the interests of the ratepayers of the area so affected. Then as to the repayment of pro- posed loans, the following are the periods allowed for such repayments in the case of loans sanctioned for the water supply purposed :— Purchase of land (freehold) . 60 years. Mains and pipes . j ; .. 80. ,, Reservoirs . : : : . 80 = ,, ‘Water towers 4 30g, Purchase of existing does 30 C=», Machinery . . : : . 1, Waste water meters ; & {09 233 Boring experiments. : 54 It should be pointed out ‘hh a local authority may apply for loans in respect of three different schemes, that is to say, for the carrying out of purely experimental works, or: for the taking over of existing waterworks, or for the construction of new works entirely. (2.) As to tHE Prosecrep Suppiy.—The Local Government Board require first of all that any scheme shall provide if possible for not less than the undermentioned quantities per day per head of the population :— 10 to 15 gallons in agricultural villages ; 16 to 20 gallons in non-manufacturing towns ; 20 to 30 gallons in manufacturing towns. 266 LOC As regards the laying of mains, cast-iron pipes should be used, not galvanized, iron, stone or earthenware, and the mains should be laid at a depth of not less than 8 ft. from the surface reckoned from the top of the pipe, and should be at least 8 in. in diameter except there be special reasons. Hydrants to be provided at all dead ends. Screw-down hydrants are to be used in preference to ball hydrants. The pumping machinery to be provided in duplicate; and all sources of supply, reservoirs, and the like to be protected by unclimbable fencing. W.M. F. “Loco” Apparatus.—aA series of drain- age appliances—bends, traps, &c.—designed by Mr. F. C. Lynde, C.E. The principle under- lying these apparatus is the law of deflection. With this purpose in view the bends, &c., are made with flat striking sur- faces in the interior, so arranged that water, &c., falling upon these verti- cally will be deflected down the horizontal drain, without, it is claimed, loss of flushing power. The principle involved is made clear in the accompanying illustration which is a longitudinal section through a “‘ Loco” bend. “* Loco” Apparatus. London Main Drainage. — The first sewers in London consisted of the natural watercourses, ditches, &c., which were covered in and converted into sewers for the carriage of surface waters only. Water-closets were introduced about 1810; but they had to be made to discharge into cesspits, as it was, up to the year 1815, a penal offence to discharge polluting matters into the sewers. Prior to 1847 the sewers of London were under the management of eight different Commissions; but in that year they were superseded by one general Commission termed “The Metropolitan Commission of Sewers,” the members of which directed their atten- tion mainly to a consideration of the kinds of sewers to be adopted and to the abolition MUNICIPAL AND SANITARY ENGINEERING. LON of cess-pits. In 1847 an Act was passed making itcompulsory to discharge house drains into the sewers, the result of which was that within about 6 years 80,000 cesspools were abolished, and the whole of the sewage of London was turned into the Thames. The river, naturally, soon became very foul, and between the years 1849 and 1854 no less than five different Commissions were formed to deal with the evils arising out of this new state of affairs. In 1856 the Metropolitan Board of Works came into being under the powers of the Metropolis Management Act of 1855. One of the first acts of the new Board was to attempt the complete interception of the sewage so as to discharge it into the river below London and beyond the boundaries of the metropolis. This they did by constructing intercepting sewers parallel to the river, into which the existing main sewers were con- nected. These conveyed the sewage on the north side to Barking, and on the south side to Crossness. Three intercepting sewers were constructed on the north side, the low-level, middle-level, and the high-level. The high and middle-level sewers conveyed the sewage by gravitation to Old Ford, from where they ran together as far as Abbey Mills, at which point the sewage from the low-level sewer is pumped into them, after having been already raised once at the Western Pumping Station at Pimlico. From Abbey Mills the sewage is conveyed to Barking by gravitation in what is known as the northern outfall. On the south side of the river there are also three intercepting sewers—the low-level, high- level, and the HKffra branch sewer. The high- level and the Effra branch sewers convey the sewage by gravitation to Deptford, at which point the sewage from the low-level sewer is pumped into them. From here the sewage is conveyed by gravitation in the southern out- fall sewer to Crossness, where the whole of the sewage has to be pumped. Storm over- flow weirs were constructed at the junctions of the old main sewers with the intercepting sewers, so that if heavy rains should cause the 267 LON ENCYCLOPADIA OF \ \ TOOMBON waMot ie \ SN i / can Tone 6 ney ane homed one eH Pym ister ene jure dang weet ae cree bet mbar ements esmnantn rcnsoe en ene PPS, ee ach. ot eens) i See ER e 4 “ 6 2 were we ee Ge n A&R seen 4 Primaries og pretend we N33uD ee peat yi AGHSAN f Foe enienl tags wees ra9 mn 7 pilav tosis Gee eel tees la = sa40N ae oe 7 venavyg- 88 SINyve g a s \ Ir S39 % + \, 4 oN =. é noaswost OMS TH NOLON isha X avaiswntd “RUTH uO a yuiyiss aw WH NUT ese” i, a +, i 4 i " TH OMI UE J ‘ a \HENESduSHAaHS: a 2A KX aot A é POR: ie THis, 5 oe nowswitva as ; \ / Nowptagyd Stes 4 Nungi ES S, z ote & i Noss WO AvMOTIOH aS i EN tT oe + en NMOL SUN cout, Ton — i” \wasuman Dias Ae. aa * “OR SHAMTS TIVALNO ‘ONILEIOWFLNI ‘NIV JO SNOLLISOd ONIMAHS NWId 4 ys ewe yearn, La . >. a se “JOWNIVEQ NIVW Nf ” oils ‘ounely = yume} = uO, LON LON flow in the latter to become excessive it could overflow into the old sewers, and thus go direct into the Thames. The construction of the intercepting sewers effected a great improvement, not only by removing the sewage to a distance before it was discharged into the river, but also by reducing the amount of flooding in low-lying areas that had formerly taken place. Under the old system the main sewers were only able to discharge their contents at or about the level of low water, the rise of the tide closing the outlets, with the result that any sewage flowing down during the period the outlets were closed was pounded back in the main sewers. In times of heavy and long-con- tinued rain, and more particularly when such occurred at the time of high water in the river, the closed sewers were unable to store the increased volume of sewage, which then rose through the house drains and flooded the base- ments of the houses. This being the case, it will be seen that the provision made for dis- charging excessive rainfall by means of the old sewers could not be satisfactory at all times. Under these circumstances the Metro- politan Board of Works, in 1879, decided to carry out the following flood relief works :— (1.) Storm relief line for the Ranelagh and King’s Scholars’ Pond sewers. — (2.) Storm relief line for the Ratcliffe Highway and Limekiln Dock sewers. (8.) Relief line for the high-level sewers at Hackney. (4.) Intercepting sewer from Putney to Clapham. (5.) Storm relief to high-level at High Street, Clapham, to discharge into Effra Creek, Vauxhall. (6.) Deptford, storm overflow. (7.) Sewer from Lee Bridge to Deptford. (8.) Sewer to relieve low-lying ground at Walworth. ' (9.) Storm sewer to relieve Holloway and Kentish Town. The total estimated cost of these works amounted to £708,000, and all the sewers were constructed with the exception of the MUNICIPAL AND SANITARY ENGINEERING. LON sewer at Walworth; but a relief sewer was made from Rotherhithe New Road to South- wark, known as the Grange Road sewer. In 1897 the Main Drainage Committee of the London County Council, who took over the control of the sewers of the metropolis in 1889, instructed their engineer, Sir Alexander Binnie, to consider the whole main drainage system, with the result that he reported that the following works were the most urgent :— Norru Sipe or River.—Two sewers, Old Ford to Barking; new middle-level sewer, Paddington to Old Ford ; new low-level sewer, Hammersmith to Bow; extension of middle- level sewer to Scrubb’s Lane, Willesden; pumping machinery at Abbey Mills. Sourn Sipz or River.—Low-level sewer, Deptford to Crossness; high-level sewer, Catford to Crossness; low-level sewer, Batter- sea to Deptford. The total estimated cost of these works amounted to £2,947,000. The greater part of them have been constructed, some are in progress, and others nearly ready for contract. In addition to these works, six pumping stations were constructed to relieve the low- lying intercepting sewers—three on the north side of the river at Lot’s Road, King’s Scholars’ Pond, and Isle of Dogs; and three on the south side—at Falcon Brook, Heath- wall, and Shad Thames. The new sewers already in operation have greatly diminished the number of discharges of rainfall into the Thames within the County of London, but in spite of their construction a considerable amount of flooding occurred in many parts of London in 1908, when a total of 35 in. of rain fell. The Main Drainage Committee of the London: County Council therefore decided in 1904 to carry out the following additional flood relief works at a total estimated cost of £737,000. SuaeEsteD Firoop Renmer Worxs.—Norru Sipe: (1) Storm relief sewer, Holloway to the Thames ; (2) storm relief sewer from middle- level sewer to Counters Creek sewer (North Kensington storm relief sewer) ; (8) extension 269 LON of Hackney Wick relief sewer, northwards; (4) Stroud Green storm relief sewer. SourHh Sipe: (5) Storm water-pumping station at Wandsworth (the Falcon Brook station already mentioned); (6) new sewers in connection with the above pumping station ; (7) storm water pumping station to deal with storm water in Southwark and Bermondsey (the Shad Thames station already mentioned) ; (8) Southwark and Bermondsey storm relief sewer. Some of these works have been completed and others are in course of construction. The bulk of the rainwater carried by the sewers is now taken to the outfalls and treated before it is discharged, and there will be a still further improvement in this respect as soon as the completed scheme comes into operation. The total discharging capacity of the out- falls and storm water pumping stations on both sides of the river, not including the dis- charging capacity of those storm relief sewers which act by gravitation, is 1,464,000,000 gallons per 24 hours. The average dry weather flow per 24 hours amounted in 1908 to 283,000,000 gallons, so that provision has been made to deal with 1,181,000,000 gallons of storm water per 24 hours, apart from the capacity of the relief sewers discharging directinto the river. This is equivalent to a rainfall of about 0°70 in. over the whole area of the metropolis in 24 hours. Originally the whole of the sewage was stored at the Barking and Crossness outfalls during the flood tide and discharged on the ebb tide in its crude state. In 1887, however, the Metropolitan Board of Works commenced the construction of precipitation works at Barking, and in 1888 at Crossness. The sewage when it arrives at the works is sub- jected to chemical treatment: the addition of 1 grain of proto-sulphate of iron (ferrous sul- phate) and 4 grains of lime to every gallon of crude sewage. The precipitation takes place in long channels. The sewage flows in at one end of each channel, and after the ENCYCLOP.EDIA OF LON heavier matters are precipitated the clarified sewage goes over a weir at the other end of the channel into the river. After a certain period each channel is shut from the inlet of sewage, and the heavier matter left in the channel is dealt with in the following manner. The water is run off from the channels by means of floating arms, and the wet sludge is pushed through screens by hand into a sump. From this it is pumped into sludge- settling channels where it remains for about 24 hours. The supernatant water on the top of the settled sludge is drawn off by means of telescopic weirs, and is treated with 20 grains of lime and 10 grains of iron per gallon, after- wards being pumped up to the outfall sewer to mix with the rest of the sewage. The clarified liquid is discharged continuously into the river at all states of the tide. The settled sludge gravitates to a sludge store, from which it is pumped into sludge ships which take it out to sea and deposit it at Black Deep in the estuary of the Thames, over a distance of from 8 to 10 miles. Six sludge vessels are constantly employed for this work, each holding about 1,000 tons, and about 8,200 tons of sludge are disposed of per diem. The area draining into the Council’s sewers in 1901 was about 140 sq. miles, and the population was 5,186,192 persons. The dis- charging power of the northern outfall sewer at Barking under present conditions is about 500,000,000 gallons, and of the southern outfalls at Crossness, 513,000,000 gallons per 24 hours. The permanent staff employed in cleansing the sewers at the pumping stations and outfall works, and on the sludge boats varies from 900 to 1,000 men. The total length of the main, intercepting, -and outfall sewers, when those in course of construction and those about to be constructed have been completed, will be nearly 352 miles. The net capital expenditure on the sewers and works of sewerage up to March, 1909, has been £11,110,389, and it is estimated that an additional expenditure of about £1,500,000 will be required to complete the schemes already sanctioned by the Council. 270 LON Much of the information given above has been obtained from a report which was pre- pared for the Council by their engineer, Mr. Maurice Fitzmaurice, C.M.G., M.A., M.Inst.C.E., from which. the accompanying plan has also been reproduced. H.C. H.5. London Water Supply.— London ‘is supplied with water from several sources and by many works, formerly under the control of separate waterworks companies, but now under the control of the Metropolitan Water Board. The sources of supply are four in number (1) the river Thames, (2) the river Lea, (8) natural springs, and (4) wells sunk in the chalk or other strata in the Lea Valley, on the North of the Thames, in Kent, and at certain other places South of the Thames. Speaking roughly about 56°/, of the total supply of London is drawn direct from the Thames, 20°/, from the Lea, 14°/, from springs and wells in the Lea Valley, 9°/, from wells in Kent, and 1°/, from wells in the southern district. The total population served by the London mains is about 7,000,000 persons, the exact total being 6,948,412 as stated in the annual report of the Metropolitan Water Board for the year ending March 31, 1908. The bulk of the London water supply being drawn from the Thames and Lea has to be purified before it reaches the consumer. The methods of purification adopted are (a) natural purification by storage and sub- sidence in open reservoirs of large capacity, and (b) filtration after storage. The storage reservoirs are generally formed by enclosing large areas with earthwork embankments made watertight by means of thick core walls of puddled clay. The filters are con- structed of sand laid upon gravel and large stones above a false bottom so as to ensure ample drainage. The water after filtration is pumped to service reservoirs which are generally roofed in order to protect the water from dust and foreign matters, and also from the action of the sunlight which, though beneficial to purification in the open storage MUNICIPAL AND SANITARY ENGINEERING. LON reservoirs, would be apt to produce a growth of green weed in the hard London water which would render it unsuitable for drinking purposes. The water which is derived from purer sources, such as wells, is pumped direct to the service reservoirs, and in some cases the well water and the filtered river waters are mixed. The service reservoirs are situated as far as possible at such levels as will supply a district or area by gravitation. Where it is impossible or inexpedient to make the high- level service reservoir large enough to hold many hours’ supply for its district a larger service reservoir is made at a lower level, and from it the high-level reservoir is supplied by pumping. The high-level reservoir in this case is sometimes merely a device for keeping the pressure in the service mains constant, the real immediate source of supply being the reservoir at the lower level. ‘lhe water thus obtained and stored is distributed in cast- iron mains of sizes which vary from 54 in. diameter as a maximum to 2 in. diameter as a minimum. These mains are governed by means of sluice valves in such a manner that any whole district, section, main or branch pipe can be shut off in case of need. Hydrants for fire and other purposes are connected to the mains in the streets and else- where, and separate connecting pipes—one for each house—convey the water to the houses; each service pipe is governed by its own valve or stop-cock outside the property to which it conveys water. No other waterworks system in the world is comparable with that of London. The vast character of the works under the control of the Metropolitan Water Board may be gathered from the following figures which are taken from the annual report of the Metropolitan Water Board for the year ending March 31,1908. In that year over 80,000,000,000 gallons of water were consumed in London, the average daily supply being 219,000,000 gallons. The average daily supply per head was 32°84 gallons. There were then 62 reservoirs for storage and subsidence holding 8,913,600,000 gallons, or 271 LON about 40 days’ supply, and in addition to this another 6,000,000,000 gallons storage was authorised, and in immediate contemplation, the works for which have since been put in hand, the reservoirs at Walton having been opened, and those at Chingford to hold 5,000,000,000 gallons having been commenced. Besides the storage reservoirs, the report already quoted describes 78 service reservoirs holding in all 243,000,142,000 gallons. The filters were 161 in number and covered an area of 161°91 acres. There were 87 pumping stations containing 257 engines having a total horse-power of 34,645, while some of the pumps were lifting water to a height of 600 ft. There were 6,116 miles of water main and 66,809 hydrants. The use to which these hydrants are put may be understood from the fact that during the year in question there were no fewer than 2,800 fires in the area of the Metropolitan Water Board. The Board have divided their area into five engineering districts :— 1. The Eastern district deriving its supply from the rivers Thames and Lea and from eleven wells in the Lea Valley. 2. The Kent district, which is independent of the Thames and Lea, being supplied solely from deep wells. 3. The New River district deriving its supply from the river Lea, the Chadwell spring, and from 18 wells in the Lea Valley, most of which feed the New River Channel, and also from the Thames by inter- communication; a small supply for non- domestic purposes is also obtained from the Hampstead and Highgate Ponds. 4. The Southern district, which derives its main supply from the Thames with a sup- plementary source from wells at Selhurst, Streatham, Honor Oak, and Merton Abbey. 5. The Western district, which is supplied only from the Thames. The intakes on the river Thames are situated at Walton and Molesey. Those upon the river Lea are at Enfield Lock, and the intake of the New River district is situated between Hertford and Ware Locks on the ENCYCLOPADIA OF LON river Lea. The present policy of the Water Board is to increase the storage capacity by constructing reservoirs, and for this reason very large works are in contemplation and in progress. The demand for water is growing; the present supply is limited and the opinion is held that the increase in population will eventually render resort to some other source than the Thames watershed imperative. It, therefore, is necessary to provide storage reservoirs in order to intercept as much water as possible at times when the rivers are full ; but there is another very important reason why a policy of constructing additional storage reservoirs has been adopted, namely, that the water in the Thames and Lea is of such a quality that it requires considerable puri- fication, and it is essential to do everything possible to guard against harmful germs, which may be present in the river waters, finding their way into the London mains. That the measures adopted are successful can be best proved by practical results, inasmuch as the general health in London is good. Dr. Houston, the Board’s Director of Water Examinations, reported to the Board to the effect that bacteriologisis were agreed that pathogenic microbes do not multiply in storage reservoirs, but gradually lose their vitality. The time required to effect the destruction of these bacteria is a matter of controversy. Each day’s storage, however, makes for safety, and if the water is stored for a sufficient period the subsequent filtration is only required to improve the chemical and physical qualities of the water. Sand filtration under the best conditions, that is, after a scum has formed on the surface of the sand, has been found to be effective for the removal of bacteria, but as this scum eventually becomes so dense that the water cannot pass through it at the required rate, it has to be periodically cleaned off. Thus, the action of the sand filter alone is not to be relied on. Under these conditions it is obviously desir- able to store water for as long a time as possible ; it is believed that danger to health by over-storage is impossible. 272 LON The water in the Thames and Lea would be utterly unfit for drinking purposes were it not for the fact that the river authorities take certain precautions against dangerous contamination. The work of the river authorities has, therefore, a most important bearing upon the London water supply. These rivers forming as they do the only possible drainage channel of their respective watersheds must necessarily receive the whole of the sewage of the population above the waterworks intakes. Everything possible is done to make local authorities and private persons purify sewage to a high chemical standard before it is discharged into the rivers, and this purification and the subsequent large dilution in the river combined with natural purification in the stream has hitherto suf- ficed. The problem is, however, a very serious one owing to the increase of the population discharging sewage, and to the increase of the population requiring a supply of water. Jt is practically impossible to say what is the ultimate supply of water available for London as gaugings taken on the river weirs do not take proper account of the enormous quantity of water flowing down the river valleys in time of floods; neither do they take into account the subterranean flow which is probably consider- able. However, some idea may be obtained from the gaugings taken at Teddington Weir on the Thames and at Fieldes Weir on the Lea below the waterworks intakes. Presum- ably in times of flood accurate gaugings are impossible as the weir sluices must be open and the floods may extend beyond the river banks. Disregarding these by no means un- important facts we tind that gaugings taken in the year ending March 31, 1908, show that on the average about 1,289,800,000 gallons per day flowed over Teddington Weir after the Water Board had abstracted their supply. In this year the daily quantity abstracted from the Thames was 122,600,000 gallons or about ‘0868 of the whole flow. Similarly in the case of the river Lea in the same year the gaugings at Fieldes Weir showed that 78,800,000 gallons of water M.S.E. MUNICIPAL AND SANIFARY ENGINEERING. LON flowed over the weir on the average per day after the Board had abstracted their supply, which was on the average 45,100,000 gallons, or about °864 of the whole flow. It will be seen that the proportion of water drawn from the river Lea is very much higher than that drawn from the river Thames. The safety of the London consumer with regard to the purity of the water supplied is guarded by the vigilance of a staff of chemists and bacteriologists who, under the control of the Board’s Director of Water Examinations, are continually testing the water. In the year. above quoted no less than 11,760 samples of water were examined either chemically or bacteriologically. With regard to the future it is probable that the existing sources of supply will continue to be used for some time to come owing to the enormous works which would be required in order to obtain an adequate supply from any fresh source. It has been proposed to obtain a supply from Wales, but it is improbable that this vast undertaking will commend itself to the London ratepayer so long as the public health remains good and the supply of water is sufficient in quantity. By comparison it would be far more economical to purify all sewage entering the Thames to a bacteriological standard and to do much more than is now being done to prevent river pollution. The natural sources of supply for London water are to be found in the rivers, and it is from every point of view desirable and essential that these rivers should be kept absolutely pure. Much unnecessary pollution which is easily preventable now takes place. Works capable of purifying sewage absolutely, bothchemically and bacteriologically, can be and are being constructed elsewhere; and other pollution of various kinds can be reduced to a mini- mum. With such remedies possible, it is, therefore, probable that the Thames and the Lea will continue to be the sources of supply for London. Further with the advance of science fresh methods of purifying water are coming into use which will be available as a further means of safety when required. H.C.H.S. 2738 T LOW Lowcock Sewage Filter.—This method, in common with that of Waring and Ducat (see “Wanrtna Sysren,” and “ Ducat Finter”), depends principally upon the direct oxidation of the sewage by strong aération. The Loweock filter contains perforated air-pipes introduced at 15 in. or 18 in. down from the surface of the filtering material. These pipes are con- nected with a small blower, and, the top of the filter being sealed with a layer of sand and closely packed upper layers of gravel, the air is passed downwards and out with the effluent. In the ‘ Waring system” the air is introduced at the bottom, and the filters are aérated upwards. The object in both cases is to increase the efficiency of the filter by artificially supplying the air necessary for the support of aérobic bacterial action. The air-pressure used is equal to a 4-in. column of water. The system was tried at Malvern in 1892 with a filter of sand and gravel, and later at Wolverhampton where sand and coke breeze was used. Lowcock filters 3 ft. 6 in. deep were also put down at Tipton in 1896, with a top layer of fine broken limestone and sand, a bottom layer of coarse coke, the intermediate portion being coke breeze. Artificial aération is costly, and the more recent development of improved methods of distribution and natural aération upon per- colation beds of simple and uniform con- struction throughout, tends to show that the complications necessarily arising from systems involving forced aération and heating are not required for the production of a good per- manent effluent. Experience also shows that for large sized works, at any rate, simplicity of construction and adherence to natural con- ditions are essential and greatly facilitate smooth working. “Made Ground.’’—A term applied to land, such as a building site, the level of which has been raised and made available by shooting or tippizg surplus earth, and débris of various kinds, so as to fill up hollows and irregularities of surface, or, in some cases, to elevate the ENCYCLOP.EDIA OF MAN surface above the flood level. ‘“ House refuse ” is often disposed of by tipping upon low lying marsh-land on the outskirts of towns as is done in some of the southern and eastern neighbourhoods around London. The owners of such otherwise undesirable sites reap a good income by allowing tipping of such material including builder’s refuse, &c., at a charge of a few pence per load. Such “made ground” sites often ultimately become ‘eligible building plots’ at sreatly enhanced values, but the practice must be condemned upon sanitary grounds, and the model building bye-laws of the Local Government Board con- tain special provisions against the erection of new buildings upon insanitary sites. Main Drainage of Towns. — (Sec “¢ SEWERAGE.’’) Manchester Sewage.—Experts’ Report.—The sewage of Manchester origin- ally found its way into the Irk and the Medlock, thence to the Irwell, and finally into the Mersey. ‘The completion of the Ship Canal necessitated some method of treatment as the above-mentioned rivers became the source of supply to the Canal. Works for treatment of the sewage by chemical precipi- tation were completed in 1898. (See article ““ MancHESTER Sewace Worgs.’’) It was recog- nised from the first that chemical treatment would be inadequate, and originally intermittent filtration through land was contemplated. The area which would be required was, how- ever, soon seen to be very large. Under the direction of Sir Henry Roscoe, experiments were carried out with small filters of clinker and coke-breeze on similar lines to Mr. Dibdin’s experiments at Barking. Favourable results were obtained, but owing, among other reasons, to apprehensions as to the ultimate cost of artificial processes, a scheme was prepared by the City Surveyor for conveying the effluent to the upper tidal reaches of the Mersey, the discharge to take place at Randall’s Sluices, a short distance below Warrington. The scheme met with strenuous 274 MAN opposition from Warrington and Liverpool and other riparian authorities, and was finally rejected on a poll of the ratepayers in Manchester. The City Council therefore resolved, in June, 1898, to appoint a com- mission of experts to consider the whole question. The commission consisted of Mr. Baldwin Latham, engineer; Professor P. F. Frank- land, bacteriologist, and Professor W. H. Perkin, Jun., chemist. Under the direction of these gentlemen, a series of experiments, on the treatment of sewage by various methods, was begun in 1898, a report was issued in 1899, and a supplement in 1900. In addition to continued observation of the results obtained from the experimental beds started by Sir Henry Roscoe, the following lines of investigation were pursued :— The treatment of raw sewage by single, double, and triple contact on bacteria beds; The treatment of settled sewage by single, double, and triple contact on bacteria beds ; The treatment of raw sewage by means of the open septic tank followed by one or more contacts on bacteria beds ; The treatment of raw sewage by means of the closed septic tank followed by one contact on bacteria beds ; The treatment of storm-water. From these experiments, it was cluded :— (1.) That the bacterial system is the system best adapted for the purification of the sewage of Manchester. (2.) That the bacterial processes are best conducted in several stages, viz. :— (i.) Settlement and screening out of the grosser solids. (ii.) Anaérobic decomposition in the septic tank. (iii.) Oxidation on bacteria beds. For thoroughly satisfactory purification more than one contact is necessary for Man- chester sewage; but the experiments showed that the area of secondary beds might be considerably less than the area of primary beds. con- 275 MUNICIPAL AND SANITARY ENGINEERING. MAN Asa result of these experiments, and after consideration of methods in use in other towns, a complete scheme for the treatment of Manchester sewage by bacterial methods was proposed, and, with modifications made by the Local Government Board, was passed by the City Council in September, 1900. G. J. F. Manchester Sewage Works.—Davy- HULME Worxs.—The main works for the disposal and purification of the sewage of the City of Manchester are situated at Davyhulme, (Station Urmston, Cheshire Lines Railway) about five miles from the centre of the city. The original works, which first came into operation early in 1894, were designed for the treatment of the sewage by chemical precipitation. The new works for bacterial treatment of the sewage were completed in 1904, so far as to permit of the whole of the flow being dealt with in tanks and primary contact beds. It was originally intended to place the second contact beds on land at Carrington and Flixton some two miles from Davyhulme. Land, however, has been acquired in the immediate vicinity of the present works, and powers have been obtained to construct the secondary beds thereon. The effluent from these beds passes direct into the Manchester Ship Canal, without any final treatment upon land. The land at Carrington and Flixton is retained in the possession of the Rivers Com- mittee of the Corporation for the purpose of future extensions should they at any time become necessary. The sewage as it enters the works passes through a system of screens and catch-pits, designed to intercept coarser floating matter and heavy detritus. The flow is either passed through open septic tanks on to the half-acre primary contact beds, or, after simple sedi- mentation, on to the storm-beds. The sludge which deposits in the sedi- mentation tanks, or which accumulates in the course of time in the septic tanks, flows by r 2 MAN gravity, or is pushed by manual labour, into channels leading to two ejectors from which it is forced under air pressure into two storage tanks near the banks of the Ship Canal below Barton Locks. From these tanks it flows by gravity into the sludge steamer and is deposited at sea beyond the Mersey Bar. Occasionally a portion of the sludge is pressed and disposed of among neighbouring farmers. There are four sedimentation tanks, two on each side of the central roadway. Hach of these is 300 ft. in length, 100 ft. in width, with an average depth of 6 ft., containing a volume of 1,125,000 gallons. There are twelve open septic tanks with a total water capacity of 15,820,250 gallons, giving approximately a time of flow through the tanks of 15 hours in fine weather. There are 92 primary contact beds, covering in all 46 acres, each being a net half-acre in area. Their general method of construction will be clear from the following: The beds are constructed in concrete and are filled with screened clinkers to an average depth of 3 ft.4 in. The bulk of the filtering material consists of fragments from 2 in. to 1 in. diameter. Larger clinkers are placed over the underdrains, and as far as possible over the whole bottom of the bed. Clinkers have been used as a filtering medium, as experiments showed them to give the best results from the point of view of purification, they could be rapidly and cheaply obtained, and after four or five years could be taken out and washed at a cheap rate, so as to eliminate the softer portions, yielding eventually, in this way, a hard resistant material, at a less cost than material of equal quality could be obtained in the first instance. There are 27 acres of storm-beds 2 ft. 6 in. deep. The filtering medium is unscreened clinkers, well underdrained. The beds are designed to act mainly as straining filters, and the surfaces have to be scraped from time to time. The population draining to the works is 577,230. The strict dry weather flow, based on the water-supply plus certain allowances ENCYCLOPADIA OF MAN for private wells, &c., is taken at 21,000,000 gallons per day. ‘The works are designed according to the usual Local Government Board requirements on this basis. The average actual dry weather flow including sub-soil drainage is approximately 27,000,000 gallons, and the average total flow including storm-water for the year ending March, 1908, was 36,700,000 gallons per day. The sewage contains a very great variety of trade-effluents, notably ammonia recovery liquors (both from the gas-works, and from private manufacturers of sulphate of ammonia), and effluents from galvanizing works and from dye-works. Owing mainly to these effluents, the composition of the sewage and the results obtained by the septic tanks and bacteria beds are not comparable with corresponding data for works dealing only with domestic sewage. It has been found possible to obain a purification of from 70% to 75% by means of open septic tanks followed by first contact beds operated at a rate of upwards of 120 gallons per cubic yard per day. A second, contact bed worked at the rate of 150 gallons per cubic yard per day has been found capable of effecting a further purification of from 65% to 70% on the first contact effluent or a total purification of 90°/, with production of a final effluent which is uniformly non-putrefactive. The total capital expenditure on purification works to March, 1908, including the cost of the original works for chemical precipitation, estimated outlay for the secondary beds now under construction, and unused land at Car- rington and Flixton, amounts to £494,614 or 17s. per head of population served. The average annual revenue cost of treatment for the 5 years ending March, 1908, exclusive of interest and sinking fund, amounts to £19,310, or 8d. per head of population. Wirnineton Worxs.—These works serve a population of 60,000 situated in the districts of Withington and Levenshulme with an average daily sewage flow of 4,185,000 gallons. The process adopted for treating the sewage is sedimentation, followed by further purifica- tion of the effluent on first and second contact 276 MAN bacteria beds. There are two detritus tanks (capacity 83,400 gallons), two sedimentation tanks (capacity 781,000 gallons), ten first con- tact beds (2,900 superficial yards each), an equal area of second contact beds, and a total area of storm-beds of 12,452 superficial yards. The sludge is disposed of by trenching into land, on which crops of various kinds are grown. ‘The sewage is purely domestic and much diluted by sub-soil water. The cost of actually treating the sewage, apart from pumping and refuse disposal charges for the year ending March, 1908, was £1 5s. 9d. per million gallons or 7°84d. per head of population. Moss Sipz Sewace Faru.—The sewage of the suburb of Moss Side is at present treated by chemical precipitation, a portion of the effluent being further purified on land. The amounfof the latter is, however, inadequate, and it is intended to divert the sewage to the main works at Davyhulme at an early date. G.J.F. Manholes.—(See ‘ SzwErace.”) Mannesmann Pipes. — Mannesmann weldless steel spigot and faucet pipes for gas and water mains are made by the British Mannesmann Tube Co., of London Wall, B.C. The pipes are manufactured in lengths up to 35 ft. and can be bent cold on the spot if required. The advantages claimed for this class of tube include saving in jointing, labour, and materials, also in freight and transport with immunity from breakage in transit or when laid. The pipes are specially coated with the object of preventing corrosion. Manometer.—A general term applied to instruments for indicating the intensity of fluid pressure. These are more commonly called “pressure gauges” or “ vacuum gauges,” according to whether the pressure to be measured is above or below that of the atmo- sphere. The simplest and most accurate manometer is that in which the pressure is MUNICIPAL AND SANITARY ENGINEERING. MAR caused to act upon a balanced column of liquid (mercury) contained in a glass tube. The displacement of the mercury increases with the pressure and thus affords an indica- tion of its intensity. The mercurial gauge is used for scientific purposes, and as a standard for testing and calibrating ordinary gauges. The U-shaped tube containing water, em- ployed by gas engineers and others, is upon the same principle. The gauges used for ascertaining the pressure of steam, air, water, &e., in practical work, are nearly always of the ‘‘ Bourdon” or “Schaffer” type. The mechanism of the former consists of a curved metallic tube of elliptical cross section; one end of this tube is closed, the other com- municates with the boiler, condenser, &c. Pressure exerted upon the interior of the tube tends to change the elliptical into a circular section and in so doing straighten the tube and cause movement of its free end. On the other hand, if the pressure inside the tube is below that of the atmosphere a contrary effect takes place. The bending action of the tube is transmitted to a pointer moving over a graduated scale. In the “Schaffer” gauge the pressure is applied to a flexible corrugated steel diaphragm. In both cases a quadrant rack and pinion are employed to amplify the range of the pointer. E. L. B. Markets. — Acts of Parliament — Cattle Markets—Site—Pens and other Departments— Markets for General Merchandise—Removal of Refuse. Acts or Paruiament, &c.— Markets and Fairs Clauses Act, 1847; Towns Improvement Clauses Act, 1847; Public Health Act, 1875; Public Health (London) Act, 1891; Public Health Act, 1908. Public bodies are em- powered to provide public markets in their towns or districts by section 166 of the Public Health Act, 1875, which states :— “Where an urban authority are a_- local board of improvement commissioners, they shall have power, with the consent of the owners and ratepayers of their district, expressed by resolution passed in manner 277 MAR provided in Schedule III. to this Act, and where an urban authority are a town council they shall have power with the consent of two-thirds of their number, to do the follow- ing things, or any of them, within their district :— “To provide a market place, and construct a market house and other conveniences, for the purpose of holding markets ; “To provide houses and places for weighing carts ; “To make convenient approaches to such markets ; “To provide all such matters and things as ENCYCLOPADIA OF MAR been provided and a large square in the centre of the town laid out as a market for general merchandise. Carrte Markets: Srts.—The site for a cattle market should be near the railway station sidings, so as to avoid the harmful and dangerous passage of the animals through the streets of the town. It should also be near the public abattoir Gf there is one pro- vided in the town) for exactly the same reason, and also because the length of the distance travelled by the animal makes a great differ- ence in the weight of the meat after killing. It may be possible to provide on the site for a ns TM ye ul) fly sopra, Ht PR === *) Market Buildings. may be necessary for the convenient use of such market ; “To purchase or take on lease land, and public or private rights in markets and tolls for any of the foregoing purposes ; “To take stallages, rents, and tolls in respect of the use by any person of such market. “But no market shall be established in pur- suance of this section so as to interfere with any rights, powers, or privileges enjoyed within the district by any person without his consent.” A study of the Model Bye-laws, issued by the Local Government Board will also prove very useful and instructive. Several of our large towns have established markets both for cattle and general goods, whereas in smaller towns a cattle market has the erection of a small disinfecting station, and in selecting the site of the cattle market this should be borne in mind. The site must be well drained, as far away as possible from the inhabited portion of the town, and in a good open quarter. It should be surrounded by a high wall and have several entrances, each of large double gates. These may be either of wrought iron or wood. Plenty of room should be allowed in the market for the easy passage of the cattle to the different sections and pens, &c., provided; and drinking troughs at each entrance and in other convenient places, several in number, should be provided. Water hydrants should be provided in large numbers to flush the paving and floors of styes and pens. The paving of the site will be a matter 278 MAR requiring careful consideration, care being taken to provide materials which will have the least tendency towards slipperiness. The whole of the site inside the enclosing walls should be paved. Itis usual to provide the following accommodation, but the needs vary with different localities, either more or less being found necessary:—1. Pens for large cattle. 2. Pens for stock cattle. 38. Pens for cows with calves. 4. Covered pens for calves. 5. Pens for sheep. 6. Covered styes for pigs. 7. Stables for horses. 8. Trotting enclosure for horses. 9. Sheds or show-rooms for agri- cultural implements, carts, wagons, ke. 10. Ditto for seeds, grain, &e. 11. Offices for auctioneers. 12. Weigh office. 13. Super- intendent’s office and house. 14. Rooms or office for veterinary surgeon. 15. Waiting- rooms for drovers. 16. Covered sheds for farmers’ wagons, carts, &c. This list is merely a suggestive one, as in some districts accommodation for other pur- poses may be found necessary. In addition to the above, ample lavatory accommodation must be provided. Before dealing with the separate sections in detail, we will consider briefly the nature of the paving for the site. The pens and lairs should he paved with (1) granite or stone setts on 6 in. of Portland cement concrete; (2) a layer of asphalte on concrete; (8) granitic paving laid, in situ, and diagonally scored, to allow of easy draining, and to give a firm foothold to the cattle. These will be found to lend themselves better for cleaning purposes, besides giving a foot- hold for calves and pigs; and the stables for horses may be paved with (1) asphalte; (2) panelled blue bricks on 6 in. of Portland cement concrete; or (3) granitic paving as above; all Jaid to falls and effectively drained. The trotting enclosure for horses should be paved with setts, and the sheds for agricultural implements and farmers’ carts, &c., should be paved with asphalte on concrete as described above. ‘I'he offices, house, and waiting-rooms will have boarded floors. 1. Pens For Larce Carrie.—These will include pens for loose cattle and pens for MUNICIPAL AND SANITARY ENGINEERING. MAR tethered cattle. The divisions should be of iron or wooden “post and rail’ fences about 5 ft. in height. Rings for tethering the cattle should be let into the paving about 4 ft. apart. 2. Pens ror Stock Carrie.—These should be constructed in an exactly similar manner. 3. Pens For Cows wiTH Catves.— These should be somewhat larger than those for cattle as above, but otherwise will be similar. Sizes, &c., are given later on. 4. Coverep Pens ror Catves.—These will have divisions and walls constructed of brick. The floors should be raised above the floor of the general site about 2 ft. 6 in. or 8 ft., as these animals are generally brought in carts and can be easily transferred to or from the carts if the floor is raised. The doors may be either of iron post and rail or close boarded. The walls should be about 3 ft. above the floor. 5. Pens ror SHesp.—These will be con- structed on similar lines to those for cattle, except that the enclosing fence will not be so high. The paving should be raised from the front to the back of the pen in a gradual incline, to show off the sheep better. 6. CoveReD Sryes For Pies will be con- structed on exactly similar lines to those for calves. 7. Srasues FoR Horszs, fitted up with manger, stalls, &c., and hay loft, harness room, and other antechambers. 8. Trotting EncLtosurE For Horsres.—A large open space with light iron post and rail fence. The other departments are of the usual type and need not be described here in detail. With regard to the sizes of pens, &c., for cattle and other animals, the Model Bye-laws issued by the Local Government Board in 1877 (which upon consultation will prove very useful), suggest the following :— For every horse 8 ft. by 2 ft. » » Oxorcow. . 8, ,, 2,, » 9 mule or ass 5 ,, ,, 15 ins. a ae, cealis Digg Ge AD 45 sheep, goat, or pig (of medium size) 4 ft. (superficial). 279 MAR If these dimensions are worked to, and inquiries made into the number of cattle likely to be brought, the sizes of the pens, &e., will be easily found. Large boards with the names of the various sections painted on should be posted up over those sections to enable drovers to easily find the pens, &c., for their different cattle and animals. Markets FoR GENERAL MERCHANDISE. — These are generally buildings of an imposing character, and are treated as buildings worthy of architectural beauty. They generally include some, or all, of the following sec- tions :— Dead meat market. Fish, game and poultry market. Fruit, flowers and vegetables market. Hardware, ironmongery, and fancy goods market. Dairy produce market. Grocery and provisions market. Drapery and clothing market. Public conveniences. Offices, &c., for market superintendent. The buildings should be lofty, and prefer- ably all sections on one floor. The floors should be level with the adjacent streets, and paved with impervious paving, e.g., asphalte or granite setts, so as to be easily washed down. Gangways should be constructed in the different sections for vehicular traffic, the portions between being raised about 4 in. above and edged with granite kerb. Drainage should be very carefully considered, and ventilation and light must be plentiful. Standposts must be placed in convenient positions, and should be plentiful in the meat, fish, game and poultry sections. Removat or Reruss.—Large manure-pits must be provided for the cattle market to receive all manure from the pens and styes. The general refuse, dirt, &c., may be swept up, and carted away immediately to the refuse depot. In the case of the general market, separate bins should be provided for refuse to each shop and stall, the contents being removed daily, especially in case of the meat, fish, game and poultry, and vegetable sections. R. H. B. ENCYCLOPEDIA OF MEC Mather and Platt’s Filters. — (See “ MecHANICAL FILTRATION.”) Mechanical Filtration (of Water Sup- plies).—The mechanical filtration of water for purposes of public supply has been practised for many years past in the United States of America,upon the Continent of Europe, and many other places, but it is only of more recent years that this method of purification has attained any considerable foothold in this country. There is no doubt as to the efficiency of the more generally adopted slow sand- filtration process as extensively employed for large supplies where it is carried out under careful supervision and control, but the capital cost of such filters is heavy per million gallons filtered, and the ground space occupied by the beds is large compared with the more intensive and compact system of mechanical purification. The ordinary gravita- tion sand filter for efficient filtration does not, as a rule, pass water at a greater rate than from 18 to 20 gallons per square yard of surface per hour, or say at about 450 gallons per square yard per day of twenty- four hours, whereas the mechanical filter is capable of efficiently treating some 160 gallons per square foot per hour, the actual speed of filtration in any given case depend- ing largely upon the nature of the crude supply and the degree of purification to be obtained. There are various types of mechani- cal filters in use, for example (1) those depend- ing on straining action only; (2) those combining coagulation and subsidence with straining worked either as gravity filters or under pressure; and (8) those utilising the oxidising effect of the imprisoned air by pumping in water under pressure and then taking out suspended impurities by mechanical straining. In the United States of America, where river and lake waters are largely used, there are many installations of the Jewell system and other mechanical processes, in most of which a coagulant is added to the water before it passes to the filter. ‘The Alexandria Water Co. 280 MEC (Egypt), has adopted the system of the Jewell Export Filter Co., of New York, for treating 8,000,000 gallons of water daily from the Mahmondieh Canal, which is in direct com- munication with the Nile. In England the Jewell filters are in use at York and Wolver- hampton. Some of the leading features of the filter are: the negative head, the screen MUNICIPAL AND SANITARY ENGINEERING. MEC in reinforced concrete, masonry, steel or wood. Other systems in use in the United States, - principally for the filtering of turbid river or lake water are the ‘‘ Hyatt,” the ‘‘ Loomis,” the ‘‘ Bowden,” and the ‘‘ Duplex.” In England, three of the best known types of mechanical filters are the Candy oxidising Fic. 1.—Candy Filters, Cape Town Municipality. system, the uniform rate of flow and automatic control of the water level over the filter bed, and the rate of filtration, a weir around the filter tank for the removal of the dirty wash water, and the arrangement of valves by which the working of the filters is controlled. Pre- vious to passing through the filters waters are subjected to coagulation and sedimentation. Iron waters are treated by the addition of lime followed by aération and then rapid filtra- tion. The filters are variously constructed pressure filters, Mather and Platt’s gravity and pressure filters, and Bell’s filters. Tue Canpy System (Figs. 1 and 2).—These filters consist of steel cylinders of the form shown in the illustration and into the upper part of which water is pumped under pressure and filtered downwards through about 5 ft. of filtering materials consisting of layers of pure silica sandwiched in between which is a layer of about 2 ft. in thickness of “ oxidium ” (see “‘Oxtptum”). The filters are of special 281 MEC service in the removal of iron from waters used for public supply, whether in solution or suspension ; for the removal of peat or other discoloration, and also for the removal of organic matters and bacteria. The principle upon which the system works is as follows :— Water is either pumped throuch the filter, or An Ly: ms i nn 4 Washwater Anni: Chi Atl 2A All ENCYCLOP.EDIA OF Ht : i | A mui MEC outlet leading to clear water storage reservoir. A special feature of the system is that when water contains iron in solution, the iron is instantaneously oxidised and thrown into sus- pension, so that it is readily removed by passing through the bed of filtering materials. The pressure under which the filters work (Waly > Ta oF TF a inh \ hina a Silica Grit for Preliminary Filtration Oxidium for Oxidixing and Purifying Fine Silica Sand and Grit for Final Filtration : a ~ Bileced Wat. ter Eales tion Flantee ; Outlet Prpe A Inlet Pipe Drain Fic. 2.—Candy Filter. passed through by the head from a gravita- tion main, which upon entering compresses the air contained within the filter to such pressure as may be arranged. This materially hastens the oxidation of iron or organic impurities contained in the water, which subsequently passes downward, through the filtering materials above mentioned, to the Section. is commonly from 5 lbs. to about 25 lbs. to the square inch, but this is a matter which must be adjusted to suit the particular con- ditions and water under treatment. The process of oxidation is hastened and intensified if atmospheric air is pumped into the filters by a small auxiliary air pump, as is done at an installation of these filters at the Tunbridge 282 MEC Wells Corporation Waterworks. The system is used for the public supplies of the corpora- tions of Hastings, Cardiff, Newport (Mon.), Merthyr Tydvil, Harrogate, Tunbridge Wells, by municipal authorities in South Africa, and by a number of water companies. The results of chemical and bacteriological analyses show the system to give an effluent of a high degree of purity. A filter 8 ft. 8 in. diameter is capable of dealing with from 8,000 to 9,000 ne n'- 0" 11-0 ap MUNICIPAL AND SANITARY ENGINEERING. MEC one-fourth of the total area being out of use for cleansing, whilst in the case of mechanical filters of the above type the capital cost per 1,000 gallons effective working capacity per day amounts to between £3 and £4. The working expenses in connection with the mechanical filters is found to be about 1s. per million gallons filtered, as compared with from 8s. to 5s. per million gallons with sand filtra- tion on large works. In the case of small cow Fic. 3.—Mather and Platt’s Pressure Filters. gallons per hour, or at the rate of 160 gallons per square foot per hour. ‘he filter is rapidly cleansed by simply reversing the flow of water through it by means of a connection to the filtered water or high pressure mains. The quantity of “ wash-water”’ required varies from 8 to ‘7°/, of the total filtered, according to the nature of the crude supply dealt with. The relative cost of mechanical versus sand filtration depends very largely upon local con- ditions, but, under ordinary average conditions, the capital cost per 1,000 gallons effective working capacity per day in the case of sand filters may be taken at about £15, allowing for Plan. works sand filtration would compare much less favourably. Tue Matuer anp Puarrt Pressure Fitters (see Figs. 83 and 4).—These consist of closed cylindrical tanks, with sloping sides and domed top and bottom, supported on four cast-iron legs. The larger-sized tanks are made of riveted steel plates, and the smaller sizes of cast iron. Inside, at the upper part of the cylinder, is fitted an annular channel through which the unfiltered water enters from the inlet valve, over-flowing the edge on to the bed of filtering material, and passing down through it to the collecting chamber at the 283 MEC bottom. The filtering material consists of quartz crystals in graded layers, with the finest at the top. From the illustration (Fig. 4) it will be seen that the bed rests on a dished iron plate which separates the filtering and collecting chambers. A considerable number of brass nozzles are screwed from the under- side into the dished iron plate, ready access being obtained by means ofa door fitted in the side of the collecting chamber, so that they einateangolae 724 (Gurder. Fic. 4.—Mather and Platt’s Pressure Filters. may be replaced without disturbing the quartz bed. The object of these nozzles is to secure the effective use of all parts of the filtering bed as well as the uniform distribution of the water used in washing the filter. The annular channel, above referred to, serves to spread the unfiltered water over the bed and to carry off the dirty water when the filter is cleansed. For cleansing the filter the direction of flow is reversed; the unfiltered water inlet valve and the filtered water outlet valve are closed, and the wash-out inlet valve and wash-out dis- ENCYCLOP.EDIA OF MEC charge valve opened. The impurities filtered from the water collect, mostly, in the top of the bed, and in order to facilitate their removal during the wash-out a rake, which can be rotated by hand, is fitted inside the cylinder, with the object of breaking up the surface of the bed during the cleansing operation. When the water from the wash-out discharge valve is seen to be clean, this valve and the wash- out inlet valve are closed and the water again Yi. + . at ae 9 rs ain Wash Oat Discharge. lo Existing WelL Section. admitted through the unfiltered water inlet valve. This water, however, is not allowed to pass to the mains, the filtered water outlet valve being still kept shut, but instead, the re- wash valve at the bottom of the filter is opened for a few seconds to allow the first discharge to run to waste, so as to clean the nozzles and collecting chamber of any dirt which may have entered with the wash-out water, and to settle the upper layers of the quartz bed into a properly compact condition. The filtration plant, illustrated in Figs. 3 and 284 MEC 4 erected in 1907 by the Bolton Corporation at Belmont Road reservoirs, is contained in a brick building 80 ft. by 40 ft., and consists of ten filters of the above described pressure type, each 8 ft. in diameter. The plant is capable of dealing with 3,000,000 gallons per day under a working pressure of 200 ft. head, equivalent to 87 lbs. per square inch.! These filters are arranged in two rows of five each, the rows being spaced 16 ft. apart from centre to centre, and the filters placed at 11-ft. centres. Between the two rows of filters is arranged a central gallery, supported by iron beams carried on brackets attached to the outside of the filter cases; from this gallery the whole of the valves, agitating rakes, and other gear can be worked. The water is delivered to the filters through a 24-in. main, the quantity being measured and recorded by a Venturi meter placed in one angle of the filter house. This main extends in a trench the whole length of the house, and alongside it is a second 24-in. main for the filtered water, while below is an 8-in. pipe to carry off the wash-out water to a suitable outlet. Beuw’s Fitters.—A typical installation of this type of pressure filter has been put down at Dunoon, where a battery of twelve filters of 8 ft. diameter each are in use for treating dis- coloured peaty water from reservoirs on the bed of the Balgie Burn. Each filter will pass 10,000 gallons per hour, but is rated at a minimum output of 6,500 gallons per hour, or 78,000 gallons per hour for the twelve. At Dunoon the water is treated chemically before it passes to the filters. This treatment con- sists in adding to the water a saturated solu- tion of lime and a solution of alum, varying in strength according to the colour of the water to be treated. The object of the treatment is to remove the peaty matter to which the discoloration is due. The internal arrange- 1The installation worked at this rate for some time removing nearly 100% of suspended matter, but as it was deemed necessary to remove the peaty stain and bacteria, sulphate of alumina was added, and the quantity of water treated daily was reduced by one half. MUNICIPAL AND SANITARY ENGINEERING. MET ments and mode of washing these filters are described by Mr. James Andrew, the burgh surveyor of Dunoon, as follows :—‘‘ Hach filter contains approximately 7 tons of fine Leighton Buzzard crushed quartz, on the top of which the raw water descends. There are 144 strainers at the bottom, conical in shape, with detachable perforated lids having counter- sunk holes. The narrow ends of the strainers are fixed to l-in. pipes, which in turn are connected to a series of 3-in. pipes, the 3-in. pipes again connecting to the filter outlet. The strainers are filled with pea gravel, and the space between the bottom of the shell and the bottom of the strainer lids is filled with concrete. This arrangement at the bottom induces the whole of the filtering medium to be continuously brought into action, the inclination of the water to descend vertically being no greater at one point than another. The period of time during which the filters run without washing depends on the condition of the water, and intimation that it is necessary to wash is conveyed by the gauge. When the water is at its best washing is necessary only once in three days; when it is at its worst it becomes necessary to wash twice in 24 hours.” Mr. Andrew also states that “the alumino- ferric used is obtained from Messrs. Peter Spence & Son, of Manchester, and costs £3 per ton delivered at Dunoon Pier. The chemical treatment costs on an average 2s. 4d. per million gallons of water filtered. The cost of treatment for labour and chemicals is 7s. 4d. per million gallons. The total cost, including interest and repayment of capital, is about 20s. per million gallons.” Metals: Attoys are not merely mix- tures of different metals, they partake more of the character of solutions; were they simple mixtures the properties of the com- pound would be the mean of the con- stituents, whereas in many cases new properties are developed. The structure of alloys has been most satisfactorily explained by considering that different metals are soluble in each other in different proportions under 285 MET different states of concentration and at different temperatures. The structure of steel has been very thoroughly worked out, and it has been shown that it consists of a solid solution of carbon in pure iron, while that of cast-iron is explained by the fact that the amount of carbon soluble in the molten iron is so great that a portion separates out, as graphite, on cooling. White cast-iron is that which has been cooled suddenly, so that the carbon remains in chemical combination, not having had time to separate out, while the same iron will become grey cast-iron if cooled slowly, a small portion only of the carbon remaining in chemical combination and the remainder being present in mechanical mixture. The most notable alloys after iron are those of copper with tinand zine. Bronze isa mixture of about 10 parts copper and 1 tin, brass is a mixture of about 2 copper and 1 zinc, gun-metal is a mixture of about 16 copper, 2 tin, 1 zine. Variations in the proportion of the constituent metals produce considerable variation in the properties. Some of the principal mixtures are :— Bronze ALLoys. Name. Copper. Tin. Zinc. Lead. Pumps (very tough) .. B2 3 1 _— Pump plungers.. . 14 1 1 — Engine bearings . 112 #18 4+ 0 — Heavy bearings .. .. 82 5 1 = Hydraulic valve faces .. 4 1 — — Valves and mountings .. 90 10 240 — Brass ALLoys. Name. Copper. Zinc. Tin. Lead. Tough for engine work .. 100 15 15 —_ For turning and fitting .. 8 — A a Stop cocks and valves .. 73 7 8 12 SOLDERS. Spelter for brazing (hard).. 3 — 2 — S wo AO I ee Tinmen’s fine solder — 30 1 es coarse solder —_ 1 — 1 Plumbers’ fine 99 —_— 1 — 3 as coarse ,, — 1 — 3 Alloys are used for various purposes with two chief objects in view, firstly to reduce friction, as in the case of bearings for machinery, and secondly to avoid corrosion, as in pump rams, cocks, bolts, screws, &c. The simple metals used in forming alloys are non-corrodible, but some of them are too ENCYCLOPAIDIA OF MET expensive when used alone, as copper or tin, and others are wanting in toughness, as zinc or lead. A judicious mixture will produce the properties most desired. Copper is the principal ingredient in nearly all alloys, its characteristics being modified by admixture as follows. Tin increases the hardness, and whitens the colour through various shades of red, yellow, and grey. Zinc in small quantity increases fusibility without reducing the hard- ness, in greater quantity it increases the malleability when cold, but entirely prevents forging when hot; 1 to 2% of zinc enables sounder castings to be made. Lead increases the ductility of brass, and makes the alloy more suitable for turning, filing, &e.; in large quantity it causes brittleness. Phos- phorus increases the fluidity and tenacity, reduces the effect of the atmosphere, and allows of tempering ; it also produces sounder castings. For brass exposed to sea-water, tin is distiuctly preservative, while lead and iron are both injurious, rendering the alloy more readily corrodible; the percentage of the two latter metals should therefore be kept as low as possible in all brass intended for purposes where contact with sea-water is inevitable. H. A. Meteorology.—Meteorology is that branch of science which deals with climate and weather. The term “Climate” may be defined as the average condition of meteoro- logical phenomena at a given place, while under the term ‘‘ Weather”? may be included the condition of the atmosphere at any moment with regard to wind, temperature, cloud, moisture, and precipitation. InstrumMENTS.—At a Climatological station the essential instruments for making meteoro- logical observations are only a Stevenson Thermometer Screen, containing dry-bulb, wet-bulb, maximum and minimum thermo- meters, and a Snowdon rain-gauge. Some stations have in addition a sunshine recorder, a grass minimum thermometer, and one or more earth thermometers, and many stations have also a barometer. Most of these instru- 286 MET MUNICIPAL ments are described in other parts of this volume. TEMPERATURE.—The “mean temperature” is usually determined by adding together the readings of the maximum and minimum thermometers and dividing the sum by 2. The ‘‘ range of temperature” is the difference between the readings of the two thermometers. The range is greatest at inland places owing to radiation, and least on the coast, where the sea has a moderating effect on the tempera- ture. On July 22, 1868, a maximum tempera- ture of 100°5° F. was registered at Tonbridge and on December 4, 1879, a minimum, temperature of — 238° F. was registered at Blackadder, Berwickshire. The mean tem- perature and also the highest and lowest temperatures, as recorded at the Royal Observatory, Greenwich, since 1841, are as follows :— AND SANITARY ENGINEERING. Extremes. Months. Mean Temperature.| Highest. Year. Lowest. Year. Deg. Deg. Deg. January 58°6 F.| 57-0F. 1848 4:0 F. 1841 February 39°5 63:9 1899 69 1895 March 41:9 71:5 1848 13:1 1890 April 47:3 81:5 1865 23:0 1847 May 53°1 87:5 1880 28°1 1877 June 59°4 94:55 1858 35°6 1869 July 62:7 97:1 1881 38°7 =1868 August 61°6 95°1 18938 | 881 1864 September 57°2 93°5 1906 | 380°6 1885 October 50°0 81:0 1859 24-7 1890 November 43°5 673 1847 18:3 1890 December 89-9 62:4 1848 8:0 1860 Year 49°6 97-1 1881 40 1841 The isothermal maps of the British Isles show that in winter the highest mean tem- perature is on the south-west to west coasts, and that it decreases towards the north or north-east; the coldest parts, however, are the eastern inland districts, while in summer the inland districts arethe warmest. The influence of the warm water of the Atlantic is shown in a very marked manner by its effects on the west coasts. MET Morsture.—The quantity of water-vapour or moisture which the air can contain is dependent on the temperature. The air at a temperature of 32° F. can contain 2°18 grains of water-vapour ; at 52° F. it can contain 4°39 grains; at 72° F. it can contain 8°27 grains; and at 92° F.it can contain 15°74 grains. Thus, the higher the temperature of the air, the greater is its capacity for moisture. When the full capacity of the air for vapour has been reached, the air is said to be ‘‘ saturated.” The instruments used for measuring the amount of moisture present in the air are the dry-bulb and wet-bulb thermometers (see ‘“‘T'HERMOMETERS”’). If there is considerable difference between the readings of the two thermometers it indicates that the air is very dry; but if the readings are almost alike, it shows that the air is nearly saturated with moisture. By means of Glaisher’s “ Hygrometrical Tables” the dew point, the elastic force of aqueous vapour, the vapour in a cubic foot of air, the relative humidity, and the weight of a cubic foot of air, can be worked out from the readings of these two thermometers. Croup.— When the air is cooled below the dew-point, or point of saturation, the moisture becomes visible in the form of cloud or fog. Much information on the conditions prevailing in the upper air may be obtained from obser- vations of clouds. ‘The nomenclature of the different modifications and forms of cloud, as adopted by the International Meteorological Comunittee is as follows :— Naine. Cirrus (Mare’s Tail) Cirro-Stratus Cirro-Cumulus (Mackerel Sky) Alto-Stratus Strato-Cumulus Nimbus (Rain Cloud) .. Cumulus (Woolpack Cloud) Approximate Altitude. 27,000 to 50,000 ft. 29,000 (average) ,, 10,000 to 23,000 _,, 10,000 to 23,000 ,, 6,500 (about) ,, 3,000 to 6,500 4,500 to 6,000 _,, Cumulo Nimbus (Thunder Cloud)... . 4,500 to 24,000 _,, Stratus .. 0 to 3,500 ,, Some idea of the kind of weather that is likely to follow may be formed by noticing the type of cloud, and also its direction and rate 287 MET of motion. It is customary to observe the proportion of sky covered with cloud. This is done by estimation, the scale adopted being 0 to 10, 0 indicating a cloudless sky, and 10 a sky which is completely covered with cloud or overcast. Raryn.—Rain is produced by the cooling of the air; and in nearly all cases this cooling is produced by the expansion of the air in ascending from lower to higher levels in the atmosphere. The rain is collected in a rain- gauge, and the water measured off in a eraduated glass jar in hundredths of an inch (see ‘‘ Rain-cauce”’). As the prevailing wind in this country is from the South-west, the air comes from the Atlantic charged with a considerable amount of moisture, and in striking the land in the western districts it has to rise until it reaches the highest ground. In doing so it is cooled in temperature, and so its capacity for moisture is greatly reduced, and consequently it has to part with some of its moisure. On descending on the eastern side the air becomes warmer, and having parted with a considerable amount of its moisture, it is muchdrier. These features are brought out very distinctly on reference to a Rainfall Map of the British Isles. It is at once seen that the western parts of the country, and especially the hilly districts, are much wetter than the eastern parts. At Seathwaite, in Borrowdale, Cumberland, the average yearly rainfall is about 135 in.; while at the Stye Head, a mile from Seathwaite, the annual rainfall is about 170 in. The driest district is over the eastern counties, where the average is only a little over 20 in. According to Dr. H. R. Mill, the director of the British Rainfall Organisation, the average rainfall over the whole surface of the British Isles is about 894 in.; over England it is about 32 in., over Wales 49 in., over Scotland 47 in., and over Ireland 42°6 in. With regard to the limits of fluctuations in the total rainfall, the late Mr. G. J. Symons, F.R.S., arrived at the following results :— (1.) The wettest year will have a rainfall nearly half as much again as the mean; (2.) the driest ENCYCLOP-EDIA OF MET year will have one-third less than the mean ; (3.) the driest two consecutive years will each have one quarter less than the mean; and (4.) the driest three consecutive years will each have one-fifth less than the mean. The spring months are the driest, and October is the wettest month. The rainfall, however, is very variable from month to month; some months may have 6 in. or more, while others may have only a few hundredths of an inch, and so at some times there may be floods, and at other times droughts. When the temperature is below the freezing point, the precipitation usually takes the form of snow (see ‘‘ Snow”). Occasionally, especially in thunderstorms, the precipitation takes the form of hail, which is frozen rain. Ordinary hailstones are small, but at times they may be very large. Instances are on record in which hailstones as large as an orange have fallen in this country. THunbERsTorms.—Thunderstorms are small atmospheric disturbances, accompanied with a considerable amount of electrical energy, which manifests itself in the form of lightning. A lightning flash may assume various forms; sometimes it is a sinuous wavy line, at others it has a number of branches, and occasionally it appears to dart all over the sky. Lightning is liable to strike exposed objects; so it is desirable that houses and buildings should be provided with efficient lightning-conductors. Sheet lightning is the reflection of lightning taking place during a thunderstorm at a con- siderable distance away. Instances are on record of lightning being so seen for a distance of over a hundred miles. Thunderstorms are usually accompanied by heavy showers of rain, and sometimes hail, as well as by a squall of wind. Sunsaine.—The best instrument for record- ing the duration of sunshine is the Campbell- Stokes Sunshine Recorder. This consists of a solid glass ball, 4 in. in diameter, supported on a pedestal in a metal zodiacal frame. A eard is placed in the focus of the ball, and on this the sun burns its own record. The greatest amount of sunshine during the year is recorded along the south coast, and the 288 MET least at inland places, especially in the neigh- bourhood of manufacturing districts, where the large quantities of smoke sent into the air obstruct the sun’s rays. ArmosrHERIC Pressurz.—The changes in the weight of the atmosphere are measured by the barometer (sce ‘“Baromersr”’). The baro- metric pressure has a variation from hour to hour during the day which is most marked in the tropics, but is slight in the British Isles. This variation consists of a double minimum and maximum, viz., the first minimum occurs about 4 or 5 a.m., and the first maximum about 10 am. The second and more pro- nounced minimum takes place at 8 or 4 p.m., and the second maximum about 10 or 11 p.m. The average height of the barometer at sea- level in London is 29°955 in. The highest recorded reading in the British Isles was 31:10 in. at Aberdeen, on January 31, 1902, and the lowest 27°332 in. at Ochtertyre, near Crieff, on January 26, 1884. The distribution of barometric pressure is readily seen from isobaric charts. These are prepared by plotting on a map the barometer readings reduced to sea-level, and drawing lines through those places which have the same value. These lines, which are called ‘‘isobars,’’ will then represent equal barometric pressure. It will at once be seen where the pressure is highest or lowest. The areas of high pressures are called “ anticyclones,” and the areas of low pressure are called ‘‘cyclones.” If on these maps the direction of the wind be also plotted by means of arrows, it will be noticed that the arrows fly nearly parallel with the isobars; round the areas of high pressure they move in the direction of the hands of a watch, but round the areas of low pressure they circulate in the direction opposite to that of the hands of a watch. This applies to the Northern Hemisphere. In the Southern Hemisphere the directions are reversed owing to the rotation of the Earth. Winp.—The direction and force of the wind are determined by the distribution of baro- metric pressure. As the pressure for the British Isles is usually lowest in the north or M.8.E. MUNICIPAL AND SANITARY ENGINEERING. 289 MET north-west, and highest in the south or south- east, the prevailing direction of the wind is consequently from the south-west. This is brought out very clearly by the following figures, which show the average number of days in the year on which the wind blows from the different points of the compass at the Greenwich Observatory :-— N. 40 days. S.E. 22 days. W. 46 days. N.E. 45, S. 35 ,, N.W. 22 ,, E. 27 ,, S.W. 106 _,, Calm 22 ,, For particulars as to observing the force of the wind see “ ANEMomMETER” and “ Winp- Forces.” Weatuer.—lIf the observations made at various places at the same hour are plotted on maps, they give a very good idea of the distribution of actual weather over a country or a continent. These maps are called synoptic weather-maps. The Meteoro- logical Office compiles daily such maps for the British Isles and North-west Europe, for 7 a.m. and 6 p.m., and upon these it prepares forecasts of the probable weather for a period of 24 hours in advance. Storm warnings are also sent to coast stations to give fishermen and others indications of the approach of storms. Upper ArmospHERE.—During the last few years efforts have been made to obtain infor- mation as to the meteorological conditions prevailing in the upper atmosphere by means of kites. The Hargrave box-kite is used for this purpose, and the object of sending it up is to carry a meteorograph for recording the pressure, temperature, and humidity of the free air. Pilot balloons are sent up for deter- mining the drift of the upper currents. On specified occasions a ‘‘ballon-sonde,” carrying a very light meteorograph, is also sent up, and such balloons sometimes attain an altitude of as much as 14 miles above the earth’s surface. The interesting point brought out from the records obtained during the ascents of these balloons, is that the temperature of the air decreases pretty uniformly up to about 6 or 7 miles above the earth, but beyond that height there is little or practically no U MET change, and in fact there is often an increase in temperature. W. M. Meters, Water.—(See ‘ Water Merers.”’) Metric System.—For more than 200 years attempts have been made to secure a system of weights and measures which should conform to the decimal system of notation in use in arithmetic all over the world, and should unify the various standards of length, weight, area, &c., by building them up from one single unit. The honour of proposing that the earth itself should provide this unit belongs to the Abbé Mouton, who published the proposition in 1670. It was realised during the first French Revolution mainly because the prevailing idea in France at the time was to start afresh with as clean a slate as possible. ‘This reaction found ex- pression in the short-lived alteration of the calendar beginning again with the year One, and renaming and changing the primary sub- divisions of the time occupied by the earth in one traverse of its orbit. What is of more importance is that the new measurements were all to be decimals, thus conforming to the ordinary radix of notation used through- out the civilised world, so that the so-called “compound” operations so puzzling to most people and so wasteful of our earlier years should no longer be necessary. As early in the Revolutionary period as 1790 it was pro- posed to realise Mouton’s idea by measuring an are of 10° on the meridian of Paris, say, 10 or 11 miles, to calculate therefrom the quadrant of that meridian, i.e., as much of it as is included between the equator and the North Pole, and to employ an aliquot part of that distance as a unit of length, and not only that, but as a unit for all measurements. This scheme was carried into execution in 1895. The are was measured by the usual surveying methods. In other words, a base line was actually measured, of course with rules made according to the old French methods, and triangulations were then made from the base, and the length of the are was calculated therefrom. Fresh calculations gave ENCYCLOPADIA OF MET the quadrant, one ten-millionth part of the result thus obtained was taken as the new standard, and a rod was made of that length as accurately as the workmanship of the period would permit. This is the metre. One unfortunate misconception must here be noticed briefly. Wonderful as it may seem now, the savants to whom we owe the ines- timable benefits of the metric system were under the delusion that they had arrived at an indestructible standard, and one not liable to be lost by any accident which might happen to the standard rod or to replicas of it. “The earth is our standard,” said they, forgetting that if a thousand remeasurements of the arc were made they would all be different, and hence the unit derived from them. This now forgotten mistake detracts in no way from the supreme advantages of the metric system. All measurement depends on arbi- trary standards, and the standard metre in Paris is just as arbitrary and unreproducible as the standard yard built into the wall at Westminster, or the measures on the north side of Trafalgar Square. There is no such thing as ‘absolute measurement.’ ‘The ad- vantages of the metric system may here be briefly recapitulated:—1. It is a decimal system, conforming therefore to all arithmetic operations by decimals, and hence workable in arithmetic without any compound rules. 2. It substitutes one standard (arbitrary although it is and must be) for different standards ; one for weight, one for area, &c., &c. 3. It provides a means for unifying measures geographically. 4. It refers to all measures except the measures of time. Decimal time has been often suggested, but no scheme has been considered practicable. The metric unit is the metre. This, primarily a unit of length, supplies all the other units :— Unit of length: metre. », weight: gramme: the weight of a cubic centimetre of water at 4° C. yy area: arc: ten metres square. », volume: cubic centimetres, decimetres, &e. », coinage: franc, five grammes of solid silver. 290 MET Before giving a table of equivalents between the metric and the British systems one more point calls for notice, and here we have yet another advantage of the metric system. Aliquot parts and multiples of a British standard are called by names which have no reference whatever to the name of the larger measure. It is not obvious on the face of it that a foot has a definite relation to a yard, or a gallon to a cubic inch. In the metric system it is managed more rationally. Re- membering that it is a purely decimal system, it is easy to see the principle governing the nomenclature. Aliquot parts are denoted by prefixing Roman numerals to the name of the standard, while a similar use of Greek numerals denotes multiples, thus :— 1 milligramme = yoyy gramme. 1 kilogramme 1,000 grammes. 1 hectare = 100 acres. lcentimetre = 74, metre. The Greek prefix deka is little used, on account of its resemblance to the correspond- ing Latin word and the consequent danger of confusion. CoMPARISON OF ENGLISH AND Metric MEASURES. (Also see note at end.) WeicutT.—LEinglish to Metric. 1lb. av. = 0°454 kilogramme. loz. ,, = 28:34 grammes. Metric to English. 1 kilogramme = 2°2046 lbs. av. 1 gramme = 15°432 grains. Lenetu.—Fnglish to Metric. 1 foot = 0°3408 metre. linch = 25-4 millimetres. 1 mile = 1609°3 metres. Metric to English. 1 kilometre = 0°621 mile. 1 metre = 39°37 in. = 8281 ft. Arga.—English to Metric. 1 square mile = 2°59 sq. km. 1 acre = 4046°84 sq. metres. 1 square foot = 0°0929 sq. metres. Metric to English. lsquarekm. = 0°'386 sq. mile. 1 hectare = 2°47 acres. 1 square metre = 10°764 sq. ft. = 1:196 sq. yds. = 1,560 sq. in. 1,000 sq.cm. = 155 sq. in, 291 MUNICIPAL AND SANITARY ENGINEERING. MIC Votums.—English to Metric. 1 cubic yard = 0°7645 cubic metre. 1 cubic inch = 16°39 cubic cm. 1 gallon = 4:54 litres. 1 cubic foot 28°82 litres. Metric to English. 1 litre = 1°76 pints. 1 cubic metre = 35°31 cu. ft. leubiccm. = 0°061 cu. in. It is not difficult to commit the following table to memory, as— 22 lbs. = 10 kilos. 22 yards = 20 metres. 22 gallons = 100 litres. 220 gallons = 1 cubic metre. It must be remembered that these conver- sions are only approximately correct, although accurate enough for all practical purposes. The number of inches in a metre is expressed by a figure which runs to many places of decimals. Micro-organisms in Sewage.—The de- composition of all organic matter, either of animal or vegetable origin, is due to the action of bacteria, and as sewage consists of such matters dissolved and suspended in water, if swarms with these micro-organisms, and whether it is allowed to putrefy and pro- duce volatile bodies with a most offensive odour, or is so treated as to render it clear and odourless and incapable of undergoing putrefaction, these changes are due to the action of bacteria. Crude fresh sewage rarely contains less than one million bacteria per c.c., and generally contains several millions. These may be divided into two classes, the aérobic and anaérobic; the former growing freely only in the presence of an abundance of air, and the latter only thriving where air is excluded. The essential constituent of the atmosphere which accelerates or retards the growth of these bacteria is the oxygen; and as the real purifying organisms are aérobic, the necessity for a free supply of air during certain processes of sewage purification is rendered evident. Whilst in the sewers the aérobic bacteria have commenced the work of decom- position, and the urea found in urine and the vu 2 MIC more readily decomposible nitrogenous matter found in excretal matter have been broken down with the production of much carbonic acid and ammonia. The Micrococcus wrea is probably the most important organism pro- ducing this change. If now the sewage is confined in a closed tank, or the access of air is in any way prevented, the anaérobic bacteria become active, and acting upon the more insoluble portions decompose them with the production of gaseous and other bodies which are more or less soluble. The destruction of cellulose, the chief constituent of the woody fibre from which paper is made, is chiefly effected under anaérobic conditions by the Bacillus amylobacter. Tf the sewage is too long confined putrefaction sets in, with the production of a relatively large proportion of sulphuretted hydrogen and other offensive products, the presence of which not only causes a nuisance, but actually impedes the action of the aérobice bacteria at a later stage of the process of purification. Confinement in a closed tank, therefore, should be suffi- ciently long to liquefy the maximum amount of insoluble organic matter without allowing the putrefactive bacteria to develop sufficiently to render the odour of the liquid decidedly offensive. The sewage, septicised or not sep- ticised, is in all cases finally purified by certain aérobic bacteria, usually grouped together and called ‘nitrifying organisms.” The changes are generally believed to take place in two stages. In the first the various ammonia compounds and derivatives are de- composed with the production of nitrites, and these acting on a further portion of the ammonia and its derivatives form stable organic compounds and give rise to evolution of gaseous nitrogen. In the later stage allied bacteria effect further oxidation, and nitrates appear in the effluent, and the more com- pletely the action is effected the less ammonia and organic matter will remain in the effluent and the greater the amount of nitrates which will be present. The bacteria causing typhoid fever and cholera have rarely, if ever, been found in sewage. Attempts to isolate the ENCYCLOPADIA OF MIC former from the sewage of a hospital contain- ing many typhoid fever patients resulted in failure. Searching for them, however, has been likened to seeking a needle in a stack of hay, but when introduced in laboratory ex- periments their presence can be demonstrated without any great difficulty. If the results of various bacteriologists are to be trusted, the typhoid bacillus lives longer in sewage than in pure water, and at the present time we are not in a position to say that any bacterial system of purification destroys the germs of typhoid fever or of cholera, though there can be little doubt that the number of such germs in a sewage effluent will be few relative to those in the original sewage. Certain bacteria appear only to thrive in the presence of animal matter undergoing decomposition, and these are of especial importance, since the detection of the pollution of potable water by minute quantities of sewage depends en- tirely upon the isolation from the water of one or more of these organisms. Many of these bacteria are either difficult to isolate or difficult to identify, or occur in comparatively small numbers, hence they are of little use as an index of pollution. On the other hand, the Bacillus coli, the Bacillus enteritidis sporo- genes, and the various streptococci occur in considerable numbers, are fairly easily isolated and identified, and their presence in a water can be ascertained. Their presence not only indicates sewage pollution, but from the num- bers it is possible for an approximate estimate to be formed of the extent of the contamina- tion. Klein and Houston, in examining the London sewage at Barking outfall, found these organisms in the numbers following, per c.c. of sewage :— Bacillus coli communis Streptococct Spores of bacillus enteri- tidis sporogenes . 100,000 to 800,000 1,000 to 10,000 100 to 2,000 There are many varieties of the Bacillus coli, and if all were included the numbers above given would have to be considerably increased. On the other hand, the characteristics of the 292 MIC Bacillus coli comnvunis can be so defined as to considerably decrease the apparent number found in sewage. The number of bacteria found in sewage effluents varies enormously, but apparently those which do occur are typical of the original sewage. The numbers may be decreased, but the proportions of the more easily recognisable organisms are not markedly altered. An effluent may be quite satisfactory from the chemical point of view, yet contain hundreds of thousands of bacteria. These can, of course, be reduced enormously by sand filtration or by passing through suit- able land. Where it may be necessary to remove practically all the bacteria, as when the effluent has to be discharged somewhat near the intake of a waterworks or near shellfish layings, their destruction can be ensured by the action of very small quantities of chlorine, either as gas or in solution, or as “chloride of lime”; and as the excess of this chemical can easily be destroyed, it is probable that this process will in the near future be employed in special cases. de Oi -D. Micro-organisms in Water.— Strictly speaking the term micro-organism includes all the forms of animal and vegetable life which require the aid of a powerful lense or of a microscope for their identification, and includes forms most diverse in character, but usually it is limited to the very minute fungi called ‘“‘ bacteria ’’ (vide section on ‘“ Germs or Diskasz”’). These bacteria are of para- mount importance, since they are the only organisms which infest all waters and which are capable of rendering it a vehicle of infec- tion. It is doubtful whether any natural water is free from bacteria. They are found in the water from the deepest wells and purest springs, though in limited number, but it is rare to find less than ten in one cubic centimetre of water from any source. In such pure waters they have a tendency to multiply somewhat rapidly if the water is kept twelve to twenty-four hours before being examined, and especially if the water attains a temperature exceeding 50° F. At lower MUNICIPAL AND SANITARY ENGINEERING. MIC temperatures growth may be retarded or prevented, hence in sending samples of water for bacteriological examination it is advisable to pack the bottle in a box containing a little ice. In waters which, when taken, contain very large numbers of bacteria, the opposite results may ensue, the number present con- tinuously decreasing. In pure water, only bacilli (rod-shaped bacteria) are found, in impure waters cocci (spherical bacteria) are occasionally found. As bacteria flourish on damp surfaces, in soil and in impure water, and are also found in the air, obviously they gain admission to water in many different ways. Fortunately very many are unable to live long in this medium, especially if exposed to light; others may live for many days without showing any marked tendency to increase in numbers, whilst others appear to find in water their normal habitat and may live in it for an indefinite period, their increase being probably limited only by the amount of nutriment present in solution. Belonging to the fungi, they can only grow and multiply when the water contains organic matter in solution, and as pure waters contain an infinitesimal trace of such matter very few bacteria are as a rule found therein. On the other hand, waters rich in organic matter, from whatever source derived, gener- ally contain an abundance of bacteria. When bacteriology was in its infancy stress was laid upon the relative abundance of bacteria in water as a test of quality, a water con- taining few bacteria, say less than 500 or 1,000 per cubic centimetre, being classed as good, whilst one containing 5,000 and upwards would be regarded as_ polluted. The bacterial contents of waters from divers sources at different seasons vary so enor- mously that these arbitrary standards can no longer be accepted, and numbers now are only regarded as of primary importance as a test of efficient filtration. The standard suggested by Koch as an indication of efficient filtration was the presence of less than 100 bacteria per cubic centimetre, such bacteria being enumerated from the colonies growing 293 MIC on nutrient jelly in forty-eight hours at a temperature of 70° F. In this country the same number of colonies is accepted, but the growth is allowed to continue for three days. This frequently makes an enormous difference, as slow-growing bacteria may develop no visible colonies in two days, but may produce colonies visible in three days. The present standard is therefore higher than that sug- gested by Koch. Of more importance than the mere numbers is the nature of the bacteria present. Of the large number of species found in waters, there are certain varieties which are rarely, if ever, found in really good potable waters, but which are almost invariably present in water from moorland surface on which cattle are grazed, in water from fertile and manured lands, and water containing sewage. These bacteria are of animal origin and flourish best at a temperature approximating to that of the human body, whereas the true water bacteria grow slowly, if at all, at that temperature. If water is mixed with a jelly made of agar instead of gelatine, so that it will withstand a temperature of 98° F. without melting, and incubated for twenty-four hours, the true water bacteria do not multiply with sufficient rapidity to produce visible colonies, whereas the foreign bacteria produce such colonies, and the number produced serves as an indica- tion of the quality of the water. As a rule pure waters produce few such colonies, whilst polluted waters produce many, but for reasons, difficult as yet of explanation, this test alone cannot be relied upon. As a confirmatory test, however, it is of considerable value. The bacteria of typhoid fever and cholera are those most chiefly to be dreaded in water, but it is only on very rare occasions that they have been discovered, even when outbreaks of these diseases have been traced to their presence. It is practically useless, therefore, attempting to isolate them. Moreover, it is far more important that the possibility of such pollution should be discovered, since it is too late to discover them when present, as their presence will have been already demon- ENCYCLOPADIA OF MIC strated by an outbreak of disease. These bacteria can only gain access to water with excrementary matter, and the presence of such filth therefore indicates the possibility of specific pollution. Reference to the article on “ Micro-or@antsms In SEwace”’ will show thas recent sewage always contains certain bacteria which are easily isolated and identi- fied, and which never occur associated save in manurial matter. Unfortunately they occur in the excrement of nearly all mammals and fishes as well as in human excrement, so that their presence does not always necessarily indicate contamination of a dangerous character, since so far as we know, animals do not suffer from typhoid fever or cholera and cannot therefore impart those diseases to man. The bacteria referred to are the Bacillus coli communis and its varieties, the spore-bearing Bacillus enteritidis sporogenes, and cocci occurring in chains (streptococci). Fresh domestic sewage generally contains about 1,000,000 bacillus coli in a cubic centimetre and from 10,000 upwards of the other micro- organisms mentioned. If, therefore, water is contaminated with one-millionth part of sewage, the pollution can be easily detected bacteriologically. This test is far more delicate than chemical analysis, which may fail to detect one part of sewage in 1,000 of water. Moorland waters and springs in fissured formations fed from moorlands almost invariably contain the Bacillus coli derived from animals of various kinds found on the watershed, and wild-fowl may pollute the water of a large reservoir. As a rule, how- ever, good moorland waters do not yield more than one Bacillus coli in 10 cubic centimetres, and this standard is usually accepted for such waters. Deep well waters come under a different category and should not contain the Bacillus coli in 25 cubic centimetres, but on occasions the organism is found in deep well waters in greater relative abundance although no possible source of contamination is discoverable. If present in very small numbers and unassociated with streptococci and the spores of the Bacillus enteritidis 294 MID sporogenes, their presence has probably no significance, but if these bacteria are also found associated in the same sample the pre- sence of pollution derived from manurial matter may be regarded as decisively proved. Other bacteria, such as the Proteus vulgaris, Bacillus subtilis and Bacillus mycoides, are frequently found in waters, and indicate con- tamination by impure surface water or dust, but so far as is at present known they have no special significance, beyond emphasising the necessity for careful watchfulness and supervision over the source of supply. J.C. T. Middens.—(See “‘ Privizs.”) Mortar; Composition and Strength of.—Builder’s mortar is a mixture of lime and sand or other gritty substance, such as burnt clay or clinker, ground to a fine powder, the proportions usually being one volume of unslaked lime to three volumes of sand or grit. All limes are not alike, and the differences between them, as well as those between different samples of sand and grit, have given rise to much controversy and misunderstanding. The various limes are known as (1) fat limes, 7.e., obtained from the best quality chalk, limestone, &c., and con- tain from 90 to nearly 100°/, of chemically pure calcium oxide (CaO); (2) feebly hydraulic limes such as greystone lime, which contains about 80°/, of calcium oxide; and (8) strong hydraulic limes, such as the blue lias lime, containing about 60°/, of calcium oxide. The fat limes are used as a “putty” for interior walls, &c., and the feebly hydraulic and strongly hydraulic limes for mixing with sand to form mortar for bonding bricks. The character of the sand and grit is equally a matter of importance, and care should be taken that this is either good clean sand or crushed clinker, free from earthy matter, by which term is meant unburnt clay, garden mould, or road sweepings, &c. The presence of a small quantity of natural clay in asand has been supposed to be detrimental, but recent researches have demonstrated that MUNICIPAL AND SANITARY ENGINEERING. MOR if the quantity does not exceed 10°/, by weight of the dry sand a decided advantage in the resulting strength of the mortar is obtained, which is confirmed by the analysis of numerous samples of Roman mortars collected from the London Wall, Allington Castle, and other authenticated ancient structures whose walls have stood the test of time. For instance, three samples from Allington Castle, collected by Mr. W. D. Caroé, F.R.LB.A., near Maid- stone, circa twelfth and thirteenth centuries, contained highly ferruginous clay equal to 8°6°/,, 3°66°/,, and 4:0°/, respectively in the sand, the sample containing 8°6°/, having a crushing strength of 144 per square inch, and that containing 3°66 °/, 90 lbs. A sample of mortar collected by the writer from the Roman wall under Leadenhall Market in the presence of the City Surveyor, Mr. Perks, and Mr. Max Clarke, F.R.I.B.A., was found to contain 3°62°/, of ferruginous clay calculated on the dry sand, and had a crushing strength of about 164 lbs. per square inch, one piece resisting even 500 lbs. per square inch. These results confirm the series of experiments submitted by the writer to the Royal Institute of British Architects, December, 1906. ‘'wo especial points to be observed in the selection and use of lime for mortar are: (1) that the lime should have been well burnt to drive off all carbonic acid and thus secure the whole of the lime being in an active state; and (2) that the lime should be thoroughly slaked before being used. In order to ensure this it is the practice of the best builders to slake the lime for a week or more before use. Unfortunately the introduction of the mortar mill has had a tendency to introduce unslaked lime into the mill with the sand, crushing the whole together and then employing the resulting semi-slaked lime on the work without further delay. Bye-laws which have been made by local authorities have specified so much lime and so much sand or burnt ballast, the latter to be crushedina mill. The builder naturally adds the two together accordingly, and the mortar is made. In one case, coming under the writer’s experience, the builder being 295 MOR aware that the lime should be first slaked dry-slaked it, and instructed his men to use the materials in the proportions laid down in the bye-laws. ‘he volume of slaked lime is greater than that of the unslaked lime, the expansion being about 1 to 14 or 1%. This was overlooked, and consequently each “shovelful’* contained less than would have been the case if the lime had been used unslaked in accordance with the bye-laws. This oversight, which led to much trouble, might have been avoided if the bye-laws had been sufficiently explicit. The fineness of the sand or grit has considerable influence on the resulting strength of the mortar. A coarse sand requires more lime than a fine one to yield the maximum strength, which, however, is from two to three times that obtained with the finer sand and normal quantity of a given lime. This difference is entirely due to the nature of the voids in the sand which must be thoroughly filled by fine sand and grit, clay, or an excess of lime. If this is not done there is a lack of that intimate contact between particle and particle which is so essential in all cases where strength of adhesion is required. In the case of three samples of mortar made with sands having 23, 28, and 40°/, of voids respectively, the crushing strength of the mortar at the endof one month was 154, 155, and 70 lbs. per cubic inch respectively, the tensile strength falling from 41 lbs. per square inch to 32 and 28 lbs. for the respective samples. It is therefore important to ascertain, in all cases where the greatest strength is required, the percentage volume of voids in any particular sand proposed to be employed. The most simple method of ascertaining the voids is to place the sand in a glass cylinder marked in separate divisions up to 200 measures. Run the sand in its natural condition into the cylinder, so that when shaken down into its naturally com- pressed condition it measures 100 divisions. Then remove the sand and fill up to the 100 mark with clean water. Now gradually pour the sand into the water and shake down. Note the height to which the water rises and ENCYCLOPAIDIA OF MOR the volume the sand now measures under water. The total volume thus measured, minus the sum of the volumes of the water taken and the volume of the sand as measured under water, gives the voids in terms of percentage volume thus :— Sand taken .. oa 100 ce. Water ,, Se ss 100 3 Volume of mixed sand and water = 163°7 ,, 5 sand under water = 990 ,, Voids equal sand under water plus water 199°0 Less volume of mixed sand and water 163°7 Per cent. 35°3 One of the questions requiring an answer from the analyst is that of the original com- position of the mortar in terms of volumes of sand and grit to lime. This cannot be stated with perfect accuracy unless samples of the original materials are available, but a close approximation may be made by the physical examination of the constituents, for which purpose the lime is separated from the sand and grit, and the weight of the latter per cubic foot noted. The lime in the absence of definite data may be assumed to have been greystone lime of 80% CaO and weighing 40 lbs. per cubic foot, but great caution must be exercised, as considerable variations arise. The weight of the commercial lime thus found has now to be increased by calculation in the ratio of the weights per cubic foot of the lime to that of the sand and grit which has been already obtained. Thus 1 cu. ft. of lime weighing 40 lbs. will have the same volume as that occupied by 90 or 100 lbs. of sand or grit, as the case may be, or of 50 or 60 lbs. of clinker, &c. The following illustrates the method: Lime (CaO) per cent. 571 Equal to commercial lime } ,, 107 X 715 _ 4. of 80% (Ca 0) oo ae Sand and grit per cent... 91:13 Moist sand and grit as used .. 107°0 Commercial lime to moist sand and grit, by weight ss st .. 715 107 Commercial lime to moist sand and grit, by volume . 19-1 107 or .. 55 a Ls fae elt # 5°6 296 MOR If the lime had been measured as dry slaked lime its volume would have been increased in the ratio of 1: °53, so that the ratio would have been 1°58 to 5°6 or 1 : 3°66. The setting of mortar was ascribed by the late Professor Graham to the fact that “on drying the mortar binds the stones between which it is interposed, and its own articles cohere so as to form a hard mass solely by the attraction of aggregation, for no chemical combination takes place between the lime and the sand, and the stones are simply united as two pieces of wood are by glue.” “From the minute division of the silica and alumina in hydraulic mortar their combination with lime is more likely to occur than in ordinary mortar. Still the fixing of hydraulic mortar seems to be due chiefly to the fixation of water and formation of a solid hydrate like gypsum.” This agrees with the experiments of the writer on mortar made with materials free from soluble silica. After twelve months no trace of soluble silica could be detected as would have been the case if any combination between the silica and the lime had taken place. This result agrees with analyses of ancient mortars in which the soluble silica is no more than would be found in the fresh mortar. For instance, the three samples from Allington Castle already referred to contained only 1:20, 0°70, and 1:00% of soluble silica ; whilst that from the London Roman Wall contained only 0°80%. In many cases where pozzuolana or trass has been employed the soluble silica will be high, and this fact has doubtless given rise to much misapprehension on the point. The manner of slaking lime for making mortar often receives too little attention. According to Mr. Clifford Richardson, slaking fat limes with two volumes of water added at once is the most advantageous procedure, and that but a small departure from these proportions on either side will result in forming a less satisfactory paste. With poorer limes much smaller volumes of water should be used. Clifford Richardson has arrived at the following general conclusions: MUNICIPAL AND SANITARY ENGINEERING. MOR “Tt appears that fat limes should be slaked with 2°5 volumes of water, added at once ina closed box, to obtain the best and largest amount of good paste; and with this three times the volume of the lime in the shape of moist sand may be mixed for fine work, such as pointing, plastering, and in places exposed to dampness, and that five volumes of sand is not too much for ordinary brick-work. “The amount of mortar which a barrel of lime, of average weight, under the same conditions as in the experiments, would yield, 1s:—— Parts Sand. Parts Water. Cubic Feet. 3 2°5 16°5 4 2°5 20°6 5 2°5 24°8 or 4 cu. ft. of lime with 2°5 parts of water, and four volumes of sand would yield 22 cu. ft. of mortar which, according to authorities, is sufficient to lay 1,000 bricks in ordinary brick-work with coarsely drawn joints. With more compact work one barrel of lime will lay 1,000 bricks. A barrel of poor or magnesian lime will not yield more than three-quarters of these quantities.” W. J. Dz Mortuaries.—The Public Health Act, 1875, provides that any local authority may, and if required by the Local Government Board shall, provide and fit up a proper place for the reception of dead bodies before inter- ment, and may make bye-laws with respect to the management and charges for its use; they may also provide for the decent and economical interment at charges to be fixed by such bye-laws of any dead body which may be received into a mortuary. Any local authority may provide and maintain a proper place (other than a mortuary) for the reception of dead bodies during the time required to conduct any post-mortem examination ordered by a coroner, and may make regulations with respect to the management of such place; and where any such place has been provided, a coroner may order the removal of the body to and from such place for carrying out such post-mortem examination. It is not infre- 297 MOR quently found that a public mortuary forms part of the municipal disinfecting station ; experience has shown that it is a wise course to adopt, as it is often found necessary to destroy filthy and infected clothing taken from an unclean body. A public mortuary, to which is attached the coroner’s court, should comprise a mortuary fitted with slabs or receptacles for the reception of dead bodies, mortuary for infected bodies, post-mortem room, with a store, w.c., and lavatory adjoin- ing, viewing lobby, shell store, doctor’s room, attendant’s room, and the coroner’s court. The Battersea Disinfecting Station and Coroner’s Court is a well-arranged building of this character. In the construction of these buildings the principal features are—plenty of light, good drainage, and perfect ventilation. The latter is of the utmost importance, there being a certain amount of organic matter given off from bodies which lie in the mortuary. In the construction care should be taken to avoid any materials which will harbour dust or dirt. The internal walls should be faced with white glazed bricks, and the floors covered with some hard substance, the inter- section of the floor and wall being rounded. The doors should be of oak, solid panelled, and the ceilings plastered and then painted and varnished. ‘The post-mortem room should be lighted from the roof, having a northern aspect. It should adjoin the mortuary so that a body may be easily removed from one apartment to the other. This room should be fitted with a vitreous enamelled operating table, sinks, and lavatory. On the walls a sufficient number of glass shelves should be provided for the storage of bottles, &e. They should be of polished plate glass, fixed clear of the walls on vitreous enamelled iron cantilevers built into the wall. The sinks and lavatory should have a good supply of hot and cold water. When the mortuary adjoins the disinfecting station the supply of hot water is easily obtained. When no supply of hot water is obtainable, then suitable geysers should be provided. The provision for viewing bodies varies; in some cases a ENCYCLOPHDIA OF MUN small apartment is arranged adjoining the mortuary, into which the body is removed ; in other cases a portion of the mortuary is formed with a window and the body placed on a slab immediately in front. In all cases the viewing room should be so arranged that the jury have not to walk any great distance from the coroner’s court for the purpose of in- specting a body. The coroner’s court, which is provided in connection with the mortuary, should be within easy access from the main entrance to the building. In addition to the court, waiting-rooms should be provided “for the convenience of witnesses or prisoners. A.C. F. Municipal and County Engineers, Incorporated Association of.—'lhe Asso- ciation was founded in 1873 with the following objects:—‘‘ The promotion and interchange among its members of the knowledge and practice which falls within the department of an engineer and surveyor engaged in the discharge of the duties imposed by the Public Health and Local Government Acts.” The Association has for its objects at the present day (inter alia):—(1.) The promotion of the science and practice of engineering as applied to the health and improvement of countries, towns, urban and rural districts. (2.) The promotion of the professional rights, interests, powers, and privileges of county, urban, and rural engineers, the improvement of the professional status, and the extension and interchange of professional knowledge and practice. (8.) The examination of persons in engineering, surveying, building construction, sanitary science and works, and in local government, municipal and sanitary law, and the granting of certificates of having passed the examination in the above subjects to candidates. At its inception in 1873 member- ship was restricted to those holding chief appointments as engineers and surveyors to local authorities; but in 1886 a class of graduates was formed, the qualifications for election to this class being the passing of the examination, which was instituted in that 298 MUN year. This was followed in 1901 by the inclusion of “ Associates,” elections to this class being made only from professional men occupying assistantships in the municipal engineering profession. Finally a class of “ Associate-Members”’ was formed for pro- fessional men holding minor chief appoint- ments or important assistantships. In 1890 the Association applied for and received the sanction of the Board of Trade to its incorporation under the Companies’ Acts, and county engineers and surveyors became eligible for full membership. In 1905 a schedule of educational require- ments was adopted for candidates for permis- sion to sit for the examination. 1,472 candidates have been permitted to sit for examination, of whom 718 qualified for the Association’s testamur. Members pay an entrance fee of £1 11s. 6d., and an annual subscription of £1 11s. 6d. Associate mem- bers (excepting those holding the testamur of the Association, who pay no entrance fee) pay an entrance fee of £1 5s., and an annual subscription of £1 5s. Associates (excepting those holding the testamur of the Association, who pay no entrance fee) pay an entrance fee of £1 1s., and an annual subscription of £1 1s. Graduates pay an annual subscription of 15s. The Association holds meetings, when pro- fessional papers are read, and periodically pays official visits to different centres in order to inspect municipal works of all descriptions. Papers read are published in the annual “ Proceedings.” The last annual report states : ‘‘The Association consists of 8 honorary members, 818 ordinary members, 78 associate members, 127 associates, and 170 graduates, making a total of 1,201. The Association publishes quarterly a digest of law cases, that are of interest to the municipal engineer.” T.C. Municipal Engineers,, Institution of. —The Institution of Municipal Engineers was founded in May, 1908, with the object of providing a body representative of the pro- fession of municipal engineering in all its MUNICIPAL AND SANITARY ENGINEERING. MUN branches, or, to quote the words of the resolu- tion :—“ That, recognising the great possibili- ties of an ‘ Institution of Municipal Engineers’ in the widest sense of the term, men holding important appointments under local authori- ties, such as electrical engineers, gas engineers, mechanical engineers, and water engineers,. shall be eligible for election to membership of the Institution.” A most important feature of the Institution’s programme is the appointment of district committees in specific centres, each committee having its local chairman (who is ex-officio a member of the Council) and local honorary secretary. By the establishment of these committees the policy of the Institu- tion is determined by the majority of its members. The carrying out of practical work being considered as the most important qualification for admission to membership, no examination is necessary precedent to membership. It is recognised, however, that many members may desire to have their special knowledge of some branch of municipal engineering tested, and it is proposed, therefore, to hold examinations of a severely practical character, for which certifi- cates will be granted, in the chief branches of professional work. It has been decided that membership of the Institution shall be announced by the affixing of the letters “‘M.I.Mun.E.” to a member’s name. The agnomen is not intended to afford proof of anything beyond member- ship of the Institution. A diploma of membership is granted upon election. The Institution publishes a quarterly ‘‘ Journal,” and has established a lending library of technical works. The offices of the Institution are at 39, Victoria Street, Westminster, London, 8.W. B. W. Municipal and County Engineers and Surveyors.—The term “Municipal Engi- neer” is unknown to the law, but it has become an accepted usage to denote by the term “ Municipal and County Engineers and 299 MUN Surveyors” the officials who are responsible for, speaking broadly, the constructional work carried out by local authorities. Their main duties are thus of an engineering character, although they have also much work to do of an architectural or purely administrative type. They are known to the Jaw as “ surveyors "’— such a description is a misnomer. The pro- fession of a surveyor is defined in the charter of the Surveyors’ Institution as “the art of determining the value of all descriptions of landed and house property, and of various interests therein; the practice of managing and developing estates; and the science of admeasuring and delineating the physical features of the earth, and of measuring and estimating artificers’ work.” If this definition be considered it will be seen that most of the multifarious and widely-divergent duties of a municipal surveyor are outside the province of the profession of a “‘ surveyor” altogether. For the present purpose it is convenient to speak of the officials dealt with as ‘ Public Health Engineers,” and it should be remem- bered that this title is coined for the purposes of the moment, and is meant to include county surveyors and the engineers to municipalities and to borough, urban and rural authorities. Public health engineers hold their offices under different statutes according to the kind of authority by which they are appointed. The county surveyor is appointed by the county council under their general powers. The duties of this official are mainly con- cerned with the maintenance and repair of main roads and bridges, and he is a direct descendant of the surveyors who were first appointed under the Statute of Bridges (22 Henry VIII. c. 5), by which it was enacted “, ,. that the same justices, or four of them, within the limits of their commissions and authorities, shall also have power and authority to name and appoint two surveyors, which shall see every such decayed bridge repaired and amended from time to time, as ENCYCLOPADIA OF MUN ” often as need shall require. . . The sur- veyor to an urban authority (7.¢., a corporation or urban district council) is appointed under section 189 of the Public Health Act, 1875. The same section fixes the salary as such amount “as the urban authority may think proper,” and further provides that the surveyor shall be removable by the urban authority at their pleasure. The effect of this section is that the surveyor is removable from office at the pleasure of an urban authority, whereas a medical officer of health or inspector of nuisances is not so removable without the consent of the Local Government Board. Inasmuch, however, as the nature of the surveyor’s duties is such as frequently to lead a conscientious official into collision with his employers, and the effective administration of sanitary legislation eminently requires inde- pendent executive officers, it would appear to be highly desirable that in the matter of Government protection the surveyor should be placed on an equality with the medical officer of health and inspector of nuisances. The surveyors to rural authorities are appointed under section 190 of the Public Health Act, 1875; and the surveyors to the Metropolitan borough councils hold their office under section 62 of the Metropolis Management Act, 1855. It is provided by section 192 of the Public Health Act, 1875, that the same person may be both surveyor and inspector of nuisances, but the Local Government Board do not generally assent to a combination of these offices in a district of large area or popu- lation. The duties of a public health engineer, though they vary according to the kind of authority which that official serves may, and generally do, involve responsibility for branches of work which have been con- veniently tabulated by Mr. H. Percy Boulnois, M.Inst.C.E., a former City Engineer of Liver- pool, under the following main divisions and sub-divisions :— 300 MUN MUNICIPAL AND SANITARY ENGINEERING. MUN ENGINEERING. BrIDGEs SEWERAGE | | | val Water Carriage Dry System Disposal | | omer i el | | | Trrigation Partially Separate Complete Earth Tubs Pails Middens a lee Separate System System Closets nie eat eyaver Precipitation ae Roap Maxine I | | | | | | Collestion Supply Traffic Macadam Paving Footways ‘ pie ee | ee er A rs Rivers | | Road Rolling 1 | | | A Constant Intermittent Stone Wood Asphalte Bricks eee 5 —_ Gude Setts ‘umpii Gathering Grounds ee Rete | Deep Wells PREVENTION or FLoops TRAMWAYS Street LIGHTING | at | I. | Cable Electric Steam Horse Compressed Air Electricity Gas ARCHITECTURE. Buintpine SURVEYOR. | | | Deneerens Structures Inspection of Plans Safety of Theatres j | Streets in Progress Buildings in Progress | j j Factories Defects House Drainage CorRPORATION BUILDINGS : | Municipal Offices Artizans’ Dwellings Markets | | | penne Stations Public Baths Abattoirs | Fire Stations Mortuaries LAW. Eectriciry Acts LiGHTING ORDERS SaniTary AcTs Gas AND WaTER Acts | | | Special Acts Bye-laws PaRLIAMENTARY WoRK ARBITRATIONS CoNnTRACTS | | | | Oppositions and Extension of L. G. B. Promotions Boundaries Inquiries MISCELLANEOUS. REMovAL or SNow ScAVENGING RoaD WatTERING | ee Collection Disposal] HYGIENE LANDSCAPE GARDENING DISINFECTION ; I | | | Recreation Cemeteries Parks Grounds 301 MUN ENCYCLOPADIA OF NIT SURVEYING. QUANTITY SURVEYING FIELD WorK VALUATIONS | Levelling ADMINISTRATION. STAFF | Tradesmen’s Accounts | | Wages ContTRACTS CoMMITTEE 7 | I | Statistics Reports Records | | | Correspondence Except in the rarest instances the public health engineer is not in virtue of his office entitled to superannuation. By the Super- annuation (Metropolis) Act, 1866, however, it is provided that the London County Council and the Metropolitan borough councils may, at their discretion, grant to any officer in their service who shall become incapable of dis- charging the duties of his office with efficiency by reason of permanent infirmity of mind or body, or of old age, upon his resigning or otherwise ceasing to hold his office, an annual allowance not exceeding two-thirds of his then salary. It is difficult to see any distinction for the purpose of superannuation between a poor law official (who is entitled by statute to a pension) and a municipal official, and it is to be hoped that the claims of the latter will soon be recognised by Parliament, especially as private Acts, on the lines of the Poor Law Officers (Superannuation) Act, 1896, have in recent years been secured by several Metro- politan boroughs individually. The usual method of entering the profession of a public health engineer is by serving a pupilage of at least three years. The premiums vary from about £75 to £300, according to the size of the town or district and the professional standing of the engineer. The next step after pupilage is usually an appointment as “junior assistant,” at a commencing salary of £60 or £70 a year, and after intermediate stages have been passed an appointment as chief assistant should be secured at an annual salary of from £130 to £250. Finally a chief appointment may be obtained, tha salaries varying from a small sum up to £1,000 or £1,500 a year which is given only in the largest cities. Full information as to these matters will be found in a little book entitled ‘‘How to become a Municipal Engineer,” by J. Free- bairn Stow, late Engineer and Surveyor to the Uxbridge Rural District Council. It has become increasingly necessary in recent years that the pupil or junior assist- ant should pass some of the examinations of the recognised professional examining bodies, e.g., The Incorporated Association of Municipal and County Engineers, The Institution of Municipal Engineers, The Insitution of Civil Engineers, The Sanitary Institute, The Sur- veyors’ Institution, &c. If he does not do so, he will find that he is at a considerable dis- advantage in the keen competition which invariably takes place for any good appoint- ment. Public health engineers have two pro- fessional organisations: The Incorporated Association of Municipal and County Engi- neers (q.v.), and the Institution of Municipal Engineers (q.v.). E.G. T. &. G. T. Nitrification.—In a sanitary sense, means the complete oxidation of the nitrogen in organic matter by its conversion into nitrate. The process naturally occurs in stages, (a) fer- mentation into ammonia; (b) nitrosification or intermediate oxidation of this into nitrite ; (c) nitrification proper, or final oxidation, into nitrate. The reverse change, denitrification takes place often when aération is deficient. Each reaction is occasioned by different 302 NIT species of bacteria, some of them working in symbiosis, the condition when two or more species act together and effect decompositions which neither of them could do separately. Whenever we find a final filter acting badly, from deficient aération or other cause, the fault is at once indicated by the appearance of a high proportion of nitrites, as nitrosification is not nearly so difficult a process to manage as the nitrification which should naturally follow. The organisms causing the latter, notably Omeliansky’s nitrobacter, require for activity that the ordinary sewage organic matter and ammonia should have been con- siderably reduced, hence the advantage of a filter in successive zones like that of Scott- Moncrieff. But the presence of humus colloids appears to preserve the vitality of nitric organisms as it does in soils, so that, in an effluent which is properly prepared and well aérated, nitrification can often be encour- aged by seeding with a small quantity of fertile garden soil. It is always necessary that a base should be present to combine with the acid formed, therefore in a sewage farm if the ground be devoid of lime, it must be added. Liquids to be nitrified must not be too strong or too alkaline, and large quantities of chlorides, as in sea-water, are unfavour- able, while iron salts assist the process. Darkness is advisable, and a free supply of air is always necessary; in unaérated filter beds a large quantity of carbonic acid accu- mulates and nitrification is hindered. It is important to notice that at the same time as the nitrogen in sewage is converted into nitrous and nitric acid, the dissolved carbon- aceous matters are also oxidised into carbonic acid, giving a double improvement. The nitrates and nitrites contain “ available oxygen” which by the process of denitrifica- tion can supplement the dissolved oxygen of a stream into which sewage may flow, in oxidising the organic matters. Hence in the case of any stream and (clear) effluent, if we ascertain the respective volumes, and the amounts of oxidised nitrogen and organic carbon (by the ‘oxygen consumed” figure), MUNICIPAL AND SANITARY ENGINEERING. OHI we shall obtain a ratio showing what volume can be discharged without fouling. A highly nitrated and well-aérated effluent can actually improve many rivers, and in irrigation has a strong fertilizing power. (See ‘‘ Ox1DaTION oF SEWAGE.”’) 8. R. Norton’s Tube Wells.—(Sce ‘‘ Anyssin1an WELLs.”’) Notification of Diseases.—(See “ Zymoric Diseases.’’) Ohio Water Supply and Sewage Dis- posal.—The Ohio State Board of Health was created in 1886. The Board was given the usual general powers regarding the control of epidemics and infectious diseases. It is com- posed of seven members, one being appointed by the Governor each year. The Board was also given advisory powers regarding public water supplies and sewerage; but had no absolute authority over these. In 1898, at the time of the cholera epidemic at Hamburg, when some cholera cases were being imported to the United States, the Ohio State Board of Health, realising the importance of protecting the public water supplies, asked the legis- lature for increased authority along these lines. Asa result, there was passed in 1893 the following law: “It (the State Board of Health) shall respond promptly, when called upon by the State or local governments and municipal or township boards of health to investigate and report upon the water supply, sewerage, disposal of excreta, heating, plumb- ing, or ventilation of any place or public building ; and no city, village, corporation, or person shall introduce a public water supply or system of sewerage, or change or extend any public water supply or outlet of any system of sewerage now in use, unless the proposed source of such water supply or out- let for such sewerage system shall have been submitted to and received the approval of the State Board of Health.” In 1908, with a view to perfecting the above law, it was amended by the legislature to read as follows: 303 OHI ‘“No city, village, public institution, corpora- tion, or person shall provide or install for public use, a water supply or sewerage system, or purification works for a water supply or sewage of a municipal, corporation, or public institution, or make a change in the water supply, waterworks intake, water purification works of a municipal, corporation, or public institution, until the plans therefore have been submitted to and approved by the State Board of Health. No city, village, corporation or person shall establish a garbage disposal or manufacturing plant having a liquid waste which may enter any stream within twenty miles above the intake of a public water supply until the location of such garbage or manufac- turing plant, including plans for disposing of such liquid waste, is approved by the State Board of Health. Whoever violates any provi- sion of this section shall be fined not less than one hundred nor more than five hundred dol- lars.’’ Since 1898, therefore, it has been neces- sary that all plans for new projects for public water supplies or sewerage be approved by the Board. In regard to works in existence previous to 1893, the Board has had until the year 1908 no jurisdiction, except to investigate and point out to local officials any conditions which need improvement. In 1898 legislation was enacted, authorising the State Board of Health to establish and maintain a laboratory for the chemical and bacteriological examination of public water supplies and of sewage effluents; in addition, pathological work was provided for. The Board was directed to annually examine and report upon the condition of public water supplies. About this time the Board also established an engineering department for the purpose of making careful investigations of the proposed water supply and sewerage projects which came before it for consideration, as well as for studying the conditions of existing works. During the years 1897 to 1902, inclusive, the board has, through its engineering depart- ment and laboratory, and with the aid of other temporary expert assistance, made a detailed study of the watersheds of all the ENCYCLOPADIA OF OHT principal rivers in the State. One or two watersheds were taken up each season. ‘I'hese studies included an investigation of all sources of pollution both from cities and villages, as well as from factories. All sewerage systems and waterworks were examined in detail, and the population using such works were deter- mined. Chemical analyses of the rivers them- selves were made at regular intervals, and the pollution of the water, in many instances, was thereby conclusively demonstrated. The results of these investigations, including maps and statistical information, will be found in the annual reports of the State Board of Health. These reports afford a very com- prehensive view of Ohio conditions as regards stream pollution. Supplementary to the above work, stream gauging stations were established on certain rivers; and these were later maintained for several years by the United States Geological Survey, under the immediate diréction of the engineer of the State Board of Health. Daily gauge readings and records of discharge, covering periods of from six months to three years, of some fifteen of the rivers of Ohio are now available. These have been of great service in studying sewer- age problems and also in other work. During 1905 the Board, acting co-operatively with the Hydro-Economic Division of the United States Geological Survey, made a detailed study of the disposal of certain industrial wastes which had long been sources of complaint. Much valuable and practical information was gained in regard to the purification of dairy refuse, woollen mill waste, acid iron waste from tube works, and the refuse from distilleries. ‘The work on this last was especially interesting, as a method was developed whereby the valuable ingredients in the refuse could be reclaimed at a very substantial profit to the distiller. In 1906, on account of the increased responsibilities of the Board, due to the many important projects for water supply and sewerage which were submitted to it for approval, the legislature made a_ special appropriation to enable it to increase its engineering and laboratory force sufficiently 304 OHI to make a detailed examination of the con- struction, methods of operation and efficiency of all existing water and sewage purification works in the State. This special investi- gation consisted of a series of detailed and systematic examinations of all the water purification and sewage purification works in operation in the State of Ohio. One of the assistant engineers devoted his entire time to the water purification works and another to the sewage purification works. Each examination occupied usually two or three days, during which time a large number of samples of the raw and treated sewage or water were collected, and observations made on rates of filtration, chemicals used, and upon other features. The bacterial samples were all plated, and most of the other analytical work done, immediately foliowing the collection of the samples, in the field. This avoided the undesirable feature of shipping the samples by express, and thus added a great deal to the value of the investi- gation. A full detailed report covering the investigation is published under the title, “Report of an Investigation of Water and Sewage Purification Plants in Ohio, 1906— 1907.” The investigation above described served to further equip the State Board of Health for the responsibilities which were placed upon it by the legislature in the spring of 1908. In April, 1908, there was passed a law, known as the Bense Act, con- ferring upon the State Board of Health the power to order, in each case with the approval of the Governor and Attorney-General, any city, village, or corporation to install a water or sewage purification plant whenever it is shown, after investigation and after granting full hearing to those interested, that such a plant is necessary. Existing works may be changed or enlarged through a similar pro- cedure. The Act further empowers the State Board of Health to secure competent operators for water and sewage purification plants. If a community or corporation believes that any order of the State Board of Health is not just, then “ the necessity for and reasonableness of M.S.E. MUNICIPAL AND SANITARY ENGINEERING. OIL such order ’ may be submitted to a commission of referee engineers who shall have power to affirm, modify, or reject such order; one of these referee engineers to be chosen by the com- munity or corporation and the other by the State, and they to choose a third if necessary. The decision of this engineer commission is to be final. In this way a municipality or corporation has ample protection against the possibility of arbitrary or unjust orders, thus removing criticism made in the past of the placing of too much authority in the hands of a State Board of Health. An important feature of the Act and one which is essential to its enforcement is that clause which makes it possible for a city or village to appropriate money for water or sewage purification works in excess of the legal debt limit for other expenditures. The plea of poverty cannot, therefore, be used as an argument against making the necessary improvements in sani- tary conditions of a community. In order to definitely place the responsibility for carrying out the orders of the State Board of Health, the members of departments or council of a municipality, or officers of a corporation are made personally responsible for carrying out orders of the State Board of Health, and are liable to a personal fine for failure to do so. The Act above discussed has been commented on most favourably by sanitary authorities in the United States as well as abroad. It is felt that this law is just and reasonable, and at the same time can be used to great advantage in preventing the pollution of streams.— R. W. P. Oil Engines.—Petroleum, or oil engines, like gas engines, are of the internal - com- bustion class and resemble the latter in that the power is generated by the explosion, in an engine cylinder operating on the Otto cycle, of a compressed inflammable gaseous mixture. In the oil engine this mixture is derived from the heavier mineral oils of which large supplies are now available, principally from America and Russia. Some of the oils commonly used in oil 305 x OIL engines are Broxbourne Lighthouse (flash point? 152° F.), American Royal Daylight (flash point 76° F.), and “ Russolene”’ (Russian ordinary) of flash point 82° F. These ails have an average calorific value per pound of about 21,000 British thermal units, and a specific gravity of about ‘81. Texas and Roumanian fuel oils are also now being used in crude oil engines. PRINCIPLE oF THE Or Eneinz.—The motive power of the oil engine is derived from the explosion, behind a piston within a cylinder, of a compressed gaseous mixture consisting of oil-vapour and air. The conditions are more complex than in the gas engine as the liquid oil has first to be vaporised within the engine Lrlel vedve From vaporiser Fig. 1. before the explosions needed to give the periodic impulses to the piston can take place, and, the design of a satisfactory ‘“ vaporiser’”’ has proved the most difficult portion of the inventor's task. The main objects sought have been to satisfactorily vaporise the cheaper, heavier, and safer oils without clogging, and to provide for the proper admixture of air with the oil vapour. Three of the principal methods by which the vaporisation of the oil is accomplished in practice are shown diagrammatically in Figs. 1,2and 3. The arrangement illustrated in Fig. 1, is that adopted in the Priestman oil engine. The jet of oil, controlled by the engine governor, and a current of air, is mixed in a spraying-nozzle in such a way as to reduce the oil to an exceedingly fine spray received 1“ Flash-point ’’ = the temperature at which oil commences to give off inflammable vapour when under atmospheric pressure. The flashing-point increases as the density increases. ENCYCLOPAIDIA OF OIL within a vaporising chamber which is heated by a jacket through which the engine exhaust fumes pass. During the outward or suction stroke, an additional supply of air, also regu- lated by the governor, enters the vaporiser where shown and forces the vaporised charge forward into the clearance space of the engine cylinder. Upon the return stroke of the piston, due to the impetus of the fly-wheel, the inflammable charge is compressed, becomes ignited by an electric spark at the moment of full compression, expands, doing work upon the piston, and finally is exhausted, the return stroke driving the products of combustion through the exhaust valve. The Priestman engine gives an explosion every second revolution, running on the ordinary Otto cycle common to most gas and oil engines. In this engine, the compression pressure of the gaseous mixture before admission is greatly reduced as the load reduces, and at very light loads the engine runs practically as a non- compression engine. The fuel consumption per indicated horse-power rises rapidly with the reduction of compression. This is shown, for example, in tests made by Prof. W. C. Unwin on a 9 I.H.P. engine working on Russolene oil, and in which the oil used per ILH.P. per hour was ‘816 lb. (at full load) 1°068 Ibs. (at half-load), and 5°734 Ibs. (running light), the mean compression being, 26, 14°8, and 6 lbs. per square inch respec- tively. Another method of vaporising the oil is shown in Fig. 2. In this there is no sprayer, the oil being allowed to drop upon a spiral or corrugated surface of heated metal. The evaporation is assisted by part of the air supply necessary for forming the explosive mixture being drawn into the vaporiser over the heated surfaces. The suction stroke of the piston draws the mixture into the clearance space of the cylinder where, by means of the valve shown, it mixes with the additional air necessary to form an explosive mixture, and, upon the return stroke of the piston the charge is compressed and exploded, thus giving the forward impulse to the piston. In a modification of this method sometimes 306 ' OIL adopted, the air valve in the cylinder is not used, and the whole of the air supply necessary for the charge is drawn over the vaporising surfaces. Fig. 8 illustrates the method of vaporisation adopted in the ‘‘ Hornsby-Akroyd” oil-engine, which is simple and effective. The vaporiser is a bottle-shaped chamber or extension of the cylinder, to which it is con- nected by a neck or contracted passage. It is Completion of air supp tor explosive nee Fie. 2. partially water-jacketed and, when first start- ing the engine, is heated by a lamp; after- wards, the combustion of the fuel within the engine is sufficient to maintain the tempera- ture high enough to cause ignition of the vapour and air mixture. The oil supply is pumped from a tank formed in the base of the engine, by means of a small plunger pump, into the hot vaporiser during the out- ward or air-suction stroke. A little air also enters with the oil thus injected. Upon coming in contact with the heated surfaces the oil instantly spreads, is vaporised, and mixes with the products of combustion re- maining from the previous charge, but the mixture does not contain sufficient oxygen for combustion. As the engine piston makes its outward or suction stroke the necessary additional air is drawn into the clearance space of the cylinder through a valve in the position shown but having no connection with the vaporising chamber. At the end of the outward stroke of the piston the cylinder is filled with air whilst the vaporiser remains charged with the mixture of oil vapour with some products of combustion. Upon the return or inward stroke of the piston, compression of the cylinder contents takes 307 MUNICIPAL AND SANITARY ENGINEERING. OIL place, and the cylinder-air enters the vaporiser, thus supplying the necessary air for its com- bustion, until, at the point of full compression, ignition takes place and the resulting impulse is given to the piston. The time taken to start the engine is about nine minutes in the medium sizes. The vaporiser is the distinguishing feature of this type of engine, which requires neither hot tube, electric spark, nor slide valve with flame for the purpose of ignition. The Hornsby cheap - fuel oil engine is now made up to 500 B.H.P. The present writer has installed a 80 B.H.P. engine of this class for waterworks deep- well pumping purposes, and, in his experi- ence, the cost of fuel per B.H.P. hour, using Texas or Roumanian oil at 24d. per gallon, was 2328 of a penny. There are many differ- ent makers of oil engines now on the market, amongst which may be mentioned the Black- stone, Britannia, Campbell, Crossley, Cundall, Gardner, Griffin, Robey, Ruston-Proctor, Samuelson, and Tangyes. The “Diesel” oil engine, which takes its name from Herr Rudolph Diesel, has now become a motor of much scientific and com- mercial interest. It is an internal combustion engine intended for working with gaseous liquid or solid fuel, and is at present developed Air inlet Vaporiser Piston Ou ; “ he ay Cylinder Clearance Fig. 3. as an oil-engine working on the four-stroke cycle, and is built vertical. The cycle of operations, though not involving new prin- ciples, is very different from the process followed in the ordinary Otto engine. The leading distinguishing features of this engine are :—(1) The attainment within the cylinder of the necessary temperature for ignition of the charge by mechanical compression alone so that no extraneous igniting device such as incandescent tube, or electric spark is required , x 2 OIL (2) The injection of the oil into the cylinder only after compression has been completed, and only during the first part of the working- stroke; (3) The oil is injected gradually into the highly heated air, each drop of the spray burning immediately and quietly, so that no explosion takes place. Erriciency anp Tgstine or O1n-ENneines.— The cost of working oil-engines varies accord- ing to the class and cost of oil used, the mechanical and thermal efficiency of the engine, and its average working load. From trials of seven different makes of engines running at full load with “Russolene ” oil costing 34d. per gallon, the cost of one B.H.P. per hour was found to range from ‘87d. to ‘99d. The consumption of oil per B.H.P. showed an increase of about 32°/, when at half-load. The total oil used at full load per B.H.P. hour varied from ‘82 to 1°68 lbs., the B.H.P. of the engines ranged from about 5 to 83 B.H.P., and the mechanical efficiency from ‘7 to °9. Tue Testing or O1n-Eneinzs is carried out in a very similar manner to the testing of gas-engines. There is difficulty in obtaining satisfactory indicator diagrams, especially when the engine is being forced with excessive oil supply, so that wherever possible the per- formance of the engine should be taken on the B.H.P. as in the case of the gas- engine. The weight of oil used should be as- certained by measurement in a carefully cali- brated tank, and where different classes of oil are used the calibration requires to be sepa- rately made for each owing to the varying density of the oils. The measurement of the air supply for combustion must also be made in order that the heat account for the engine may be made up. Thisis sometimes taken on the volume of the delivery of the air-pump where such is used, or may be approximately measured by an anemometer placed in a suit- able air conduit or tank. W. H. M. Open Spaces.— Commons — Parks and Recreation Grounds and Gardens — Squares, Crescents, and other Inclosures — Disused ENCYCLOPADIA OF OPE Churchyards and Burial Grounds—Tree Plant- ing in Thoroughfares— Laying Out and Main- taining Grounds—Rights of Way and Wayside Wastes—Statistics—The open space movement owes its origin to the continuous growth of population during the past 40 or 50 years in urban, as compared with rural areas, and to the consequent necessity for providing open spaces where fresh air, recreation, and exercise may be obtained by the ever-increas- ing number of town dwellers. The education of public opinion in regard to the import- ance of this subject has been largely due to the sustained efforts of certain societies, viz. : The Commons and Footpaths Preservation Society (1865), concerned chiefly with the preservation of common lands now to be found generally in rural areas on the outskirts of towns and of rights cf way; the Kyrle Society (1877), which was formed for bringing beauty home to the people; and the Metropolitan Public Gardens Association (1882), which takes steps to secure the provision of parks, gardens, playgrounds, gymnasia, the planting of trees and the placing of seats in thorough- fares, &c., within or near populous centres. These bodies have, inter alia, obtained the passing of many Acts of Parliament for the protection of commons and open spaces, and for endowing public authorities with powers of acquisition and management in regard thereto. Of more recent date are the London Playing Fields Society (1890) and the National Trust for Places of Historic Interest or Natural Beauty (1894), whose objects are sufficiently indicated by their titles. With this intro- duction the subject may be divided under certain main heads :— 1. Commuons.—Under the Commons Act, 1876 (89 & 40 Vict. c. 56), schemes can be sanctioned by the Inclosure Commissioners (now the Board of Agriculture and Fisheries) embodied in a provisional order and confirmed by Parliament, for the regulation and im- provement of commons for use by the public, with due regard to the interests of the lord of the manor and commoners, conservators being appointed to carry out schemes and 308 OPE exercise general powers of management. This Act, although not absolutely prohibiting the inclosure of common lands (which under the Inclosure Acts, were being rapidly inclosed and divided up all over the country), placed a most desirable check upon this policy by declaring that future inclosures should not be made, unless it were proved to the satisfac- tion of the Commissioners (now the Board of Agriculture and Fisheries) and of Parliament that such inclosures would be of benefit to the neighbourhood generally, and not merely to private interests. The Law of Commons Amendment Act, 1893 (56 & 57 Vict. c. 57), contains a provision of great importance, rendering it needful to obtain the consent of the Board of Agriculture and Fisheries to any inclosure or approvement of any part of a common purporting to be made under the Statutes of Merton (20 Hen. III. c. 4), and Westminster the Second (13 Edw. I. c. 44). The Local Government Act, 1894 (56 & 57 Vict. c. 73, ss. 8 and 26), confers powers relating to commons on urban, rural, and parish councils. The Commons Act, 1899, marks a further step in advance by simplify- ing the procedure of the 1876 Act and enabling the Board of Agriculture and Fisheries itself to give full effect to a scheme of regulation without the necessity for obtaining Parlia- mentary sanction, where no opposition to the scheme is raised by the lord of the manor. It also gives the widest, interpretation to the “common” lands, which may be regulated under its provisions. Commons within 25 miles of the City of London boundary and outside the County of London may be acquired and managed by the Corporation of London under the Corporation of London (Open Spaces) Act, 1878 (41 & 42 Vict. c. exxvii.). Burnham Beeches, Coulsdon, Riddlesdown, Kenley, and West Wickham Commons have thus been secured by the Corporation. 2. Merropotitan Commons.— Under the Metropolitan Commons Acts, 1866 to 1898 (29 & 80 Vict. c. 122; 82 & 38 Vict. c. 107; 41 & 42 Vict. c. 71; 61 & 62 Vict. c. 43), all MUNICIPAL AND SANITARY ENGINEERING. OPE commons and commonable land wholly or partly within the Metropolitan Police District (the Greater London of the Registrar-General) are specially exempted from inclosure, whether under the Inclosure Acts or otherwise, and schemes can be certified by the Board of Agriculture and Fisheries, with Parliamentary sanction, for the improvement, protection, and management of any such lands in the interests of the public, with due regard to private rights. 3. Parks, Recreation GRoUNDS, GARDENS, &o.— The Recreation Grounds Act, 1859 (22 Vict. c. 27), enables land to be conveyed to trustees for public recreation. The Public Improvement Act, 1860 (23 & 24 Vict. ¢. 30), enables a two-thirds majority of ratepayers of any parish to secure land for public walks and playgrounds. The Public Health Act, 1875 (88 & 89 Vict. c. 55, s. 164), the Public Health Acts Amendment Act, 1890 (58 & 54 Vict. c. 59, ss. 44 and 45), and the further Amendment Act, 1907 (7 Edw. VII. c. 58, ss. 76 and 77), give urban authorities power to acquire and manage public walks and pleasure grounds. These three Acts do not apply to London. The earlier Acts of 1859 and 1860 and the isolated provisions in the Public Health Acts must give place in importance to that comprehensive measure, the Open Spaces Act, 1906 (6 Edw. VII. c. 25), embodying several previous Open Spaces Acts, which gives full powers to local authorities in England, Wales, and Ireland (including London) to acquire and maintain open spaces of various kinds for public recreation. Under the Public Libraries Act, 1892 (55 & 56 Vict. c. 58, s. 18), public spaces are protected from conversion into library building sites; and the London Government Act, 1899 (62 & 63 Vict. c. 14, s. 82), prohibits borough councils from alienating recreation grounds. 4. Squares, CRESCENTS, OVALS, AND SIMILAR Inciosures.—It is very necessary to preserve all such areas, whether or not open to the public, as they form valuable oases and breathing spaces in the midst of crowded surroundings and afford grateful relief to the 309 OPE eye of the passer-by. The Gardens in Town Protection Act, 1868 (26 Vict. c. 18), provides for the protection and upkeep of all such carden inclosures and the levying by the local authority of a special rate on occupiers entitled to use them. The Open Spaces Act, 1906 (6 Edw. VII. ec. 25), contains special pro- visions and procedure for the: transfer by trustees and others of such areas to the local authority with a view to their maintenance as public gardens. In London the Metro- politan Public Gardens Association has been able to secure and lay out many such grounds and transfer them to the appropriate authority to maintain for public use. ‘The London Squares and Inclosures (Preservation) Act, 1906 (6 Edw. VII. c. elxxxvii.), marks the very desirable commencement of making such areas, of which 67 are included in its schedule, ineligible for building purposes. 5. Disusep CuHurcHyarDS AND Buriau Grounps.— Until the year 1884 such areas, at least in towns, were too often allowed to fall into a neglected and insanitary condition, or were quietly sold and transformed into building sites. The Disused Burial Grounds Act, 1884 (47 & 48 Vict. c. 72), as amended by the Open Spaces Act, 1887 (50 & 51 Vict. c. 82,8. 4, and schedule), prohibit building thereon. The Metropolitan Public Gardens Association has taken the lead in rescuing many of these areas from utter neglect and laying them out as bright and pleasant public gardens. The requisite procedure is contained in the Open Spaces Act, 1906 (6 Edw. VII. c. 25). In the Metropolis the London County Council has special powers for enforcing the observance of the Disused Burial Grounds Act, 1884, under the Metropolitan Board of Works Various Powers Act, 1885 (48 & 49 Vict. ¢. elxvii.). 6. Tree Puantine in THOROUGHFARES.— The planting of trees in roads of suitable width is not only desirable from an hygienic point of view, but the foliage provides grateful shade and welcome relief to the eye in the midst of bricks and mortar. Public authori- ties outside London are enabled to under- ENCYCLOPADIA OF OPE take this work by the Public Health Acts Amendment Act, 1890 (58 & 54 Vict. ¢. 59, s. 43), and in London by the London County Council General Powers Act, 1904 (4 Edw. VII. c. cexliv., s. 49). Great care has to be taken in regard to planting, pruning, watering, and main- tenance. Irreparable injury is too often done by entrusting such work, especially pruning and lopping, to unskilful and untrained hands. Only certain trees will flourish in the smoke- laden atmosphere of large towns, ¢.g., planes (par excellence), certain varieties of poplar, robinias, catalpas, limes, &c. ‘The purer the air, the greater becomes the choice. Care has to be taken to avoid gas, water, and other pipes. Soil in suitable and adequate quantities must be imported where needful. Useful information on this subject is given by the Metropolitan Public Gardens Association. 7. Lavine our AND MAINTENANCE OF GROUNDS ror Pusztic Use.—It is impossible within the limits of an article to give any detailed direc- tions. The skill and knowledge of a trained landscape gardener is desirable in order to make the most of a ground, with due regard to its size, use, and environment. In the case of commons and heaths the endeavour should be to preserve all natural features and avoid artificiality or elaborate treatment, which not only add greatly to first cost, but involve heavy annual expense for maintenance. Also over laying-out tends to curtail the chief function of a ground as a place to be used for exercise and recreation and not merely to be looked at. The public much prefer to walk and enjoy themselves on grass and under the shade of trees than to be shut out therefrom and confined only to footpaths by the introduction of unnecessary flower-beds and shrubberies. In really small grounds, however, appearance assumes more impor- tance, and greater elaboration is admissible. 8. Rieuts or Way anp Roapsipe Wastes. —It is the duty of district councils, whether they be highway authorities or not, by the Local Government Act, 1894 (56 & 57 Vict. c. 78), to protect all public rights of way, to prevent obstruction, whether within or 310 OPE adjacent to their district, and to institute or or defend legal proceedings. District councils can be set in motion by parish councils, and in rural districts an appeal lies to the county council in case of inaction. Under the same Act it is obligatory upon district councils to prevent unlawful encroachments on roadside wastes, which add so much to the appearance of a road and to the pleasure of those using it. As in the case of footpaths, parish councils can put district councils in motion with an appeal to the county council in case of neglect. County councils have power to move indepen- dently in the event of encroachments on main roads. 9. Srartstics.—In 1888 in the area of the present county of London there were 1038 spaces of various kinds available for public use, about 4,000 acres in extent, which gave 1 acre of public space to 950 people. At the present time (1910) in the same area there are 320 spaces, aggregating over 6,000 acres in extent, or 1 acre of public space to 750 people. In 1883, 46 selected cities and towns (excluding London) of the United Kingdom possessed 178 public spaces over 8,000 acres in area, equivalent to 1 acre of public space to 760 people. In the same localities there are now (1910) over 500 public spaces, about 14,000 acres in area, or 1 acre of public space to 640 people. 7 10. Conciuston.—Great strides have been made during the last 25 years in regard to the provision of open spaces. Public authorities no longer look askance as they once did at proposals brought to their notice by open space societies or private individuals. But the continued existence of societies is none the less necessary in order to be on the watch to take advantage of favourable oppor- tunities, to harmonise conflicting interests, to initiate and put schemes into workable shape, and, it may be, to find part of the money from voluntary sources before bringing them to the notice of one or more public bodies con- cerned. It has begun to be perceived that open spaces are just as needful for the health and welfare of the community as roads or MUNICIPAL AND SANITARY ENGINEERING. OXI drainage schemes. Prevention is better than cure, and fresh air and open spaces are better than hospitals. So far the movement has not been systematised, but has proceeded hap- hazard, and too often the slums of the older part of a town are repeated in the newly-built suburb through lack of forethought. It is therefore very needful, especially in new locali- ties where building proceeds apace, for the local authorities to take time by the forelock and secure open spaces ere too late. Under the Housing, Town Planning, &c., Act, 1909, the need of systematic provision is to some extent recognised, as no town planning scheme will be complete which does not provide for an adequate supply of open spaces. B. H. Otto Cycle.—(See “Gas Enarnes” and “ Or ENGINES.’’) Outfall Sewers.—(Sce ‘‘SeweErace.’’) Oxidation of Sewage is effected naturally by atmospheric oxygen, or artificially by oxidising chemicals. Natura Oxipation.—In this case the gas must first dissolve in the liquid and then must be aided by bacteria, as in sterilised sewage there is little or no action. For the conversion of the carbon and _nitro- gen of the organic substances into carbonic acid and nitrites or nitrates a large quan- tity of oxygen is required; thus to nitrify in a sewage five parts of N per 100,000 will demand about half its volume of air, or about 15 volumes of fully aerated water (7 c.c. O per litre) (see “ Nrrrirication’’). The absorption of a gas by a liquid is hindered by the layer of vapour of the liquid which is constantly form- ing on the surface. This layer is not affected by currents in the liquid as long as the surface is tranquil, and is only penetrated by gaseous diffusion. Therefore, calm and deep water when deprived of oxygen by bacterial changes is only slowly re-aerated by the atmosphere. The absorption is quickened by winds, and by fountains, cascades and weirs, but Fowler 311 OXI found at Manchester that ‘‘ even when air is forced through the liquid for some days the improvement was less than that effected by bacterial filters in eight hours.” Several processes of sewage treatment have included forced aeration, but the results do not justify the expense, and a free natural ventilation of filters is sufficient. Green alge give off oxygen in light and so favour oxidation in waters. One of the chief tests of a sewage or effluent is the amount and the rate of its consump- tion of oxygen (which is only approximately judged by its permanganate consumption), and the Royal Commission on Sewage have pro- visionally laid down that after filtration through filter paper, when it must not show more than 3% of suspended solids, it should not absorb more oxygen, dissolved or atmospheric, than, in parts by weight per 100,000, 0°5 in 24 hours, 1:0 in 48 hours, or 15 in five days. The Commissioners pro- pose for the determination an apparatus devised by Dr. Adeney, but a _ simpler method preferred by the writer and others is to completely fill a number of 250 c.c. stoppered bottles with the sewage (diluted if necessary) or effluent, previously saturated by shaking with air, and to determine the dis- solved oxygen by a rapid process, such as Rideal and Stewart’s modification of Winkler’s, Analyst, 1901, p. 141, successively in the samples at 12, 24,48 hours, or longer, at the same time noticing the odour. ArtiIFicIaL Oxipation.x—For this purpose chlorine and ozone are the only practicable agents. Manganese compounds have been tried, but are precluded by expense and for other reasons, and a similar remark applies to peroxide of chlorine (Bergé). (See “ Nrrrirt- cation,” ‘“Conpy’s Fuuip,” ‘‘ CHLORIDE oF Lime,” ‘‘ Evecrrouysis,”’ and ‘ Ozons.’’) 5. R. “ Oxidium.’—An indestructible highly porous mineral substance used as a filtering material between layers of silica in the Candy Compressed Air and Oxidising Waterworks Filters. It possesses properties somewhat ENCYCLOPAEDIA OF 0ZO similar to those of spongy platinum, and is of voleanic origin. It is treated by a special patent process in order to impart to it the peculiar property of rendering more powerful the oxygen contained in the air with which the water in the filter is first saturated. The atmospheric oxygen is occluded upon the microscopical and interstitial spaces of the “oxidium,” and is utilised for the instan- taneous oxidation of the iron contained in solution in the water treated by these mechanical filters. The “ oxidium’”’ is hard and quite insoluble, and simply acts in con- junction with the oxygen in the air within the filter. Oxychloride is a chemical preparation produced electrolytically by a company named Oxychlorides, Ltd., and used for the deodori- sation of septic tank liquors, &c., as, for example, in cases where the sewage is more offensive than usual through the presence of brewery refuse or other wastes. It has been used at Stone in Staffordshire, and Guildford. Oxynite.—A precipitant for purifying sewage introduced by the Oxygen Sewage Purification Co., Ltd., which has for its active principle compounds of manganese. Ozone in Air.—Ordinary oxygen exists as the molecule Os, but by electric, preferably silent, discharges, or in some slow oxidations, a portion of it is condensed to the molecule O3; the extra atom of O is called its “active oxygen,” since it rapidly oxidises and is removed by sulphuretted hydrogen, sulphur- ous acid, most metals, and organic substances. Certain tests point to ozone in minute quantity as a normal constituent of the atmosphere; more in sea air than inland, at high than at low levels, and little or none in towns ; more after thunderstorms, and least in damp and foggy weather; more in summer than in winter, at night than in daytime, and most at dawn. It is looked for by suspending papers (protected from dust, rain and direct sunlight) 312 0ZO moistened with various solutions. The follow- ing is a table of reagents in use and of the effects on them of other possible constituents of air. a 3 5 & o a I well fe 8 a 5 mb ; > é ZS e3 gees iS ee lee 1 | i 8 oe Ba QP ogee 3 qi og oO o qo © ogo ® Bg) & fe 25 862 a 2 oR 2H FANQ a 2 ° os Q é a > S oO ovo oO ° i/ 2922113 z 2 Ps mn s| 2 Sites’ iil | = 3 3 wu a Seas 8 ee ot 4) (bees 2 | 2 mq 4 a rel aEer a a a] Ee ap oO on fo) > 348% =. one: 2 ¢ | gS e gtr “eg* Pas oe - 5 Hoe o S| SBagteweo Fag sa os °° ov 25 o ogo 4g cSHeSE S Sa gg ea sQ oa fs A Sustoes 1S ae ee “—~N a Sa oS n ~~ ro io +e fa a ® oS 3 s Sw. FB 2 : ° oa oH : = gq go ate ‘Oo BA So ° a a 8s $8 s 3 a oF 3 3 o ds a’g > ~~ @8 €8 d Fea] rH a 92 54 B a oO ope oo o Oo q a rmo> Po ~~ & a a s eS a £2 28 G § 3 7 og ° bo ° 3 b>2 wma @ ~ 2 wh a o& a B= oe gq 4 og 2} wn OL HH ao aoe oS o “eat oS oO H a M ee de 4 ea oH awe wo SG KF wo + 1 Blued at once by gsroo0 by weight of ozone, and slightly by 0:0002 to 0:0003 mgm. (See Report on Ventilation of House of Commons, 1906, p. 100; it was concluded that peroxide of hydrogen, and not ozone was present.) Paper dipped in phenolphthalein and KI is reddened by ozone and browned or blued by C1 or nitrous. 2 Tt is said that browning due to ammonia is distin- guished by not being immediately blued by guaiacum. MUNICIPAL AND SANITARY ENGINEERING. 0ZO Approximate meteorological measurements (“ ozonometry’’) are made by comparison with standard tints produced by known quantities of ozone. Its actual amount may be determined by aspirating a large measured volume of air through a wash-bottle containing permanganate, then through caustic soda, and finally into a solution of pure KI, and titrating the liberated iodine with thiosulphate. Houzeau judged the maximum proportion at ordinary levels to be one volume in several hundred thousand of air. (See “Arr, ATMOSPHERIC, Purity oF.’’) 8. R. Ozone (Purification of Water by).— Ozone is the ideal agent for purifying, since it leaves behind it only ordinary oxygen, and nothing foreign to the water. It was first tried for this purpose by Fréhlich, and Ohlmiiller proved that it energetically attacked bacteria in water from which any excess of inert organic matter had been previously removed. These experiments followed the construction of large industrial ozonisers by Siemens & Halske at Berlin, which firm in 1898 erected an experimental plant at Martini- kenfelde, and afterwards larger installations for the towns of Wiesbaden and Paderborn. Air ozonised to 24 to 8 grammes per cubic metre passed upwards through a tower filled with flints, and met a descending current of roughly filtered water. The cost was about 22d. per 1,000 gallons of water treated, and a very impure water was sterilised down to 2 to 9 organisms per c.c. Earlier, in 1898, Tindal started his apparatus at Oudshoorn, Holland, and in 1895 worked it experimentally at Paris, also at Brussels and Ostend, and it was adopted for limited supplies at several other places. Leon Gérard estimated the cost at 0'45d. per 1,000 gallons. The bacterial reports of Van Hrmengem, Marmier, and Roux were satisfactory. ‘Tindal’s apparatus attained intimate admixture and duration of contact by passing the water and ozonised air, either in the same or an opposite direc- tion, through towers divided by perforated 313 PAI diaphragms “or other equivalent dispositions” ; another form had pulverisers or spray jets; and the partially exhausted air at the exit could be dried, re-ozonised, and returned. Subsequently, in 1897, appeared the Marmier- Abraham? and Otto patents. The former had a mixing tower filled with flints or bricks ; the latter injected the water and ozonised air together by means of a pulveriser, called an “emulsor,” and later (1905) added a column of flints through which a second current of ozonised air was ascending. These patents are now amalgamated, and are at work on the town supplies of Nice and Chartres, and (experimentally) at St. Maur, Paris. Tindal’s previous patent after his death was acquired by De Frise, who has improved the apparatus and process, and has introduced into his plant an ozoniser similar to the Siemens, and an ozone-recuperating circuit. An installation on this principle at the Paris Municipal Water- works, St. Maur, applied to treating sand- filtered Marne water, which is coloured and bacterially impure, was examined by Rideal in September and October, 1908. He found that the sterilisation was effective and the de- colorisation complete without other change, that the working was successful, and that the De Frise process is a satisfactory method of ensuring a standard of purification for a muni- cipal water supply. Miquel’s examination in March and April, 1908, had led to a similar. conclusion. The total cost of the process would be about 0°33d. per 1,000 gallons of water treated, and the actual amount of ozone added at St. Maur was equal to 0°542 gramme of active oxygen per cubic metre (parts per million). This is chemically equivalent to 2°4 parts per million of available chlorine, which was the figure found for tertiary effluent at Guildford. (See ‘‘ CHLORINE Purification’ and ‘‘ Kuecrricrry.’’) S. R. Pail System.—(See “ Priviss.”’) 1 Tried at Lille, 1898, later at Schiedam, and at Moscow in 1901. See also Electrochem. Jnd., February, 1903, and Hclairage Electrique, December 12, 1903. ENCYCLOPADIA OF PAI Paint-Spraying Machines.—When these appliances were first brought out they were much ridiculed on the ground that it was impossible to apply paint serviceably except by means of the brush ; but it has been shown that this is quite a mistake, and in certain cases,notably when the surface is rough, a great deal of saving may be effected by the use of a good paint-spraying machine. If a perfectly smooth and highly finished surface was required, such, for example, as a front door of a private residence, a paint-spraying machine would be useless, but for bridge work, lime- washing, rough brickwork, such as railway arches used for storage, &c., andin many other cases, the paint-spraying machine possesses many advantages over the old-fashioned plan. It will be understood that the paint or lime- wash is forced by means of compressed air from the nozzle of the apparatus into a fine spray, which becomes more diffused the further away the nozzle is held from the surface, but the inequalities and holes are all well covered in a short time, and in a manner which would be impossible if a brush were used. Paint- spraying machines are now made with two nozzles side by side, and by means of their use a surface may be painted or whitewashed in a remarkably short space of time. A. 6. J. Paints and painting.—General Survey— Washable Distempers—Painting Iron—Removing Paint.—The municipal engineer usually con- siders paint chiefly from the point of view of its protective qualities against decay, and not for its decorative value. The base of most paints used for white work is white lead, but on iron work other pigments are generally preferred. ‘The preference for white lead is based upon the fact that this pigment, when ground in linseed oil, possesses the quality known by painters as “body,” which means the property of hiding, or masking, the surface to which it is applied. This, however, has really nothing to do with the actual durability of the paint, because one which has little or no body might resist the destroying action of atmospheric conditions, water, chemicals, &c., 314 PAI much longer than the white lead. Still, the object in painting is as a rule to obscure the surface, to hide the knots in the grain of wood, and the paint which has the most body effects this object in fewer coats than the one which has less body. For purely protective purposes it is now generally recognised that an admixture of pigments produces the best results, and that, while there is no ideal pig- ment, or one which possesses the whole of the virtues, yet, where one falls short of perfection, the deficiencies may be made up by adding the proper proportion of another. Generally speaking paint may be said to be composed of either white lead, zinc oxide, or other white pigments, mixed with the necessary colour pigments to produce the desired shade, tint, or hue, or of certain natural earth colours, such as ochre, sienna, oxide of iron, &e. In most cases these pigments are produced in the form of a dry powder, which is ground in a vehicle, almost invariably linseed oil. The durability of such paint depends principally upon, first, the quality of the linseed oil, that is to say, whether it is pure and of the best grade, secondly, upon the degree of fineness to which the pigment is ground, and, thirdly, a thorough admixture of the whole. The fine- ness of pigments is a point to which much attention has been drawn in recent years, but it is well recognised that within reasonable limits the finer ground the pigment is, the better paint it makes. The question of purity may almost be considered as a side issue ; taking white lead as an example, there can be no doubt that exceedingly finely-ground white lead mixed with 25% of barytes will probably be very much more durable than a pure and coarsely-ground white lead. Painters, as a rule, purchase their white lead or other pig- ments in the form of a stiff paste, and they then thin it for application by means of a brush by adding a sufficient quantity of linseed oil, either raw or boiled, and American turpentine. The proportion of these “ thin- ners,” as they are technically called, depends upon the condition of the surface to which the paint is to be applied. If it is absorbent, MUNICIPAL AND SANITARY ENGINEERING. PAI such as plaster or open-grained wood, much more oil and turpentine will be required than is the case with iron, which is looked upon as practically non-absorbent, or at least after the first coat. Driers are used to facilitate the absorption of oxygen from the atmosphere, and this quickly affects the drying or hardening of the coat of paint. The proportion of driers used varies largely with the kind of pigment. Vandyke brown and the blacks require a very large proportion of driers, while red lead is in itself a dryer and requires no addition. White lead is also, to some extent,a dryer, and very little additional driers should be em- ployed. The quantity of turpentine is, perhaps, not so important as the other con- stituents of the paint, because all, or at least the greater part of it evaporates when the paint dries. Still, too much turpentine would render the paint too thin for practical purposes. Only recently, American turpentine was looked upon as a sine qua non in all good paint, but the continued high price of the product has caused the paint manufacturer to look very closely into the question, and what is known as “white spirit” in its various forms, frequently mixed with a proportion of American turpentine, is now successfully used as a substitute. White spirit, it may be remarked in passing, is petroleum distilled in such a manner that it has no oily residue, while, at the same time, it does not evaporate so rapidly as to interfere with the manual application. In many cases the municipal engineer will desire to use paint which is simply preservative, quite irrespective of its “body,” or covering, and in such a case pro- bably a mixture of white lead and barytes in equal proportions will be as effective as any- thing. Zine oxide may also be employed for the same purpose, but the price is slightly higher than white lead, although lower in reality, because it spreads over or covers, when made up into paint, at least 25% greater surface. Red lead possesses advantages when hard wear and tear has to be resisted, as, for example, in painting barrows, carts, &e. (See “ Rep Leap.”) The protection of ironwork is 315 PAI obviously of great importance, and there are various special paints made for this purpose. Some engineers consider oxide of iron the best protective paint for iron, while others are just as strongly in favour of red lead. The Tower Bridge was repainted from end to end with white lead only, although this is contrary to the usual practice. There is at this time a strong tendency towards the use of graphite paints, z.e., those made from plumbago ground in oil. The pigment used for this purpose is often mixed with silica and various other materials. Graphite paint is very exten- sively used in the United States of America, and other places, and it appears to be certain to succeed equally well here when its merits become more widely known. In a table drawn up by Mr. J. Cruikshank Smith which gives the comparative durability of various paints, it is clearly shown that graphite paints are superior to all others when the following points are taken into consideration : —First, the prime cost; second, the average time the paint will last, 7.e., the period before repainting will be necessary; third, the spreading capacity—that is the surface a given quantity will cover when made into paint ; and fourth, the cost of application. It cannot be too strongly urged that the actual cost of labour in applying a paint is a very material item in determining its economic value. Some authorities place the cost of application at two-thirds, but, even taking it at one-half the cost of the paint, it will be seen that itis by no means economical to use a paint which requires to be frequently renewed. Of late years the subject of painting has been dealt with on a scientific basis, and the old idea that the best paint for all purposes is necessarily a mixture of white lead, linseed oil, anc turpentine has been shown to be erroneous, and engineers are recognising the fact that a paint which would be very suitable and cheap for one purpose might be wholly unsuitable for another. It is also becoming recognised that an admixture of pigments, which has already been referred to, is a plan by means of which the best and most econo- ENCYCLOP.EDIA OF PAI mical paint can be obtained, always provided that the thinners are of the proper kind and are used in the right proportions. There is also a tendency towards a departure in another direction, viz., that of varying the con- stituencies of the several coats of paint. 2 Fic. 25.—Nail Welt. Fic. 29.—‘‘ Shute” Discharge over R. W. Head. Fic. 26.—Roll to Lead Flat. SF / ) jares =| Fic. 27.—Roll Ends to Lead Flat. Fic. 30.—Section of Roof Cesspool with Overflow. 332 PLU be had to the width of the sheets of lead to be used or waste may occur; the width of the bays should be arranged to enable a sheet of lead to be cut down the centre ; with a standard (7 ft.) sheet this would be 3 ft. 6 in. and the distance between the rolls should be 2 ft. 8 in., Fic. 31.—‘ Bird’s Mouth”’ Outlet to Cesspool. allowing 3 in. for “undercloak ”’ and 7 in. for * overcloak.”’ Roor, Cesspoons, anp SHoots.— Where pos- sible, the best arrangement for discharging the water from lead-lined gutters is to allow the gutter to pass through the wall and dis- charge over a hopper head, forming a “ shoot.” Where the foregoing is undesirable, cesspools Fig. 32.—Lead Cesspool to Asphalt Flat. may be used; the outlet pipe should be wiped in, and an overflow—also wiped in—provided ; care should be taken to keep the overflow below the drips discharging into the cesspool. Lead cesspools are frequently provided to asphalt flats and gutters; by their use a sound MUNICIPAL AND SANITARY ENGINEERING. PLU connection may be made between the outlet pipe and asphalt. CovERING Stone Cornices.—Stone cornices, especially when of large dimensions, are frequently covered with lead. To allow of movement where the cornices weather out- wards it is best to turn the lead up on the face of the wall, and not bed the same as the erection of the wall proceeds. The pieces of fl oe Copper Tack Leaded in fed mu Fie. 33. Fig. 34. Lead Coverings to Stone Cornices. lead may be joined by welts, raised or sunk. Where cornices weather inwards, a channel or gutter is formed into which the lead is dressed ; if the cornice will permit of shallow drips being formed it is preferable, as it permits the lead to be used in smaller pieces than when drips are not possible. To prevent the lead being blown up soldered dots are sometimes used; these, however, hold the lead too rigid, 333 PLU resulting in a fracture around the edges of the dots; a much better method is to form lead dots similar in appearance to rivets, or to run in lead “ under tacks ” and turn the lead under the same as in securing the edges of lead on dormer tops. W.F. Plumbism.— Another name for “lead- poisoning” (see article ‘‘ Warer Svuppty,” action of water upon lead). Polarite (see “Internationa, Process or Sewace Purirication”’) is the commercial name for magnetic spongy carbon which is obtained from a certain kind of iron found in parts of South Wales. This material has been tested by Sir H. Roscoe, F.R.S., who has stated that the “ porous nature of the oxide, its com- plete insolubility, and its freedom from rusting, constitute its claim to be considered a valuable filtering material.” Population, Estimation Of.—In Great Britain and Ireland a census enumeration of the population is undertaken every ten years, and it is therefore only once every ten years that we have the exact numbers and ages of those living in any community. During inter-censal periods the population has to be estimated, and there are several ways of effecting this. One simple method of obtaining a close approximate estimation involves an enumeration of the number of inhabited houses in the district (a figure obtained from the rate books), and allot- ment to each such house of the average number of inhabitants found to be occupy- ing a house at the last census. The average number of persons per inhabited house may vary from 4°5 to 9 according to the size of the house and the social class of the occupants ; according to the census of 1901 it was 5°19 in England and Wales. In addition to the number thus calculated one individual should be allowed for each empty house, in order to account for caretakers and their families. Another means of estimating the population ENCYCLOPADIA OF POP is by the birth-rate, where this remains fairly constant for a series of years ; under the latter circumstance and when applied to large popu- lations the computation is found generally to closely approximate to the truth. By this method the population is represented by the number of registered births in the year multi- plied by a thousand and then divided by the mean birth-rate for the previous ten years. The practical drawback to this method is that the population of the current year cannot be estimated, inasmuch as the data for the calculation are not available except in respect of a past year. On the whole the method used by the Registrar-General is the most satis- factory and serviceable. It involves the use of logarithms and is carried out as follows :— from the logarithm of the population according to the last census is deducted the logarithm of the population from the immediately preceding census. The difference will indicate the logarithm corresponding to ten years’ increase in the population. A tenth of this figure will represent the logarithm of one year’s increase. Now assuming that it is five years since the last census was taken we shall then have to provide for five years’ increase in the popula- tion, together with an extra quarter of a year’s increase, in order to take into account the fact that the census was taken at the end of the first quarter of the vear and the population is always estimated to the middle of the year. The logarithm of one year’s increase is there- fore multiplied by 54 and the result represents the logarithm of 5} years’ increase ; this, added to the logarithm of the population by the last census, gives us the logarithm of the population five years later, and the number corresponding to this logarithm furnishes the calculated population. This method assumes that the population is increasing or decreasing, since the last census, in the same ratio as between the last two censuses, and it is here that a fallacy may arise: and the estimates of popu- lation so obtained often present a considerable departure from the actual truth when fresh census figures become available for comparison. H.R. K. 334 PNE Pneumatic Sewage Lifts. (See “ Esuc- TORS.” Precipitating or Settling Tanks.—In any system of sewage treatment the first stage towards purification is the removal of the grosser solids such as rags, feces, orange peel, sticks, miscellaneous small articles thrown down the drains, and road silt, sand, &e. This is done by means of preliminary screening, followed by precipitation in tanks either with or without the use of chemical precipitants. Such tanks are constructed either upon the ‘‘absolute rest” principle (see ‘‘ ABsoLuTE Rest Precipiration Tanxs’’) or upon the “‘ continuous flow” method. The latter is the plan most generally adopted, as it economises tank capacity and fall in con- struction. The sewage should not pass through the tank in less than two hours, and suitable chemicals are requisite for producing the clearest of effluents. For purely domestic sewages such tanks may be provided with a number of submerged cross-walls carrying iron screens, and these, together with scum- plates, remove sufficient of the suspended solids preparatory to the second stage of the purification process without entailing the expense of chemical precipitants. It may be worked either intermittently or con- tinuously, and should be cleaned out once every three days, or at least once a week. If not cleaned frequently the deposited sludge soon ferments, generates gas, and foul matter is carried to the surface of the liquid, which spoils the quality of the effluent. Taking the maximum sewage flow per hour at 8°/, of the daily flow, and allowing for a minimum of 2 hours’ stay in the tank, the capacity should be 16°/, of the total sewage to be dealt with. To meet practical working conditions this volume should be multiplied by 8, which would thus bring the total tank capacity up to say 50°/,. This should be divided amongst three or more independent tanks, so that whilst one tank was empty for cleaning, two would be available for the ordinary sewage and fluctua- tionsin storm flow. It will be obvious that the MUNICIPAL AND SANITARY ENGINEERING. PRI division of the tank room into several small tanks will be more serviceable in practice than the same capacity in larger units. If the tank liquor is to be passed on to filters formed of fine grade material, the period of flow through the tank would require to be increased to 10 or 12 hours. Pre- cipitation tanks are used “in parallel” or ‘‘in series.” With ordinary sized tanks the minimum rate of flow is obtained by the former method. Where tanks are worked ‘in series,” after a certain percentage of solids has settled out, no great advantage is gained by passing the sewage through another tank at the same rate. For further deposition of solids quiescent settlement is necessary. For various special forms of settling tanks, see articles on ‘‘ DortmMuND Serrning Tanx,” ‘“ CosHam PRECIPITATING Tank,” “Ive’s Tanx,” “Canny SErrLine Tank,’ and ‘‘Dunprum Serrninc Tank.” W. 4H. M. Precipitation Tanks. (See “ Szwace Disposau.’’) Privies.— Frequently made use of for cottage property in country districts in the absence of water-closets or suitable conditions for earth closets. They are of two kinds: privies proper, intended for excrementitious matter only, and privy-middens, provided for the disposal of ashes and general refuse in addition to excreta. In the former the excreta is collected in a pail or other suitable remov- able receptacle which by the Model By-laws is restricted in capacity to a maximum of 2 cub. ft, so as to insure frequent emptying. The privy apartment should be provided in the open and have no direct communication with the dwelling-house. The floor must be of non-absorbent material and at least 6 in. above the surrounding ground, while that portion under the seat on which the pail rests must not be less than 8 in. above the ground. The apartment should be well lighted and must be ventilated by at least one opening communicating directly 335 PUB with the open air and placed as near as possible to the roof. The walls of the space enclosed by the seat must be impervious, and the pail should be removable from the outside. Privy-middens are usually provided with a fixed receptacle or non-absorbent pit, which by the Model By-laws is limited to a capacity of 8 cub. ft. to ensure at least weekly removal] of its contents. This pit is most conveniently so built that one-half is situated in the privy apartment, while the other half projects outside the building. Over the former the seat is fixed, over the latter half a flap is provided through which ashes and other dry house refuse are thrown in. That this should be regularly mingled with the excreta is important. A coarse sieve may be provided in the opening for the purpose of screening the ashes from the cinders. With the excep- tion of the receptacle, the construction of the privy apartment does not differ from that above described. Public Health. (See “Hycrenz anp Pustic Heatrtu.’’) Pumps and Pumping Machinery.— The principle of the action of the pump, like that of the siphon and other similar hydraulic applications, depends upon the balance of weight between a column of water of a cer- tain height and the atmosphere. The best results are obtained from 10 ft. to 15 ft., and with high speeds the shorter the suction the greater the efficiency. The different classes of pumps here illus- trated are the common suction pump (Fig. 1), the lifting pump (Fig. 2), the single-acting piston pump (Fig. 3), the plunger pump (Fig. 4), the horizontal plunger pump with air vessel (Fig. 5), the double acting piston pump (Fig. 6), and the combined plunger and bucket pump (Fig. 7). In all of them the suction valve must be within the usual limit of height from the surface of the water to be raised, but by a suitable arrangement of valves within the barrel of the pump the water may be lifted to any desired elevation. Thus in Fig. 2 it ENCYCLOPADIA OF PUM will be observed that the common suction pump is converted into a “lifting pump” by attaching a rising pipe in the place of the ordinary spout and placing a valve at the EP Wen Fic. 1.—Common Suction Pump. lower end of this pipe to prevent the return of the water. As this modification causes con- siderable pressure within the pump-barrel, its upper end is securely covered down and the Fic. 2.—Lifting Pump. piston-rod works through a stuffing-box as shown. It is clear that each rise of the piston forces some portion of the contents of the pump-barrel upwards into the rising-pipe, also 336 PUM that the power required to work the pump must be sufficient not only to fill the barrel from below but also to lift the column of water in the rising-pipe. The retaining valve at the foot of the rising pipe is not necessary to the action of the pump because, the barrel being full, the suction valve retains the water, but it is employed as an additional check and relieves the valves below it of excessive pressure and prevents leakage. “ Srurrine-Box.”’—An enlarged sectional view of a ‘“‘stuffing-box” is given in Fig. 8. It may be described as a device for rendering a joint impervious where there is a hole through which a movable cylindrical rod or plunger, such as the piston rod of a steam engine or Fic. 3.—Single-Acting Piston Pump. the plunger or rod of a pump, slides to and fro, and which requires to be kept water or steam-tight under pressure. Generally, it consists of a box or chamber, made by an enlargement of part of the hole, thus forming a space around the piston rod for containing packing which is pressed home and made to tightly fill the space by means of a sleeve, called a “gland,” fitting loosely around the rod, and pressed down upon the packing by tightening the bolts shown in the illustration attaching the gland to the box. The single acting piston pump (Fig. 3) is used to force water up to any required height. It differs from the lifting pump in that the piston contains no valve and the top of the M.S8.E. MUNICIPAL AND SANITARY ENGINEERING. PUM pump barrel need not be covered down. A little water poured in at the top of the barrel makes the piston air-tight. When the piston is raised, the valve at the foot of the rising- pipe closes and the suction valve opens, admitting water from below into the barrel. Upon the return of the piston downwards, the suction valve closes and the retaining valve (at foot of rising-pipe) opens and water is forced up the pipe. In the plunger pump (Fig. 4), the delivery is on the down stroke as in the case of the pump last described, and the action of the valves is also similar. In this case, however, a solid plunger is substituted for the piston, whereby the expense of turning the cylinder Fic. 4.—Plunger Pump. true is avoided, and the plunger also better resists the wear from grit, &c., within the pump barrel. The top of the barrel must, however, be tight, and the plunger therefore works through a gland and stuffing-box. At each stroke this pump raises a volume of water equal to.that of the plunger. A plunger pump with air vessel attached is. shown in Fig. 5. The object of this is to make the working of the pump smoother and the flow of the water more uniform. ‘The air vessel is attached at the foot of the delivery pipe, and, during the inward stroke of the plunger, part of the water leaving the pump- barrel passes into the delivery pipe and a 337 Z PUM portion into the air vessel and compresses the air contained in its upper end. On the out- ward stroke the air thus imprisoned and com- pressed exerts a force upon the water and forces it out into the delivery pipe, thus main- Delivery Pipe Fic, 5.—Plunger Pump with Air Vessel. taining a more uniform flow, and acting as a sort of cushion to absorb the otherwise marked effect of each stroke of the plunger. An air vessel also economises the power employed to work the pump as it imparts to the water a constant forward motion. In the double-acting piston pump (Fig. 6) there are two suction valves and two delivery Fic. 6.—Double-Acting Piston Pump. valves placed as shown in the figure, all open- ing to the left. Water is delivered upon both the up and down strokes. On the up stroke, water enters the pump barrel through the suction valve D, and passes into the rising-pipe through valve A. On the down stroke, water ENCYCLOPEDIA OF PUM is forced through valve C, and enters above the piston at valve B, thus maintaining a constant discharge. The double-acting pump shown in Fig. 7 ‘ig a combination of a plunger pump discharg- ing water on the inward stroke and a bucket qm pg Gland Rising Fic. 7.—Combined Plunger and Bucket Pump. pump discharging on the outward stroke, thus giving a continuous flow. The area of the cross-section of the plunger is made half that of the pump barrel, so that on the up stroke half the water raised by the bucket goes to fill the space left by the plunger and the other J Fic. 8.—‘‘ Stuffing-Box.” half is passed up the rising-pipe. On the down stroke the plunger displaces half of the water raised by the bucket and forces it into the delivery pipe. This form of pump was invented by Perkins, introduced at the Lambeth Waterworks in 1848, and is exten- sively used in most of the large waterworks. 338 PUM The working barrels, buckets, and valves of pumps should be made of brass, gunmetal, or phosphor-bronze, as, though initially costly, these metals will be found to be more durable and give greater satistaction in working. They are not liable to corrosion by the action of the water, will be found more accurate in their operation than iron, and are less liable to injure the leather attached to the bucket and valve, which are parts frequently requiring attention and repair. In foree pumps the Fig. 9.—Clack Valve. packing of the piston or box is an important matter, and is usually made of waste tow soaked in tallow and rammed tight, or, where there is great pressure, cup leather packings are employed. In the close-topped pumps working through a stuffing-box the rising- pipe and suction are frequently made about two-thirds the area of the working barrel. In the case of quick-running pumps the diameter of the suction should not be less than that of the working barrel, and every means should Vi Fic. 10.—Conical Valve. be adopted to enable the water to reach the pump very readily. The force required to work a pump, or the pull on the pump rod, is equal to the weight of a column of water having a base equal in area to that of the bucket or plunger, and a height equal to the height to which the water is being raised. For hand pumping from ordinary wells under 30 ft. in depth, a convenient size of 339 MUNICIPAL AND SANITARY ENGINEERING. PUM pump for one man to work is a 4 in. working barrel with a 9-in. or 10-in. stroke. This pump will throw 24 gallons per minute froma 20-ft: well. Between the depths of 30 ft. and 70 ft. a 384 in. diameter working barrel with a 9-in. or 10-in. stroke may be employed, but for wells over 70 ft. a strong three-throw pump consisting of three working barrels standing side by side upon a horizontal valve- box common to the three barrels, and worked from the top by means of pump-rods actuated ) Fic. 11.—Flap or Hinged Valve. 2 = = by a three-throw crank, wheel and pinion, driven by either horse-gearing or steam oil or gas power, will be found the most suitable type. Pump Vatves.—Pumps are placed between the water to be raised and the point of delivery, and have, therefore, to perform two distinct operations, viz., to suck or draw the water into the pumps, and then to force it to the required elevation. Valves are therefore a necessity for the control of the water so raised, their function being to open freely to the forward Fig. 12.—Conical Disc Valve. motion of the water and to close against its return, and so prevent loss of the work done by the pump, piston, or plunger in giving the water its forward motion. The valves of every pump thus form a most important part of the apparatus and require careful attention in their design and maintenance, otherwise a large proportion of the power expended in pumping will be lost through excessive friction or “slip,” and the cost of pumping per 1,000 Zz 2 PUM gallons raised will become excessive. To pre- vent slip the valves should offer little resistance to the passage of the water in one direction and close quickly and tightly in the opposite direction, but without shock. The construc- tion of the valves of a pump largely determines the speed at which it may be worked. For fast working low lifts are necessary. The weight of a valve should be sufficient to close without knocking, and should at the same Fiac. 13.—India-rubber Dise Valve. time be light enough to be lifted without great resistance to the water. In the case of high lifts the weight of the valve is very generally estimated at 1 lb. per square inch of area, equal to a head of about 24 ft. of water, whilst for low lifts it may be from 1b. to 3 1b. per square inch of area. A small lift in a valve is desirable, as it enables the valve to close quickly, thus reducing shock as well as slip. The velocity of the water through a Fic. 14.—Butterfly Valve. valve should not exceed about 5 ft. per second, and in a well-made pump the slip should not exceed from 5 to 7 %. Valves of the “‘ butterfly” type allow more slip than “‘ double-beat”’ valves. Various classes of valves are shown in Figs. 9 to 16; generally speaking, they may be divided into two classes, viz., hinged or door valves, and spindle valves. The ordinary ‘clack ” valve and “conical” valve as used in ENCYCLOPADIA OF PUM the common suction pump are shown in Figs. 9 and 10. The flap or hinged valve consists of a flap of stout leather stiffened with metal plates and working on a hinge. Fig. 12 shows a conical metal disc valve work- ing on a central spindle. The conical edge Tria. 15.—Mitre Valve. fits accurately upon a corresponding seating sloped at an angle of 45° with the valve axis. The lift of the valve is limited by a stop placed above it, and the amount of the rise should not exceed one-fourth of the diameter of the valve. An india-rubber disc valve is given in Fig. 18; it consists of an open Fic. 16.—Double-Beat Valve. grating covered with a disc of india-rubber surmounted by a perforated guard, against which the force of the passing water raises the india-rubber. On the return of the water pressure downwards the india-rubber is forced back tightly upon its seating. The apertures in the grating are made at an angle, thus producing a circular motion in the valve as 340 PUM the water passes through, which prevents the valve falling in the same position and cutting the rubber. Strong dark-blue rubber is used for heavy work. The “butterfly” valve (Fig. 14) is formed of semi-circular discs hinged at the centre as shown, and is made of leather and metal plates similar to the hinged valve. The mitre valve (Fig. 15) consists of a circular metallic dise with conical face. The short stop above the valve limits its lift, and feathers below guide the valve on to its seat. ‘he ‘‘double-beat’’ valve (Fig. 16) is an extensively used form of valve, and was designed to overcome the great wear and tear of the flap valves. It consists of two circular rings on which the upper and lower parts of the valve respectively beat, thus forming the “double beat,’’ as illustrated. The beats are of lignum-vite, leather, or white metal, and are fixed to the valve and beat on.a gun-metal seat. Owing to the two openings for discharge, this valve has the advantage of a small lift, and the shock caused by closing is thus reduced in consequence. The webs connecting the parts together, being made at a slight angle, cause the valve to rotate during the passage of water, which tends to keep the beats perfect and to prevent grooving. In the double-beat valve adapted for heavy lifts the bottom beats are usually of gun-metal and the upper ones may be of hippopotamus hide or similar leather. More complicated valves than the foregoing are also used, such as three- and four-beat valves, made on the same principle as those referred to above, and taking their names according to the number of the beats. The Riedler valve has been largely used on the Continent with much satisfaction, and has also been employed in four compound pump- ing engines supplied to the Grand Junction Water Co.’s works at Hampton. In ordinary pumping engines of this class it is difficult to run fast owing to the concussion and vibration occasioned by the sudden closing of the pump valves at the end of each stroke. In the Riedler engines the pump valves are mechanic- ally closed much in the same way as the valves MUNICIPAL AND SANITARY ENGINEERING. PUM of a steam-engine, and by these means the difficulty of fast running is overcome. In the design of pump valves it should be borne in mind that all types break up and impede the advancing water column to some extent in passing through the pumps, and that in this way friction is caused and a certain proportion of power of the engines is consumed. The object to be aimed at, there- fore, is to reduce these losses to a minimum by avoiding unnecessary division or deflection of the water by the valves and short bends or contractions in the water passages. Formerly, the increase of the sizes of valves in the building of large pumping engines gave rise to considerable shock and vibration upon the valves coming upon their seatings, the impact of which often made the whole machinery and buildings shake. This difficulty led to the practice of dividing the valves into nests of the double-beat form, and in many large works the valves are of the four-beat class, or Husband’s model. The valves of some pumps are also divided into nests of a dozen or more of the rubber-dise type as above described, and by this means the shock of the water- hammer produced when the valve falls on its seat is reduced, but each sub-division increases the frictional resistance to the flow. Pumps of the ‘‘ Worthington ” type and many modern steam fire-engines are fitted with nests of rubber-disc valves, this class being largely used where the motion is rapid and the pressure great. For general waterworks use valves of the “Cornish” class are in great favour, but the more complicated modifications of this type sometimes give trouble from noise, vibration, sticking, and undue friction. For metal valves flat faces are as a rule better than conical faces, especially if the water is gritty. Sharp angles or bends should be avoided and all connections made with easy curves. Where bends are unavoidable air cocks should be provided for the escape of the air and to insure good circulation of the water. Clack valves are sometimes used for low lifts on small pumps where the water contains much 341 PUM sand, and when this class of valve is used for larger pumps a small valve is provided on the top of the large one to reduce the shock, as the small valve, on account of its smaller area, closes and opens first, and so relieves the impact of the water. MiscELLangous Types or Puwps.—In addi- tion to the classes of pumps already referred to, there are several kinds largely employed for various purposes, e.g., the centrifugal, the pulsometer, borehole pumps, the semi-rotary, and the high lift turbine pump. CenrrirucaL Pumps are much used where large quantities of water have to be raised through low lifts, such as for the drainage of low-lying land, as in the fen districts, emptying docks and reservoirs, raising large quantities of storm-water, pumping on to filter beds, and other like purposes. Centrifugal pumps are driven at a rapid speed by means of good wide belts from shafting, or by a steam-engine combined direct with the pump. Having no valves, the centrifugal pump lends itself well for the pumping of sewage or other liquids carrying a large proportion of solid matter in suspension, but it is desirable to exclude such matters as pieces of yarn, rope, cloth, &c., by means of a coarse screen or grid on the suction. The duty of the centrifugal pump below 20 ft. lift compares favourably with any other class of pump, but above that height the efficiency falls off. A maximum efficiency of about 70 %/ is reached at from 15 ft. to 20 ft. lift. The speed of the water should not exceed about 8 ft. per second, and sudden changes in its path through the pump should be avoided as far as possible. Tue Putsomerer Pump is an indispensable appliance for contractors’ use upon engineering works where large quantities of dirty water may have to be removed. It is easily and quickly suspended in almost any position, and is operated by the admission of steam from the top past the steam ball valve. This presses upon the surface of the water con- tained in the body of the pump, thus depressing it and driving it through the discharge outlet into the rising main. The steam pressure at ENCYCLOPAIDIA OF PUM the pump should not be less than from 20 lbs. to 30 lbs. per square inch for lifts from 20 ft. to 40 ft., and from 380 lbs. to 50 lbs. for lifts between 40 ft. and 80 ft. Borenoue Pumps are fitted in a working barrel inside the steel lining of the well and placed at a sufficient depth to insure a good draught of water. The pumps are commonly worked from a bell-crank in the engine-room by means of iron guides steadied by guides working against the lining of the well. Such pumps should be drawn for inspection and overhauling at periodic intervals, as the wear and tear is often considerable. Tue Sewt-Rorary Wine Pumps of the “Willcox” type are very useful for temporary purposes, and have a high capacity compared with the small power required. The pumps suck vertically a height of 25 ft. with the use of a suction or foot valve, and will deliver to a vertical height of about 110 ft. Piston on Pruneer Speep or Pumps.—The possible speed of the plunger depends upon the proper filling of the pump during each single stroke. The readiness with which such filling takes place depends greatly upon the size and design of the suction valves, and upon the length of the stroke. The length of suction, suitable plunger speed and length of stroke, and the good design of the pump valves, are first essentials to the smooth and satisfactory working of pumps, freedom from “ knocking,” and other troubles. It is impossible to lay down any fixed rule as to the plunger speed of a pump, since this will vary with the different conditions to be met. Usually the longer the stroke, and the greater the ease with which the water reaches the pump, the greater the piston speed per- missible. A high piston speed in an engine tends to economical working, as the cylinders, having less time during which to become cooled between the successive admissions of fresh steam, give less loss from initial con- densation. In order to secure the advantage of a high steam-piston speed with a low 342 PUM pump-plunger speed, gearing is frequently resorted to, but usually with some unavoid- able sacrifice of mechanical efficiency. The mean piston speed of an engine is ascertained by multiplying twice the stroke in feet by the number of revolutions per minute. Thus, an engine having a 40-in. stroke and making 23 double-strokes per minute, has a piston speed of 153°4 ft. per minute. Vertical direct-acting pumping engines usually run at from 20 to 25 revolutions per minute. Pounding in pumps is a common trouble and may arise from too sudden closing of the valves, through the valves having too great a lift, or from other defects in the water cylinder. Want of lead in the steam valve, insufficient clearance, defective piston rings, and worn bearings may also produce the pounding effect. Too heavy a duty for the pumps is another cause. Packings to piston rods of steam cylinder and to pump pistons is a practical detail of much importance. Neglect on this point may lead fo serious scoring or grooving of the piston rod, to undue friction on the rod causing waste of power, to leakage of steam, and other defects. Some of the materials which have been used for steam cylinders are asbestos, spun yarn, hemp, French chalk, metallic packing, and ordinary cotton rope with a French chalk core. With all packings the stuffing-box should not be over-filled, and the gland should be screwed up evenly all round. For the packing of pump pistons leather of the best quality, layers of cotton and rubber, and metallic rings of cast iron, steel, and gun- metal are used. Springs are employed to expand some of the metallic packings, but these require careful adjustment or an uneven and unnecessary frictional loss may be caused. For large pumps plaited hemp makes a good packing, and for small pumps ordinary gasket is used when well greased with tallow. Sreiection or Pumpinc Macuinery.—In the great majority of waterworks the provision of the most suitable and efficient class of pumping machinery forms a leading factor in their proper equipment and design. MUNICIPAL AND SANITARY ENGINEERING. PUM Great variety exists in the class and arrange- ment of machinery which may be employed, and in practice each case will require to be separately considered in the light of the special circumstances to be met. The engi- neer must take into account the question of the most suitable type of machinery for the case in point, the capital cost of the engine, pumps, boilers, buildings, foundations, and other accessory works; and also the probable annual working expenses which will be incurred in wages, fuel, repairs, and other charges. The class of motive power to be adopted and the convenience for the delivery of fuel to the site should also largely influence the decision. It is usually advisable to carefully compare the cost of alternative proposals, and for this purpose the various items of yearly expendi- ture should be capitalised and added to the initial cost of the buildings and plant involved by each alternative proposal, so that a comparison upon an equal basis may be made. In motive power the various alternatives - lie mainly between steam, gas, oil, and elec- tricity—the final choice depending largely upon the size of the water undertaking, the relative prices of coal, gas, or oil delivered to the site, and other special facilities which may operate in favour of any one of these agents named in preference to others. Where there is a large amount of pumping to be done, high pressure steam used expan- sively will usually be found to be by far the most economical and reliable motive power ; but in the case of small rural works, or at small isolated stations of larger undertakings, gas and oil engines will frequently be found the most serviceable and convenient agents to employ. The latter will also be found advantageous in cases where the pumping is intermittent and continued for short periods only according to requirements. In every pumping works it is necessary to have a certain proportion of “stand-by” plant in order that the regular supply to the town may not be interrupted in the event of a temporary break-down of an engine or any 343 PUR part of the machinery. In small works it is customary to have the pumping plant in duplicate, but in large stations this is not necessary as here the pumping power is usually made up of a number of pumping units, the break-down of any one of which will, as a rule, not seriously incommode the supply. In such a works the stand-by plant need not be more than one-third, one-fourth, or even one-fifth of the whole, according to the size of the works, the power of the pumping units employed, and the amount of high level storage between the pumps and the water consumer. Another important question affecting the amount and arrangement of pumping power and the quantity of stand-by plant required is the system upon which the supply is delivered into the town. Where the water is pumped-direct into the mains, the pumps must be fully equal to the maximum rate of supply and must closely follow the fluctuations of demand during the different periods of the 24 hours. There must be ample stand-by plant, and the whole pumping arrangements and staff must be ready to meet any emergency promptly, whether it be from break-downs, excessive consumption through drought, leak- age, fire, or other causes. A more satisfactory mode of supply, and one entailing less anxiety at the pumping station, is that in which the engines deliver into a high-level storage reservoir containing a day or two’s con- sumption, or oftentimes much less, upon which the town may draw during a temporary cessation of pumping. Again, where there is no such reservoir, the fluctuations of con- sumption are balanced for brief periods in some cases by the use of stand-pipes and water-towers. W. H. M. Purification of Water. (See “ Finrra- TION.” Rain-water Cistern, Venetian.—Rain- water reservoirs are the chief sources of water supply along extensive tracts of the Italian coast. In most parts of the country the reservoirs, like those of the East, are entirely ENCYCLOP.EDIA OF RAI or partly sunk in the ground and covered over, the rain from roofs passing through strainers before entering the cistern. The Venetian type is an improvement on the above. ‘I'he cistern is divided into two equal sections by means of a partition descending from the domed or flat roof to within a few inches of the bottom. Both sections are half filled with filtering materials, generally consisting of three layers of equal thickness—sand being at the base, protected by a layer of fine gravel, with coarse gravel on the top. Rain passing through strainers enters one section of the cistern, and passing downwards through the filtering material makes its way through the slit at the base of the partition into the second division rising through the filtering materials. The water is raised from this section either by means of buckets, an opening in the roof, generally arched over to afford protection, being provided; or, better still, by means of a pump. A sealed manhole should be placed in the roof of each section. In this country, where the air is apt to be contaminated with dust and soot, it is advisable to use a “rainwater separator” (q. v.) in place of an ordinary strainer. Rainwater from a cistern built on the above principle by Dr. Poore at Andover was analysed chemically and bacterioscopically by the Royal Commission on Sewage Disposal in 1901, with the following result :— Parts per 100,000 spy Wetcur. Ammoniacal nitrogen . . 0°064 Albuminoid 5 ‘ : : . 0020 Nitrite . 0°033 Nitrate ‘ . 0°086 Oxygen absorbed from jat once . 0°23 permanganate at 80° F./ after 4 hours 0°48 After incubation at 80° F.) at once . 0°23 for 6 days te 4 hours 0°79 Combined chlorine . 016 Dissolved oxygen ere per 1,000 by volume) , . 2°8 25 bacteria pees c.c. were found on gelatine at 20° C., and 7 per c.c. on agar-agar at 37° C. Tests for bacillus coli and b. enteriditis sporogenes gave negative results. 344 RAI Rain-Gauge.—This is an instrument for measuring the rainfall. It is best made of copper, and should have a circular funnel of 5 or 8 in. diameter. It should be of the Snowdon pattern—that is, have a deep rim to retain snow—and should be placed with its rim 1 ft. above the ground, in an open and well-exposed situation. The measurement of the rain is affected by pouring out the contents of the can or bottle into the glass measure, and reading off to hundredths of an inch. The gauge should be examined daily at 9 a.m., and the rainfall, if any, entered to the previous day. When snow falls, that which is collected in the funnel should be melted and measured as rain. By an inch of rain is meant the height to which the water would stand on the level, provided it did not run off, or soak into the ground, or evaporate. An inch of rain over an acre of surface is equal to 101 tons of water. In mountain districts where the rain- gauge can only be visited once a month, the inside can should be large enough to hold 20 or 80 in. Self-recerding rain-gauges such as those by Halliwell, Negretti and Zambra, Beckley, Richard, &c., yield most valuable data on the rate of fall, the intensity, and the duration of rain. To the engineer and sur- veyor information on rainfallis mostimportant. Where sewage has to be pumped it is necessary to know what has to be provided for as an average, and what as a maximum, so that the engineer may know when he will have to give up pumping and have resort to storm over- flows. The matter of water supply is, to a great degree, a question of the quantity of rain that can be depended on. W. Mz. Rams, Hydraulic. Rams.”’) (See “ HypRAULIC Reeve’s System of Sewage Treatment. —In this system a chemical precipitant and deodorant called ‘‘ thamisin ’’ is used in both the sewage and the sludge treatment. The sewage is then settled in tanks, the top water drawn off and treated on land or filters, and MUNICIPAL AND SANITARY ENGINEERING. REF the sludge disposed of on land as a fertilizer. The process is in use at Staines and Henley. Refuse Collection. — The powers and obligations of local authorities in the matter of refuse removal are dealt with in sections 42 and 48 of the Public Health Act, 1875, to which reference should be made. Any person who obstructs the local authority in carrying out their duty under these sections is liable to a penalty for each offence of £5, whilst, on the other hand, if the authority have themselves undertaken or contracted for the removal of house refuse from premises, and, after written notice from the occupier, fail, within seven days, to remove such refuse, they are liable to pay to the occupier of such house a penalty not exceeding 5s. for every day of default. When organising a system of refuse collec- tion if is important, at the outset, to know exactly what classes of material are to be removed. These generally include domestic house refuse, trade and shop refuse, garden refuse, and street refuse. These terms are not defined by the Public Health Act, 1875, and are somewhat indefinite in their use and application, and differences occasionally arise with householders as to what classes of material are to be removed. Itis important, therefore, the matter should be made as clear as possible to all concerned to avoid misunderstandings. Some help is afforded by the Public Health (London) Act, 1891, which contains the following definitions :— “House refuse’? means ashes, cinders, breeze, rubbish, night-soil and filth, but does not include trade refuse. . “Trade refuse’? means the refuse of any trade, manufacture, or business, or of any building materials. “Street refuse’? means dust, dirt, rubbish, mud, road scrapings, ice, snow, and filth. “‘Ash-pit” means any ash-pit, dust-bin, ash- tub, or other receptacle for the deposit of ashes or refuse matter. The material to be collected usually consists in varying proportions according to the locality and habits of the people, principally of cinder 345 REF and ashes, coal and coke, fine dust, straw, rags, waste paper, bones, vegetable and animal refuse, bottles, glass, crockery, old iron and tins, hardware, &e. Of this material London is said to produce about 14 million tons per annum or about 4 to 5 cwt. per head per annum. In the North of England an average of about 8 ewt. per head per annum is collected. The actual amount in any given case will, however, vary according to the mode of collec- tion and other local details. The main questions to be considered in connection with this subject may be dealt with under two heads, viz. :— 1. The means of temporary storage on premises pending “collection.” 2. The different methods of collection. Srorace.—To comply with the requirements of modern sanitation it 1s necessary that the accumulations of refuse at the occupier’s premises be as small as possible, and that there should be frequent removals. To meet this demand there is nothing better than the portable galvanised iron pail with tight-fitting cover, sufficient to hold a collection not exceed- ing one week’s refuse. In many parts of a town, where there is very little open space in the rear, a daily collection of refuse is often found to be necessary on sanitary grounds. Brick or fixed ash-pits are very undesirable, frequently become a nuisance, and should be abolished wherever possible. CoLLEction.—With regard to the different methods of collection, whilst it is impossible to lay down any one system as being suitable to all towns, generally speaking, the following systems, or some modification of them, are those usually adopted :— Tue Portasie Iron Part Systeu.—By this method the refuse is deposited in small port- able pails placed in front of the premises for removal by the scavengers as they pass through the streets on their rounds at certain fixed intervals. This method is an expedi- tious and economical one so far as the carrying out of the work is concerned, as it saves a good deal of time owing to the fact of the scavengers not having to enter upon the premises to carry ENCYCLOPADIA OF REF out the refuse. An objection is often raised in the better class residential streets,and where there is shop property, to the display of dust receptacles (of great variety in design) for an uncertain period of time in the front fore- courts or gardens of houses. On sanitary and economical grounds the method is a good one, but these are frequently outweighed by other considerations often more or less sentimental. Tur ‘Bett Carr” Sysrsw.—In this the carts pass through the streets and a bell attached to the horses warns the householders to bring out their refuse. As a matter of fact occupiers often bring the refuse out before the cart arrives, and it thus becomes blown about or upset by dogs or mischievous boys. The noise of the bell is also objected to by many. Tur “D Carr” Sysrem consists in the occupier placing a card bearing the letter Din large type in the window when a call from the scavenger isrequired. The object of the card is to save time on the rounds of the collectors by enabling the men to avoid making needless calls. This is not a good method, on sanitary grounds. Cauuinc on Recerpt or Notice from the occupier has been adopted, but the plan is a bad one, as on the neglect of the occupier a large and objectionable accumulation of refuse may arise. The amount of manual and team labour required from day to day is also an uncertain and variable quantity, and therefore very difficult to organise. Pertopican ConLecrion from house-to-house at fixed intervals without notice is a better plan, and more certain and satisfactory in its results, but the time occupied-—and hence the cost—will be greater. CotLection rrom Pusiic Dusr Bins fixed by the local authority in suitable positions in order that householders in their immediate locality can place their refuse into them—their clearance being effected by the authority as necessary. This system is found useful in the poorer and more densely populated parts of some towns, but the placing of the bins so as to avoid objections is a difficult matter. 346 REF MUNICIPAL AND Dust anp Scavencine Carts.—These should be sanitary tip-carts or vans, with sliding iron covers, removable in sections, similar, for example, to the “‘Champion” dust van of the London County Council pattern made by Messrs. Glover, of Warwick. The principal points to be kept in view in organising a proper system of house refuse collection are as follows :— 1. The collections must be frequent so as to admit only of small accumulations, thus pro- ducing the maximum of benefit to the public health. 2. A thoroughly systematic and regular daily routine must be adhered to, so that householders may know as precisely as is possible when the scavengers will appear, thereby giving rise to the minimum of incon- venience to the public, and inducing their fuller co-operation, which will considerably facilitate the work of collection. 3. There should be an inspector whose duty should consist of making house-to-house visits to see that all refuse is properly removed, to supervise the collectors when on their rounds, and to attend promptly to any com- plaints. 4. Householders should be well informed as to what is house refuse, and as much garden, vegetable, and other organic matter as possible should be consumed or buried on the premises. 5. There should be a proper method and recognised charge per load for the removal of “trade refuse,” in the absence of any definite rule providing for its free removal. 6. The work of refuse collection is essentially one in which questions of economy and effi- ciency must be closely studied, bearing in mind the sanitary advantages to the public health to be gained by prompt removal, especially during hot weather. W. H. M. Refuse Destructors. (See Destructors.”) Refuse Disposal—tThe different kinds of “refuse” collected from towns may be de- scribed as either ‘‘house refuse,” “trade SANITARY ENGINEERING. REF ’ > refuse,” “street refuse,” or “ garden refuse’ —the first three descriptions being parti- cularly defined by the Public Health (London) Act, 1891 (see article “‘ Rerusz CoLLEcTION ’’). In most provincial towns the total amount of material collected is largely augmented during certain parts of the year by the production of considerable quantities of ‘garden refuse,” which has an important bearing upon the question of “disposal” as well as that of “ eollection.” Most authorities, however, find it necessary, on the ground of cost, to impose a limit upon the amount of garden and trade refuse to be removed at the public expense. The sanitary disposal of refuse collected from human habitations is a matter of primary importance and a first step towards the building up and maintenance of a high standard of public health. The methods of disposal selected in different districts depend largely on local conditions, but very commonly the cheapest plan avail- able has the preference. Frequently this may be no better than a mere makeshift, and the means of disposal for many years may be nothing better than a hunting about from one makeshift to another, until, finally, other means having been exhausted, a specially- built refuse destructor (see article ‘‘ Desrruc- rors’) becomes an absolute necessity. The chief methods employed for the disposal of the refuse collected from towns are the following :— (1) Depositing upon waste or low-lying land, filling of pits and excavations, or raising the level of marsh land, such sites being tem- porarily described as “tips” or “shoots.” This is a very favourite and cheap means of getting rid of the refuse, where suitable sites exist within close proximity to towns, but it can- not be considered sanitary. Refuse tipped in large quantities invariably takes fire through spontaneous combustion due to the heating of the vegetable material and garden refuse con- tained therein, and when once started usually continues to smoulder and smoke, causing considerable nuisance from smell in the immediate vicinity of the “tip.” Such sites 347 REF are usually resorted to by the poor, by rag and bone pickers and such like, for the purpose of sorting over the material deposited day hy day, and it is thus not only liable to become a centre of infection, but offers an unhealthy occupation to persons of the poorer class, amongst whom sanitary precautions are pre-eminently needful. (2) Mixing housebold ashes, dust, &e., with pail excreta for the purpose of their common disposal by sale or otherwise to farmers for agricultural purposes. ‘his method is prac- tised in some of the northern towns where the “ pail-system ” for the removal of excreta is in use, but it cannot be regarded otherwise than as an offensive and insanitary business. (3) Selling or giving away to brickmakers is a less objectionable plan, especially where the handling and picking over of the refuse is not permitted. The refuse is usually screened, and the fine ashes mixed with the brick, and forms the ‘‘ firmg’’ element, whilst the “ breeze,” or cinder portion, is used for firing the kilns when the bricks are in the “ clamp.” Present- day refuse contains, on the average, less cinder and ashes than formerly, owing to the extended use of gas fires, and the large pro- portion of vegetable material, paper, tins and packings of all kinds of artificial foods and preserved fruits, and such like. (4) Mixing with sewage sludge and plough- ing or digging into the soil of sewage farms. This may be done to advantage where suitable land of sufficient quantity can be obtained within a reasonable distance from the town, and yet at the same time sufficiently free from inhabited dwellings to avoid any possibility of nuisance from smell. (5) Mixing with precipitated liquid sewage sludge, or with pressed sewage sludge-cake, and cremating in destructor furnaces. These processes have been carried out at Kaling and Leyton, and, though costly, may, in certain circumstances, prove a convenient means of riddance of two objectionable classes of materials. (6) Crushing or pulverising the refuse by machinery and employing the resulting pro- ENCYCLOPADIA OF REF duct as a manure or in the manufacture of fuel with an admixture of tar. Fuel briquettes are manufactured by reducing the refuse by means of a crusher to a fine uniform con- sistency, mixing with tar, and then passing the admixture through a briquette press. The approximate cost of a plant, including a mani- pulator or crusher, mixer, press, buildings, and power sufficient to deal with 10,000 tons of town refuse yearly, is about £2,500, or, say, 5s. per ton of refuse per annum. The fuel thus produced has an average calorific value of one-third that of the best coal. (7) Riddling, burning the cinders and vege- table refuse to generate steam, and using the fine dust in connection with a manure manu- factory, the old iron being sold, and the pots, &e., used for the foundations of roads, forms another convenient method of disposal where conditions are suitable. (8) Selling by tender yearly is sometimes adopted where offers can be obtained, but in the majority of cases this is not possible. (9) Barging away down canals to country districts is done by some metropolitan boroughs. Although this entails considerable expense, in many cases it proves less costly than burning in destructors. (10) Taking out to sea in specially-built hopper barges and sinking the refuse in deep water is another means of riddance of this material. This method is followed at Liver- pool, and the cost of disposal is about 1s. 6d. per ton. Care has to be exercised in selecting the time, tide, and site for discharging the refuse into the sea, as the lighter portions are very apt to float ashore and cause complaints. (11) Utilising by “sorting” by hand or by machinery and selling the ingredients for use in such trades or manufactures as can employ them, as is done in dust contractors’ yards. This cannot be considered a satisfactory mode of treatment, as it involves a good deal of handling of the refuse, and is necessarily an unhealthy operation for the workpeople employed. (12) Destroying the crude refuse, as col- lected, by fire in suitably-built refuse destruc- 348 REI tors, and utilising the residual clinker and surplus steam generated by the heat of com- bustion for various useful purposes. Where properly carried out, this is, without doubt, the most sanitary method of disposal. The plant employed should be of the latest and most approved high temperature type, and suitable means should be provided to dispense with the handling of the refuse as far as is possible. The system involves a considerable amount of capital expenditure, and the work- ing expenses are heavy, but where suitable conditions exist some part of the expense may come back from the sale of residuals and the use of surplus heat. (See articles “ Destructors”’ and ‘‘ Reruse CoLLEcrion.’’) W. H. M. Reinforced Concrete or Ferro-Concrete. —KEssential Features—Expansion and Contraction —Adhesion to Steel — Expanded Metal—Shear Stresses — Mixing Concrete — Foundations — Retaining Walls — Bridges, Sewers, &c. — Corrosion. EssentiaL Fratures. — The principle of reinforcement is that Portland cement con- crete, which is very strong in compression, is used in conjunction with mild steel, which is very strong in tension, and the two are so arranged that the concrete shall take the compressive stress while the steel takes the tensile stress. The result is that the com- bination forms a cheap and very efficient mode of construction that may be adapted to almost every kind of structure. Fire- resisting floors composed of these materials first took the form of steel joists embedded in the lower side of a concrete slab. ‘his was convenient because the rolled joists could rest upon the walls without any special provision to receive them, and the concrete was easily filled in between and over them. It was soon found, however, that to give sufficient covering to protect the lower flange of the joists from the action of fire a total thickness was required that was not economical, and smaller sections were adopted for the reinforcement, such as tee bars and Columbian MUNICIPAL AND SANITARY ENGINEERING. REI sections, which were placed closer together. This produced a better distribution of the two materials, and a very simple investigation showed that further improvement would be obtained by using the steel in still smaller sections and placing it very near the lower surface of the concrete. Expansion anD Contraction.—Considerable doubt was felt at the time as to the stability of such a floor under the action of heat, owing to the popular idea that steel expanded much more than concrete under the same increase of temperature; but it was shown that their expansion and contraction were almost identi- cal. As a matter of fact, the linear change for a given variation of temperature is about 15 °/, less for concrete than for steel; but when the actual figures are compared the difference is very trifling. Taking the range of temperature between summer and winter as 70° F., the change of length in 100 ft. produced by this variation of temperature will be for steel 0°546 in., and for concrete 0°464 in., the difference between the two materials in a length of 1 ft. being less than a thousandth of an inch. Apuesion to Steent.—The next doubt was whether the concrete would adhere sufficiently to plain steel rods or bars to enable them to receive the full tension without drawing through the concrete, and numerous patents were obtained for bars that should have a direct hold upon the concrete, such as twisted, corrugated, indented, and stud bars. Experi- ment, however, showed that there was a strong adhesion between the concrete and the metal depending upon the condition of the surface of the latter and the closeness with which the former was packed against it. The best adhe- sion was obtained when the steel was slightly rusted all over and painted with cement wash just prior to placing the concrete. Prof. Bauschinger found the ultimate adhesion to be from 569 to 668 lbs. per square inch. The Royal Institute of British Architects recom- mend 100 lbs. per sq. in. as a working allowance, and at this figure the embedded length of steel that would leave the tensile 349 REI strength and adhesion equal would be equal to 16,000 times the sectional area of the bar in square inches divided by 100 times the surface area per inch in length, or briefly 160°, so that a 4 in. square bar embedded for a length of not less than 20 in. in either direction from a given point, would be equally strong against tearing or slipping, and similarly a 1 in. round bar would need to be embedded for a length of 40 in. In other words, 40 times the diameter in inches gives the requisite overlap or length for embedding any plain round or square bar to be equally strong against tearing or slipping; the smaller the rods the ENCYCLOP.EDIA OF REI the shear stress. The first and most obvious means of doing this was by turning up some of the tension bars diagonally at the outer ends. Where four bars were required in the centre, only two were wanted beyond the middle third of the span; but the four were there, so they were bent up to take this other duty. This was only a crude method and not altogether sufficient. Then various forms of stirrups, vertical or inclined, were intro- duced in connection with the longitudinal bars, placed closer together towards the ends where the shear stress was greater. These were at first put in loose, and then the Kahn bar was introduced. ‘This consisted of a Lines of principal compressive stress — ~ S - Fic. 1.—Loaded Beam failing by Shear. larger the proportionate surface for a given length. Expanpep Mrrau.—The reduction in size of the rods naturally led at an early date to the substitution of wire in the form of rectangular netting; but expanded metal with lozenge- shaped openings soon received more favour than the netting, and is now largely used. Over the supports it is kept near the upper surface of the concrete, and droops in the centre of the span to be near the lower surface; but it does not permit of the close approximation of the stresses that is given by rod construction with shear members. Sugar Srresses.—This leads to considera- tion of another difficulty which arose in the early designs. Everybody was aware of the direct stresses of compression and tension in the upper and lower sides of the beams and how to calculate them approximately, but they overlooked the shear stress that is a necessary accompaniment, and it was not until failures took place by diagonal cracks near the ends of the beams, as in Fig. 1, that attention was called to the need of providing specially for + Y Nunes of principal tensile stress Fic. 2.—Curves of Stress in Beam. square bar placed diagonally with longitudinal fins or webs projecting on each side which were sheared at intervals and bent upwards at an anvle of 45°. Then various forms of shear rods were introduced twisted tightly on to the main rods at such intervals as were necessary exactly to meet the shear stresses, such as the twisted “ Paragon” wires of the British Reinforced Concrete Engineering Co. The actual stresses in a beam may be repre- sented by the curves in Fig. 2. Usually the stresses are treated as if they were simply longitudinal and transverse, the former being tension and compression and the latter shear. They can, of course, be met in this way by suitable reinforcement; but it should be remembered that the shear to be resisted in a ferro-concrete beam is more in the nature of a diagonal tension, and should be provided for by diagonal reinforcement. While these modifications were going on it was found that further economy might be obtained by making the floor slabs “continuous” over the beams, and the beams “continuous ” over the columns; this caused reverse stresses over the supports 350 REI and necessitated the inversion of the system, which was a comparatively simple matter, additional longitudinal bars being put near the upper surface over the supports with the shear bars projecting downwards. When this system of construction was adopted for the walls of the buildings the floor slabs and beams were con- nected to them in the same way as if the wall was one side of an inter- He mediate support, and this made the connection equivalent to ‘fixed ends” in girder work. Mrxine Concrere.—For all re- inforced concrete work it is essential that the utmost care should be taken in mixing and placing the concrete. For thin slabs the usual proportion is one part of standard Portland cement by measure to two parts of clean, coarse sand, and four parts of larger aggregate. Before the days of reinforced concrete it was con- MUNICIPAL AND SANITARY ENGINEERING. Ie REI The elongation of a test piece is about 20 °/, in a length of 8 in., with a contraction of area at point of fracture of about 40 °/, ARRANGEMENT oF Burtpine.—The general arrangement of a ferro-concrete building is somewhat as follows :—First, the founda- tions are made wide enough to spread the -Floor st ab = aa eS wee le eae ee ee em) HBR = Main R Cross seam seam Column Fic. 3.—General Type of Floor Section. load over a sufficient area of the subsoil to avoid risk of settlement, being wider where the piers will be placed to support the floor and roof beams. Instead of the thick mass of concrete seen in ordinary foundations, only about one-third of this thickness is required sidered sufficient if the aggregate was broken to pass a 14 in. ring, and for this new purpose it was reduced to a uniform gauge of 1 in. Now the material is generally specified to range from 4 in. to # in., the vary- ing size being necessary to enalle it to pack closely. For fire-resisting floors the best material for the aggregate is hard brick broken as stated, but coke breeze has many advocates. Broken pumice stone makes a light floor, but has a low crushing strength, while broken lime- stone calcines and loses its strength entirely, and flint pebbles burst under the action of heat; but both these materials are suitable in foundations. Clinker may contain free lime and cause disruption by delayed slaking. The steel is usually in the form of round rods of mild steel from 4 in. to 1 in. diameter, having an ultimate tensile strength of from 29 to 32 tons per square inch, and a modulus of elasticity of about 29 million pounds, or 13,000 tons. Section = S. x s 2e a RAS oe SS or ag Ts yo Nes Le OR ine Goma GOe done oe Wiese sae nagS gc Hsz24 5 Peet Beam po Mee sald Ss iv~als arlG iam is f " (= Al Fie. 4,—_Section through Floor and Column showing Reinforcement. in the case of ferro-concrete, the side wings, as they may be called, of the foundations being strengthened so that they act as 351 REI cantilevers. Then the walls, instead of being uniform in thickness, consist of piers and panels, the piers to carry the weight of the floors and roof, and the panels merely to form a screen from pier to pier. Reinforcing rods are embedded throughout. At each floor ferro-concrete beams are built across the room from pier to pier with cross-beams in Section Fic. 5—Section through Foundation of Column. the case of large spans, and then floor slabs to form the filling between the beams. In a few cases the roofs are also constructed in a similar manner with flat or sloping tops. The work is not finished off a piece at once, but the rods and connections are put in place con- siderably in advance of the concrete, and timber “forms” are built up to give the I t | I I I ee Sein pee a eee 1 1 4, a t ! ede ieee ; | i ' ' i | ' | Sit = 3 SE Ie era t ' ' i U ; ' ' ae te) ape l= ee be qa eee ek | yt 2 Pete op ef Sar tie oS eae aie sl eee aaa. 1 i 1 nmr ( ' 1 1 4 ' H AP ae pe ae on, a ! 1 ' | ! fb NG -M-4-4-4-4-4-4-5 | boa 1 t Hooton Plan Fic. 6.—Plan of Foundation of Column. . required external dimensions to the concrete. The concrete is then put in place in small quantities, packed round the rods and connec- tions, and gently rammed. This description is sufficient to give a general idea of the mode of construction usually adopted, and some of the details are shown in the illustrations. Fig. 3 shows a typical section of a ferro- ENCYCLOPEDIA OF REI concrete floor, consisting of main beams, cross beams, and floor slab supported on columns. All junctions are made gradually by 45° gusset pieces or fillets, and this gives an interior very much the appearance of heavy timbering, especially as the grain of the wood used in supporting the concrete sometimes shows on the face of the latter. Fig. 4 shows a larger Fic. 7.—Section of Heavy Foundation. section through a column and floor beam with the Paragon shear stirrups twisted firmly on the reinforcing bars. In the column the bars are prevented from spreading by encircling wires, every fourth wire being twisted round each of the bars. The lower part of this figure shows a common form of RS cut away [Fis" har: steel rod by VEC point Fic. 8.--Ferro-Concrete Pile. reinforced base for spreading the load carried by the columns. Founpations. — Fig. 5, elevation, and Fig. 6, plan, shows more fully how such a foundation is constructed, the shear stirrups here being placed vertically in the Hennibique manner. When bad soil has to be contended with, and particularly where very heavy loads 352 REI have to be carried, the foundation is more elaborate, as in Fig. 7, the load being spread by rolled joists over the reinforced concrete, and this in turn supported by ferro-concrete piles. Fig. 8 shows the detail of a pile. The lower end is shod similarly to a timber pile, Fic. 9.—Steel Cap for Driving Pile. the shoe having a cast point and wrought straps; but the upper ends of the straps are bent inwards and embedded in the concrete to keep them in place. The piles are driven by an ordinary pile engine, or better by a Lacour steam driver; but the top needs some protection to prevent it from being broken up by the falling ram. Sometimes a wooden WO —7.6"~ Fic. 10.—Section of Retaining Wall with Counterforts. dolly is interposed. The more general method is, however, td place upon it a steel cap, as Fig. 9, with sand or sawdust in it to dis- tribute the blow. To drive any pile, and particularly a concrete pile, with the least resistance, it is important to keep it on the M.S.E. : MUNICIPAL AND SANITARY ENGINEERING. 353 REI move; and this is the advantage of the steam driver in giving a rapid succession of blows, not leaving time for the soil to settle against the faces of the pile. After driving, 5 in. or 6 in. of the concrete is cut away from the top RE : Ig oy Fic. 11.—Sections through Bridge and Wing Wall. to enable the steel rods to be bonded with the superstructure. Reraininc Wauus.—Perhaps the greatest departure from past methods of construction occurs in the new form for retaining walls. Hitherto they have been designed to resist thrust and overturning simply by their mass ; now they practically have no mass and rely for stability upon their strength being utilised in carrying the mass they have tosupport. Fig. 10 shows a typical wall with base and counterforts. The earth that is to be held up rests upon this base so that the wall cannot tilt without lifting it, and it thus becomes a main element of the stability. The effect of the counterforts is AA REI solely to connect the base to the vertical wall; some walls have them omitted, and on two of the American railroads plain Land T sections are largely adopted; but the omission of the counterforts must greatly increase the risk of failure of the walls owing to the excessive stress caused at the junction between wall and base. Bripces, Sewers, &c. — Ferro-concrete bridges of widely different design and span have been constructed, and no definite type has yet been determined to be the best. Some of the early ones were very ugly; but numerous bridges of good architectural elevation have now been erected. Fig. 11 shows a plain railway bridge with abut- ments and wing walls. The construction is very simple and self-evident. The reinforcing bars are placed in two sets, near the inner and outer surfaces of the arch, those on the inner face are doubled in the centre of span, and those on the outer face are doubled from the haunches to the abutments. Fig. 12 shows the section of a large con- erete sewer reinforced on the Kahn system. This type of sewer construction has been very largely used in America and is applicable to culverts, tunnels, conduits, and subways. The details are of course modified according to the nature of the soil passed through. The finest illustration of ferro-concrete construction is, perhaps, given by the Marlborough Blenheim Hotel, Atlantic City, N. J. The front portion of this building is twelve storeys high, surmounted with a dome, 30 ft. diameter. The entire structure is built of reinforced con- crete on the Kahn system, and shows that with care considerable architectural effect can be obtained. Corroston.—The Science Committee of the Concrete Institute has under consideration at the present time various important details con- nected with this form of construction, among which may be mentioned the standardisation of formule and notation ; the conditions under which embedded steel may corrode; the characteristics and mode of using various ageregates ; the supporting power of concrete QO ENCYCLOPADIA OF RET piles; the waterproofing of concrete, &c. It is now generally conceded that the best protection for the steel is to let it get slightly rusted, then to brush it all over with a wire brush sufficiently to remove any loose rust, and paint it with a wash of Portland cement before embedding it in the concrete. Treated in this manner, it has been found bright after some years although only a short distance from the face of concrete exposed to the action of sea water. Where any corrosion has occurred it has been found to be due to cracks permitting of direct access from the outside, or to the action of sulphur contained in the aggregate. Asan instance of the protection afforded to the metal by the concrete, some reinforced concrete waterpipes (12 in. thick) were constructed in Grenoble 22 years ago. After 15 years, two lengths of pipe were raised for inspection, and it was found that although the water had been flowing through them and they had been embedded in soil for all those years with only 2 in. of Portland cement concrete protecting the steel, the metal was as bright as on the day it had been put in. H. A. Retaining Walls are strong walls of masonry, brickwork, or concrete, built at the side of an excavation to support the adjacent earth and resist its thrust, such as those round a sunk reservoir or dock, at the sides of an urban railway cutting, or on a sea front or canal. The thrust is the primary element for consideration ; it varies with the nature of the soil and the difference of its level on the two sides of the wall. A heap of earth left to itself will in course of time weather down to an angle with the horizontal called its angle of repose or natural slope, varying generally between 25° and 45°, as in the following tables. Rankine, ¢ = Dry sand clay and mixedearth 87 to 21 Damp clay 45 Wet clay : 17 to 14 Shingle and Gravel 48 to 35 Peat . 45 to 14 RET Unwin, ¢ = Fine dry sand : 37 to 31 Sand, wet. ; : ; 26 » verywet. ; : 82 Vegetable earth, dry . : 29 35 » moist . . 49 to 45 5 » very wet. 17 < », consolidated and dry : 49 Loamy earth : : ‘ 40 Clay, dry : ‘ 29 » damp, well drained ; 45 » wet 4 : s ‘ 16 Gravel, clean 2 : : 48 » with sand . ; 2 26 Loose shingle ; : s 39 Molesworth, ¢ = Gravel average. 3 é 40 Dry sand ‘ ‘ . : 38 Sand. ‘ , : 22 Vegetable earth i z ‘ 28 Compact earth : ; : 50 Shingle : ‘ : ‘ 39 Rubble ; : : 45 Clay, well drained. : : 45 » wet ‘ ‘ ; : 16 Author’s Practice, ¢ = Wet sand, clay or vegetable earth . . ; : ; 15 Dry sand, clay or vegetable earth . , ‘ 30 Loamy earth, loose nee, clay well drained : 40 Firm gravel and hard fey vegetable earth . : : 45 If the earth were left without support and with a vertical face, it is assumed that the first failure would be the breaking away of a wedge of earth contained between the vertical face and the bisection of the angle between the vertical and the line of natural slope, called the line of rupture, indicated by the shaded portion in Fig. 1. It is this wedge of earth that the retaining wall has to support, and the wedge action due to its shape and weight causes a tendency to slide down the line of rupture and produce a horizontal thrust 355 MUNICIPAL AND SANITARY ENGINEERING. RET against the back of the retaining wall, increasing uniformly in intensity from the top to the bottom, with the centre of pressure at one-third the height, as shown at P in Fig. 2, which shows the section of an ordinary retaining wall. The wall is so designed that its weight combined in a parallelogram of forces with the thrust of the earth shall give a resultant passing through the base at one- third of its thickness from the outer edge. This produces a distribution of the reacting forces in the foundation shown by the triangle below the wall, with a maximum compression at the outer edge, reduced to nothing at the back. Then the moments of the forces in action will be equal, Px = Wy. When the resultant falls within the middle third of the base it means no more than that there will be no tension on the inner edge of the base. It is generally supposed that under these con- ditions any wall will be safe, but this is not necessarily the case. With a high wall its weight may increase the compressive stress beyond the safe limit, and with a low wall itis often possible to be within safe limits when the resultant is only one-fourth of the thickness from the outer edge. ‘The thrust of the earth may be found entirely by calculation, or partly by calculation and partly by graphical con- struction. By calculation the formula is T = } wh? tan? ( = ), or, the same thing i pats hee ZT’ = horizontal thrust in lbs., w = weight of earth in lbs. per cubic foot, h = height in feet, @ = angle of natural slope in degrees. The second method is to deal with 1 ft. run of this wall and earth, mark the centre of gravity of the wedge of earth as in Fig. 8, and drop a vertical line to cut the lineof rupture. Calcu- late the weight of the wedge of earth and set the amount up to scale from the intersection with the line of rupture, from which point also draw a horizontal line, and from the upper end of the marked amount draw a line parallel with the line of rupture. This will cut off a horizontal distance equal to the total thrust AAQ in another shape, 7 = ee RET measured with the same scale. The centre of gravity of the wall is then found by setting off the width of base on each side of the top, and the width of top on each side of the base, and drawing diagonal lines which will intersect at the centre of gravity of the wall. Then trans- ferring the thrust in the same horizontal line beyond the centre of gravity of the wall and setting off the weight of 1 ft. run of the wall to the same scale below it, the parallelogram is completed and the resultant produced to cut the base. Wherever the resultant cuts the base, if tension may be allowed, the formula Fia. 2. Fig. 1. Back of wall or vertical, face of earth ENCYCLOPADIA OF RET ‘ w pression at outer edge will be 3 X Wi where W = weight of wall and d = distance of resultant from outer edge of base. It will be self-evident from Fig. 2 that a wall of the section shown will be more efficient than an upright wall of parallel thickness, as, owing to the battering face, the centre of gravity is thrown further back and the weight acts with a greater leverage. The usual batter varies from 1 to 8 in. per foot according to circum- stances, and the courses of the brickwork or masonry are always laid at right angles to Horizontal Fic. 1.—Wedge of Earth pressing against Wall. Fic. 2.—Distribution of Pressures on Wall. Fic. 3.—To find Stability of Wall. for the stress at outer and inner edges will be w al wall in lbs., ewts., or tons, A = sectional area of base in square feet = thickness X 1 ft., Af = bending moment weight of wall x distance in feet from centre of base to point where the resultant cuts it, Z = section modulus of base = 4 of the width of base in feet squared. The + value gives the com- pression per square foot at outer edge and the — value gives the compression or tension, as the case may be, per square foot at the inner edge. When no tension can be allowed this formula will apply so long as the resultant does not pass beyond the middle third, but if it passes beyond this the formula for the com- oh oa where W = weight of 1 ft. run of the face. The back of the wall is usually stepped in half-brick (43 in.) set-offs, at such intervals that the mean line is vertical, and the top is surmounted by a stone coping, or blue bricks on edge laid in cement mortar. From three to six courses of foot- ings are usually carried out beyond the face of the wall but none on the back, and the wall is usually built on a cement con: crete foundation, thicker at the front than the back, in order that the under-side may be level. The earth filled in at the back of the wall must be punned in 1 ft. layers inclined away from the wall to reduce the tendency to slip, and if there is an existing bank to the earth it must be benched, or cut in steps, before the filling-in takes place. 356 RET When the wall has earth on one side and nothing on the other, provision must be made for carrying off any water that may collect behind it by forming vertical rubble MUNICIPAL AND SANITARY ENGINEERING. RET walls. A complete design for a retaining wall is shown in Fig. 4. A wall to resist the pressure of water may be designed upon exactly the same principles, bearing in mind Stone coping or blue vitrified capping [SS > AL headers at foe Of each > G6 Pinan a) pac oes PP Ooze pao Ce 7 a Surface of ground WARY TRIB SIRS RSORSIIIRY, WAY, sel ~-Orf fk { 4. OR Es u gee § ee. e- X & t £3 0 « R Oo < @ g [ EN id G K Vd d o & 3 Sele v x ; x <% 7. y S ov 2 « P sd o KX g Ay s ee hk S y 8 ae @ g CY 1 f 2 s Og AY ‘Z, Ce R Lae 8 . eg, y! ee % french ararn TH COILITILIOUS $ 8 = horizontal 8 9 Ry Rail level TST a eh /2° socketed! =A rain pipes yi Wy, aS tft, a Qe | ota ae ea aa an ae a ‘a2? Qi ag PE ek ae a ss Fic. 4.—Complete Design for Retaining Wall. drains at intervals of 10 or 12 ft. with weep holes near the bottom, and connecting them by a horizontal French drain. THis will not be required in the case of reservoir or dock that the natural slope of water is nil and that the assumed line of rupture will therefore be at 45°. When there is earth on one side of a wall and water on the other, the thrust from 357 RET each must be worked out and. both resultants should generally fall within the middle third of the base, but the actual stresses should be calculated in every case. The triangle from which the thrust is scaled in Fig. 8 may be set off in another way, which is rather more convenient, as it applies equally to walls with sloping backs, battering or overhanging. In Fig. 5 is shown a concrete tank wall, with the excavated material banked against the outside, and the thrust triangle drawn by <— ZJ’O'H Se, farth 100 toss. Per chih.fe. f Xu AS Fic. 5.—Concrete Tank Wall. setting up the weight of wedge vertically above one-third of the height, drawing a line at right angles to the back of wall for the direction of the thrust, and then setting off the angle of the wedge 4 (90 — ¢) to complete the triangle. Any division wall in the tank, unless perforated and used as a strut only, must be sufficiently thick to resist the full pressure of water on one side of it while empty on the other, asin Fig. 6. Having drawn graphic- ally the forces and their resultants, the stresses would be calculated as follows. In Fig. 5 the stresses due to the thrust of earth only will be W , M __ 4820 , 4820x4_ = i ee Pa eS eS 1,890 lbs., or 0°85 ton per square foot com- ENCYCLOPADIA OF RET pression at A, and 270 lbs. or 0°12 ton per square foot compression at B. From the com- bined thrusts of earth and water the stresses : 4800 xX 1°5 1200 + 2700 = 8,900 lbs. or 1°74 tons per square foot compression at B, and 1,500 lbs. or 0°67 ton per square foot tension at 4A. In the case of the division wall Fig. 6, the ; W , M _ 6280 , 6280 x 1'5 stresses will be 7 + 7B + r(1 x 6%) Water 6242 Lbs === 0 7/2 vk NS ¥ ee bes — 829 t.9 Eos gs $s cog d vs c a ee gep fi Sy fale | = /- Res D ¥ | Ly e vis a ea ican ma Fic. 6.— Concrete Division Wall in Tank. = 1046 + 1570 = 2,616 lbs. or 1°66 tons per square foot compression at C and 524 lbs. or 0°24 ton per square foot at D. It will therefore be evident that the walls might have been reduced in thickness probably by 6 in. When a retaining wall supports a bank of earth sloping upwards above its own height, it is said to be surcharged, and the thrust is greatly increased. The simplest way of find- ing the thrust is by using Rankine’s graphic method shown in Fig. 7, and worked as follows :—Let A BC D be the section of the proposed wall, D E the line of surcharge, the natural slope and line of rupture being drawn as usual. Then set up BF making angle > with back of wall, produce EZ D to F, bisect 358 RET BF in G, and from G as eentre draw the semicircle B F. From D drop a perpendicular CL DIE ul Ss of Zz 2’6" >} ch v —~ c¢ SH OS e g Earth Oo ! CX N2 lbs per, $ & yg cl“ FE a5 1 {ay o ¥ iS Q y J 30° @ o A N ¢ S aR 02 ‘9 | K yt ce M fy HAC ’ a ou p 6) SINT LA rR \ ? 4 t | ra ey T : Ate, 4! Gg" . 7448 ' Ql! 8 1/ % 8 1 i/ 3a! ' - sla a Fic. 7.—Surcharged Retaining Wall. on to B F cutting it in J, and continue D J through to HZ. From centre F, with radius F H, cut B F in K. Then the horizontal thrust will be found by the formula T = }w (BK)? = 4 x 112 x 5? = 1,400 lbs. acting at one-third of the height as shown at ML. Draw L N parallel with the line of sur- charge, and cut it off by the vertical M N, then N L gives the actual thrust against the wall. Drop a line through the centre of gravity of the wall, and produce N JL to intersect it in P; then P R = thrust, MUNICIPAL AND SANITARY ENGINEERING. RET W , M_ 4680 , 4680 me A*+Z~ 45 +i x 45% = 1040 + 347 = 1,887 lbs. or 0°62 ton per square foot compression at A, and 698 lbs. or 0°31 ton per square foot compression at B. The maximum safe load on brickwork being from 3 to 10 tons per square foot, according to quality, there is an ample margin of safety, but if the wall is reduced in thickness the maximum stress will rapidly increase, so that it may be left as given. When the slope of surcharge is parallel to natural slope, BK = BF. When the earth at the back of a retaining wall is loaded in any way, some allowance must be made for the increased thrust produced against the wall. There is no generally recognised method of doing this, but the following is put forward as a reasonable suggestion for the purpose. Let two loads be carried as in Fig. 8, Wi = 1 ton per foot run, W, = + tons per foot run, at distances of 2 ft.and 8 ft. from back of wall. From the point of application of the load Wy draw a line parallel to the line of rupture to cut the back of the wall, and assume this to be the point of application of stresses will be gs g aS Ik Yao SS m g Ig kK 3/0” >+<2'0% Zz'o” & fe bes as 5 J /owe. per / yeu. Fe. i ff a) 47 / @O cwts and P @ = weight of wall, the resultant P S cuts the base at 7, 3 in. from centre of base, the vertical component being 4,680 lbs. Then the maximum Fic. 8.—Wall Loaded at Back RET the thrust from this load, the value being found by triangle in the ordinary way. Com- bine this thrust with the weight of the wall, and draw the resultant. Combine this resultant with the thrust due to the weight of the wedge of earth and draw the second resultant; then combine this resultant with the thrust from load JW’, found as above described, to give the final resultant cutting the base as shown. Then the vertical com- ponent of the final resultant being 72 cwts. and the point of intersection with the base Sj exe “mesh 2 | wre Fabric Fic. 9.—Ferro-Concrete Retaining Wall. 09 ft. from the toe of wall, the maximum compression will be 2 ‘= =2xX a= 534 cwts. = 22 tons per square foot. When a reservoir is built above the surface of the ground, the containing wall may be very much lightened if built in reinforced concrete. Fig. 9 shows a section through the 600,000 gallon reinforced concrete reservoir, 80 ft. diameter and 15 ft. deep, constructed at Cos Cob, Conn., U.S.A. It is founded on solid rock and is without any surrounding fill, thus making some exterior embellishment very desirable. Accordingly ENCYCLOP.EDIA OF RIC the wall was designed with a cornice and a slightly projecting base, and the flat belt between was relieved with a series of arched indented panels, 40 in number, giving somewhat the effect of an arcade. The concrete wall has a 4-in. lining of brick laid in cement mortar to protect the waterproofing coat. It is reinforced circumferentially with steel cable, varying in diameter from 13 in. at the base to 2 in. at the top, forming a con- tinuous spiral with 12-ft. splices made with 16 Crosby clips where the ends of two sizes of cable are joined. The pitch of the spiral varies somewhat as indicated on the drawing, but is in general about 1 ft. Inside the cable spiral is a continuous sheet of 3 in. by 12 in. mesh Clinton wire fabric, placed in vertical strips which extend 6 ft. into the floor foundation. About 10 days after the filling of the wall-forms had been completed the forms were removed and the derrick was taken out of the tank. The floor was then concreted to an even surface, and a 4-ply waterproofing coat of Hydrex felt was applied to the inner surface of the wall in vertical strips and to the tank floor. Hydrex compound was used to cement the layers of felt together. A 4 in. protective covering of concrete was laid over the floor of the reservoir on the waterproofing coat and extending a little way up the side to give a footing for the 4 in. brick wall lining. The bricks were laid with cement mortar with a solid backing of mortar between brick and waterproofing. H. A. Richmond Sewage Disposal System.— The method of treatment at the Richmond Main Sewerage Board’s works at Mortlake consists of chemical precipitation, filtration through beds of gravel and sand, and reduction of sludge by filter presses. There are eleven precipitation tanks, each 100 ft. by 80 ft. by 7it. 6 in. deep, the total capacity being 1,210,000 gallons. These tanks can be worked either on the intermittent or continuous flow system. The effluent is further dealt with on eight filter beds, fonr high and four low-level beds, each 107 ft. by 100 ft. The filtering 360 RIS material averages 8 ft. 6 in. deep, and consists of a layer of 9 in. pipes overlaid by gravel and sand of graduated sizes, finished with 3 in. of loam, and sown down with grass. The filters have been in use for some years with occasional renovation of the surface soil. The board’s engineer, Mr. W. Fairley, A.M.1.C.E., states that the process of precipitation con- sists of, first, a small dose of carbolic acid and iron salts mixed with the sewage as it enters the pump well. After being pumped the sewage receives about 4 or 5 grains per gallon of milk of lime and 7 grains per gallon of a mixture of sulphate of alumina, iron, &c. The tank liquor is then passed through the filters, from the outlets of which it is discharged on the ebb tide into the Thames. The expense of chemicals per million gallons varies from 22s. to 25s. Rising Mains.—Rising mains are laid in cast-iron pipes, with a thickness of metal suited to the pressure to be withstood. They should be in as direct a line as possible, with the least possible number of bends, and should be of ample diameter to pass the volume of water required without creating undue loss from friction in forcing the water through them. In deciding upon the internal diameter it should be remembered that most probably in the course of a few years the discharging capacity of the pipes will become considerably reduced from incrustation, in which case a large increase of head may be thrown upon the pumping engines. The question of size is one which requires very careful considera- tion, as every additional inch in diameter involves a material increase in weight of metal in a long pipe line, whilst the error of providing too small a main results in a larger coal bill to be paid annually owing to the machinery having to work against a head partly due to the increased frictional resist- ance. The interest upon the additional capital outlay involved by a main of larger diameter, or on the cost of duplicating a main which may have become insufficient for present requirements, must therefore be set against MUNICIPAL AND SANITARY ENGINEERING. RIS the estimated annual reduction of coal bill which would result from the provision of increased main capacity, the pumping engines having to develop less power to raise the same quantity of water. Where the mains are of ample capacity the extra head due to friction will not exceed about 20 ft. per mile. The incrustation in a main often occurs, not as a uniform coating around its internal surface, but in numerous irregular nodules or lumps, thus greatly retarding the flow. The nature of the incrustation will of course depend greatly upon the character of the water pumped. For economical working the velocity of flow through the main should not exceed from 24 to 3 ft. per second or the friction will be greatly increased. The calculations for engine power and main capacity in connection with the recent Coolgardie water scheme were based on an assumed flow of about 2 ft. per second through a pipe 30 in. in diameter. The frictional effect of increase of velocity in a main is shown by the following comparison of velocities in a clean 12 in. pipe:—A velocity of 3 ft. per second gives a frictional head of a little over 3 ft. per 1,000 ft. of length, whilst a velocity of 5ft. gives a head of 8°5 ft. per 1,000 ft. The frictional resistance in a pipe increases in the proportion of the square of the velocity of flow, and it is thus readily seen that a very material waste of power may arise from this cause. In the same way a great loss of “head,” due to insufficient main capacity, occurs in the mains of a distributing system. On long lines of rising main of considerable head, reflux valves should be inserted at suit- able intervals in order that the pumps may be relieved of pressure, and, in the event of a burst pipe, one section of the main only will be discharged to waste, and that under a much reduced head or pressure. A relief or safety valve should also be provided in the delivery pipe close to the air vessel, and should be weighted a little above the usual working pressure so as to give relief in the pipes in case of stoppage therein. 361 RIV Rivers Boards: Central Authority.— As a result of the Sewage Commission of 1869, the first central authority having con- trol over river purification was established, viz., the Local Government Board. The Public Health Act Amendment Act of 1875 stipu- lated that the Local Government Board should only sanction the raising of loans for sewage disposal after the schemes had been favour- ably reported upon by an inspector of that Board, who had held a local inquiry. The control exercised by the Local Government Board has been mainly confined to criticism of schemes thus brought before them. The Mersey and Irwell Joint Committee was formed in 1891 as a result of a petition from the county councils of Lancashire and Cheshire, and obtained special powers under the Mersey and Irwell Act, 1892. A similar committee, the West Riding Rivers Board, was appointed by Provisional Order in 1893, followed by the West Riding of Yorkshire Rivers Act in 1894. The function of these boards and others of a similar character, such as the Ribble Joint Committee, is mainly administrative, their chief activity being directed to see that local authorities and manu- facturers duly carry out the provisions of the Rivers Pollution Acts in their respective dis- tricts. Although the inspectors of these rivers boards in their personal character are often very helpful to authorities by indicating measures which may properly be taken in certain cases, the Board takes no responsibility officially for such advice, for which, of course, no remuneration is given, nor are experi- mental investigations undertaken for other than the private information of the Board. The Massachusetts State Board of Health, which was founded in 1886, has from the first undertaken experimental researches of great and fundamental importance. The re- sults of these are published annually in Reports, and the officials of the Board not only examine schemes and supervise the construc- tion of works, but also continually inspect the works in operation. Similar State Boards have been founded in ENCYCLOPEDIA OF RIV other parts of the United States, e.g., Washing- ton, New York, and Ohio. In 1901 an Imperial Council of Health, having jurisdiction over streams, was formed in Germany by several Federal States. In the same year the question of river pollution was taken up by the Prussian Government, and the Royal Prussian Testing Institute was founded with a very extensive staff and equip- ment, to collect all necessary information on which the action of authorities could be based. Valuable reports are issued by the Institute from time to time. A similar testing station has been estab- lished at the Pasteur Institute at Lille, under the direction of Professor Calmette, and very important reports have been published. The Royal Commission on Sewage Disposal, appointed in England in 1898, has from the first advocated the formation of a central authority to deal with questions of water supply and sewage purification. Such a central department would consist of an administrative head, assisted by highly qualified bacteriological, chemical, and engi- neering experts. Among the more important questions which would have to be dealt with by such an authority would be the following :— 1. Disputes between local authorities and manufacturers as to the terms and conditions on which trade effluents should be admitted into sewers. 2. The control of shell-fish layings. 3. The protection of water supplies from pollution. 4. The collection of information as to the water supplies available in various parts of the country. 5. The collection of information as to the need of water in various parts of the country. 6. The settlement of standards for different reaches of water. 7. Conferring powers on local authorities, in suitable cases, to provide separate systems of sewers for surface water and to enforce the provision of separate drains. 8. The settlement of questions as to the 362 RIV extra amount of sewage which a local autho- rity should be required to treat during storms. The authority would also undertake special investigations of general importance and col- lect and collate the work done by others, for the benefit of local authorities throughout the country. G. J. BF. Rivers Purification.—It has long been recognised that the prompt removal of human excreta from the vicinity of dwellings is one of the first essentials of sanitation. For this reason water-closets were introduced in 1810, and at first discharged into cesspools. In early days sewers were largely sewers of deposit, and were cleansed at intervals by manual labour. It was afterwards recognised that discharge into a river outfall was pre- ferable to methods such as these. With the growth of population and the increasing pro- vision of sewers, serious pollution of rivers occurred, and from 1848, the date of the first Public Health Act, to the present day, numerous Royal Commissions and Select Committees have reported on the best methods of preventing the pollution of rivers, and a number of Acts have been passed (see references at end of article). All the Commissions prior to the one now sitting, which was appointed in 1898, concurred in recommending land treat- ment in one form or another as the most satisfactory method of purifying sewage before discharge into a stream. This method was exemplified in the case of the Craigentinny meadows, which received the sewage of Edinburgh as early as the 18th century. Application to land was effected either with a view to the growing of crops, by the method known as “broad irrigation,’ where the sewage was applied to the land simultaneously with the growth of vegetables, or by means of “intermittent downward filtration,” a method introduced by Sir Edward Frankland in 1870, in the First Report of the Royal Commission of 1868. By this method the sewage is run on to an area of specially prepared land, and allowed to filter through, a further dose being applied after a period of rest. No attempt is MUNICIPAL AND SANITARY ENGINEERING. RIV necessarily made to grow crops, and the land must be kept open by ploughing. More sewage can be treated on a given area by this method than by broad irrigation; but there is no essential difference in principle between the two methods, The amount which can be dealt with by either method is increased by preliminary removal of solid matters, either by simple settlement in tanks, or by the use of various chemicals as precipitants, of which lime, either alone or in combination with salts of iron or alumina, is chiefly used. The results from land treatment properly carried out on suitable land were so good, that until recently the Local Government Board refused to grant borrowing powers for sewage schemes, even where artificial filters were provided, unless provision was also made for final treatment on land. Owing to the increasing difficulty of obtaining such land in the neighbourhood of large centres of population, great attention has been given during the past twenty years to various methods of treatment by artificial filters of various descriptions. In 1898 a Royal Commission was appointed to consider the whole question, and has issued numerous reports. It was able in its first interim report, issued in 1901, to give the following important finding :— “We are satisfied that it is practicable to produce by artificial processes alone, either from sewage, or from certain mixtures of sewage and trade refuse, such, for example, as are met with at Leeds and Manchester, effluents which will not putrefy, which would be classed as good according to ordinary chemical standards, and which might be discharged into a stream without fear of creating a nuisance.” Although the Commission is still sitting, and consequently no legislation has yet taken place, the Local Government Board have recently granted borrowing powers in several cases where artificial methods have been exclusively employed, without having recourse to land. At the present time the administration of 363 RIV the River Pollution Prevention Acts is in the hands of various Conservancy Boards, ¢.¢., tle Thames and Lea Conservancy, the Mersey and Irwell Joint Committee, the Ribble Joint Committee, the West Riding Rivers Board, and Special Committees of County Councils. The degree of purity required before an effluent is allowed to enter a stream is somewhat differently defined by these various bodies. Thus the ‘limits of impurity” allowed by the Mersey and Irwell Joint Committee are 1 grain oxygen absorbed from permanganate by 1 gallon effluent, O°1 grain ‘ albuminoid ammonia’ obtained on analysis, per 1 gallon effluent; while the Ribble Joint Committee and the Derbyshire County Council attach less importance to the ‘‘ oxygen absorbed” figure, and more to the presence of nitrates and the consumption of “dissolved” oxygen by the effluent. The Thames and Lea Con- servancy, on the other hand, having to safe- guard the purity of the Thames, which supplies a portion of the drinking water of London, impose more exacting standards. The present Royal Commission have recom- mended a central authority (see above) for the control of the purification of rivers and of water supply throughout the country. This central authority would act in conjunction with the present Rivers Boards and others likely to be appointed. They suggest that one of the functions of such an authority would be to formulate standards suitable for differing conditions. They recommend that the purity of an effluent should mainly be judged by the suspended matter present, and by the dissolved oxygen absorbed under defined conditions. Owing to the fact that neither filtration by means of artificial filters nor through land can be relied upon to produce, under all circumstances, effluents free from pathogenic organisms, considerable attention has recently been given to the possibility of sterilising effluents, especially when they have to enter streams which are used as drinking water supplies. Although it has beeu found possible, within practicable limits of cost, chiefly by ENCYCLOPADIA OF ROA the use of chlorine in the form of hypochlorites, or oxides of chlorine (obtained by electrolysis), to sterilise effluents from isolated installations, such as hospitals, or even under some circum- stances the dry weather flow of town sewage, the difficulty of the sterilisation of storm- water has so far proved an obstacle to the adoption of such methods on the large scale. Rererences.—Reports of Royal Commission on Sewage Disposal, 1901—8. London: Wyman & Sons, Ltd., 109, Fetter Lane, E.C. An excellent reswmé of the progress of legis- lation on River Pollution is given in the evidence of Mr. A. D. Adrian, C.B., Assistant Secretary to the Local Government Board. Royal Commission, Interim Report, Vol. II., 1902, pp. 1—14. The general law relating to sewage disposal in England and Wales is to be found in the Public Health Act, 1875, supplemented by the Rivers Pollution Prevention Acts of 1876 and 1893. G. J. F. Roads, Streets, and Pavements. — General Consideration—Location, Gradients, and Drainage—Width of Roads—Retaining Walls— Embankments—Materials and Methods—Metal- ling—Repairs—Rolling—Paved Carriageways— General Method of Laying Wood Pavements— Asphalt Pavements— Tar Macadam — Brick Pavements—Paving Setts and Blocks. GeneRAL.—The rapid growth of traffic during recent years calls for the construction of roadways upon the soundest and most permanent principles, embodying a solid and adequate foundation, good subsoil and surface drainage, together with a sufficient coating of durable road-metalling suited to the class of traffic to be accommodated. Many of the highways of this country, formed in earlier years, have proved to be far too weak and inadequate to withstand the demands of modern conditions, mainly due to the absence of a sufficiently rigid foundation and to the employment of unsuitable materials for purposes of surface repairs. The practice of using the cheapest stone obtainable in the locality cannot be defended 364 ROA on the score of economy, inasmuch as the recent extended employment of tougher qualities of metalling has been amply justified from every point of view. In some cases it may be found sufficient to’ provide a top coating of flints or granite upon the existing natural foundation, especially where the traffic is light and where the bottom consists of chalk or solid clay; but with the present day heavy traffic care must be exer- cised to insure that the foundation is of the best, and of a thoroughly firm nature. Such a substructure is essential to all good roads, and, although the first cost may be heavy, its provision will be found to be the cheaper course in the end. Location, GRADIENTS, AND Dratnace.— When new roads are to be laid out, the route is generally governed by existing roads, villages, and towns. In all cases careful surveys should be made of the district through which the road is to be constructed, and, where practicable, the route for the road should be one with the least amount of hills, provided the length is not unduly increased thereby. When making the reconnaissance the work will be simplified by the use of contour maps of the country traversed. On the route-map the engineer should note the available materials for embankments, where these appear necessary, the nature of the ground to be passed through, and any geological peculiarities on or near the route decided upon, with conditions in favour of or against the particular route to be adopted, and other alternative routes. When the route has finally been decided upon, stakes should . be driven into the ground at frequent intervals along the centre line. Levels should then be taken longitudinally, with cross-sections at all necessary points. After these have been plotted the finished level can be decided upon, and the amount of excavation, filling, and banking, can then be ascertained. Roads that are constructed of steep gradients are constantly requiring repairs, these being chiefly due to the erosion caused by rains, the abrasion by motor tyres in ascending, and the use of skids and brakes on vehicles descending MUNICIPAL AND SANITARY ENGINEERING. ROA hills, which cause disintegration of the surface. It is difficult to give limits to the permissible gradients, as so much depends on the local circumstances of the case, and the materials used. Several, however, have been given, and we may consider them at this point. Thomas Codrington has suggested 1 in 80 as the limit of gradient for macadamised roads. Sir John Macneil was of opinion that no road ought to exceed a gradient of 1in 40. Sir Henry Parnell found by experiments conducted on the Holyhead road, north of Coventry, that a gradient of 1 in 85 should not be exceeded. Where roads are to be constructed through hilly districts, long, steep inclines should be divided up as far as possible into short lengths, with intervals of road of lessinclination. This practice is especially recommended in the case of curved roads, these in addition being slightly.embanked on the near side for the safety of descending traffic. Short lengths of smaller gradients not only tend to reduce the heavy strain upon horses drawing loads uphill, but are conducive to the safety of fast-driven vehicles and other traffic when descending, especially where the road has concealed turnings. Perfectly flat roads are not desirable, as they cannot be well drained, and consequently remain damp for long periods, thus enhancing wear and tear, and gradual deterioration of the metalling. A moderate inclination of, say, 1 in 150, is about the flattest grade desirable, so as to enable the channel-water to be effectually drained away. A slight gra- dient also facilitates the draught of horses. Even the hardest classes of metalling deteriorate more rapidly when constantly wet and damp, and for this reason it is advis- able to insure, as far as possible, that the road should be open to the moderate action of the sun and wind. When traversing undu- lating country, the road should, if practicable, be constructed on the northern side of the valleys, and it is found that all obstructions, such as overhanging trees, high walls and fences and such like, are detrimental to the durability of the road. 365 ROA It is not to be assumed, however, that it is permissible to go to the opposite extreme, and so subject a roadway to excessive exposure, as very strong drying winds have the effect of a3 Benes hs PUPREAPEEE IDS e NESSES oa he a eee UNDERDRA/NAGE FOR 4” abe LANOWATER AND SPRINGS srereing 70) Fic. 1. 2 removing the ‘ binding” material from the surface, and thus causing the roadway to disintegrate under traffic. When passing through hilly country, in laying out a new line of roadway, it often becomes necessary, in order to find the ground over which the ruling gradients can be maintained to contour the hill- slopes, to cut into the side of the hill, and to embank on the down-slope, as shown in Fig. 1. The footpath should be arranged on the outer side, in order that the heavier vehicular traffic may be carried on the natural solid ground. Greater stability of that portion of the road which is embanked on the outer side is secured by “stepping” the added portion as shown, which tends to prevent slipping. All springs or land water of every kind L Naureawarive woe OF AOAD DRAINAGE should be properly and permanently drained away to a point of discharge upon the solid ground, well below the outer retaining wall. Top-water above the upper wall should be intercepted by a suitable catchwater drain. ENCYCLOPAIDIA OF ROA Roads of this description through hilly country often involve heavy engineering works, and are costly to construct, but very frequently the cost is materially mini- mised by the fact that good quality stone is obtainable from the ground traversed. Other principal classes of roads are (1) ordinary country main roads; (2) country secondary roads; (3) roads of a suburban and residential class; and (4) pitched or paved roads of busy cities. These all require special types of construction, appropriate to each individual case, some examples of which are given in Figs. 2—4. Country main roads require to be a minimum of about 21 ft. in width, or suffi- cient for three vehicles abreast, with two footpaths of 6 ft. width each. aeecrare® 225 srorm wage O SEWER Fig. 3. Suburban and residential roads are com- monly 40 ft. wide overall, having two footpaths of 9 ft. width each, and a 22 ft. carriageway. The trunk or main arteries through large towns may advantageously be 60 ft., and in special cases even 100 ft. in width, so as to accommodate ordinary vehicular, tramway, and pedestrian traffic. The widening of important roadways through populated centres necessarily be- comes a very costly undertaking, having regard to the fact that, usually, valuable properties on each side have to be purchased, including the trade interests of the various premises affected, in addition to which the cost of the structural works involved have also to be met. Under some circumstances, particularly in 366 ROA districts with widely varying levels, what is known as “‘ hanging ”’ and “ double-hanging ”’ roadways have to be formed. Typical roads of this class are shown in Figs. 5 and 6. An important point in all such cases is to secure the proper removal of the surface water, and 1 8 nf ae yee ‘ . ~ = gof —-$0 Gee ew ee He HHH Oxi0 gi * S ween got a . wnoese™ v «Gone IES . Cre concgere(6 rm/) Fie. 4. to see that the cross gradients are suited as near as possible to the requirements of the traffic. Sometimes it is necessary, in im- portant cases, that a full-sized section of this cross contour should be built up, so that the effect of the finished road surface can be properly appreciated. It is argued by some that a road with a concave centre is preferable to the common convex form, inasmuch as, it is suggested, the centre channel divides the traffic into up and down lines, one line of channelling and street gullies is needed, and the road-slop and water is drawn to the centre of the road, away from the footways, thus preventing the splashing Hanging RoAgway Fia. 5. of pedestrians in wet weather. Although this form of road may possess some good features from certain points of view, it must be remem- bered there are many disadvantages, and, on the whole, the balance is decidedly in favour of the ordinary form of road, except in certain special circumstances. Rerarninc Watuis.—These should be con- structed of brick, stone, ordinary and rein- forced concrete, and be of sufficient strength to successfully resist the thrust from behind. MUNICIPAL AND SANITARY ENGINEERING. ROA The thickness should be carefully calculated by means of reliable formule or graphically, the latter being the more expeditious method. Sir Benjamin Baker considered that the thick- ness, in average ground, should be one-third of the height of the walls, measured from the top of the footings, and in cases where the backing and foundations are both favour- able a wall one-quarter of the height in thickness similarly measured, having a batter of 1 in. or 2 in. per foot on the face will be sufficient. Walls with a slightly curved face in vertical section, give better results and are more effective in sup- porting the thrust. Th esuccess of retaining walls depends largely on a well-distributed rigid foundation and upon proper drainage at the “MWOSTREET QULLY Dovacé HANGING OR CONVEX ROAD UP AND DOWN TRAFFIC DIVIDED BY LAMP STANDARDS Fig. 6. back. Breast walls are not usually built to resist pressure from behind, but merely to protect the natural earth from the effects of the weather. Empanxments.—There are many ways of constructing these, among them being the tip-wavon system. This is an expeditious method of carrying out the work, but is somewhat unreliable. The best method appears to be that in which the work is built up in successive layers or courses, each layer being concave in form and thoroughly consolidated as the work proceeds. Stability will thus be obtained for the whole structure, and especially is this the case when embankments are formed with slopes con- sisting of material resting at its natural angle of repose. The angle of repose of different materials in the table on page 368. For embankments and cuttings exceeding 4 ft.in depth, Sir H. Parnell has recommended a slope of 3 ft. horizontal to 1 ft. perpendicular. For cuttings in chalk or marl a slope of one to 367 ROA one will be sufficient; in solid, hard, and uni- form sandstone slopes of one-quarter to one will suffice. Where the sandstone stratum is in alternate layers with clay or marl, the stone becomes detached and will slip, and for that reason hard and fast rules are difficult to give. NATURAL SLOPES oF Eartu (witH HorizontTaL Liye). Earth. = 1B ie EOL ee Desien ae ERODES Friction. | Natural Slope. Dry sand, ciay, From ( 0°75 1:33 to 1 and mixed earth | 30° to 21° | | 0°38 2°63 to 1 Damp clay eee 45° 1:00 ltol Wet clay.. Fe From ( 0°31 3°23 to 1 17° to 14° | | 0°25 40 tol Shingle and gravel From 111 09 tol 48° to 35° | | 0°70 1:48 to 1 Peat From { 1:00 1 tol 45° to 14° | | 0°25 4 tol Fic. 7.— Drainage. Slopes should be finished with a suitable material for grass growing, or, in cases where there is an excessive amount of water, with ballast. Drainace.—Care must be exercised in the formation of embankments, cuttings, and roads generally, to insure an efficient system of subsoil and surface drainage, as the stability of these works depends largely on their foundations being kept as dry as ENCYCLOP.EDIA OF ROA possible. The subsoil water from rising ground should be intercepted and carried away in the manner shown in Fig. 74. This intercepted water can either be carried along the catch-water drain to the low-lying ground, or in a pipe drain down the slope, discharging al frequent intervals into the side channel of the road or into a covered drain. Land water drains can be either open roadside trenches constructed beyond the fences, or covered soaking drains, as shown in Fig. 7z. The latter are to be recommended, and may be formed of land pipes laid in the ditch and covered with large stones up to the level of the surface in the following manner :—The bottom of the trench is covered with hard material upon which is laid the open-jointed pipes. These are covered with large stones about 6 in. in diameter at the bottom and gradually reduced in size to- ward the top. The box-drain C and D (Vig. 7) is usually adopted in districts where stone is plentiful, the stone “bolt” taking the place of the drain pipes. Cross drains should be laid at distances varying from 25 ft. to 50 ft., according to the nature of the subsoil, and be connected to the covered drains in the sides, ditches, or trenches. In ordi- nary town macadam roads subsoil drains are rarely necessary, but when occasion arises they should be laid down the centre of the road parallel to its direction and connected to the surface water sewer. Water is carried off the surface of the road by form- ing its cross section to a slight camber. This will vary according to the material used, the following being found serviceable ratios :— Macadam roads 1 in 80 to 1 in 40. Wood paving . 1 in 45. Asphalte. . Lin 55. The water thus removed is conducted to channels formed at the sides of the roads and 368 ROA is caught in catch-pits or gullies provided at frequent intervals varying from 80 ft. to 120 ft. according to the gradient. These pits and gullies are connected to the surface water sewer or covered ditch drain as the case may be. In order to provide a sill between the footpath and water channel a kerb is laid longitudinally along the road at a height of from 3 in. to 7 in. from the channel and the footpath is finished level with its upper surface. The materials used for such kerbing are either granite, stone, or iron. Granite and iron are the best materials for roads with heavy traffic, and for roads with light traffic sandstones, Kentish ragstone, cement concrete, or petrified fireclay block will be found suitable. The sizes used are usually as follows :—12 in. by 8 in. laid flat, slightly tilted towards the road; 6 in. by 12 in. laid on edge; 4 in. by 9 in. laid on edge. The lengths should not be less than 3 ft. The top surface and front face of stone kerbs should be hammer dressed, the back being dressed to a depth of 3 in. from the top. Allends should be dressed at least 6 in. from the top, to give close joints, and overflows should be cut in the kerb over each gully or catch-pit. The bed should be formed of 6 in. of cement con- erete extending beyond the back face to a dis- tance of 2in. Channels may be constructed of granite in the form of lengths of kerb or setts of varying sizes, the beds being of concrete similar to that for the kerb, and extending beyond the face to a distance of 3 in. Marerimats aND Mersops EmpioyED IN Broxen Stone Roaps.—Before treating of the covering or road surface the formation of the foundation must be dealt with. After the line of road has been excavated and shaped to the desired contour, material of various kinds is laid upon the surface to form the hardcore foundation. This consists either of (1) boulders or large stones laid “ hand pitched,” the stones being about 9 in. in depth, and, as a cover- ing and also to fill in the interstices, a layer of smaller stones about 8 in. in diameter is then spread, and the whole well rolled solid ; or (2) hardcore consisting of broken bricks, stone, clinker, or other similar material spread M.S.E. MUNICIPAL AND SANITARY ENGINEERING. 369 ROA in layers, each layer being wel! rolled, the total depth of material varying from 9 in. to 15 in. according to the traffic the road will have to withstand. Upon the foundation is spread the top sur- face coating, formed with such materials as the engineer has proved by experience to be the best. When deciding this, many points must be kept in view as to the requirements of a good carriageway, and among them are the following :— 1. The cost of construction and maintenance must be economical. 2. The material used must be durable and as noiseless as possible. 8. It must be firm and hard, and safe for horses, giving them a good foothold. 4. It must be sanitary, and as free from mud and dust as possible. 5. It must be impervious to moisture and impurities of every kind, and be easily cleansed. 6. It must be easily taken up and laid down again when required, after being broken up for gas, water, electric light, drains, and other trenches. 7, Whenused for a tramway the material laid down alongside the rails must be capable of with- standing the wear caused by the wheel flanges. Major Isaacs, in a paper read before the Royal Society of Arts on the merits and demerits of road-making materials, compiled the following table from experiments bearing upon the above points, showing, in order of merit, the results of the different materials used. First. Second. Third. Public hygiene .. | Asphalte | Granite Wood Noiselessness .. Wood Asphalte | Granite Safety for horses under essing | Wood | Asphalte | Granite conditions Cleansing Asphalte | Granite Wood Durability Granite | Asphalte | Wood Economy. . .. | Granite Wood | Asphalte Facility of repairs | Asphalte ‘Wood Granite Facility for tram- id aks i wage Granite Wood Asphalte Broken stone roads continue to be in good BB ROA favour, and when the materials used have been carefully selected and properly laid, they can be adopted with economy on country and other roads subjected to medium and light traffic. They are, however, open to objections from a sanitary point of view, and constitute one of the chief difficulties in the dust pro- blem. These objections have been dealt with in the article on “‘ Dust Prevention.” Mareriats.—The materials used in forming macadam roads should be tough and of uniform hardness and durability. Brittle stones do not wear well and rapidly grind away into dust. Atmospheric influences affect many descriptions of stone, and care must be taken to choose one that will satisfy all the above conditions. To ascertain the wearing and other qualities of stone, trials should be made by laying lengths of different classes of stone in streets subjected to the same amount of traffic. The results can then be compared, and will include not only the result of the effect of the traffic on the stones, but also the effect of the weather and atmo- spheric influences and the binding properties of each. It has been found that moderately hard and tough stones are better than exces- sively hard stones for binding purposes. The engineers of the French Ponts et Chaussées have endeavoured to arrive at a comparative numerical value of the qualities of materials used on the national roads, and the coefficients of quality for the various materials are given as follows :— Coefficient for Coefficient for Wear. Working. Basalt .. 12°5 to 24:2 | 12:1 to 16:00 Porphyry 14:1 to 22°9 | 85 to 16°3 Gneiss .. 10°38 to 19 13:4 to 14°8 Granite. . 7:3 to 18 77 to 15°8 Syenite . . 11:6 to 12°7 | 12:4 to 13°00 Slag 6 145 to 15°3 | 7:2to 111 Quartzite ae .. | 18°8 to 80 12:2 to 21°6 Quartz Ore Sandstone | 14°3 to 26°2 9°9 to 16°6 Quartz .. 12°9 to 17°8 | 12°38 to 18°2 Silex .. 9°8 to 21°3 | 14:2 to 17°6 Chalk Flint 3°5 to 16°8 | 17°8 to 25°5 Limestone 6°6 to 15°7 6°5 to 13°5 The coefficient 20 is equal to excellent, 10 ENCYCLOPADIA OF ROA to sufficiently good, and 5 to bad. Space will not admit of a full geological description of the formations from which these various rocks are obtained, but the reader is referred to geological books and survey maps from which the information can be obtained. The majority of road stones contain from 45 to 70°/, of silica, and have a specific gravity varying from 2°50 to 29°5. > KC Hes SKS YY; Fig. 7.—Clyde Bank Intercepting Sewer, Glasgow. cement, and an outside layer of cement con- erete on the upper part of the exterior. The usual side walks are also provided for inspec- tion and clearance of deposits, &c. . aigall Mack. LE ” The cards should be about 9 in. square, and placed about 50 or 60 ft. from the eye, and compared with the smoke issuing from the chimney; the lines and spaces give at this distance a grey effect. Such a method is crude, and, except for comparing the smoke from the same chimney at different times, or from chimneys of similar diameter, is of little use. The shade of the smoke depends as much on the thickness of the layer looked through as on its density. Any such method should, to be at all accurate, take account of the diameter of the chimney. The advisability of preventing smoke arises, not only from the loss of fuel involved in its production, as from its injurious effects on animal and vegetable life, as well as on buildings. Few plants thrive in smoky cities, the air of which is especially fatal to conifers; the plane tree is one of the few that can survive such con- ditions. ‘The effect of smoke on buildings is due to the deposit of its solid matter, which not only disfigures them but acts as a vehicle for the sulphur acids evolved with the smoke; these attack limestone and iron-work, and rapidly destroy them. Turning now to methods of prevention: 442 SMO certain primary conditions must be fulfilled ; these are :— (1) Enough air must be supplied to com- bine with the carbon of the fuel. (2) This air must be mixed intimately with the gases from the coal. (3) The temperature of the gases must not fall below 700° C. until combustion is com- pleted. The undue cooling of the gases is probably the most potent cause of smoke, as it is more common to have too much air supplied than too little, and this reduces the temperature of the gases below the ignition point. Such cooling also results from the contact of flame with a cold surface, such as that of water-tubes or boiler-plates ; hence it is important to provide in boiler furnaces a sufficient space for com- bustion to be completed before the, flames come in contact with the comparatively cold surface of the boiler. This means the pro- vision of a sufficiently large fire-brick-lined combustion chamber. When we consider domestic fires, which are a source of a large proportion of smoke, we see that it is practically impossible to fulfil the above conditions. Too much air is admitted, the gases are cooled below their ignition points, and the flames come in con- tact with cold surfaces at many points. We may say, therefore, that no method has ever been devised which prevents the issue of smoke from domestic grates burning bitumin- ous coal. The solution of the smoke problem lies in a different direction, and will doubtless be the burning of a smokeless fuel, either solid or gaseous. Of solid we have a choice of anthracite, coke, or partially coked coal ; and of gaseous we have at present only coal- gas to consider. In a country where electricity can only be produced on a large scale by the combustion of coal we can hardly look. to electric heating as a solution, owing to its cost. Domestic heating by means of ordinary coal or coke fires, anthracite burnt in specially constructed stoves, and gas fires, when the fires are run continuously, costs approximately as follows, based on tests in rooms of about MUNICIPAL AND SANITARY ENGINEERING. SMO 4,000 cub. ft. capacity :—Coal 0°026 to 0°0338, coke 0°087, anthracite 0°01, and coal gas 0°11, in pence per hour per degree F. of rise in temperature of the room air. It is probable that the solution of smokeless domestic heating will be eventually found in the production of some form of cheap gas at the coalfields, and its supply to our cities through high-pressure mains. The case of large furnaces for steam raising is different, and these can be successfully operated with bituminous coal with a practical absence of smoke. It is chiefly a question of stoking, but the furnaces must be properly constructed and proportioned in the first instance, with ample grate area and com- bustion chamber. It has been found that while theoretically hand stoking can be so done as to practically prevent smoke, too much depends on the stoker, and mechanical appliances are more successful. Mechanical stokers may be roughly divided into three classes :— (1) Coking stokers. In these the coal is fed mechanically to the front part of the furnace, where the gases are distilled off; these are passed over the incandescent fuel at the back, and there burnt. As the gases are driven off, the coke left is pushed gradually towards the back of the furnace and there burnt. (2) Sprinkling stokers. These act by scat- tering over the incandescent fuel in the furnace small quantities of fresh coal at regular intervals. The quantity being small is consumed with little or no smoke. (3) Underfeed stokers. In this type the fuel is forced up from below at a regular rate into a specially constructed furnace. ‘The gases distilled off are therefore forced to pass up through the incandescent fuel on the surface, and are thus consumed. Smoke may be prevented also by forcing jets of heated air into the furnace near the back. Turning now to the legal aspect of the question. The Public Health Act of 1875 contains the statutory law relating to smoke 443 SNO emission London. The Public Health Act (London) of 1891 includes the sections relating to smoke in the Act of 1875, making them applicable to the administrative county of London. Both of these Acts make it an offence to emit from any chimney, not being the chimney of a private dwelling-house, ‘“ black smoke in such quantities as to be a nuisance.” It is curious to observe that there is prob- ably no such thing as “black” coal smoke ; it is usually of a brownish shade, hence the presence of the word black renders the appli- cation of the Act difficult. J. 5. O. throughout England, excepting Snow.—When the temperature of the air is about or below the freezing-point, precipita- tion usually takes the form of snow instead of rain. Snow-flakes are six-pointed crystals, and are of great variety. Scoresby, Glaisher, and others have made a large number of drawings of snow crystals; and during recent years photographs of snow-flakes under the microscope have been obtained, notably by Mr. W. A. Bentley, of Jericho, Vt., U. S. A. These all show the crystals to be of extreme beauty. When snow is falling, if any one will catch some of the flakes on the sleeve of his coat and look at them under a mag- nifying glass, he will be charmed by their exquisite beauty. Their size varies, but it is generally from one-tenth to three-tenths of an inch in diameter. Although snowflakes are so small, yet when they accumulate they often do a great deal of damage, especially if the wind is high and causes snow-drifts. These render traffic almost impossible, and often cause loss of life to both human beings and animals. Snow is measured by the rain- gauge; that which is collected in the funnel being melted and measured as rain. A foot of snow is roughly equal to an inch of rain. Snow, however, varies greatly in density; with very loose snow as much as 16 in. may only produce an inch of water, while at other times, especially in blizzards, snow may ENCYCLOPAEDIA OF SPR be granular, something like sand, and then 7 in. may produce an inch of water. W. M. Soil Pipes. (See “ Piumsine.”) Sol.—A term introduced by Graham to denote the apparent solubility of colloidal matters (q. v.). Sparge Pipe.—aA pipe having fine holes drilled throughout its length so as to deliver a spray of water as is required for flushing. Spence’s “Alumino Ferric” (Treat- ment of Sewage).—Alumino-ferric and lime are used as precipitants at Chiswick, on the advice of Dr. Tidy, chemist. Seven grains of lime to the gallon and five grains of the alum in solution are incorporated with the sewage by agitation. After precipitation the tank effluent is filtered. ‘To each hundredweight of wet sludge are added 14 lbs. of lime pre- vious to pressing in filter presses. The sludge is burned in a “ Horsfall”’ refuse destructor. Sprinklers for Sewage Beds. (See “‘Sewace DisposaL”’ and “ DisrRIBUTORS, FOR SEwace.’’) Springs.—These are of two classes, “ Land Springs” and ‘‘Deep Springs.” The land springs rise from superficial beds of sand or gravel lying upon an impermeable stratum of clay or rock; consequently their flow is irregular, are immediately dependent on the rainfall, and are generally dry during summer. Deep springs are supplied from deep-seated water-bearing stratum, such as chalk, green- sand, &c. The water therefrom is usually free from organic and suspended matters, having filtered through considerable thick- nesses of strata. Spring-water often contains dissolved inorganic matters taken up from the rocks through which it has percolated. The flow or yield of a deep spring, though variable, is more constant than that of land springs, and, generally speaking, the deeper the stratum from which the supply is obtained, the more regular the flow. Very commonly the yield is lowest in October or November, 444 STA and highest in the following February or March, but is dependent upon the rainfall. Various conditions determine the amount of rain which percolates the ground: (1) nature of the soil; (2) configuration of the land;. (3) temperature and movement of the air. Clay is almost impervious, gravel or a loose sandy soil absorb about 96°/,, limestone about 20°/,, chalk about 42°/,. In a flat district evaporation may amount to 50 °/, less than in an undulating one. ‘‘ Land” springs are derived from shallow beds of gravel, and their flow is uncertain. “Main springs” come from deeper strata; their yield is more constant, and usually of a better quality. Where springs afford the supply to a town, the ‘‘gathering grounds” require to be kept under close observation to detect any possible sources of pollution. As instances of good supplies from springs may be men- tioned the chalk-water springs of Amwell and Chadwell in Hertfordshire, the supplies to Malvern and Tunbridge Wells. Some of the best spring waters are derived from granitic, jurassic and cretaceous strata. Spring and deep well waters form a favourable medium for the propagation of certain germs, and should, therefore, be carefully guarded against pollu- tion in the course of delivery to the consumer. Stable Construction and Sanitation.— The essential conditions in stable construc- tion from a sanitary standpoint, as distinct from the architectural, are :—Lighting, venti- lation, paving, and drainage. Ample light makes for health and cleanliness, and, as glass is cheap, windows and skylights may be freely used if so placed and arranged as not to create draughts. Where economy is a consideration the admission of light may be arranged for by the insertion of squares of rough plate-glass or of glass tiles in the roof. As regards ventilation, this is amply provided for during the day by the windows and doors, which latter it is usual to hang in halves, so that the upper half may be left open while the lower is closed. It is during the night and at other times at which stables are closed MUNICIPAL AND SANITARY ENGINEERING. STA that ventilation must be chiefly arranged for. This is best done by inlets fixed under the mangers and louvred outlets in the roof, or near the ceilings where there are rooms above the stables. Stable paving must in all cases be impervious, and may consist of grooved bricks made for the purpose, or of blue bricks on edge grouted in cement, or of concrete, granolithic cement, and similar materials. It is desirable that such surfaces be provided with shallow channelling, on the one hand, to facilitate the draining away of moisture, and, on the other, to prevent horses or other animals from slipping. The floors should be laid to a slight fall towards a collecting channel or gulley in the centre or at the back of each stall, the latter being the more desir- able. This fall should not exceed 1 in 40, as a steeper inclination causes discomfort to animals. The gradient named is quite suff- cient for the object in view, if the floor is reasonably well laid. The collecting channels may be formed in the flooring itself with cement or blue bricks, &c., or they may take the form of cast-iron stable channelling having longitudinal slits in the cover which, while admitting liquids to the channels below, will exclude from them straw or other bedding materials. These covers should be removable in order that the channels may be occasion- ally swilled with water and brushed out. The channels should be carried through the wall to the exterior and arranged to discharge over gully traps, which in their turn may be connected to the general drainage scheme, or arranged to discharge into a properly-con- structed tank in cases where it is desired to collect the liquid for manurial purposes. Channels in stables are preferable to collecting gullies, as the drains from these are not so readily kept clean as the channels. If used, the gullies should be provided with double gratings to exclude straw, &c., from the drains. The drains from them should also be arranged to discharge over gullies in the open, as the seals of the traps in the stables are liable to be destroyed by evaporation. As regards the walls, partitions, and the general 445 STA construction of stables, it may be said that all should be as smooth as possible so as to minimise possible lodgment for dust, dirt, and bacteria. For the same reason all angles and corners should be rounded. The walls and partitions should further be so constructed and decorated that they may be easily washed down. G.J.G. J. Stand-pipes. (See “ Warer Suppry” and “Pumps anD Pumping Macuinery.’’) Stand-pipe and Air-Vessel.—Thiese are important accessories in connection with any system of pumping machinery, their function being to absorb the excess and to compensate Fic. 1.—Cylindrical Air-vessel on Delivery Main. for the deficiency of delivery by the pumps. Excess of delivery causes the water column in the stand-pipe to rise, and this falls again when needed to balance any deficiency of supply. The work thus expended in lifting the water column, or of forcing water into the air-vessel against the cushion of compressed air contained in the upper part of the dome, is given out again to the advancing water in the main and so equalises any weakness of pressure occurring therein. The air-vessel also relieves the valves from severe shocks, and is of special use on high lifts and heavy pressures. Air vessels often enable pumps to be worked at increased speeds, and should be so arranged as to be readily recharged with air to replace absorption by the water. In considering the size and shape of an ENCYCLOPAIDIA OF STA air-vessel the degree of pressure and the ratio of excess of delivery of the pumps are the important factors to be kept in view. In practice the sizes vary, according to cireum- stances, from four to fourteen times, or more, the capacity of the barrel of the pump. Air- vessels are made proportionately larger when subjected to high pressures. To prevent the Reservowr | 8 Valve Three-legged’” *”~Velve Stand- pipe Fic. 2.—Three-legged Stand-pipe on Pumping Main water being forced too high into the air-vessel and the rapid absorption of the air by the water, the vessel is usually made with a long narrow neck, as the larger the surface in con- tact with the water the quicker the absorption. Sometimes a disc of wood an inch or two smaller than the diameter of the air-vessel is placed on the top of the water in the vessel so Fic. 3.—Elevation of Stand-pipe on Pumping Main. as to reduce the surface in contact with the air. Provision must be made by means of a small air-pump, or by a “‘ snifting-valve,” for replenishing the air in the vessel thus gradu- ally dissolved in the water. An air-vessel, to be most effective in the prevention of shocks due to the momentum of the water in the opening and closing of the valves, should be placed close to the pump on the delivery 446 STE main and connected up by a branch pipe of large diameter. Where a large mass of water is put into motion in the suction-pipe by each stroke of the pumps, it is advisable to provide the suction with a foot-valve and also to fix an air-vessel in the suction pipes to effect a more gradual arrest of the water and reduce the impact on the pump-valves. The balloon-shaped air-vessels retain the air longer than those of cylindrical shape. The vessels are made of cast-iron, should be of ample strength according to the pressure to be borne, and be provided with air-cocks at the top and draw-off cocks at the bottom to admit air or drain the rising main if required. In the United States it is the practice to employ huge cylindrical metal towers or tank stand-pipes which are frequently of sufficient capacity to serve as service reservoirs, and hold a full day’s domestic consumption and several hours’ fire consumption of water, or more. At Sandusky, Ohio, is a stand-pipe 25 ft. diameter and 229 ft. high. The diagram (Fig. 2) illustrates the application of a ‘“‘stand-pipe”’ to a pumping or rising main, which is brought into use by closing the valves A and B when the water passes over the top of stand-pipe and gives the additional ‘‘head”’ gained by its height—any surplus water pumped passing down the third leg C and into the low service reservoir adjoining. The application of an “‘air-vessel” to an ordinary delivery or pumping main is shown diagrammatically in Fig. 3. Steam-Engines.—In classifying steam- engines and machinery for waterworks and general pumping purposes, a great many independent characteristics in regard to their general arrangement of parts and methods of working must be taken into consideration. They may, for example, be divided into con- densing and non-condensing, compound and non-compound, single and double-acting, geared and direct coupled, direct and crank- shaft, rotative and non-rotative, and vertical, horizontal, inclined, or inverted cylinder engines. MUNICIPAL AND SANITARY ENGINEERING. STE Non-condensing engines exhaust their steam direct into the atmosphere or into a receiver where the pressure is greater than that of the atmosphere. The steam is used at full pressure either partially or throughout the stroke, sufficient allowance being made to “cut off” and avoid back-pressure. Con- densing engines exhaust their steam after forcing the piston from the beginning to the end of the stroke into a separate chamber termed a ‘‘ condenser,’ which is maintained in a state of partial vacuum, the steam being therein condensed by contact with a nest of tubes through or around which cold water is constantly circulated (surface condensing), or, in some forms, a jet of cold water is sprayed into the condenser and meets the incoming steam (jet condensing). The condensed water and air are removed from the condenser by an air-pump usually worked from the engine, and the water, having a probable temperature of about 115° F., is used for feeding the boilers. The advantages of condensing are very con- siderable, and the process should be adopted in all but quite the smaller sized engines, as a great economy of steam consumption is effected thereby. Engines are classified as compound or non-compound according to the number of expansions of the steam obtained in the cylinders. The non-compound or simple engine consists of a single cylinder in which the steam does its work, and is then exhausted either directly into the atmosphere orinto acondenser. In the compound engine the steam, after having partially expanded and done work in the small or high pressure cylinder, is exhausted into a larger or low- pressure cylinder, where it undergoes a further expansion before being exhausted into the condenser. In the triple and quadruple expansion engines the steam does work in three and four successive cylinders respec- tively before being finally exhausted into the condenser. A single-acting engine is one in which the steam acts upon one side of the piston only. In a double-acting engine it acts upon both sides of the piston alternately. Both single 447 STE and double-acting engines are made either of the condensing or non-condensing type. Another important distinction in the classifi- cation of pumping engines and machinery lies between geared and direct-coupled machinery. In geared pumping machinery high speed engines are employed, and the pumps are driven therefrom by means of gearing, toothed wheels, or by means of belting, chains, or ropes. By these means the engine is usually run ata greater speed than the pumps, and some economy of steam consumption per indicated horse-power should be secured. Another advantage looked for in this system is that of less capital cost for the engine and lighter foundations. There will, on the other hand, usually be a lower mechanical efficiency (probably not more than from 65 to 75°), greater liability to break down, increased wear and tear, noise, and vibration. In direct-coupled pumping machinery the pumps are connected to the steam ends, the number of reciprocations of the pumps is the same as in the engine, and the mechanical efficiency may be as high as 92°/,. There is less wear and tear, less liability to break down, and the vertical direct-acting type of machinery is usually the most satisfactory for large stations. A distinction is also to be noted between direct and crank-shaft with fly- wheel engines. In the direct engine the piston- rod of the engine and the piston-rod or plunger of the pump are continuous, there being no crank-shaft or fly-wheel. Roughly speaking it may be said that a typical direct-engine consists of two cylinders placed side by side, the admission of steam being controlled by ordinary three-ported slide valves. As the piston of one cylinder is moving towards the other end of the cylinder it strikes a lever actuating the slide valve of the other cylinder, and in this way each piston alternately actuates the slide valve admitting steam to the other cylinder. Frequently, however, one of the two cylinders named is simply a very srcall one, the function of which is to actuate the slide valve of the large cylinder. Engines of this class are quite self-acting, convenient, ENCYCLOPADIA OF STE and compact, but are not economical, there being no expansion of the steam. Of later years, however, very great improvements have been made by “compounding” and by the introduction of “ high-duty gear,” the function of this latter improvement being to absorb a certain quantity of power at the beginning of the stroke and to give it off again towards the end—the steam working expansively in the cylinder. The most modern direct-engines embodying the latest improvements in the economical use of steam are thus amongst the most efficient pumping engines employed. The “beam engine” is the earliest form of crank-shaft and fly-wheel engine, many examples of which are still in use, though this type is gradually being superseded. The advantage of the modern forms of crank-shaft pumping engines is that they lend themselves favourably to the expansive working of steam, and various ways are adopted in practice of arranging the cylinders and cranks in the compound and triple-expansion engines of this class. The best form is that in which there are three cylinders, each working a pump by means of a “ three-throw ” crank— the cranks being placed at angles of 120°. From such a pump the delivery of water is quite uniform, which is an important con- sideration, especially where the water is delivered direct into the distributing mains. When the reciprocating motion of the piston of an engine does work simply upon a reciprocating piece the engine is termed non- rotative, but when the work is done upon a continuously revolving shaft, as is more generally the case, the engine is then of the rotative class. Usually the crank pin of the revolving shaft is connected directly with the piston-rod by a connecting-rod, and the engine is said to be direct-acting. Engines are also sometimes classified according to the position and arrangement of the cylinder, and are then described as horizontal, vertical, or inclined cylinder engines respectively. If the cylinder is above the connecting-rod and crank, as in many vertical engines, the engine is described as of the inverted cylinder class. 448 STE The duty or effective work of a pumping engine is expressed by stating the ratio of the product in foot-pounds of the weight of water raised into the height it has to be lifted with relation to 1 cwt. (112 lbs.) of coal consumed in lifting the water. In America 100 lbs. of coal is adopted as the unit of measurement, and some misunder- standing not infrequently arises by the comparison of results reduced to these different standards. In refined experiments the weight of ashes and clinkers is deducted and the unit of fuel taken on the combustible portion of the coal used. According to the dynamic theory of heat, 1 lb. of average good coal contains about 14,000 units of heat which aredeveloped.into a force capable of doing a definite amount of work when burned to produce steam. In actual practice a very large proportion of these heat units are lost in various ways, such as by escape up the chimney, by condensation of the steam in pipes and cylinders, by leakage past the piston or valves, and by escape with the exhaust steam into the condenser, so that in the end only some 10 or 12°/, are usually transformed into actual useful work. Any successful efforts, therefore, to reduce these several sources of loss to a minimum will result in increased efficiency and economy of working. The efficiency of the steam-engine is repre- sented by the ratio which the power developed in the cylinders (stated in thermal units) bears to the heat units supplied to the engine. The mechanical efficiency of an engine is the inverse ratio which the I.H.P. bears to the power given off at the crank-shaft or fly-wheel (B.H:P.). The efficiency of the pump is the inverse ratio of the latter to the work done. The work done is stated in foot-pounds, and is represented by the pro- duct of the weight of water raiséd (in pounds) into the actual lift or head (in feet). The steam-engine is a heat engine, and the true measure of its efficiency is the amount of heat consumed in the performance of a definite amount of useful work; but as the total units M.8.E. MUNICIPAL AND SANITARY ENGINEERING. 449 STE of heat in a pound of dry steam differs but little through the pressures commonly em- ployed,! it is regarded as a sufficiently approximate and convenient means of com- paring the efficiencies of engines to state the pounds of dry steam used in the cylinders to generate 1 h.p. of work. In good class engines the following results of steam con- sumption per horse-power hour are readily obtainable :— Per Hour. Non-condensing engines . 25 lbs. steam per I.H.P. Condensing 5 . 18 Ibs. i Compound 5 14 to 16 lbs. ,, Triple-expansion ,, 12 to 18 lbs. ,, It will also be convenient here to state what may be considered good results in coal consumption per horse-power for various classes of engines :— Non-condensing engines a oak per I.H.P. Condensing i ; Compound 55 4 a 12 Ibs. ,, Triple-expansion ,, to 1$ lbs. ,, A small coal consumption indicates an economical engine and boiler, but a large consumption does not necessarily prove the reverse, so that the rating of an engine according to the coal burned is not a reliable method, as many other questions are also involved, such, for example, as the quality of the coal and the manner of stoking. In any trials for efficiency it is necessary to dis- tinguish that of the steam-engine from the efficiency of the boiler. For further information see also articles on “ ConDENSING,” “ InpiIcaTor,”’ “STEAM RalsinG,” *« RconomIsEeRs,”’ ‘‘ Horse-PowEr,”’ ‘‘ BoILERs,” “ RuEL.” W. H. M. Steam Raising.—In modern economical steam raising various devices are employed with the object of producing steam with a minimum consumption of fuel by economising all waste heat as fully as possible, and of reducing the losses due to condensation of the steam during its use. Some of the 1 At absolute pressure of 80 lbs. per square inch the total heat in 1 lb. of steam from water at 82° F. is 1,177 British thermal units; at 150 lbs. pressure it is 1,191-2 units. GG STE methods employed are, the use of superheated steam, of economisers or feed-water heaters, steam dryers and purifiers, and steam jacketing. SUPERHEATED StEAM.—Steam formed in an open boiler under atmospheric pressure (14°7 Ibs. per square inch) has the same temperature as the boiling water, 212° F. When the boiler is closed, as with a weighted valve, steam is formed at a higher temperature, because of the greater pressure. The vapour of water boiled in a partial vacuum will have a tem- perature below 212° because of the lower pressure. Steam formed in contact with water, as in an ordinary boiler, and containing watery particles is called wet saturated steam. When all the water has just boiled away and the saturation point is reached—all the latent heat required for the steam having been taken up—we have dry saturated steam. Saturated steam, which is perfectly dry, contains in a given volume, and at a given temperature, the maximum weight of evaporated water, and has the maxima pressure and density attainable at such temperature. Dry saturated steam is only approximated to in practice by providing domes to boilers in order to remove the steam as far as possible from the water. Applying heat still further, after having removed the steam from the presence of water, it becomes surcharged with heat, and is then said to be superheated steam, that is, steam which has its temperature raised above formation point. The more it is heated the more nearly will its properties approach those of a perfect gas. Superheated steam cannot exist in the presence of water, as the latter will absorb the surplus of superheat and the steam thus reverts to the saturated state. The advantages to be derived from the use of superheated steam are the prevention of condensation and consequent fall in steam pressure in passing from the boiler to the engine, and, in the engine, the elimination of condensation losses within the cylinder due to exchange of heat between the steam and metal cylinder walls. The object to be achieved therefore is to deliver the steam into the cylinder with such surplus heat as will prevent condensation, thus keeping the ENCYCLOPADIA OF STE steam as dry as possible throughout the stroke. The advantages of superheating were demonstrated by Hirn as long ago as 1855, but troubles were experienced at the super- heater, and the cylinder lubricants were burned up, resulting in the abandonment of the process in 1870. Upon the introduction of safer superheaters and heavy mineral lubricating oils the original objections were removed, and a revival of superheating has taken place since 1890, producing an important improvement in the thermodynamic economy of engines. The gain from superheating may be taken at an average of about 25°/,, but varies from 10 to 50°/, with 50° to 100° of superheat according to the efficiency of the engine. Mr. M. Longridge has given it as his opinion that 400° F. of superheat in the cylinder is sufficient to prevent initial con- densation, and that the superheater, to be efficient, should have a head of about 400° F. above the temperature of the superheated steam. In practice, the steam to be super- heated is led off from the boiler into a separate vessel or accessory appliance called a ‘“ super- heater,” and in which it is subjected to the additional heat. Superheaters are either of the flue-fired class or are independently-fired. Flue-fired superheaters are placed in the down-takes of Lancashire and Cornish boilers, where they are heated by the gases from the furnace flues, thus utilising what would other- wise pass away as waste heat. With boilers of the water-tube class independently-fired superheaters are mostly used. Some highly economical results, not obtainable from steam in any other way, have been obtained by Mr. Schmidt, whose experiments have shown it possible to employ steam superheated by as much as 300° F. In trials of the Schmidt engine and superheater, the consumption of steam has been well below 10 lbs. per Indicated H.P. hour, and the consumption of coal in boiler and superheater together, it was found, was as low as 1:8 lb. per Indicated H.P. even with small engines. In these trials, after the hot gases had passed the superheater, as much of the remaining heat was utilised as possible 450 STE in an economiser or feed water-heater for the interception and return of the heat to the boiler. Stream: HiquivaLeENt WEIGHT oF WATER As EvaPoRaTED FROM AND At 212° F.—For the purpose of comparing evaporative boiler tests, the results obtained must be reduced to a common standard, which is usually reckoned from and at 212° F. The method of calcu- lating these results will be best understood by the following example :— From the tests made, suppose that 1 Ib. of the coal used has been found to evaporate 9°71 lbs. of water, with boiler feed at 145° F. and steam pressure 90 lbs. per square inch, as shown by the gauge. Steam at 90 lbs. gauge pressure is equivalent to 90 + 15 lbs. (atmo- spheric pressure), that is, 105 lbs. absolute. By reference to Regnault’s tables of the properties of saturated steam (to be found in the majority of engineering pocket-books), it will be seen that the temperature of steam at 105 lbs. absolute is 331°3° F., and also that the total heat in 1 lb. of steam at that pressure from . water at 32° F. is 1,183 British thermal units. The latent heat in 1 1b. of steam at 212° F. is 966°6 British thermal units (see tables), and the equivalent weight of water evaporated per pound of coal from and at 212° F. is there- fore represented by the following equation :— —— toa O w — Ht — 82) 966°6 in which,— W = the equivalent weight of water evapo- rated from and at 212° F.; H = total heat of steam (in British thermal units) at the temperature corresponding to the pressure, from water at 32° F.; = temperature of boiler feed during the test; w = weight of water actually evaporated per pound of coal from temperature (¢) of feed, Substituting the numerical values in the above example, we have— 1188 — (145 — 32) xX wv, w= 9666 xX O71 1070 BE. aes oy W = 9666 xX 9°71 = 10°748 lbs. 451 MUNICIPAL AND SANITARY ENGINEERING. STE Sterilisation of Water can be effected by (1) heat, (2) filtration, (8) certain chemical agents. (1) Heat.— Boiling is an efficient means on a small scale, but the expense is prohibitive when large quantities have to be regularly dealt with, and the resultant liquid is de- aérated and less palatable. In the Rouart, Geneste-Herscher, and Vaillard-Desmaroux sterilisers the water is heated for a short time to 118-116° C. in a closed vessel, or a system of coils, whereby the outgoing is made to heat the incoming water, at the same time being itself cooled to near the ordinary temperature. In this way the natural gases are retained, very little earthy deposit occurs, and the sterilised water is protected from air. A deposit, however, does accumulate, and the narrow coils sometimes block, and are difficult to clean. In the Forbes apparatus, used in the United States army, the water is only boiled for a few seconds, so that it preserves most of its original gas and taste ; it then passes over a weir into a temperature exchanger. The working is regulated by a valve. Other types used in America are the Kny-Scheerer, Maignen, and Von Siemens. In England the Lawrence steriliser and softener has been in use for some time at Guy’s Hospital and elsewhere. Its boiler is a vertical cylinder fitted with depositing trays above the water line and plates called ‘‘locators” below it. The water boils up over the trays and deposits its lime and magnesia carbonates on the trays and locators (which are removable for renewal or cleaning), and passes to an interchanger. The writer’s results with different heat sterilisers showed that sterility, even with very varying rates of flow, can with care be insured. Fitrration.—Sand and mechanical filters in good condition, and under favourable circum- stances, yield a sterile effluent, but such a result can only be depended upon with a much finer medium. The only filter that has stood all tests is the Pasteur-Chamberland “ candle” filter of biscuit porcelain, in which the water passes from the outside inwards, under pres- sure from the main, a force pump, or exhaust. Ga2 STE The tube is very carefully cleaned, and should be sterilised by boiling at intervals. The average yield per tube is estimated at 4 gallon per day with only an ordinary head of water, and 8 gallons per day with pressure. The tubes can be arranged in “batteries” of any number, and the joints must be carefully attended to. CuemicaL Acents.—For chlorine, ozone, and permanganate, see respective articles and *Conpy’s Fuurp.” It has long been known that acids generally, and many metallic salts, are antagonistic to bacteria, but for sterilisa- tion of ordinary water an agent is required which is not costly and is non-poisonous to higher life, and this limits the application to special cases. 0°072°/, of sulphuric acid is effective against B. typhosus in 15 minutes, and 62 grains per gallon is sufficient to destroy typhoid organisms in the usual drainage from an isolation hos- pital or other infected area. B. enteritidis Sp. cholere,; intestinal worms and ova,! are also killed, and the free acidity is soon neutralised on mixture with ordinary sewage. For sterilising water in campaigns bisulphate of soda, 15 grains per pint, is portable and effective.? With the same object Schumberg in the German army has used bromine, 6 parts per 100,000, followed by a tablet of sodium sul- phite and mannite, but among the objections have been the difficulty of transporting the bromine, and the presence of bromides in the water.2 Allain at Marseilles used iodine, and Nesfield in India has employed a tablet con- taining iodide and iodate and another contain- ing tartaric or citric acid; together, when used as directed, they liberate 5 parts of jodine per 100,000 of water; after 2 to 5- minutes any excess of iodine is removed by a tablet of sodium sulphite. The writer found that the sterilisation was satisfactory. (See 1 Valerio, ‘“ Bull. Soc. Vaudoise Sci. Nat.,’”’ 1902, No. 1438. 2 Parkes and Rideal, ‘‘ Epidem. Soc.,”’ 1901; Lancet, Jan. 26th, 1901. 8 Public Health, Sept., 1902, p. 709. 4 J. of Prevent. Medicine, Oct., 1905; Indian Med. Gaz., Aug., 1905. ENCYCLOPADIA OF STO “Anam In Warer Svuppuies”; “ FILTERs, Domestic”; “ Frurration”’; “ WaTtER SupPLy, Domsstic.’’) Copper salts in small quantities have been repeatedly tried. One in 8,500 of the sulphate, or 1 in 18,500 of the chloride, kills B. colt in 3 hours; 1 in 7,000 of sulphate, or 1 in 10,000 of chloride, kills Staph. aureus in 2 hours. One in 1 to 10,000,000 prevents the growth of alg, and in this small quantity it is not poisonous to man or to fish, and is removed after a time by natural precipi- tation. S. BR. Storm-water.—The quantity of storm- water or dilute sewage coming down to the outfall works during rainy periods is a very variable quantity in different districts. The proportion of the total rainfall reaching the sewers depends largely upon the character of the district; obviously, a much greater flow would be experienced from a hilly area with a clay or other impervious soil than would be derived from a flat chalky or other porous and absorbent area. district is built upon, and the proportion of paved areas, also influences the total of storm- water to be provided for. Another feature is the condition of soundness, or otherwise, of the sewers and the consequent extent to which subsoil water may be able to gain access thereto. Where the sewers are old, leaky, of porous or defective brickwork, and such like, the amount of subsoil water draining away through them may easily be far in excess of the sewage proper. The ordinary dry weather flow of sewage should closely approximate to the amount of the water supply of the district. This may be anything from about 25 gallons to 35 gallons per head per day. All sewage flow beyond this amount would, therefore, be due to rainfall or subsoil soakage, and, to a less extent, in some cases to manufacturers’ wastes, in so far as the water supply for such 1 “ Bulletin U.S. Department of Agriculture,” 1908 ; “ Zeits. f. Hyg.,” 1908, p. 495; J. R. San. Inst., 1904, p. 591; ibid., 1906, p. 556; J. Prevent. Med., July, 1904; ‘‘ Chem. Centralblatt,” 1900, ii., 208. 452 The extent to which the -- - STO trades was derived otherwise than from the town supply. In a very hilly district the storm-water is more difficult to cope with than in one of a less undulating character, because in the former case the storm-flow is relatively larger and reaches the outfall works much more suddenly. In other words, the rate of flow is more rapid, though of possibly shorter duration, and the provision to be made for the reception of such abnormal discharges must be relatively larger and more complete than in cases where the delivery is less violent. One inch of rainfall in an hour occurs but seldom in this country, as in the case of excep- tionally severe storms, so that a provision of sewer capacity to remove that amount should be ample. In fact, to further increase the sizes of sewers beyond this limit would seriously decrease their efficiency under ordinary working conditions, besides greatly enhancing the cost of sewering the district without any proportionate advantage. The London sewers were designed to remove only 01 in. of rainfall per hour in addition to an allowance of 5 cu. ft. of sewage per head per day. It was estimated that only five-eighths of this rainfall would reach the sewers—the remaining three-eighths being evaporated or absorbed. Experience has shown that this allowance is too small. The sewerage system for Edinburgh gives provision for 42 gallons per head per day, one-half of this to flow off in 8 hours. Only in exceptional cases would the flow exceed 50 gallons per head per day. In some districts small natural streams find their way into the sewers, and these in rainy periods become quickly swollen, so that the ordinary calculations of the volume of storm- water to be dealt with are not applicable to such cases. There is no doubt that the first flush of storm-water delivered at the outfall is very foul and heavily laden with suspended matter, especially where the main sewers are in a defective condition. Storm overflows or reliefs should therefore not come into action until the rate of flow has increased to several times the normal. The provision of such “ yeliefs’’ or overflows is an essential part of MUNICIPAL AND SANITARY ENGINEERING. STO the sewerage system. In a hilly district their absence might readily lead. to the bursting of a main sewer owing to the volume of water coming down from the higher parts of the district heading up for the want of a free outlet, and so unduly increasing the pressure within the sewer. The flooding of premises in the lower parts along the line of sewer would also result. There is a difficulty in fixing storm over- flows to pass sewage at any fixed or uniform degree of dilution because the ordinary flow in sewers varies throughout the 24 hours—the sewage coming down during the morning hours, say 8 a.m. to 12 noon, is many times greater than the night flow from, say, 8 pm. to 6 am., so that if the overflow is fixed for a dilution of six times the morning-flow, the night-flow, owing to its smaller volume, will necessarily be diluted to a much larger extent before any liquid passes the storm-overflow, and, as a result, the purification works will be saddled with a larger quantity of weak sewage during the night than is necessary. Purification works are much relieved by the provision of separate sewers for storm-water, as distinct from soil sewers, but in cases where the sewage is discharged into the sea a combined system will be most economical. Dr. Houston, the expert bacteriologist engaged by the Royal Commission on Sewage Disposal, upon inves- tigations in this connection regards storm- waters as being “as potentially dangerous to health as normal crude sewage,” but recognises the impracticability of treating the whole flow during storms. Where sewage farms are in use for dealing with the sewage an ample area of pasture land should be specially reserved for the overflow of storm-water. Such storm-water areas should not be used for taking part of the ordinary flow of sewage, but should, as far as possible, be reserved in a condition of readiness to receive large volumes of dilute sewage for short periods. The treatment should be one of surface irrigation without under-drainage. Where land is not available, it has been the 453 STO practice of late years to provide special storm- water filters which act as mechanical strainers of the suspended matters from storm- waters and pass the liquid at the rate of about 500 gallons per square yard per day. These have frequently been simple excavations in the earth, filled with gravel, broken stone or clinker, but they have not, generally speaking, proved very satisfactory, and, on the whole, do not justify their cost. The money spent in the construction of storm-water beds would, in most cases, be more advantageously used in the provision of larger permanent filters upon which the ordinary flow of sewage is treated. By this means the whole area of beds may be kept in a mature and working condition, and a better average effluent pro- duced, as the filtration can be done at a slower rate per volume of material. Special storm- filters, on the other hand, lie idle for long periods, and the money spent on their con- struction is thus not continually employed to the best advantage. The filters, too, become dry, and their oxidising efficiency is much impaired. The Royal Commission on Sewage Disposal (fifth report, 1908) report unfavourably upon storm-filters, to the effect that they ‘‘are not usually efficient and should not be provided,” but that the ordinary dry weather flow beds should be increased by 14 times so as to allow of the filtration of three times the mean dry weather flow by working at a permissible increased rate during storms. The Com- missioners think it is practicable to filter this quantity—viz., three times the mean dry weather flow—and they doubt whether, as a general rule, the filtration of any larger amount will be found to be necessary to prevent nuisance. Dealing with the past practice of the Local Government Board in the matter of storm- water, the Commissioners observe that ‘‘ the usual requirements of the Local Government Board in regard to the treatment of storm- sewage are that any increase in flow up to three times the normal dry weather rate should be fully dealt with by the ordinary ENCYCLOPADIA OF STR complete plant, and that a certain number of additional dilutions—up to a total of six— should be treated on special storm-filters. These requirements should, we think, be modified ; they are, in our opinion, not sufficiently elastic, and, moreover, experience has shown that special storm-filters, which are kept as stand-by filters, are not efficient. We find that the injury done to rivers by the discharge into them of large volumes of storm-sewage chiefly arises from the excessive amount of suspended solids which such sewage contains, and that these solids can be very rapidly removed by settlement. We therefore recom- mend, as a general rule, that—(1) Special stand-by tanks (two or more) should be pro- vided at the works and kept empty for the purpose of receiving the excess of storm-water which cannot properly be passed through the ordinary tanks. As regards the amount which may be properly passed through the ordinary tanks, experience shows that in storm times the rate of flow through these tanks may usually be increased up to about three times the normal dry weather rate with- out serious disadvantage; (2) Any over-flow at the works should only be made from these special tanks, and this overflow should be arranged so that it will not come into opera- tion until the tanks are full; (8) No special storm-filters should be provided, but that the ordinary filters should be enlarged to the extent necessary to provide for the filtration of the whole of the sewage, which, according to the circumstances of the particular place. requires treatment by filters.” W. H. M. Street Cleansing.— Necessity and Objects— Orderly System—Mechanical Sweepers—Disposal of Refuse—Removal of Snow. Necesstry anp Oxssects.—It is important, in order to maintain a high standard of public health, that the streets of all towns be cleansed. Wet and muddy streets cause dampness in the subsoil, and the moisture arising therefrom contaminates the atmo- sphere. Over-dry streets and roadways wear 454 STR badly, the surface becomes covered with gritty particles, and detritus is soon ground up by the traffic into fine dust, which is easily blown about, and becomes injurious to tradesmen’s goods and to the public health. The exist- ence of mud increases the difficulty of traction, renders the surfaces of pavements and roads slippery and dangerous, especially when paved with wood and asphalte. These materials become exceedingly slippery when covered by a thin greasy film of mud, but if kept clean, even though wet, are safe to travel on. It is therefore necessary to keep streets clean for sanitary reasons, for safety to traffic, for personal comfort, and also for the sake of appearance. Colonel Haywood ascertained the respective quantities of dust arising from the worn road surface of a granite pavement, and the amount of detritus collected each day. The wear which took place on 3-in. Aberdeen Granite setts in 9 years over an area of 3,950 super. yds. was equal to 2 in. measured vertically. This amounted to 2192 cu. yds., and in the state of fine powder would probably amount to about one- tenth of a cubic yard per day. The amount of detritus, however, removed daily in fine weather was 80 times that quantity, thus illus- trating the necessity of cleansing paved as well as macadam surfaces. Paved surfaces produce much less dust from ground-up materials, as compared with macadam, but they require frequent cleansing to keep them from becoming slippery and unsightly, and the difference in cost is not so great as might at first sight appear, but in times of frost, falls of snow, or wet weather, there is a decided saving in the cleansing of paved roads. To ensure success in street cleansing well organised plans must be thought out so as to systematically cleanse all the streets in the district within reasonable spaces of time. Gangs of men should be so arranged that the main roads are swept first and the side roads after. To these gangs separate and distinct districts should be given and the work so arranged that all streets within each district are cleansed at least once a week. The first MUNICIPAL AND SANITARY ENGINEERING. STR part of the work (viz., cleansing main streets) should be commenced in the early morning by the mechanical broom, if the surfaces and weather are suitable for its use. After this has swept the detritus to the sides of the roads, small gangs of from four men to six men should follow up with hand-brooms, shovels and carts, and pick up this detritus and cart it away to the slop shoot. Main streets through busy towns should be cleansed at least once a day, and all the work on them (except the removal of horse-droppings) done by 6 a.m. OrpreRty System.—This is a system in which men or boys remove the horse-droppings and other detritus on the surface at once. They are provided with either small scoops and short-handled brushes only, or with orderly trucks and the scoop and brush. In the former case, the droppings, &c., collected are deposited into orderly bins placed at the side of the road, and which are emptied at night-time. These bins are now being replaced in several towns by collecting pits sunk beneath the foot- path, close to the kerbs, and covered over by hinged doors. Openings are left in the side facing the channel through which the droppings are pushed. These pits are emptied at night and can then be used as store places for orderly barrows, brooms, scrapers and squeegees. In some cities and towns the orderly boys place the refuse removed from the roads into bags pro- vided for that purpose, and which are suspended from hooks on the side of a hand-cart. This is the system adopted in Paris, where the bags are usually placed inside a light wrought-iron hand-cart, some, however, being suspended on the outside in certain cases. The bag system saves considerable time in the collection of the refuse, and the offensive process of emptying the orderly bins or pits is done away with. The bags used should be of thick canvas and be made with iron framed lips, and with handles for carrying or hanging on to the hooks on the hand-carts. In Paris a large number of women and boys, as well as men, are employed in street cleansing. They commence from 3 a.m. to 4 a.m., according to the season of the year, and finish an hour before midday. “ABS STR In the city of London principally men and boys are employed in this work. The men cleansers commence work at 8 p.m. and con- tinue through the night until morning, and the orderly boys commence work an hour before the scavengers leave work, and con- tinue during the day. The system by which men are employed in the early part of the night from 9 p.m. to 1 a.m., or 5 a.m. to 9 a.m. in the main thoroughfares, and the adoption of boys during the day-time, should work well in provincial towns. The men who cease work on the main thoroughfares will continue during the day cleansing the minor streets and other places. MecuanicaL Sweepers.—These were first introduced by Sir Joseph Whitworth. There are many makes of these upon the market. The general principle is to attach a series of broad brooms of varying width (about 30 in.) to endless chains turning upon pulleys attached to a wrought-iron frame, the whole apparatus being attached to the back of a cart, having its body near the ground. The pulleys are attached to the cart-wheels and revolve with them. The sweepings are carried up an inclined plate and drop into the body of the cart. The brooms can be raised or lowered by hand. Haulage can be accomplished either by horse or motor-power. When the mud isina stiff condition, a water-cart should precede the sweeper to convert the mud into slop, when it can easily be swept up. The brushes last about 180 hours, and it is estimated that the machine is equal to the work of 10 men. Disposat or Reruse.—Many methods are adopted for the disposal of street sweepings. The slop, after being removed.from the streets, is carted to waste lands or special slop shoots where quarries or disused pits are to be filled up. Street sweepings and horse-droppings are sold or given to farmers as manure. On no account should road sweepings be sent to building sites for making up uneven surfaces. Epidemics of disease are liable to be caused by this system. Where cost will permit, the best method undoubtedly is to burn all street sweepings (with the exception of horse- ENCYCLOPAEDIA OF STR droppings, which can often be disposed of for manure) as soon as possible after collection. If this is impracticable, H. P. Bulnois, in the “Municipal and Sanitary Engineers’ Hand- book,” suggests that where possible they should be taken out and dropped into the sea in large hopper barges and sunk in deep water. It may, however, be possible to wash them at a small cost, and they can then be used as a matrix for mortar. Removan or Snow.—This is always a diffi- cult and costly matter. Snow should not be removed while the fall continues, but directly it ceases, all available men and carts should be employed. Snow-ploughs are used for clear- ing the roadways, these being usually con- structed of wood, and loaded when in use by being filled with snow or stones. Two or more rough-shod horses are required to draw an ordinary plough, and great care must be taken in using it that damage to the road surface is prevented. Sand should be sprinkled on the roads and footpaths to prevent slipperiness in frosty weather and after the removal of snow. Receptacles containing sand or fine gravel for sprinkling by hand labour should be placed at convenient intervals along the streets, especially in those paved with wood or asphalte. Space should be first cleared in the main thoroughfares, to allow of a double line of traffic, the snow being heaped in ridges at the sides of the road, and openings cut at frequent intervals for pedestrian traffic. The channels should be left clear in the case of a sudden thaw. Salt has been used of recent years to assist in the removal of snow from the carriage-ways, with good results. It should be spread as soon as any considerable amount of snow has fallen, as the traffic hastens the melting process. The slush formed can be easily swept to the sides of the road by the machine-broom and carted away, water-carts following up this process to wash the remain- ing slush and mixture off the surface. Salt has no detrimental effect on wood, granite, or asphalte carriage-ways, but causes con- siderable damage to macadamised carriage- ways, owing to the quantity of mud formed. 456 STR The amount of salt necessary depends entirely upon the conditions and amount of traffic. Foot-paths should be cleared as rapidly as possible, salt being used for this purpose. The slush formed by the salt should be removed very quickly owing to the great danger to the health of the public, MUNICIPAL AND SANITARY ENGINEERING. SUB bridgeshire, Lincolnshire, and elsewhere, have by draining been made habitable and healthy, and many thousands of acres have been brought into cultivation. The natural drain- age of land is by means of ridge-furrows, “Pipes may be laid round edge thats with. ene bends at 26" below surface of excavated site caused by the lowered temperature. The snow should be shovelled into carts and deposited upon waste land and left to thaw. The system of tipping the snow down the manholes into the sewers is adopted in many towns, but care must be | taken that the snow does not block up the sewer, as it takes a considerable time \ to melt. Where a town is near a river the snow should & be tipped into it. | F.L. & R. H. B. 1 Streets. (See “ Roaps anp STREETS.’’) Subsoil Drainage.— _ ' Extensive drainage of land renders the climate drier and 1 more healthy by loweringthe _y level of subsoil water and removing the miasmatic or malarial influences which accompany low-lying clay and water-logged, or marshy, —_ de" brick catchpie Yor sediment brought lo surface with manhole cover Drains to be laid Cowards lowest side. /f very wet lay 110" cdleeper. Site of building Le — slo be covered with 6"of cement concrete 0 Plain earthenware PNOLE. 4a" space Setween ends |-No trees to be planted or this area Tile under and over each junction wr Face site Catchprte ror “a sechinent 4" socketed cement Jointed ple soils. The land itself is Ditch or sewer or fire reservoir rendered more pervious to the action of the air, so that the oxidation of waste pro- ducts occurs more readily and germination is promoted, making bogs and marshes available for cultivation. The flow of the rivers is improved because the water formerly left to soak through the land is carried at once to the rivers either by gravitation or pumping. The fen lands of Huntingdonshire, Cam- Drainage to terminate ina well and pump if 770 atch or sewer or suttable outlet Fig. 1.—Plan of Drains. ditches, watercourses, streams and rivers; this is effective for ordinary soils and circum- stances, but in certain situations pipe-draining is necessary. Shallow drains for clay soils consist of 2 in. field pipes, from 18 in. to 2 ft. deep, and 10 to 20 ft. apart, laid with the fall of the land, or about 1 in 150, to the 457 SUB nearest ditch or watercourse, or to dry steined wells or to ‘“soak-aways” if there is no natural outlet. A soak-away is a square pit sunk in the ground and filled with rubble or brick-bats to admit water freely and let it Upper end of drain WR Fic. 2.—Section through Upper End of Drain. soak away gradually. For light and porous soils deep drains are desirable, say from 3 in. to 4 in. diameter, 3 ft. 6 in. to 6 ft. deep and half a chain to a chain (88 ft. to 66 ft.) apart. Yoper end of arain Ss Larth filling Tammed in Senching r¢or foothold ! % by 6" 2 Peso I L-Lorge gravel, ' (/ chatk, broken rSOU/ store or brick, | SO=y clinker or burnt C) Clay ballast Wen ce ss Fic. 3.—Section through Lower End of Drain. In the heavy lands of Norfolk the drains which answer best are 24 ft. deep and one- third of a chain (22 ft.) apart. Land planted with trees can only be drained by open cuts, as the roots would inevitably choke pipe ENCYCLOPADIA OF SUB drains. Drain pipes should not be less than 20 ft. away from growing timber. When a house has to be erected on a wet site the sub- soil should be drained by agricultural pipes covered with brushwood or rubble to prevent the clogging of the pipes by the soil being carried down. Fig. 1 shows the plan of such drains, Fig. 2 section through the upper end ; | Trenching toot 4 Vic. 4.—Trenching Tool. of drain, Fig. 8 section through lower end of drain, Fig. 4 a trenching tool or spade, Fig. 5 a bent iron rod for laying the pipes in position. In open country, if the ground falls towards the house and brings down much water, a deep trench or ditch about 10 yds. away from it on the upper side will intercept Fic. 5.—Iron Rod for Laying Pipes. much of the water, and the cutting may if desired be filled in as a rubble drain or pipe drain with a deeper soak-away at each end. Where it is practicable it is often better to make the ditch or trench all round the house so as to draw away the moisture from beneath the footings and leave the foundation soil undisturbed. H. A. 458 suc Suction of Pumps.—In the installation of a pumping plant every effort should be made to keep the suction of the pump as short as possible. All pumps work most smoothly with the water almost gravitating into the pump. The weight of the atmosphere (14°7 lbs. to the square inch) will balance a column of water 34 ft. in height, but in order to attain this depth of suction the pump must be absolutely perfect and capable of maintaining a complete vacuum. Such conditions are impossible to attain in practice, and, as mentioned above, the shorter the suction lift the better will be the working of the pump. Too long a suction is a frequent cause of trouble in the working of pumping machinery. It often happens that such a pump will not fill, and, upon the return stroke, the piston meets the rising column of water with a violent blow liable to cause considerable damage. Long suctions are especially unsuited for high-speed pumps, and it may be taken as a rule that the greater the speed of the pump, the shorter should be the suction. Horizontal length of suction is not so detrimental to the action of a pump as is excess of vertical height, but it should be avoided as far as possible, as it greatly increases the weight of water to be set in motion and stopped at each stroke, or at any rate alternately accelerated and retarded. With a vertical engine the arrangement of the suction is conveniently managed, as in this case the pumps are usually fixed below the engine-room floor level and within easy reach of the water to be raised. Correspond- ing facilities do not apply in the case of the horizontal type of engine. “ Three- throw” pumps, as conveniently worked from a crank-shaft of a triple-cylinder engine, have the advantage that the flow of water in the suction, and also of course in the delivery pipes, is more uniformly maintained than in other forms. All suction pipes should be as straight as possible, any unavoidable bends being made of large radius; the suction should also be perfectly air-tight, and be provided with foot or retaining valves, especially in long suctions or heavy lifts, MUNICIPAL AND SANITARY ENGINEERING. SUR so as to keep the pump ready charged with water. The suction must be of larger diameter than the delivery, and additional diameter allowed if of great length. Strainers, with ample area of strainer-holes, should be fitted at the end of the suction to ex- clude foreign matters. At any unavoidable bends or possible air lodges in the suction pipe, air-cocks should be provided for the purpose of discharging the air and preventing “ air-locking.” W. H. M. Surface Traps. (‘‘ See Guuuius.’’) Surveying, General Principles of.— Chain Surveying—Angle Measuring Instru- ments — Theodolite — Ordnance Survey.—The fundamental process of surveying consists in setting out upon the area to be mapped a series of lines to form a basis of measurement. Cuan Surveyine.—In “chain” survey- ing, all the lines are measured, and as the angles of a three-sided figure can -be deter- mined if the sides are known, angle measuring instruments are not essential, although it is often convenient to employ the simpler forms. A simple survey of open accessible country can usually be made with a chain, a tape, 10 arrows, 1 doz. ranging poles, some pegs, &e., and a “ field-book” in which to enter the measurements and sketches taken on the ground. Extensive and more complicated surveys are carried out upon the trigono- metrical principle that if the length of one side of a triangle and the angles included between this side and the others are known, the lengths of the remaining sides may be calculated. To conduct a “ trigonometrical ” survey a theodolite for measuring the angles will be required in addition to the apparatus used in chain surveying. The chain (Gunter’s) generally used in surveying is composed of 100 steel wire links, each measuring 7:92 in. from centre to centre; the total length (including the handles) is, therefore, 66 ft. As the statute acre contains 10 square chains, cal- culations of area are simplified by adopting a chain of this length and division. In some 459 SUR cases, however, such as for town work and levelling, a chain with 100 divisions of a foot is more convenient. The tape is of linen or steel; one side is divided into links, the other into feet and inches; a usual length is 66 ft. Before commencing each day’s work both chain and tape should be tested between Fig. 1. gauge marks set out upon a level surface ; this is imperative when the survey is being made for legal purposes. Arrows are merely stout steel skewers about 15 in. long, with a small piece of red cloth attached to each to render them easily distinguishable; they are used to temporarily mark the number of chain lengths. The ranging poles are from 6 ft. to 10 ft. long, and are painted in alternate bands of black or red and white ; they are shod with steel, and sometimes have small flags tied to them. A 10-link “offset staff” is often used for taking measurements on either side of the chain, but it is not indispensable, as this can be done with aranging pole. The field-book is about 8 in. by 4 in. and opens lengthwise; each page is divided in the direction of its length by a central line (sometimes two parallel lines) which repre- ENCYCLOPADIA OF SUR sents the chain line; upon it the distances on the chain are recorded and also the points at which offsets are taken, roads crossed, &c. To either side of this line (or lines) the distances to objects on the right or left of the chain line (“offsets”) are entered and sketches made of fences, buildings, &c., together with any other notes that may be required. Hach chain line is started from the bottom of a fresh page, working from the end of the book. At the commencement of a survey a reconnoitre of the ground is made and the principal lines ranged out with the poles. These lines should lie as near boundaries and other main features as possible in order that the offsets may not exceed about 50 links. Besides these lines, others, known as “proof” or “tie” lines, must be established as a check. The survey lines thus set out should be marked on a rough plan. The ends of the lines and their junctions with others constitute “stations” ; the latter are marked on the ground with pegs or poles, and in the field-book by a small oval. Fie, 2. Fig. 1 represents an area lined out in the manner aforesaid. It will be noticed that the lines divide it into a series of triangles; these are purposely made as nearly equilateral as possible. The actual work of ranging and chaining cannot well be explained here; suffice it to say that the line must lie absolutely straight between the stations. The arrows are 460 SUR put down by the “leader” and withdrawn by the “follower”; thus the number of chain lengths may be easily counted. When the follower has acquired the 10 arrows an entry is made in the field-book, and the leader retakes possession of them. Asa plan is the horizontal delineation of the ground surface, all measurements taken upon an incline of, Cc D E F aoe A B| a Hq Fie. 3 say, more than 5° must be reduced to their horizontal value. If the slope is not very steep this can be accomplished by holding the chain, or a portion of it, horizontally and marking the distance with a pole placed vertically, or preferably a plumb-bob; this is known as “ stepping.” Another method is to calculate the horizontal distance from the angle of the slope. It frequently happens that a chain line is interrupted by some obstacle such as a river ora building. In the former case, if A B (Fig. 2) is the line, and the river is too wide to chain across, but the distance B C is required, range point C in line with A B and set out perpendiculars A D, B E, range EL with C D, then :— _ABXBE OS Be If the obstacle interferes with the line of sight, the chain line may be continued by setting out 4 C, BD (Fig. 3) perpendicular to A B and equal to each other, and ranging & F with C D and erecting perpendiculars equalto A Cand B DatH GandFH. A perpendicular is best set out with some angular instrument, such as an optical square, but it may be done with 80 links of the chain by placing arrows 40 links apart on the chain line, as a base, and forming the hypotenuse and perpendicular of a triangle with 50 and 30 links respectively (see Fig. 4). Fig. 5 represents a chain survey of a small estate; the pages of the field-book correspond- MUNICIPAL AND SANITARY ENGINEERING. SUR ing thereto are shown by figures. In plotting the work on paper the chain lines and stations are first laid down and checked by the tie lines, the detail being afterwardsadded. This drawing would be kept for reference and a tracing or copy, omitting the survey lines, made from it. The compass point, corrected to the true meridian, is always inserted. AnetE Mezasurinc Instruments. — To adequately describe the many instruments used in surveying would need a treatise ; only the more important ones can here be mentioned and their chief uses indicated. The optical square has already been alluded to; it is an inexpensive pocket instrument by which right angles may be set out. This is sometimes done, but not so reliably, with the eross staff. The angle of a line with the magnetic meridian may be observed with a prismatic compass, another pocket instrument. It is often used for filling in the detail work of a large survey. The box sextant is equally portable, but capable of a nicer adjustment ; angles in a vertical, as well as a horizontal, plane can be determined by it. Of all angular measuring instru- ments, the theodolite isthe |} mostimportant. It consists | \. of a telescope (similar to N that of a “dumpy”’ level, x except that the diaphragm x markings are different) which may be moved™ N through vertical and hori- \ zontal planes. Means are provided for - closely measuring the angular * movement of the optical axis of the telescope; spirit-levels and a compass are also fitted. The bearings of two lines from the observer’s station to two distant points, one with the other, either in a vertical or horizontal plane, may therefore be taken with great exactitude. The relation of a horizontal line with the magnetic meridian can also be ascertained. Fia. 4. 461 SUR SURVEYING WITH THE THEODOLITE.—Many surveys would be extremely tedious and diffi- cult, and even impossible, without the theodo- ENCYCLOPADIA OF SUR ascertained with great accuracy by the use of the theodolite, the number of check lines may be reduced. With the theodolite the principles 12 aes as & Line 10 156 30 14 8q 15 6 10 ne G 4, =. 4 Li ae Fie. lite or its equivalent. The long lines of extensive surveys, especially when over undu- lating ground, are best set out with it. As the angular bearing of these lines can be oO. of trigonometry can be applied to determine the position and distance of various points and the height of inaccessible objects. In trigo- nometrical surveying a suitable base line and 462 SUR the principal stations are carefully chosen and the ground triangulated as in chain surveying. The stations at the extremities of the base line need not necessarily be visible from one another, but it should be possible to observe them easily from the surrounding country. As the system of triangulation is built upon the base line, it is necessary to measure it with the greatest care; in important surveys this is usually done twice. If required, a base line can be extended by angular measurement from suitable points. Although the length of the sides of a triangle may be calculated if the base and the angles included by it and the sides are known, it is necessary to measure at least one of the distant sides of the triangula- tion as a check. After the main system has been established it is subdivided into smaller triangles and the details worked out as in chain surveying. Lakes, marshes, woods, &c., may be surveyed by inclosing them in a system of lines and observing the angles that these lines make with each other. As the sum of the interior angles should be equal to 90° multiplied by twice the number of sides that the figure formed by the lines contains, less 360°, a proof of their accuracy may be _ established. If, in plotting the work, the first and last lines do not meet, there is an error in the lineal measurement. This method of surveying is known as a ‘closed traverse.” If done with a chain it would generally be necessary, owing to the difficulty in taking diagonals, to prolong the lines and so form exterior angles, checking the same with tie lines. The courses of winding roads, rivers, &c., are also “‘ traversed’; this again can be more accurately and expeditiously accom- plished with the theodolite than by the chain. The line of traverse, along the road or the bank of the river, is usually arranged to start from a definitely fixed point in the general survey and finish on another. In some cases the angles of the various sections of the line are determined in relation to the magnetic meridian. When extreme accuracy is not essential this may be done with the prismatic compass. In town surveying the shape of the MUNICIPAL AND SANITARY ENGINEERING. TAP streets precludes triangulation, so that the angles of the survey lines must be measured. To obtain a sufficiently long base line is often a matter of considerable difficulty ; in some cases a space outside the town is selected for this. Tue Orvnance Svurvey.—The whole of Great Britain has been most elaborately sur- veyed, and maps to the following scales are published by the Ordnance Survey Depart- ment. These may be obtained in London through the appointed agent, Mr. Edward Stanford, of 12 to 14, Long Acre, W.C. Natural Inches to One Natural Inches to One Scale. Mile. Scale, Mile. he 126°720 | zs00 25°34. 1056 60°0 63360 10 Besides the above, four smaller scales are also used. séoth Scale-—Most of the towns of Great Britain have been published to this scale, which generally shows hydrants, lamp-posts, manholes, &c., besides the thickness of walls, spaces between buildings, &c. zdsath Scale.—The plans of London, Dublin, Belfast, and-some small towns are on this scale. zsooth Scale.—The whole of the cultivated districts of Great Britain (Ireland is in pro- gress) are obtainable on this scale, which shows woods, rough pasture, rocks, &c., in character. The acreage of fields and levels of bench marks are included in the later editions. 1otsoth Scale—Maps to this scale have generally the same detail as the 524,th, but they do not give areas or parcel numbers. gsscoth Scale.—This is the general road map of the country. In addition to the above, maps of the Geological Survey of England and Wales may be obtained. (See “ Levenuine, GENERAL PRINCIPLES oF.’’) E. L. B. Taps. (See ‘‘ Vatvus.”’) 468 TES Testing Apparatus.—Drain Pives.— Made of various patterns, these are all con- structed on the same principle. They consist of two metal dises—one fixed to and the other passed over a screwed spindle—between which rests an indiarubber ring. By screwing up a fly-nut on the spindle the two plates are pressed together and the rubber ring expanded and forced out against the periphery of the drain, which is thereby plugged. In the majority of plugs the spindle is hollow and fitted with a cap. This allows of the attach- ment of the nozzle of a smoke machine, and is useful for the gradual emptying of a drain after testing with water when the pressure is high. Drain Baes.—India-rubber or waterproofed canvas bladders, which, when inserted in a drain to be plugged, are inflated by means of a small air-pump. They adapt themselves better to any unevenness in the shape of the drain than do drain plugs. Smoxe Macuines.—Utilised for the genera- tion of smoke used in drain-testing. They are made of various patterns, but consist generally of a combustion chamber and a pump, fan, or bellows for forcing the smoke into the drains. Smoke is produced by burn- ing oiled cotton waste or “touch paper,” which latter is specially prepared brown paper. The machines are provided with a length of tubing for connecting up to the drains. Smoxe Rockers on Smoxe Cases.—Cylin- drical cardboard cases about 7 in. long and 2 in. in diameter filled with a compound which on ignition generates dense volumes of smoke. ‘T'wo strips of wood are attached, which, when spread out,. keep the rocket off the invert of the drain. SmetL Tresters.—Made in many varieties. Consist of small tubes filled with assafctida or other strong-smelling compound, closed by caps which are held down by paper. When passed into the drains the paper is wetted and thereby softened and broken, allowing the contents of the tubes to be discharged in the drains. Water being thrown into the drainage system, the chemical is passed to all parts of ENCYCLOPAIDIA OF TES the drains, which it charges with its distinctive smell. Testing Drains.—The two most reliable tests made use of for proving the soundness of drains are the hydraulic or “ water ” test and the pneumatic or “air” test. The former is applied by securely plugging the outlet end of the drain (or system of drainage) and filling up the piping with water. When the drain is full, the water level is carefully marked and watched for, say, half an hour. If it remains stationary, the drain is proved sound, in the opposite event a leakage exists. In applying the pneumatic test, all openings on the drain- age system or of a section thereof—such as gullies, closets, vent-pipes, &c.—are carefully sealed and air pumped into the drains. The pressure attained is indicated on a gauge (which may simply consist of a U-shaped glass tube charged with water) attached to a plug closing one of the openingsin the drain. The gauge being carefully watched after the desired pressure has been obtained, the soundness or leaking conditions of the drains under test will be indicated by the constancy or the diminution in pressure respectively. The pneumatic test in drainage work is superior to the water test in that, in the former, the pressure applied is of uniform severity on each part of the drainage system, whereas it varies greatly in intensity in the case of the water test ; the lower portion of the drain having to withstand a much greater pressure under this test than the upper end. The other tests made use of in drainage work are the “smoke” test and the “olfactory” tests. The former is valuable in that the positions of leakages are at once made apparent by the escape of smoke from the drains at the defec- tive points. If the test is applied under pressure it is as valuable as the air test. Without pressure, the results are unreliable, as the absence of escaping smoke does not necessarily imply that the drain is sound, particularly if the pipes are covered by earth. A thin coating of sewage or grease over a, defect will also prevent the escape of smoke iff 464 THE little or no pressureis used. Under the smoke test, smoke generated in a smoke-machine is pumped into the drain through a manhole or other opening in the drains. After the drain- age system has been fully charged, all open- ings are closed and pumping continued until the test has been completed. For convenience of carriage, ‘‘ smoke-rockets” are frequently made use of in preference to the cumbersome “machine,” but as neither the quantity of smoke applied by these, nor its movement in the drains can be controlled, they are of no practical value in the majority of cases. Olfactory tests consist in charging the drains with some pungent or otherwise dis- tinetive smell, that should be detected at points at which defects exist. Oil of pepper- mint mixed in a bucketful of hot water and poured into the drains is frequently made use of; while many proprietary testers similarly used are available. These latter are prefer- able in that the smell is not generated until the interior of the drain or pipe to be tested has been reached. While frequently useful, smell tests are unreliable and cannot be used for proving soundness. G.J.G. J. Thermometers.—An ordinary thermo- meter consists of a fine glass tube with a bulb blown on at one end, and is partly filled with mercury or alcohol. This liquid expands on being heated, and contracts on being cooled. When it expands it passes up along the tube, and by the amount of this expansion the temperature is measured by means of a scale marked off on the tube. In this country Fahrenheit’s scale is in general use. In this the freezing point is 32° and the boiling point 212°, the intermediate part of the scale being divided into 180 degrees. In most foreign countries the Centigrade scale is used, in which the freezing point is 0° and the boiling point 100°. All good thermometers have the scale etched on the tube, and it is desirable that they should be verified at the Kew Observatory, so that their errors may be known and allowed for. There are two patterns of maximum thermometer, viz., M.S.E. MUNICIPAL AND SANITARY ENGINEERING. 465 THE Negretti & Zambra’s and Phillips’s. In Negretti & Zambra’s maximum thermometer the bore of the tube is reduced in section near the bulb in such a way that whilst the expand- ing mercury forces itself into the tube, on contraction the column of mercury in the tube breaks off, so that its upper extremity shows the highest temperature that has been attained. In Phillips’s maximum thermo- meter the index is formed by a small portion of the mercurial column, separated from the main thread by a minute air-bubble; this portion is pushed on before the column when the temperature rises, but does not return with it when it falls. The detached portion of the column therefore rests at the extreme position to which it has advanced, and the end of it furthest from the bulb registers the highest temperature which has been attained. Both instruments are set by holding them bulb downwards. In the minimum thermometer spirit is employed instead of mercury, and in it there is immersed a pin or index. When the temperature falls the surface of the spirit draws the index along with it, but on rising again the spirit passes the index, leaving it at the lowest point to which it has been drawn, the end furthest from the bulb thus registering the minimum temperature. The instrument is set by raising the bulb and allowing the index to slide to the end of the column of spirit. The instruments used for measuring the amount of moisture present in the air are the dry-bulb and wet-bulb thermometers. The dry-bulb is an ordinary thermometer, and shows the temperature of the air; the wet- bulb is a precisely similar thermometer only it has the bulb covered with a piece of muslin, which is kept wet by a conducting thread passing into a vessel of water. If the air is dry it evaporates the moisture from the damp muslin, and in doing so lowers the tempera- ture, and consequently this thermometer reads lower than the dry-bulb. For meteorological and comparative pur- poses the dry-bulb, wet-bulb, maximum and minimum thermometers should be mounted HH TID in a Stevenson screen, which is a louvre- boarded box, with their bulbs 4 ft. above the ground. Other thermometers in use at meteorological stations are earth thermo- meters, for ascertaining the temperature of the soil (the most suitable depths are 1 ft., 2 ft., and 4 ft.); sensitive minimum ther- mometer on grass, for determining the intensity of terrestrial radiation at night ; black-bulb and bright-bulb maximum ther- mometers in vacuo, for determining the intensity of solar radiation. Much interesting and valuable information may be obtained from a self-recording thermometer, such as the Richard thermograph. W. M. Tidal Valves.— Comparatively heavy metal flaps fixed on the outlet ends of drains dis- charging into tidal waters, streams liable to Tidal Valve. flooding, and in similar positions. The flaps are hinged to the crowns of the pipes in such a way that water or sewage passing through the drains will raise them and issue, while a reverse movement of water (caused by high tides, &c.) will exert a pressure on the valves and close them tightly against the mouths of the pipes ; thereby preventing the backing-up of water into the drains. Tides on Sewer Outfalls, The effect of.—The majority of towns situated on the sea-coast are sewered with one or more outfalls into the sea. In selecting the positions for these outfalls, due attention must be given to tidal currents, and experiments and obser- vations are necessary to determine the direction ENCYCLOPADIA OF TID of flow, the effect of prevailing and other winds, the rise and fall of the tide, and the conditions of the sea bed, whether suitable or otherwise for outfall purposes. The engineer should be acquainted with the peculiarities of the subject of coast work and conditions appurtenant thereto. The question of tidal rivers must also enter into the category, having regard to their tendency to silt up the adjacent sea bed. Tidal rivers, however, frequently afford an advantage in discharging sewage, as the tide ebbs for a longer period than it flows. Great care should be taken to avoid an eddy current, which is common in some situations. Those tides or currents which have a circular movement will frequently pre- vent the effectual removal of the sewage, and cause it to be deposited on the shore. Sea outfalls should not be constructed to discharge against sea currents unless unavoidable. The chief disadvantage in so doing is that the dis- charge is impeded, whilst by adopting direc- . tions which are parallel with the currents, the flow in the outfall will frequently be consider- ably accelerated. Attention should be paid to the relative position of outfalls, with regard to the situation of towns, care being taken that the sewage, after being discharged into the sea, does not flow in front of the thickly inhabited parts of the district. It should rather be carried directly away from all town beaches and seaside attractions. Inattention to this important consideration may result in destroying the chief attractions of many places, by rendering their bathing beaches insanitary. One of the most important ques- tions requiring attention is that of the rise and fall of the tide. This must be accurately ascertained, and taken into consideration, in conjunction with the survey of the district to be drained. It will then be seen whether or not an outfall site can be secured, by which the sewage will all flow and discharge by gravitation, or whether pumping or other means will have to be resorted to. Although spring tides rise to a higher level than neap tides, the engineer often has greater difficulty in effecting a good outfall on the neap tides. 466 TID Spring tides present not only the highest, but also the lowest tide levels, but the reverse obtains in the case of neap tides, as these neither ebb so low nor flow so high, and therefore the sewer outfall is partially ob- structed during this latter period. The dis- charge chart must be calculated on the difference of head of water within the sewer and over it during neap tides, having due regard to the influences of prevailing winds, which will in some situations have consider- able effect in checking the flow of the tide. In a large number of cases where a gravitating out- fall cannot be provided on account of insuffi- cient levels, a system of storage can be adopted to meet the requirements of the district, avoiding the initial and working costs of a pumping plant. If it can be so arranged, the outfall should be placed in such a position as will allow a combined system of storage and gravitation as designed and carried out by the writer for the West Penwith District Council. In this case the outfall was carried diagonally under the foreshore, to a discharging point beyond the boundary, and in the favourable direction of the currents and prevailing winds. The sewers from both the high and low levels were by this means caused to converge to- wards a central point, and whilst the sewage from the lower district was impounded at cer- tain periods of the tides, that from the higher levels discharged through the one outfall pipe, common to both districts, continuously. It was found necessary to store one-third of the combined sewage and rainfall from the low level district on each tide. A tank sewer was constructed for this purpose, having a pen- stock and valve chamber with midfeather, at the outfall end. The main sewer for the high levels was terminated in the outer chamber, and, on account ofits greater head, discharged through the outfall pipe at all states of the tide, whilst the low level remained locked back by self-acting balance valves, fitted on the midfeather and chamber, for the purpose of shutting out the tides until such times as the valves were freed and the sewage released by the inside pressure overcoming that on the 467 MUNICIPAL AND SANITARY ENGINEERING. TOW outside. In constructing outfalls, particular attention should be directed to the foundation ‘upon which the pipes are to be carried to pre- vent the undermining action of the waves and currents. F. L. Town Planning. —General Principles— Existing Powers — Example of Germany—Zone System—Town Planning Act—Sweden—Holland —Houses per Acre—Town Planning in England. —Parliament, and most municipal experts now recognise how important it is to establish and regulate a proper system of town develop- ment, which shall provide for the organised dispersion of the population of overcrowded centres to residential suburbs, industrial villages detached from the main centre, and to an agricultural belt on the outskirts. The developments that are taking place in the transmission of electric power point to large movements in this direction, because they will make it possible not only for industries to be carried on at distances from the centre, but also for such a cheapening and improvement of the means of transit for both goods and passengers as will tend to minimise the obstacles of. time and distance, which at pre- sent (though to a less extent than formerly) render it necessary to crowd factories and population in central districts. Cheap tran- sit alone, however, has inflicted on us jerry- built suburban houses of the wrong type, overcrowded on area, and has inflated the price of land for the benefit of the speculators, who too often absorb the difference between the old rent paid on the dear land in the centre and the true economic ground-rent that should be paid for the agricultural land on the out- skirts. Hence it is vitally important that the control and ownership of suburban land should be more in the hands of the community than at present, and that one and the same authority should have powers over transit, land, and housing, so as to prevent the crea- tion of new slum areas and excessive increases in the cost of acquiring land for housing and other public purposes as well as to provide for open spaces, main roads, and streets of HH2 TOW adequate width in the proper direction, and in sufficient numbers to meet future needs, before the land near them is forced up to speculative building prices. Town plan- ning is the art of planning towns in respect of the distribution of buildings and open spaces and the provision of streets and roads suitable to each area. It implies a public authority, possessed of power to control, guide and regulate the growth and development of towns, especially as regards building sites, their approaches and surroundings. Existing Powsrs.— At present, in the United Kingdom, the majority of these matters are settled by the owners of the land, subject to local by-laws applying practically the same methods and principles to all parts of the town. It is true plans of “ new streets’ must be submitted to the local authority for approval, but, except in rare instances, no such authority can insist on a plan of the whole of a building estate showing the rela- tions of the intended “new streets” to others adjoining. In most towns there has been no power to vary the direction or position of the streets shown on the owner’s deposited plan, but Leeds, Nottingham, Barrow-in-Furness, Blackburn, Bournemouth, Bradford, and Brighton have certain powers in this respect subject to a compensation clause. The Public Health Act, 1907, sections 17 and 22, makes these powers general wherever the Act is adopted. Ina great many towns the corpor- ation has obtained power by means of a local Act to prescribe a building line subject to a compensation clause. There are also limited powers, varying considerably as between one town and another, for regulating the area of air space at the side or rear of dwellings, from a minimum of 100 sq. ft. in Bacup to a minimum of 500 sq. ft. in Croydon, but the most generally prescribed area is about 150 sq. ft. As to width, streets are divided into classes in respect of which the require- ments of towns vary considerably. The normal width prescribed is 36 ft., but by means of local Acts, streets are classified in some towns such as Cardiff, Nottingham, Leicester, ENCYCLOPADIA OF TOW Bolton, Huddersfield, and Sunderland, in various widths, according to their situation and probable uses. Barrow-in-Furness’ local Act prescribes varying widths of 80, 60, 40, and 20 ft., and gives power to the corporation at their discretion to reduce the width of the street if an open space is left along one or both sides of the street, in front of the houses. Even when used to their fullest extent, however, these powers are inadequate to prevent the growth of ugly suburbs and mean streets, or to secure for the inhabitants a sufficient supply of the essentials of a healthy life viz., sunlight, fresh air, and vege- tation. There are at present no statutory powers capable of effectively dealing with the question of town planning in the United Kingdom, yet consideration of this subject dates back at least 4,000 years, and there are numerous examples of what was done in this connection by the Romans and Assyrians, and even in this country, the town of Winchelsea was planned by Edward I. in the Middle Ages. In Continental towns, notably in Germany, matters are more advanced, and although many parts of these towns are planned on wrong lines, especially as regards the width and nature of streets, yet many of the evils from which our towns suffer have been avoided, while the division of building land near towns into plots, and the choice of the style of building is regarded as the concern of the community, and one coherent official plan is supplied by the town councils to the whole of the unbuilt-on land within the town boun- daries, deciding beforehand the general char- acter of building to be allowed in the various parts of the area, according to their antici- pated needs. Mr. T. C. Horsfall has done much to familiarise us with German experience in this connection. Tue ExampLe or Grermany.—In Germany, town plans are generally prepared for so large an area that ‘‘the needs of the near future” are provided for, and this phrase is generally taken to mean about 25 years. Dr. Stubben, a great German authority on the subject, says that the first thing to be settled in a town 468 TOW plan is the position, direction, and width of the principal streets, and this should be followed by a general indication of the mode of division of the land into sites, which must be so arranged with regard to each other that the demands of traffic, health, and beauty may be complied with as fully as possible. While streets and open squares serve for traffic it is important so to construct them that they may be of pleasant appearance, and this can be gained by securing a variety of street forms and well inclosed squares, avoiding in all cases too long straight lines. Principal traffic streets ought to be from 60 to 120 ft. wide, secondary traffic streets 40 to 60 ft., sometimes with front gardens, and streets used mainly for access to the dwellings in them, 25 to 40 ft., often with front gardens. It is this narrowing of the macadamised area, and increase of the open garden space that is so much needed in German town planning to-day. Dr. Mewes, of Dusseldorf, in laying down the elements of a town plan, urges that there should be a general plan, providing for main roads and transit facilities, careful grading of districts in zones providing for different types of buildings in each, but with one or two districts for mixed buildings; varied streets and open spaces ; reservation of front gardens for future widening of streets if necessary, and, as in Baden, Hamburg, and Frankfurt, plots belonging to different owners should, where necessary, be pooled and re- apportioned. The law under which this last- named operation is effected in Frankfurt is known as the “ Lex Ordickes.” Within the area covered by the town plan, there should be varied building by-laws providing for restrictions on the extensive use of land according to its position, and also on the height of buildings, besides providing for cheaper types of streets in purely residential quarters, and relaxed conditions as to the construction of buildings. Zone System.— An important feature of town planning is the principle of dividing land which is going to be built on into different districts, each, or each group, of MUNICIPAL AND SANITARY ENGINEERING. TOW which has its own building by-laws. Under this system (known as the “ Zone System ”’) some districts are reserved for factories and works, other districts are reserved for dwell- ings, to the exclusion of factories and works, while yet other districts permit of a mixture of the two classes of buildings. In districts given up to buildings near the centre of the town, five-storey houses built in rows, and covering a large proportion of the site, are allowed; in other districts, the limit is four storeys, and the unbuilt-on area of the site is larger ; in other districts, no houses may have more than three storeys, while towards the outskirts, where land is cheaper, only detached or semi-detached houses of two storeys are permitted, and with a good deal of land round them, so as to interfere as little as possible with the supply of air passing towards the central districts. In Germany, nearly all town councils of important towns, after having plans prepared by their own skilled officials .under the direction of a committee of the town council specially qualified for this work, submit such plans for revision to experts of reputation for their skill in suggesting how to make towns convenient for traffic as well as healthy and beautiful. When the plan has received the alterations that these experts suggest, itis sub- mitted to public examination, and any citizen is at liberty to make any objection he likes to any of the proposals. When these alterations or suggestions have been considered, the plan becomes law, with or without the necessary corrections, and all land-owners, in developing their estates, have to comply with the direc- tions laid down. Town Prannine Act.—The Town Planning Act of 1909 was a considerable step forward in the housing legislation of the United Kingdom. By it future developments will be carried out on quite a different system to that prevailing in the past. Town planning schemes may be prepared by either a local authority or land- owners in respect to “any land likely to be used for building purposes and of any neighbouring land.” In any such scheme provision shall 469 TOW be made for open spaces, roads, streets, parks, pleasure or recreation grounds, or for any work incidental to a town planning scheme, whether in the nature of building work or not. Provision is made for the modification or extension of any original proposals. The approval of the Local Government Board is necessary, and this shall be published in the London Gazette. Any objections must be made within twenty-one days of publication, and if this is done, then the draft order con- firming the scheme must be laid before both Houses of Parliament for thirty days. Should either House present an address against the draft no further proceedings can be taken. It is important, however, not to confound town planning with site planning. The former deals with towns as a whole, and includes all the points mentioned in the preceding para- graphs relating to Germany, whereas site planning is merely the planning of patches of land in one part of a town, without necessarily considering its relations to the development of the town as a whole. While eminently desirable in itself, this latter pro- cess would not meet the case of municipalities, who, in the past, have had to spend enormous sums for widening streets, and may have to do so in the future. In order to ascertain how to apply town planning to England it will be useful to study the principles embodied in the town planning laws of other countries. Some of the most recent town planning provisions are those contained in the General Building Law for the Kingdom of Saxony, of July ist, 1900, as follows :—‘ Local authori- ties must prepare a building plan for all unbuilt-on land, and may prepare a plan for a district already built on.” The plan may regulate (1) the building lines upon which the sites may be built on, and by which the areas intended for traffic or for front gardens are to be divided ; (2) the mode of building; (3) the distance of buildings from the street lines and, therefore, the boundaries of adjoining sites ; (4) the height and depth of buildings; (5) the permissibleness of trade buildings in certain districts; (6) the provision of a suit- ENCYCLOPAEDIA OF TOW able supply of water and proper drainage ; (7) the prevention of disfigurement of streets or squares; (8) the adaptation of street and building lines to the configuration of the land; (9) the securing of an adequate supply of sunshine in the dwellings; (10) the width and nature of streets and foot-paths according to the requirements of local traffic. The graduation of the width of streets is as follows:—Private back roads, 20 ft.; macada- mised area of streets used only for dwellings, 25 ft.; all streets with continuous buildings, 40 ft.; those with much business or through traffic, 56 ft. wide, at least. The gradients in streets must be distributed as evenly as possible, and long straight lines avoided :— In determining the directions of streets, care must be taken to provide short and convenient connection between streets and the chief centres of traffic. Open spaces and public shrubberies must be arranged in convenient and accessible positions. Sites for churches, school buildings, and public playgrounds must be provided in sufficient number. Continuous lines of buildings must be inter- rupted in sufficient measure by streets. In the outer districts, a suitable restriction of the density of building and population must be made. Front gardens must, as a rule, have a depth of at least 15 ft., and courts and back gardens must be permanently secured as such by regulations respecting their area and position, or by back building lines. Every person who builds must supply, at his own cost, the land for the streets indicated in the building plan along his building plot to a width of 84 ft. in the case of streets which will have buildings on both sides, and he must open up the land, and make it over to the town ; unless the town itself undertakes this, he must make it into part of the street, and sewer it. In the interests of traffic or of health, existing buildings in a whole district may be compulsorily acquired by the town council, with the sanction of the Ministry of the Interior, while power is given to purchase immediately, by compulsion if necessary, any land shown on the building plan as a proposed 470 TOW open space. Local by-laws may be made, providing whether houses must be detached or semi-detached, or built in continuous rows. Ugly or disfiguring buildings can be pro- hibited, and by-laws may prescribe higher demands in respect of architectural character and appearance of buildings to be erected in certain streets or parts of streets. Town Prannine in Swepen—The Swedish Town Planning Law of 1874, Section 12, lays down some of the main points to be aimed at in town planning, as follows :— (a) That streets shall be wide and shall run in the directions most suitable for traffic. (b) That large and suitable sites shall be provided for markets, harbours, and other places where there will be much traffic. (c) That wide promenades or boulevards, with shrubberies in the middle, and roadways on either side, or with other suitable arrange- ments, shall traverse the town if possible in various places and in different directions. (d) That as many as possible other public planted open spaces shall be provided in the town. (e) That on the one hand the -residential districts shall not be so large nor so crowded with houses as to prevent the free passage of fresh air, or to interfere with the work of extinguishing fires, and, on the other hand, that in the said districts, the building sites shall be of sufficient size to allow of the erection of commodious dwellings, and the provision of open and well-ventilated yards. Section 18 prescribes widths’ of roads as follows :— Normal width, 584 ft. Specially exempted short streets, roads at sides of boulevards, and streets with buildings only on one side, may have a width of only 39 ft. ‘‘ Streets which have front gardens on one side or on both sides of them, provided that the distance between the two rows of houses is at least 594 {ft., may also have a width of not less than 39 ft.” Hotuanp.—Under the Housing Act of 1901, Local Authorities in Holland have large powers of land purchase in connection with town planning schemes. Amsterdam has MUNICIPAL AND SANITARY ENGINEERING. TOW purchased 4 square miles of land, and its suburbs, of which 2 square miles were taken compulsorily, and half the total (2 square miles), has been planned as follows :— Streets, canals, and squares, 420 acres, or 35 °/, of the area. Sites for exhibitions, recreation ground and parks, 300 acres, or 25 °/o. Sites for dwellings in streets or terraces, 280 acres. Sites for villas and separately-built dwell- ings, 200 acres. No street can be built without the consent of the Municipal Council, which has to approve the width, level, direction, and method of construction. Local authorities are also empowered to prohibit building or re-building on sites that have been reserved for streets, canals, or squares, in any part of the existing towns. Housss per Acre.—In considering that part of town planning which is concerned with the proportion of building sites that may be covered by buildings, the following table may be of interest :— Goimtey.. | ReovorMon pt Baling ie ntmny be Austria . | 85 % in majority of cases. Belgium .| 80 %. Germany . . | 88 to 66 %. Holland .| 75 % in most cases, varying, how- ever, from 20 % in rural districts to 80 % in urban areas. Ttaly . -|The working-class houses must occupy not more than 80 %. (In Turin the proportion is 66 %.) In Belgium the height of buildings is determined by the width of streets, so that, generally speaking, the building may have a height equal to the width of the street, . plus 20 ft.; in France, the free space opposite a window must be over 15 ft., and in some parts of Paris 30 ft. Town Puanntne in Eneuanp.—In the application of town planning to England the following requirements are desirable: (1) pro- vision for an agricultural belt, which should 471 TOW be kept permanently free from any large number of buildings ; (2) the planning of the district as a whole, providing for “reserves” of open space and for large main roads for motor traffic and trams, with side roads for shops, factories, dwelling-houses, and public buildings, while roads little used for thorough- fares should be of quite a different type; (3) the development of separate sites by means of a special application or modification of the by-laws limiting the number of rooms per acre according to circumstances. Before preparing a town plan there should be a pre- liminary survey and inquiry to collect detailed information, historical, recent and present, as to all the factors affecting the growth of the town. Maps and plans should be prepared ; drawings, photographs, pictures, statistics, and other detailed information should be secured dealing with means of communication, present and anticipated growth, movement, occupa- tions, and distribution of population, with anticipated requirements; lines of growth and expansion, and local changes affecting streets, open spaces, and amenities. There should also be collected town plans from other cities, and the whole of the material so obtained should be exhibited in order that suggestions could be offered by the public in the Press, and by experts, in addition to the proposals drawn up by the municipal autho- rities. Suggestions and designs should be invited from all quarters, and utilised or rejected after due consideration. Professor Geddes offers a valuable warning when he urges that the essential problem is to dis- cern “the different character and spirit of each town, small or great, Chelsea or West- minster, Dunfermline or Edinburgh, Galway or Dublin, and to collaborate, plan, and work towards a design which shall increasingly express and develop all that is best in these, and here (as in individual life) we may best correct faults by developing qualities. Town plans which omit this individual point of view, which has nowhere been sufficiently considered, are not even adequate as ‘town patches.’ Thus, the great American sea- ENCYCLOPEDIA OF TRA port would not copy the modern defects of Berlin if it knew the best, say, of Hamburg and Lubeck, old and new.’ He also does right in urging us to “avoid a too crude and hasty adoption of city plans, inspired not by local life, by love, or knowledge, but by imita- tion of the costly and meretricious pomposities of great Continental capitals. Haussmann’s Paris, the Ecole des Beaux Arts, Modern Ber- lin and Vienna, have, in this respect, a widen- ing influence upon their annually increasing multitude of visitors from America and Britain; and already the visitors to almost any important city of these islands, must see this influence. For this increasingly threatens us with dreary perspectives and conventional ornament, relieved only by occasional extra- vagances, and is thus, as with the least artistic sense and training any one can see for him- self, even uglier than the, as yet, prevalent industrial squalor and garishness of our poorer quarters, or even than the featureless monotony of our respectable ones. In a word, an immediate danger in America (and in Britain also) is to repeat the mistakes of the French ‘city improvers’ of the Second Em- pire, and the corresponding developments of Berlin, Strasburg, kc.” W. T. Trade Effluents.—The rapid development of industries producing effluents containing waste products either in suspension or solu- tion has greatly increased the pollution of rivers in manufacturing centres. The puri- fication of these effluents either alone or when mixed with ordinary sewage forms a special problem and has been the subject of consider- able special legislation. ‘The polluting effect of trade effluents may be due to the presence of: (a) an excessive quantity of suspended solids; (b) substances capable of fermentation or putrefaction and consequent production of nuisance; (c) colouring matters such as vege- table or artificial dye-stuffs; (d) substances poisonous to aquatic vegetation or fish life ; (e) oily matters, fat and soap. The detailed description of these various classes of effluents and their respective 472 TRA methods of treatment is briefly indicated in the following paragraphs, it being understood that one effluent may fall under more than one head. (a) Tannery effluents contain large quan- tities of lime in suspension; effluents from plants for the recovery of ammonia from liquors produced in the distillation of coal in gas-retorts or coke ovens contain large quan- tities of lime and calcium sulphide and sul- phate in suspension; effluents from coal- washing plants contain much fine coal in suspension; pottery effluents contain clay; effluents from aniline stills may contain large - quantities of magnetic oxide of iron; effluents from dye and bleach works may contain much flocculent matter from waste ‘‘filling” or mordanting substances and fibrous material from the cloth itself; paper-mill effluents may also contain fibre and “‘filling.”” Most of these can be clarified by simple subsidence in suitably constructed settling tanks. In certain cases, ¢.g., for paper-mill effluents, mechanical filters or fine screens may be employed. (b) Among important fermentative or putre- factive effluents are those from breweries and distilleries, from tanneries and hide-dressing works, from beetroot sugar factories, starch works, wool-scouring works, bone manure and glue factories. All of these can be purified by suitably-arranged biological tanks and filters, either at the actual works producing the effluent, or mixed with sewage at the works of the local authority. It should be noted that liquids capable of undergoing acid | fermentation, e.g., starchy effluents or brewery effluents are not well suited for anaérobic treat- ment. (c) Colouring matters from dye-works may be of vegetable origin, such as indigo or logwood, or belong to the numberless varieties of so-called “aniline” or artificial dye-stuffs. The former and certain of the latter, e.g., alizarine derivatives, which are fixed by mor- dants, can be precipitated by means of iron or aluminium salts. A large proportion of artificial colouring matters are not capable of removal in this way. They are generally destroyed in biological filters when mixed with MUNICIPAL AND SANITARY ENGINEERING. TRA sewage, but apart from their colour do not constitute a dangerous element in effluents. (d) A great variety of injurious substances may be discharged under this head, ¢.g., alkaline sulphides from alkali waste heaps, from the vulcanising of india-rubber, from dyeing pro- cesses employing sulphur dye stuffs, and in certain cases the effluents from ammonia recovery stills. It is highly important that these should be treated either with excess of lime or a mixture of lime and ferrous sulphate (copperas), and the precipitated sulphide settled out in tanks, before the effluent is discharged either into a sewer or a water- course, or there is almost a certainty of seri- ous nuisance or even fatal accidents arising from the evolution of sulphuretted hydrogen, due to chance contact of such an effluent with free acid. Acids and alkalis unless present in very minute proportion should be neutralised before discharge into a stream or sewer. Chlorine either in the free state or as hypo- chlorite in bleach works effluents, unless present in very large quantities, is not likely to be very troublesome when discharged into a sewer, but it is important, from the point of view of fish life and aquatic vegetation, that only nominal quantities should be allowed to pass direct into a stream. Numerous tarry products such as benzol and naphthalene washings containing sulphuric acids of ben- zene and naphthalene, various phenolic deriva- tives, &c., are very injurious to the microscopic life of streams, and may in some cases quite upset the natural balance of aquatic life. When sufficiently diluted and mixed with sewage, they are amenable in general to bio- logical treatment. The same applies to the very troublesome effluents from ammonia stills treating the liquor from the distillation of coal in retorts or coke ovens. In addition to phenolic derivatives these effluents contain sulphocyanates, thiosulphates, and sometimes sulphides. The effluents from paper and cellulose works obtained after boiling raw cellulose material with alkaline sulphites is very difficult to treat and is generally 473 TRA evaporated. (e) Free particles of grease and fat, c.g., from tripe-dressing works, &c., can usually be intercepted by specially devised grease traps, of which there are several, e.g., the Kremer apparatus and the Eric Mesten apparatus. Soaps, e.g., such as are produced in wool- scouring works, are first broken up by acid, when the fatty acids rise to the surface and can be separated and purified. In the case of ordinary laundries it is often simpler to precipitate the soaps with lime. Law as To Trapz Erriuents.—The general law as to trade effluents is to be found in the Public Health Act, 1875, the Rivers Pollution Act, 1876, The Public Health Acts Amend- ment Act, 1890. The difficulties of inter- pretation of the law have centred round the liability of local authorities to take trade effluents into sewers, when either these were insufficient in size or when, the sewers being adequate, the purifying works were over- burdened. A further difficulty has arisen in regard to responsibility for pollution of a stream, when a manufacturer discharges into a sewer belonging to a local authority. Typical cases illustrating each of these three difficulties are, respectively: Peebles v. Oswald- twistle Local Board, 1898; Brook, Ltd. v. Meltham Urban District Council, September, 1908; Butterworth d Roberts v. West Riding Rivers Board, November 26, 1908. All of these have-been decided on appeal in a sense favourable to the local authority. It is generally the wish of the local authority to encourage manufacturers as far as possible, and several towns have special by-laws of their own obtained generally by mutual agree- ment with manufacturers, confirmed in some cases by special Acts of Parliament. Thus, the towns of Bradford and Halifax have power .to impose a charge upon manufacturers, according to the volume and quality of the effluents sent into the sewers; Manchester has special powers regulating the composition of the effluents discharged into the sewers, but does not make any charge for treatment. These powers are based on similar ones pos- ENCYCLOPEDIA OF TRA sessed by the London County Council. The Royal Commission on Sewage Disposal recom- mended in their third report, 1908, that in general local authorities should receive trade effluents into sewers, but that either prelimi- nary treatment should be adopted by the manufacturer or he should pay a special charge to go to the cost of treatment of his effluent. Points of difference likely to arise between manufacturers and local authorities, they recommend, should be referred to the central authority which they are of opinion should be appointed. G. J. F. Tramways, Municipal.—Overhead Trolley System — Conduit System— Surface Contact System—Comparison of Tramway Systems.— A tramway system comprising not more than twenty or thirty cars should purchase its electricity from some large electricity supply station, wherever’ such is available. The multiplication of small stations is a mistaken policy, and is largely responsible for the unsatisfactory commercial results which have been obtained in the case of a large percentage of the tramways in this country. For tramway undertakings of any consider- able extent, the electricity should first be delivered from the supply station in the high pressure three-phase form. In this form it should be transmitted through three-core paper-insulated lead-covered cables to sub- stations located at appropriate points on the tramway route. The sub-stations should be equipped with motor-generators, by means of which the high pressure three-phase elec- tricity is transformed into continuous electricity at the low pressure of 550 or 600 volts. This low-pressure electricity is transmitted from the sub-stations to the tramcars by one or other of the following three systems : 1. The Overhead Trolley System. 2. The Conduit System. 3. The Surface Contact System. 1. OverHeaD Troutitey System.—A copper conductor, usually between 2/0 and 4/0 s.w.c. is supported on insulators at a height of 474 TRA some 20 ft. above the track, by -means of transverse steel span wires carried by poles. This overhead copper trolley wire conducts the electricity from the sub-station to the tramear. The tramcar is supplied with a trolley pole carrying a wheel or bow at its upper end. The wheel or bow travels on the lower surface of the overhead wire, collecting the electricity, which is then conducted to the motors and controlling apparatus on the car. After passing through this apparatus, the electricity is conducted to the car wheels, and thence to the rails. The rails are connected to one another by copper bonds, and thus con- stitute a conductor by means of which the electricity is conveyed back to the sub-station. Sometimes the rails are welded together instead of being bonded. 2. Conpuir System.—The most modern example of tramway construction on the conduit system is that laid down by the London County Council in many parts of London and its suburbs. The conductors are located in a conduit situated midway between the track rails, and the current is collected from these conductors by means of a “ plough”’ passing through a slot in the road bed, and suspended from the car. In one of the earlier forms of conduit construction, the conduit was made a component part of one of the track rails. The track rails were formed by two bull-headed rails, placed side by side, with sufficient space between to allow the collector or “‘ plough” to passthrough. The advantage ’ of this side-slot construction is that it does not require keeping gauged, but a strong dis- advantage is the impracticability of obtaining a substantial permanent-way for the heavy cars. The London County Council system has the slot midway between the track rails, the slot being formed by Z section rails, bolted at intervals to heavy cast-iron yokes, the width of the slot being maintained as near ? in. as possible. The slot rail is of steel weighing 60 lbs. per yard, and is 7 in. in height. Two forms of yokes are used in the system, one, of light weight, to which the slot rails only MUNICIPAL AND SANITARY ENGINEERING. TRA are bolted, and another, the full width of the track, to which both the slot rails and the track rails are bolted. These two types of yoke are, in special places, such as at curves, &c., placed alternately, but in straight track the full-width yokes are placed about every three yokes, the distance between each yoke being 5 ft. The slot rails have to be stiffened by means of ties fastened to the track rails in order to prevent the slot from closing under the influence of the crushing effect of other traffic upon the paving between the slot and track rails. The conductors are two in number and are of soft steel tees weighing 22 lbs. to the yard. They have a contact surface 34 in. in depth, and are supported on special insulators, spaced 15 ft. apart, and situated between the yokes. The depth from the top of the slot rail to the bottom of the conduit tube is 1 ft. 94 in., and to the base of the yokes, where the latter bear in the concrete bed, 1 ft. 1lin. Thus, during the construction of a conduit system, all gas, water and other pipes, cables, sewers, &c., must be sunk at least 23 in. below the surface of the road, before the conduit can be laid down. The “ plough ” or collecting device consists of two soft cast-iron shoes, supported by’ pieces of maple wood, which are stiffened and supported by means of mild steel plates, passing through the slot, these steel plates being flexibly hung from the under-frame of the car. The shoes are pressed against the face of the tee conductors by means of sub- stantial springs. ; To allow proper draining and sanitation of the conduits, they are, at intervals along the route, connected to the main sewers, which generally run along the side of the conduit. 8. SurFace Conracr Systrm.—There have been many surface contact systems invented, but few have actually been put into practice. These latter have, moreover, usually proved utterly unreliable. The surface contact system consists essentially of contact studs, located at intervals of about 15 ft. apart, situated midway between the track rails, and 475 TRA from which the current is collected by means of “skates.” The two essential conditions which must be fulfilled in a system of this kind are :— (1) The contact stud must not be alive when the car is not over it, i.e., when the car is not drawing energy from it, and (2) Some arrangement has to be provided to make the contact stud alive when the car approaches it. Apparently one of the least unsuccessful of all the systems on these prin- ciples is that commonly known as the “G. B. System.” In this system the current from the generating station is conveyed through a bare stranded galvanised iron cable, carried on insulators in a 5 in. stoneware pipe which serves as a conduit. Connection between the conductor and the contact stud is effected magnetically by means of powerful magnets carried on the car. When these car magnets come over the contact stud, a plunger switch, having a carbon contact, immediately makes contact with the iron cable conductor. When the car leaves the stud, the plunger switch is immediately dis- connected by means of a powerful spring. The excavation necessary with this system does not exceed 19 in., and this can be con-~ ‘siderably reduced in special places where so great a depth is inexpedient. CompaRISON OF Tramway Systems. — The most important applications of the overhead trolley systems are in country districts and in towns of fairly small population. In some large towns, overhead trolley systems are often prohibited. In residential districts, objections based on esthetic grounds are often brought up against the system. Nevertheless very nearly all of the tramway undertakings in the United Kingdom are constructed on this system. The capital cost of the conduit system precludes its use in purely residential districts. Conduit systems are only appro- priate in large towns where a dense service can be maintained, and where, for other reasons, the trolley system is undesirable. Under normal conditions the cost of track- work per mile (excluding cables and other ENCYCLOPHDIA OF TRA items common to all three systems), is somewhat as follows, for the three different systems :— Conduit System ... £17,000. “G.B. Surface Contact System ” £11,000. Overhead Trolley System £10,000. From these figures we see that the conduit system involves a capital outlay approximately £7,000 greater per mile, than in the case of the overhead trolley system. In order to understand the significance of this difference let a simple example be taken. Suppose a tramway system is one mile in length, and a service of two-and-a-half minutes for 16 hours per day is maintained. Then, if we consider a double track the whole length of the system, the car miles per year will amount to 9 (# x 60 X 365 2°5 Allowing 10°/, for interest and depre- ciation, then this £7,000 difference in capital cost between the two systems is equivalent to £700 expenditure per annum. Thus the difference in interest and depre- ciation per car mile amounts to some 700 x 240 280000 Cae The conduit has to be kept clean, both for insulation and sanitary purposes, and this maintenance cost is certainly at least 0°3d. per car mile in excess of the trolley system. Thus the total difference between the two systems amounts to 0°60 + 030 = 090d. per car mile. Assuming an average operating cost of 6°5d. for the overhead trolley system, this maintenance and capital cost will represent an extra 18 °/,, or a total operating cost of 74d. per car mile for the conduit system. In the conduit system there are no electro- lytic actions occurring in water pipes and elsewhere, due to currents leaking from the return conductor, because an insulated con- ductor in the conduit itself serves to carry the return current, whilstin the trolley system the current is returned through the track rails. It is with a view to minimising electrolytic damage to underground pipes and structures ) = 280000. 476 TRA that the Board of Trade require that, with the overhead trolley system, the drop of pressure in the rail return shall never exceed 7 volts. From the point of view of the safety of the public, the conduit system undoubtedly possesses some advantage. ‘here are no “live” wires above the ground, and it is impossible to touch the conductor in the conduit by any ordinary means, through the slot opening. With overhead construction, the Board of Trade require protection for telephone wires and cables which may happen to cross the trolley wire. That is to say, if a telephone wire breaks, it must not be possible for it to fall across the “live” wires. To prevent this, grounded “ guard” wires are suspended above the trolley wires. As regards durability, the steel conductors of the conduit system have a longer life than the ordinary copper trolley wire. The latter in ordinary services will last some 4 years. A disadvantage of the conduit system lies in the fact that the slot is very liable to close, due to the pressure of the wood or stone paving. Thus the plough is liable to become wedged in the slot and cause delay in the traffic. The serious difficulty with the surface con- tact system is its unreliability. Experience has proved that the studs are sometimes left alive, in spite of every precaution to render such occurrences impossible. In view of this difficulty, extra skates are sometimes pro- vided on each car. These trail behind the collecting skate, and in case of a stud being left alive the trailing skate directly short- circuits the stud with the track rail, thus putting the stud out of action for the time being. The maintenance costs of the surface contact system are certainly not less and are usually far higher than for either the trolley or conduit systems, and this will occasion no ’ surprise when it is remembered that hundreds of switches per mile have to be kept in thorough working order. Acts oF PARLIAMENT AFFECTING THE OPERA- rion oF Municipan Tramways.—Provisional MUNICIPAL AND SANITARY ENGINEERING. TRA Orders authorising the construction of tram- ways were granted under the powers of the Tramways Act of 1870. It was stated, how- ever, when the Bill was introduced, that power would be given local authorities only to con- struct tramways, but not to work them. The “ Purchase Clause ” of the Act of 1870 imposed upon the private tramway companies the liability of compulsory sale to the local authority of the district. Under this clause the local authority may, within 6 months after the expiration of 21 years from the granting of the tramway order, and within 6 months after every subsequent period of 7 years, require the promoters to sell their undertaking. It is now possible under the present rules, for municipalities to. operate tramways, as well as to construct them. No Act of Parliament, however, authorises them to do so without special grants, and it was due, among other reasons to the difficulty of coming to an understand- ing as regards lease, &c., with the companies, that led certain municipalities to obtain these special grants. A municipality is allowed to construct tramways outside its own area, providing the consent of the local authority of the new area ‘is obtained. The local authority of the new area still, however, retains its power of com- pulsory purchase under the conditions given in the Purchase Clause of the 1870 Act, given above. The local authorities must obtain the con- sent of the Board of Trade with respect to the power of borrowing capital. With regard to constructional obligations, the 1870 Act contains clauses to the effect that no tramway may be so laid that for a distance of 30 ft., less space than 9 ft. 6 in. intervenes between the foot-path and the rail, if one-third of the occupiers abutting on that part of the road dissent. The tramway constructors are bound to keep the roadway in repair to the extent of 18 in. on each side of their rails, and between double lines. The Light Railways Act of 1896, although 477 ENCYCLOPADIA OF TRA TRA LTO mH Dw Cn Rese a PS RPOHPaAs rsa stieawmog os Heaps oe Jsaooguwqaesysweogrkh o oo. fal eo Ae os ‘a HH O19 n wm Mom “4 Pe Sg EST SSMS Seg s SSagEeSSeiGs CRGAee2 B2aggee se ee SB Bs 4 Sy eB D nHeser Ar oO .42 6 oe .« 3 o 8 a ® 5s oR “Bo gf k ep Pees eta s Bg Suc. 8M Sa Ss bade & severee aoe CR se a3 =a Bap fot as — 3 Pees BOD a a + pont dess eA 8 .SShe se seogaF, > S Ese * a0 Aho BSE. 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GIFT | 000'S68'S6S'T | LF8'FFE'ZZ8'T | 000°E06' sol 000‘S23'S61 218" ozs" 061 PeH1wD s1esuessvg Jo lequny 000°6¢FS9T | OOO'FFS‘e8T | TFE'zs6'90e | OOO'DFS'EFI | 000‘Sez‘09T | sas‘seo'zst | OOO'ETT'ss | 000'6Rz'Fs | EFO‘eFE'Fs UNY SIL IO Jo Taquny 9¢-F E83 $9.29 LB-£99% 99-6861 49-1313 62-183‘ SOF 1&F 86-18% PIL SESERL 30 yysueT 96-0F 86-9F 0-9F OF-9F 18-9F FLOF CEFF OL-SF EGF ‘yeyideg ~ JO OOTF ted qyorg 4aN Jo qunowy 6F-1¥ 96-17 89-1¥ 98-0F 08-3# OF-6F 69-0F 68-0F 68-0¥ Teydep Jo OOTF sted aarasay pue uowepordeg TOF peplacig qunoury 98.9% COLE LLF 91-8F ST-6F 06-6F F6-F¥ C6-9F 06-9F yeqdep jo OO1F wed qYorg sso1y Jo Junouy 000'z60'%F | ooo'oTe‘ezs¥ | oos‘ooL‘sy | O00‘OOs'TF | ooO‘OZT‘z# | Oog‘ege’zx | ooo'zesx | ooo'roex | oos'zFey * spueplaiq pue ‘ qsarequf TOF s[qQvpIwVae YYOIg JON OOLFOLE 008'68LF 008'ST6# 000'¢99F 000°9¢L¥ OOF LES OOL'TEF 008 LoF 006'29F 3 SAdasey PUB WOLyeroordaq, ooo'6os'eF | OOL'919'eF | OOO‘O9F's¥ | OoO'OES'c¥ | OOL‘oIZ'ex | COOFEE¥ | OOO'6IEX | OOF SOT YOIT sso1y 000°206'F¥ | ooL'tEs'c¥ | OOO‘O6S‘E¥ | OOO‘OOS'r¥ | OoL‘9geF¥ | COO'6sSF | OOO'ZO9F | OD0'SCOF $3809 Suyezi0dg OOO'OTS'SF | OOO'TYT'6F | OOO‘OSe'9F | OOO'O6I'Z | OOG'LFI'SF | OOO'RO8F | OOO‘VZO'T | OOS'EIO'LT SOOINOY [[B Wo sNMIAdY [IO], OOF ISTE Osteo e 000'801¥ 000°621F OSL'SE1¥ 006° Ca¥ OOF sSF 00g’ oeF SOOINOG TOYO WOIZ aNUOASY 000'080'L¥ | 000'8E0'8F | 00€'66'8F | O00'0FZ'9F | OOO‘OLO'LF | OOE'600'8F | OOV'OFSF | COO'896¥ | OO0'S86F ; anuadsy oer, 000°098'FEF | 000'009'SEF | NOO'6SFIFF | OOO'OOT'SZF | OOO'OSS'TEF | OOF‘968'tE¥ | OOO‘09L‘9F | 000'080'LF | OO9'zEs'oy wok JO pug yvomnypuadxg peydep z6 $6 +6 OL GL GL BB &% 61 é SBULYBepuy JO Jequnyy (9-¢06T) (4-906D (8-L061) “yNy [eooT | “YN [eooT | ‘ynY [e00T 9-061 1-906I 8-L061 C061 9061 LOGI IwaX [eouUrULy (go61) ‘deaog | (9061) “Aet0g | (L061) ‘duro *(saryoyyny [eo0'y snid sataedurog) [eyo], “‘sorpLoyyNy [ev0'T “sotuedwo0g “SONIMVIUAGN() AVMAVAY, OLULOATY AO sauoory dusluvyWAng 478 TRA undertakings owned and worked by local authorities for the financial years 1906-7 and 1905-6. In the last two columns, these separate figures for companies and local authorities are added under their equivalent financial years. For notes with regard to the generation, transmission and transformation of the elec- tricity required for the propulsion of tramcars, ‘see article on ‘‘ Execrriciry.” Trap.—A term applied to the dip or bend in a drain or pipe, which, by retaining water, serves to break the direct line of connection between the air contained by two portions thereof. The water retained is said to “seal” the trap ; the effective seal being the portion contained between the standing level of the Trap. water and the lowest point of the soffit at the dip of the trap (A—B in the illustration). It is the depth of this portion which is referred to by the phrase “a water-seal of so many inches.” One-and-a-half inches is considered the minimum seal admissible, and 23 in. the seal generally accepted as the standard. Traps may be subdivided into traps of fittings, gullies, disconnecting traps and grease traps, as to which see under respective headings. Traps for Fittings are necessary to exclude from the house foul air generated in waste pipes and surface traps, &c. In the case of water-closets and of most slop hoppers the trap is made as a part of the fitting itself. With lavatory basins, baths, sinks and urinals the trap must be specially provided, and should be fixed on the waste pipe close up to the fitting. Such traps must be, as far as possible, self-cleansing, and should provide an MUNICIPAL AND SANITARY ENGINEERING. TUR efficient seal with a minimum quantity of water. The only traps at present available which comply with these requirements are the siphon traps drawn from lead piping and made in various forms, such as the “8,” “P,” and others. All other traps—such as the “ Bell” trap, ‘‘D” trap, ‘* Bottle” trap, and the ‘‘ Mechanical” traps in which latter are floating balls or valves—are either ineffi- cient or uncleanly. ‘The traps used must be of the same or of a smaller sectional area than those of the outlets under which they are fixed; due allowance being made for the space obstructed by the outlet gratings. If larger, they will not be properly flushed and cleaned by the discharge of the fittings. Turbines.—In an ordinary water-wheel only a portion of the periphery is acted upon by the water, but in turbines it is, with few exceptions, directed by guide blades to every vane in the revolving part; the wheel of a turbine thus receives the pressure, or in some cases the impulse, of the water throughout its circumference. For this reason it is much smaller and revolves at a far higher speed than a water-wheel of equal power. Both guides and vanes are curved in such a way Fic. 1.—Headrace and Supply of Water to Turbine. that the water passes from one to the other without shock or break of continuity and herein lies the cause of the high efficiency, amounting, under favourable circumstances, to over 80%. Turbines may be of the “pressure” or the ‘‘impulse” type. The former are those in which the spaces between the vanes are full and under the pressure of the water. In impulse turbines, such as the ‘Girard ” the water acts by impulse, leaving the guides with a velocity proportionate to the head, and entering the wheel to glide over 479 TUR the concave surface of the vanes without filling the passages. In some cases the guides of impulse turbines are only applied to a portion of the wheel—this is known as ‘partial’ admission. The “ Pelton wheel” belongs to this class—in this case one or more ENCYCLOPADIA OF TUR ° the guide blades, which are then made mov- able for that purpose, or by throttling the supply with a cylindrical sluice working between the guide chamber and the wheel; in a few cases, however, an adjustable gate is placed at the intake. The first plan gives the 3 VNINVN NSB Fic. 2.—General Arrangement of Fixing of Turbine. tapering nozzles direct a jet of water into double cups placed around the rim of a wheel. Turbines may be classified as ‘ outward,” “inward,” ‘parallel’ or “mixed” flow, according to the direction in which the water passes through them. In the first type, (Fourneyron’s) the guides form the central part of the turbine, the wheel containing the vanes being placed outside it and in the same plane. ‘I'he water enters the inner portion and is directed by the guide passages to the annulus of vanes surrounding it, giving motion to that part by pressure and reaction and afterwards escaping at its periphery. In the second type (‘‘ vortex ’’) the water enters through guide passages on the outside of the wheel and discharges at the centre. With the parallel flow turbine (“‘ Jonval”’ type) the guides are placed above, or if the shaft is horizontal to one side of the vanes, and the water passes through in a direction parallel with the axis. The mixed type is a combina- tion of the inward and parallel flow, and is represented by the “ Francis,” ‘ Hercules,” “ Little Giant,’ and others. Turbines are usually regulated by varying the opening of most economical regulation under varying loads, but it is more complex and therefore higher in first cost. For low falls where the quantity of water is large, pressure turbines of the parallel and mixed type are the most suitable. Under these circumstances the SUCTION TAL RACE Fic. 3.—‘ Double Vortex” Turbine. water is conveyed to the turbine by a “flume” of timber or masonry, the general arrange- ment being usually as shown in Fig. 2; the dotted circle indicates how a breast wheel might be replaced bya turbine. For moderate falls of 10 ft. and upwards it is generally preferable to inclose the turbine in an iron 480 TYP case to which the water is conducted by piping. By causing part of the fall to act by suction, a turbine may be placed well above the tail race and the machinery driven by belting or coupled directly to its shaft. Fig. 8 shows a “Double Vortex” installed in this way, but the arrangement would apply generally to any other incased turbine with a horizontal shaft. Fig. 4 illustrates the mode of fixing a Little Giant turbine; in this example the turbine replaced an overshot wheel, the pentrough of which was utilised in the manner shown. A Girard turbine could be similarly arranged except that it would be placed a few inches above tail water to insure a free discharge. Suction tubes cannot be employed in an impulse turbine owing to the passages being only partially filled; therefore, to obtain the full effect of the fall, which in one of low head is important, it must be placed close to the tail water, in which position it is liable to have its efficiencyimpaired during floods. With high falls a slight sacrifice of head is not of so much consequence, and to them, impulse turbines of the Girard type are specially applic- able, as partial admission can be adopted. By this means the diameter of the wheel may be increased and its rotative speed, which in very high falls would tend to become excessive, reduced in proportion. Another feature of the impulse turbine is that its efficiency is practically constant throughout all degrees of admission. When the last consideration is unimportant, the Pelton wheel is very suitable for high falls. (See ‘‘ Warer Power, WATER WHEELS.”’) E. L. B. Typhoid Fever.—This disease appears to affect all communities, and is especially prevalent in urban districts with impure water supplies and imperfect sewerage systems. Fewer cases occur, in proportion to the popu- lation, in rural districts, even where the water is notoriously impure and where sanitary conditions generally are unsatisfactory. The explanation doubtless is that amongst the M.S.E. MUNICIPAL AND SANITARY ENGINEERING. TYP more scattered population the risks of per- sonal infection are far less than in the more densely populated towns. The disease has a marked tendency to increase in prevalency during the autumn, and if for any reason several cases have occurred in the summer quite an outbreak may occur later when the season is more favourable for its spread. The PENTROUCH Fic. 4.—Method of fixing “ Little Giant”? Turbine. cause of these autumnal outbreaks has not yet been discovered. The infecting agent is a bacillus which can be cultivated outside the human body, but which is somewhat difficult to recognise and exceedingly difficult to isolate when associated with the bacteria found in sewage. In fact, it is not always possible to find it in water which may be known to be causing disease. ‘The bacilli can frequently be discovered in the blood of persons suffering from typhoid fever, but they are far more numerous in the urine and feces at certain stages of the disease. Recent researches have shown that in some instances, which may be far more numerous than we surmise, the feces may retain the bacilli many years after recovery from an attack. Such persons are called typhoid “ carriers,’ and several epidemics in public institutions and numerous isolated cases have’ been traced to these “carriers.” From the urine or faces the bacilli reach the drains and the sewers, and the most recent research has proved that if there is any splashing in such sewers, or any 481 Il TYP stagnation leading to putrefaction and the bursting of bubbles of gas, bacilli are dis- charged into the air, and may be detected at the ventilating openings. No doubt also when infected slops are thrown over badly paved gullies the bacilli may get into the air and infect water, milk, or articles of food. A typhoid carrier of uncleanly habits may spread the disease wherever he goes, but unless some article of food or drink used in common by a large number of persons is infected the cases will not be numerous. When such infection does occur an epidemic may follow. Epidemics are generally due to infection of water, milk, or shell-fish; but some occur which cannot be definitely attri- buted to these causes. Such outbreaks usually commence in the autumn and follow a series of isolated cases. Usually also it is found that they are associated with grossly insani- tary conditions, uncleanliness, overcrowding, defective privies or water-closets, defective drains and sewers, fixed uncovered ash-pits, filthy badly-paved yards, &c. Taking 77 recorded outbreaks which have occurred in this country since 1881, 18 were definitely traced to water, in 17 instances the water was gravely suspected, but absolute proof was wanting, in 4 milk was the cause, in 3 oysters, in 1 cockles, and in 1 watercress. In the remaining 38 cases the cause, could not be ascertained, but almost invariably the sanitary circumstances of the districts invaded were bad in the extreme. Water outbreaks would probably be more numerous were it not that the typhoid bacillus rapidly dies out in that medium. Several bacteriologists have demonstrated that 99°9°/, of the bacilli die within 7 days. Where a water has been pur- posely and largely impregnated with the bacilli, an odd bacillus may possibly be discovered for many days afterwards, but whether these more resistant organisms are dangerous or not there is no means of ascer- taining. This fact, however, is of great practical importance as showing the great advantage of storage, but whether storage beyond 7 to 10 days is of any great utility ENCYCLOPADIA OF TYP from this point of view is very doubtful. Water and milk outbreaks, and outbreaks due to infection of other articles of food or drink, may occur at any period of the year and attack all classes indiscriminately, whilst outbreaks due to unknown causes or to insanitary conditions usually, if not invariably, occur in the autumn and affect the uncleanly and the poor in an excessive proportion. When a town has a common water supply naturally all the persons attacked will have partaken of the water, but unless the disease is fairly uniformly distributed throughout all classes and throughout the town, or through- out an area supplied by a particular main, the water supply cannot be the cause. If the outbreak is localised, or only occurs amongst certain classes, and especially if limited to the more insanitary areas, some other cause than the water must be sus- pected. Milk may be infected at the farm, or the dairy, or even during distribution ; and in the first instance nearly all the patients will be consumers of the implicated milk, though at a later date personal infection will commence. So far as is known, animals do not suffer from typhoid fever, and there is no record of any outbreak having occurred from the contamination of water or milk by animal manure. The bacilli may live for considerable periods in sand and soil, or on dirty surfaces, but most contradictory results have been obtained by different observers. There are reasons for believing, however, that under very favourable circumstances it may survive for many months in surface soil. It is destroyed in a few minutes by a temperature of 70° C. In infected urine and stools it may be killed by a very liberal use of disinfectants, allowed to act for, say, an hour to penetrate the more solid matter. Although it is doubtful whether it can survive even a few hours in sewage, it is now usual to supply each typhoid patient, not removed to an isolation hospital, with a special pail containing disinfectants for the reception of the urine and feces. These are changed at regular intervals by the scavenger, and fre- 482 TYP quently the contents are mixed with sawdust and petroleum and burnt. Experiments made with the common house-fly show that it can convey the bacilli on its feet, and that these may live for some days in the intestine of the insect and be afterwards found in the spots of fecal deposit. It is probable, therefore, that they can convey infection, and one outbreak attributed to infection of water cisterns by this means has been recorded. J.C. T. Typhus Fever.—This fever was for a long period the scourge of Europe, but during the last century it nearly disappeared from England, Wales, and Scotland. Many outbreaks, how- ever, occurred in Ireland during periods of famine. Cases still occur occasionally in our crowded cities, and invariably where the poor are densely aggregated together amidst squalid surroundings. It is one of the most contagious of diseases, more frequently than any other attacking the medical attendant and nurses, or those coming into close contact with the patient. We are unfortunately ignorant of the specific cause, but there is every reason to believe it is a “germ” disease. Its practical disappearance is due to many causes; the improved housing of the poor, diminution of overcrowding, greater general cleanliness, and the higher standard of living. When an out- break occurs the patients should be promptly removed to an isolation hospital or other place where they can have an abundance of fresh air. Contacts should be carefully watched to detect the earliest symptom of infection. The pre- mises infected should be thoroughly cleaned and disinfected, and every article of bedding or clothing which has been used by the patient should be sterilised by steam or, if of com- paratively little value, destroyed by fire. If there is overcrowding of persons in houses, or of houses on space, these matters should receive attention. If cases tend to occur in the same locality it will probably be found to be an insanitary area requiring clearing and the consideration of a housing scheme. J. C. Ts. 483 MUNICIPAL AND SANITARY ENGINEERING. UND Under-drainage.—The object of under- drainage is to keep down the level of the subsoil water, so that the soil and the upper layers of the subsoil may be properly aérated and afford a proper feeding ground for the roots. of the crops. The need for under- drainage is greatest with clays and heavy loams, and in districts with heavy rainfalls. Open sands and gravels, on the other hand, rarely require under-drainage ; but when such land is to be irrigated with sewage or sewage effluent it should generally be drained. Various materials have been used for under-drains ; unglazed earthenware pipes with butt joints being by far the best. The size of the pipes and their depth and distance apart will depend on the nature of the subsoil and on the rain- fall. For stiff clays 2 in. pipes may be laid at a depth of 3 ft. and in lines 20 ft. apart, while in a gravelly subsoil 23 in. or 8 in. pipes will be required at a depth of 5 or 6 ft., and at distances as great as 80 or 100 ft. In irrigated land the spacing will generally be closer, and the size of the pipes should not be less than 3 in. or 4in. Larger pipes should, of course, be used for the mains. The pipes should be butted tight together, and in filling the trenches, especially in irrigated Iand, care should be taken to consolidate the material so that the water may not take a short cut through it from the surface down to the pipes. The neglect of this precaution in many cases has done much to bring under- drainage into disrepute. A. J. M. Underground Water.—Many towns de- pend for their water supplies upon subter- ranean sources obtained by means of sunk wells or borings. Such waters accumulate through percolation of rainfall into the “ out- crop” of porous strata and often travel many miles underground until the lowest subter- ranean basin is reached. Almost any porous formation containing fissures or “vents” is capable of holding large quantities of water, especially when impermeable strata occur below. Good supplies are frequently derived from the chalk, new red sandstone, oolite, 112 UND magnesian limestone, Ashdown sands of the Hastings series, and other porous formations. It should, however, be understood that the quantity obtainable from any given strata varies considerably in different situations according as the rock into which the boring or well is sunk proves to be compact or much fissured. Chalk, for example, is one of the most favourable sources from which water may be obtained, but even this in some cases has proved to be so compact as to yield little or no supply. Briefly stated, the main con- ditions determining the quantity of water obtainable from subterranean sources are :— (1) The mean annual rainfall occurring over the “catchment area” feeding the under- ground basin, and the proportion thereof i LN Fic. 1.—Conservation of Underground Water Supplies. percolating in at the “outcrop” and ulti- mately finding its way to the subterranean store; (2) the extent of the outcrop of the water-bearing strata and the degree to which the slope of adjoining inpervious areas may contribute by conducting the rainfall falling thereon on to the porous outcrop; (8) the area of the underground contributing area or watershed; (4) the degree of porosity or permeability of the water-bearing strata, and the percentage of the total percolation which is again recoverable by means of pumping stations; (5) the extent to which artificial works may have been carried out for the purpose of retaining the rainfall upon the catchment area, and so preventing its rapid escape to streams and rivers, and the means adopted to intercept the flow of underground water into the sea or river-beds. Notwith- standing the fact that underground water is very largely used for purposes of public supply, but little attention has been given to the ENCYCLOPEDIA OF Oe yo 7) Sy) as aig aa UND question of the conservation of subterranean water, probably owing to the fact that, in this country at any rate, underground storage is fairly regularly replenished by natural means before any very alarming depletion arises. It is also difficult in the majority of cases to locate, with a sufficient degree of precision, the most favourable site and nature of works likely to be effective. Where suitable condi- tions are known to exist, however, the quantity of water recoverable may be augmented by methods similar in principle to those illus- trated in Fig. 1. Here an artificial dam or puddle wall is employed to intercept water flowing through permeable beds on its way to the sea towards which the water-bearing strata “dips.” Water is also conducted on to the porous outcrop of the per- meable strata by means of a ae conduit from an extensive catch- ment area or adjoining hillside. Much information as to the water-bearing capacity of any Ge given locality is obtainable from a careful study of the detailed geology of the surrounding district. The most practical means of doing this is by first collecting particulars of all local borings or wells, the levels of the different strata passed through, and the rest and pumping levels of the water in such borings. These data should be utilised, with the assistance of reliable geological maps of the district, for the purpose of building up an accurate section of the strata in the manner illustrated in Fig. 2, which diagrammatically represents a case investigated by the present writer for public water supply purposes. The section covers a stretch of country about 14 miles in length, the surface levels of which were obtained from ordnance maps, whilst the levels of the different strata shown were derived from various borings, three of which are given in the figure. Upon care- fully plotting to scale all available informa- tion and reducing all levels to ordnance datum, it was found the rest levels of water in all the borings coincided very closely, 484 UND showing the water-bearing sand-rock to take the form of a wide basin some 12 miles across, and to be uniformly saturated up to the level shown. The section also revealed the fact that a well or boring placed at A would be favourably situated for yielding a strong supply of water, which, on being tapped upon reaching the sand-rock at the depth of 200 ft. from the surface at once rose in the boring under an artesian head of 100 ft. The great importance of the study of practical economic geology has long been appreciated by the Geological Survey Office which has given much attention to the ques- tion of underground water supply, and has Outcrop 4 of fissured sandrock ay s SEES He ae yess -------+--12 malas - MUNICIPAL AND SANITARY ENGINEERING. SClapbed 2d 20010 Did A SSSRS ahs 5 ae EES oe: sae S SESS IE SEASON, & Sees SER oR MoneSorsei sy, SOLS SIS URI qualities appropriate means must be adopted to properly prepare the water for the ordinary requirements of domestic and trade supply. W. 4H. M. Urinals, Public. (See “ ConvenrEncEs.’’) Urinals, amongst sanitary fittings, are the most difficult to keep in a wholesome condition owing to the urea contained in urine, which decomposes very rapidly, and the uric acid which, being but feebly soluble in water, is very liable to. adhere to all surfaces with which it comes in contact. Even the. best of these fittings are frequent sources of nuisance, Outerop i of fissured sanclrock EBs oe SCR a CaN A ae a ig A as San “ Li REG ese Strata | accel Fic. 2.—Section of Water-bearing Data, ascertained from Data on various Borings. accumulated a large amount of information upon the subject. The data so collected is now being made accessible to the public by the publication of a series of ‘memoirs ” dealing with the underground water supply and well borings of different counties, and the approximate yield available. Underground water is usually of great organic purity, but its composition naturally depends very largely upon the nature of the strata through which it has percolated. It is commonly highly charged with mineral constituents, and not infrequently of great ‘‘ hardness,” a large part of the latter quality oftentimes being “ per- manent.” Very “soft” waters are also some- times met with, and in some cases the supply will be highly charged with iron either in solution or suspension. For all these varying and for this reason urinals are best avoided within dwelling-houses. Nor are they essen- tial in such positions, as their place may well be taken by the water-closets. Where the necessity exists, only the most efficient fittings must be provided. The following conditions are essential in urinals :—(1) The soiling sur- faces with which the urine comes in contact must be as small as possible consistent with convenience ; (2) there must be an entire absence of angles, corners, and unevenness that would tend to retain deposits of urine or of dirt; (8) the materials of which the fittings are made must be smooth, impervious and incapable of being acted on by uric or other acids; (4) an abundant supply of flushing water applied each time the urinal is used; (5) thorough ventilation, abundant light, and 485 VAL a cool atmosphere in the urinal apartment. (See also “ ConvENIENCES, PuBuic.”) Valves. (Sce ‘‘ Pumps.”’) Valves (Water Supply)—Cocks or taps fitted with a loose valve or diaphragm acted upon by a screw spindle with handle or wheel. In screwing down the spindle, the valve is forced down upon its seating and the water gradually shut off. When unscrewed, the pressure of water forces the valve off its seat in some cases, while in others the spindle raises the valve, leaving the water free to flow through in either case. Valves may be divided into ‘‘ stop valves” placed on a pipe to regulate or shut off the Screw-down Valve. supply of water and “draw-off valves ” made use of over sinks and other fittings for drawing water. A subdivision of the latter are ‘‘ spring valves” so constructed that water can only be drawn when the valve is held open by pressure of the hand. When released the tap is closed automatically by a spring. Of these only those that close gradually and without concussion should be made use of when the water is under pressure. The spindles of all valves should be made of gun-metal, but all other parts may be of hard brass. The valves themselves must be fitted with washers of oil- dressed leather and for hot water with vege- table fibre of the best quality, unless they are ENCYCLOPADIA OF VEN metal-faced as in the case of Lord Kelvin’s tap. Varnish.—Considered generally varnish may be defined as being made from a fossil resin dissolved with heat in linseed oil or turpentine, but such a definition must neces- sarily be vague and there is no possible manner of specifying varnishes except by the nameof the manufacturer or by the price. There are many grades of varnishes ranging from “white Coburg varnish’”’ or ‘‘ body varnish,” costing from 24s. to 82s. per gallon down to the cheapest varnishes which may be had as low as 8s. per gallon, or less. The classification of varnishes in general is roughly as follows :— “white marble varnish,” ‘‘ white oil varnish,” “white Coburg varnish,” and “‘ body varnish,” ‘French oil varnish,” ‘white copal,”’ and the best “carriage varnish,’ range from 18s. to 24s. per gallon. ‘Maple varnish.” “extra pale copal varnish,” “‘ flatting varnish,” and ‘‘ second grade carriage varnish,” range from 12s. to 16s. per gallon. ‘‘ Copal oak varnish” can be had at 10s., and second grade of the same at 8s. Also may be added black varnishes or ‘‘ Japans,”’ as they are sometimes called, which are sold at from 10s. to 20s. per gallon, and are specially suitable for iron- work. Enamels come under the same cate- gory of varnish and vary very largely in quality, costing from 10s. or less to £1 1s. per gallon. (See ‘‘ Hnamets.’’) Velocity of Flow. (See “Fiow in Prrzs.”) Ventilation of Buildings.—Amount of Air Required—Natural Ventilation—Artificial Ven- tilation—Cottages—Public Halls.—Pure air is as essential to human life as good food, although the fact is not fully appreciated, and before proceeding to deal with ventilation schemes it will be as well to study briefly the composition of the air. The following table gives the proportions of an average sample of air taken by Parkes :— Oxygen Nitrogen 209°6 per 1,000 volumes. 790°0 5, ” 486 VEN Carbonic acid Watery vapour 0°4 per 1,000 volumes. Varies with temperature. Ammonia es Trace. Organic matter (in vapour or suspended, organised, unorganised, dead or living) Variable. Ozone Salts of audlhnnn 2 Other mineral substances. . Oxyeen is the chief constituent of air, and the great purifier of air, as well as the princi- pal aid in combustion. It is upon this gas that the heat and energy of our bodies depend. Carzonic Actp.—Among the impurities in air this is probably the greatest. The late Sir Douglas Galton stated that 1°5 parts per cent. produce nausea, depression, and headache ; 2°5 °/, extinguishes a candle, and 5 parts per cent.is fatal. It will be evident from this that systems of ventilation must be such as will reduce this dangerous element to a minimum. The amount generally allowed as a safe quan- tity is 6 per 1,000 cu. ft. The burning of gas in houses and factories is a great defaulter in polluting the air, and it has been found that 1 cu. ft. of gas will consume the entire oxygen of 8 cu. ft. of air, in addition to imparting impurities in the form of compounds of sulphur and carbon. The effect of impure air on the system is very detrimental, producing a lowering of the vital functions, and thus tends to the contraction of disease and pro- longs the period of recovery. Quantity or Arn Requirep.—It has been found that an average adult gives off by res- piration °6 cu. ft. of carbonic acid (CQ2) per hour. By referring back to the table giving the composition of the air we find air contains ‘4 cu. ft. of carbonic acid per 1,000 ft. By adding this amount to that given off by respira- tion a total of 1:0 cu. ft. of carbonic acid per 1,000 cu. ft. of air is obtained. This is more than has been laid down as the standard, viz., ‘6 cu. ft. per 1,000 cu. ft. of air. The amount of air required per person per hour is 3,000 cu. ft., and the air of rooms MUNICIPAL AND SANITARY ENGINEERING. VEN should be changed with sufficient frequency, according to their size, to maintain that standard. This changing of the air is a matter requiring careful attention, in order not to give rise to draughts. Air which moves at a greater velocity than 2 ft. per second will cause draughts, and the system must be so arranged that this velocity will not be exceeded. The above amount of 3,000 cu. ft. of air per person per hour is an ideal state, and in practice it is found difficult to reach that standard. The usual amount in cottages is about 250 cu. ft. per person—e.g., if we take a small room of 10 ft. by 10 ft. and 8 ft. high we get 800 cu. ft., but allowance must be made for furniture, which will occupy about 100 cu. ft., and if the room is occupied by three persons this gives 230 cu. ft. per person. The following table extracted from different sources, including the model by-laws of the Local Government Board, will give an idea as to what is generally required :— 150 cu. ft. per person under 10 years of age. 800 cu. ft, for adults for sleeping only. 200 and 400 cu. ft. respec- tively for rooms when not used for sleeping pur- poses. 600 cu. ft. per cow. 250 cu. ft. per person. 400 cu. ft. per person for overtime. Houses let in lodgings. . Dairies, &c. as ad Factories and workshops ” ” ” Schools (Education Department) .. 80 cu. ft. per head.! Public Halls 1,200 - 1,500 cu. ft. per head.? Hospitals (ordinary) 1,200 cu. ft. per head.? 3 (infectious) .. 2,100 - 3,000 cu. ft. per head. It is a mistake to imagine that lofty rooms take the place of air space. The amount of space available for ventilation purposes should be taken at a height of not less than 12 ft. and not more than 13 ft. There are two 1 “ Architectural Hygiene,” B. F. Fletcher, p. 146 (1902). 487 VEN methods of ventilation: (1) natural, and (2) artificial. It is proposed to deal with the principles and different appliances that are used in each system. It is impossible to carry out an efficient system of ventilation without having due regard to the allied questions of heating and lighting, and the reader is referred to the articles dealing with these subjects, as it is important to know how to utilise these two essential factors in any scheme of ventilation. The forces which tend to move the air in rooms are two: (1) the wind, (2) the difference in temperature between the outside air and that in the room. The wind is a great factor in ventilation, and causes the air to move rapidly. Cold air is heavier than hot and upon entering a room falls to the bottom, dis- placing the hot air in the room. If the incoming air is unwarmed before it enters, it causes a draught and the inlet is closed by the occupants. The following table compiled by Scott & Co. gives the powers of fans manu- factured by them, and will be useful :— Foun AIR EXTRACTED UNDER CERTAIN HEADS oF WATER. 24 in. fan. Water pressure, lbs. per sq. in. 26 ee .. 60 50 40 30 Air per min., approx. cu. ft. Revolutions per min., approx. 4,000 3,000 2,000 1,000 500 850 220 150 Water per hour, gallons 120 100 60 45 fin. supply. 1} in. drain. 18 in. fan. Air per min., approx. cu. ft. 2,000 1,500 1,000 800 Revolutions per min., approx. 650 450 300 200 Water per hour, gallons .. 90 60 50 £40 4 in. supply. 1} in. drain. For many purposes water-driven fans would be unsuitable and electricity may be conveni- ently used. Messrs. Blackman make fans which are extensively used for this purpose, and for long buildings where the rooms are scattered and numerous, the ‘‘ Guibal”’ type of fan appears to be the best. Naturat VENTILATION.—This, as its term implies, means the conveyance of fresh air ENCYCLOPADIA OF VEN into the buildings by natural methods, such as ordinarily occurs through doors, windows, fireplaces, &c. As previously pointed out the forces necessary in this system are the wind and the difference in temperature, between the outside and the inside air. Intet anp Outiet Tusss.—When bringing in the air by tubes, they must be arranged to have as few sharp bends as possible, as these greatly diminish the carrying power of the tube. Allowances must also be made for friction when calculating the size of the tubes to be used in the ventilation of rooms. They must be large, smooth inside, free from bends, and vertical and short as far as possible, and preferably circular in shape. The joints of the tubes must be thoroughly air-tight. The position of the openings must be carefully considered, as the cold air should not. be allowed to fall directly into the room before it is slightly warmed. The height of air inlets above floor level generally adopted in practice is from 5 to 6 ft., preferably the latter. The size of the inlets should be proportional to the number of persons occupying the room, and Dr. Corfield recommends that 24 sq. in. sectional area be allowed for each person. In calculating the sizes, the net opening only must be taken, and due allowance made for bars, &c., obstructing the opening. Hood. has given the following table for finding the sizes of the opening, taking into consideration the number of persons and lights, and size of the room :— ; Number of | Number of Net Size of Size of Room. | Occupants. |Gas-burners| Ventilator. 10 ft. by 10 ft. | 2or38 2 9 in. by 3 in. 16 ft. by 12 ft. | 3or4 3 9 in. by 6 in. 20 ft. by 16 ft. | 4or5 4 9 in. by 9 in. The outlet must be in a high position, and as the warmest and foulest air is always at the top of the room, near the ceiling, the outlet should be in that position. The agegre- 488 VEN gate area of the inlets should be somewhat in excess of that of the outlets, and the inlets should be placed as far away as possible from the outlets, so as to insure a thorough cir- culation of the air in the room. | System or Boyne’s VENTILATION FOR Inrectious Hosprrats. — Boyle’s system of Ventilation for Infectious Hospitals, as described by the Building News, May 26th, 1899, is as follows :— “This appliance, which Mr. Boyle has named ‘ Bactolite,’ is intended to be employed in small-pox and other infectious-diseases hospitals . . . destroying the disease germs contained in the air of an hospital, as it passes, or rather is drawn, through an asbestos furnace situated in the roof, and connected with an ‘air-pump’ ventilator, effectually consuming the poisonous germs, and preventing them from passing into and contaminating the outer air and spreading infection. “With the ‘ Boyle’ system of ventilation, as applied to small-pox hospitals, the air inlets communicate direct with the external air through specially-constructed openings made in the walls, fitted with self-acting valves to prevent the air of the hospital passing by any chance out through these openings. The incoming air is warmed in cold weather to an agreeable and healthy temperature by means of Boyle’s ventilating radiators, without the deterioration and discomfort which result from hot-air heating. “Arr SCREENS.—In warm weather, thefresh- air supply is cooled in its passage through adjustable refrigerating chambers attached to the radiators, and is washed and purified by filtration through saturated and medicated screens. The outlets and inlets are accessible in ali parts for cleansing purposes. It would appear, from the tests which have been made by scientific experts, that air-screens are more effective when the air is drawn through at a low velocity by natural extraction than with mechanical propulsion. Sir Douglas Galton says: ‘If air is forced rapidly through a screen, it cannot fail to carry dust with it.’ MUNICIPAL AND SANITARY ENGINEERING. VEN Important features in the system are (1) the fresh air is brought directly into the room from the external air, there being no long, tortuous, and inaccessible channels to harbour dust and dirt; (2) the air supply not being overheated, its health-sustaining properties are unimpaired.’ ”’ ARTIFICIAL «© VentILation.—This system hi depends for its working upon mechanical means for propelling air into, or extracting foul air from the room or rooms. Itis divided into two systems, plenum and vacuum. The former method is that in which air is pro- pelled into the rooms by fans or air pumps, thus forcing out the foul air. The vacuum system consists of extracting the foul air by means of furnaces, gas jets, fans, or exhaust pumps, and allowing the fresh air to enter to take its place. With regard to the admission of the cold air from the outside, this should be brought in at a point above the people’s heads and in an upward direction. It then becomes slightly heated before descending, but not warm enough to allow the already heated air to stay in the room. The only methods which appear satisfactory in large buildings are those involving propul- sion or extraction by fans. The air thus pro- pelled should be first brought through a heating chamber if only for one room, and if for a number of rooms should be brought over a series of heated coils (see ARTIFICIAL VENTILA- TI0N below). One of the largest installations of ventilation on the “plenum” system is that introduced into the Birmingham General Hospital, by Mr. Kenman, F.R.I.B.A., and is described in ** Architectural Hygiene,”’ by B. F. Bnd H. P. Fletcher (1907), p. 189, as follows :— No fireplaces are used, the air being forced i in by fans, cleansed, and brought to a proper hygrostatic condition by filtering through moistened screens, warmed when required by means of steam coils, and propelled through the wards into extract flues, whence it passes into the open through flapped and louvred openings, constructed so that the varying 489 VEN movements of the outer atmosphere can exert no influence upon the outflow. ... . The air is sucked in from windows in the basement (carefully selected so as to be out of the way of contaminated air) by a fan, passing first through a screen of strained cocoanut fibre, kept automatically wetted every quarter of an hour. The air is then carried through a series of horizontal steam pipes, heated to the required temperature, then through the fan and into the basement tunnels. These tunnels (or “ducts” as they are called) start in sectional area 11 ft. by 8 ft., and only in a few cases are they so little as 8 ft. in width at the extreme ends in a few branch ducts. From these ducts are taken the vertical ducts to the rooms above. At the mouth of each of these vertical ducts is aseparate steam radiator to give extra warmth if required for different departments, in excess of that supplied by the main collection of steam coils.” The foul air is forced into the outlet flues at the bottom of the room near the floor level. In the example above quoted, to insure success in the working of the scheme, all the windows are hermetically sealed. The reader may judge for himself as to the success after read- ing the following extract from an article in The Hospital, April 1st, 1899, commenting on a visit to the above hospital:—‘‘.... The visit in question was paid with an open mind, and in conjunction with others anxious to observe in practice a previously carefully studied theory. . . . The point most generally commented upon was the apparently unnatural stillness of the atmosphere, whereas the air was being much more rapidly changed than is usual. ... It seems that this subjective sensation is almost invariably experienced by newcomers to the hospital, though both nurses and patients gradually become accustomed to what scientists assert should be a natural (but which to most of us at present appears to be a somewhat artificial) atmosphere. It hag been stated that this feeling of oppression does not meet with the entire approval of the visiting staff, as exercising upon them an indefinably depressing effect. The atmosphere ENCYCLOPADIA OF VEN of those wards visited struck the party as somewhat close, lacking in freshness. . . .” The opinions of many authorities appear to be strongly opposed to propulsion of fresh air into rooms, and the following extract from a report laid before the United States Congress by the Government Com- mission on Ventilation will be of interest. “The relative merits of the upward versus the downward systems of ventilation may be estimated from the following considerations :— (1) The direction of the currents of air from the human body is, under ordinary conditions, upwards, owing to the heat of the body. This Fic. 1.—Movement of Air in a Room with ordinary Fireplace. current is an assistance to upward, and an obstacle to downward, ventilation. (2) The heat from all gas flames used for lighting tends to assist upward ventilation, but elabo- rate arrangements must be made to prevent contamination of the air by the lights if the downward method be adopted. (8) In large rooms an enormous quantity of air must be introduced in the downward method if the occupants are to breathe pure fresh air, or about three times the amount which is found to give satisfactory results with the upward method. (4) In halls arranged with galleries, the difficulty of so arranging downward currents that, on the one hand, the air rendered impure in the galleries shall not contaminate 490 VEN that which is descending to supply the main floor below, and, on the other hand, the supply for the floor shall not be drawn aside to the galleries, is so great that it is almost an impossibility to effect it. Perfect ventilation would not be obtained, for this would only provide for the dilution of the impure air, while in perfect ventilation the impurities are not so diluted, but completely removed as fast as formed, so that no man can inspire any air which has shortly before been in his own lungs or in those of his neighbour. For these and other reasons the Board are of opinion that the upward method should be preferred.” MUNICIPAL AND SANITARY ENGINEERING. VEN therefore become lurking places for dust and germs. The plan is quite unsuitable for Gs ee, eli] il seat ati i Fic. 3.—Sheringham Valve. hospitals, and should certainly never be used ‘where there is likely to be infection. Besides, it is also open to the same objections as ventilation by open fires, viz., that it tends to draw away the air of the lower part of the ward, where it is always the least impure.” PracticaL VENTILATION OF Various CuassEs oF Bur.pines : Corraces.—Fresh air is gene- rally admitted to cottages either by air-bricks or per- forated gratings or other patent Fic. 2.—Movement of Air with Dalton’s Fireplace. Dr. John Hayward, in a paper on ‘“‘ Hospital Construction,” read before the Liverpool Architectural Society on November 7th, 1898, also wrote as follows: — ‘To the plan of abstracting the foul air near the floor, there are at least four grave objections: (1) It is opposed to Nature’s laws of atmospheric pressure, and therefore requires the use of special abstracting power by means of furnaces for its accomplishment. (2) By drawing down the foul air it causes it to be breathed over again, which recently breathed air ought never to be. (3) The fresh air supplied is apt to be forced in over-heated, in fact burnt, and so made unhealthy. (4) The long tortuous flues cannot be kept clean, and will ventilators. These should be placed high up in the room. A flue may also be built in the chimney to admit the outside air and having an inlet for air into the room high up Fic. 4.—The “‘ Leather” Inlet Ventilator. in the chimney breast, the cold air thus being warmed before it enters into the room (see Fig. 2). 491 VEN Pusric Hatus.— The inlets for air may be of various kinds and shapes. Fig. 3 is an illustration of the Sheringham valve, and Figs. 4 and 5 are illustrations of an inlet valve patented by Mr. Leather, of Liverpool. Leather Inlet Valve. Fic. 5.—Section. It will be seen that the adjustable portion is divided into four compartments, two of which are covered by perforated zinc. Fig. 6 is an illustration of an inlet tube of the “Tobin” tube type. These are formed of boarding and lined with zinc, or made entirely of metal, having an adjustable part for regulat- ing the supply of air. They are in some cases built in chases in the wall (see Fig. 7). Air may also be brought in over heating coils or radiators, thus being warmed before it enters the room (see Fig. 8). Extrac- tion should be by means of a fan or an alr-pump venti- lator. Factories AND WORKSHOPS. —Ventilation in these build- ings is comparatively an easy matter. There are, however, several important points to be borne in mind, and different methods must be adopted for different trades. Under the Factory and Workshops Act, 1901, bake- houses are classed as workrooms. It will be impossible to deal with every special trade and its requirements for ventilation, but a few will be touched upon briefly. The Factory and Workshops Act, 1901, gives the following WY AIK Fia. 6. ENCYCLOPADIA OF VEN air-space for the particular factories men- tioned: — General Factories, 250 cu. ft. of fresh air per person; 400 cu. ft. of fresh air per person (overtime). An Order gazetted February 11th, 1902, provides for: 600 cu. ft. of fresh air per person in humid textile factories (other than cotton cloth factories). An Order gazetted January 1st, 1904, pro- vides for: 500 cu. ft. of fresh air per person in underground bake- houses; 400 cu. ft. in bakehouses where work is carried on in artificial light other than electric light between 9 p.m. and SO \ WO KWo FLOOR LINE W 6 A.M. aby For cotton cloth fac- tories, the Factory and Workshops Act, Bee, 1901, s. 94, states that ventilation shall be so carried out that during working AK WY W x Wy \\ FRESH AR g /NLET Fig. 8. hours the proportion of carbonic acid in the air shall not be more than nine 492 VEN volumes of carbonic acid to every 10,000 volumes of air. Strict enforcements are laid down for these and other humid factories with regard to temperature and moisture, and architects having these buildings to design and superintend should refer to the 1901 Act, s. 90. In factories where dust and other fine matter is produced as refuse from manufactured articles, arrangements must be made to extract it by means of exhaust fans, so that the fresh air coming into the workroom or factory will not scatter these particles about. All windows should have some portion madé to open. Tobin or similar tubes should be fitted of sufficient size and number to convey the required quantity of fresh air according to the number of per- sons employed. If the air brought in must be warmed inlets should be made near the floor at the back of the steam warming pipes. These inlets should deliver air into a small closed-in chamber having a perforated cover or sides, through which the warm air will pass into the room. Foul air may be extracted, at a point near the ceilings, either by means of an exhaust fan, or by openings made in the walls, covered by perforated cast-iron gratings, of the same size and number as the fresh air inlets. R. H. B. Ventilation (of Sewers and Drains).— The object of sewer ventilation is to regularly remove the gaseous impurities given off by the decomposition of sewage matters, com- mencing immediately upon their deposition, and to supply fresh atmospheric air from the outside. Sewer air ordinarily contains many impurities, amongst which may be mentioned a large proportion of complex hydro-carbon and nitrogenous vapours derived from decom- posing animal and vegetable matters, consider- able carbonic acid, ammonia, ammonium sulphide, sulphuretted hydrogen, and marsh gas. In the liquid sewage are large numbers of bacteria of various kinds, and these break up the organic matters into simple chemical MUNICIPAL AND SANITARY ENGINEERING. VEN compounds, and gases are evolved in the process. The bacteriological contents of sewer air has been the subject of much careful investiga- tion. The conclusions arrived at in 1893 as the result of an investigation on behalf of the London County Council were—(a) that the number of micro-organisms in sewer air is smaller than in the fresh air examined at the same time; (2) that the species of micro- organisms in sewer air are identical with those of fresh air, and not with those of sewage; (c) that moderate splashing does not influence the bacterial content of sewer air, even within 4 ft. of the disburbance; and (d) that stag- nant and putrescent sewage does not influence the organisms in sewer air. The subject was further reported upon in 1894 by Dr. Andrewes and Mr. Laws, when they were unable, by means of the methods of research then avail- able, to find any evidence that sewage gives up any of its bacteria to the air in contact with it. As a result of investigations made up to that period, the opinion had become general that under ordinary conditions sewage does not contaminate the air with which it is in contact with its own specific bacteria, but the improvements which have more recently been made in the technique appropriate to an inquiry of this kind has now warranted a modification of these opinions. Dr. F. W Andrewes in his ‘Report on the Micro- organisms present in Sewer Air and the Air of Drains,” which appears among the appendices of the report of the medical officer of the Local Government Board for 1906—07, says, “Under certain circumstances, at all. events, sewage gives up its bacteria to sewer and drain air. Such bacteria may form but a small proportion of those present in sewer air: this is likely, for they would not other- wise have escaped detection by previous observers. But it is probable that the cir- cumstances under which sewage gives up its bacteria are common and ordinary circum- stances in sewer and drain construction, for the employment of selective culture media has enabled me to discover them wherever so far 493 VEN looked for in the air of drains and sewers. . . The importance of the subject is plain, for though the organisms which I have been able to detect in sewer air are not in them- selves known to be prejudicial to health, being for the most part well-known saprophytes of the normal alimentary tract, yet their value is evident as indices of the possible presence of more harmful sewage-borne microbes.”’ The typhoid bacillus does not thrive well in sewage, and their death is probably only a matter of a few days, or at most one or two weeks. Prolonged inhalation of sewer air may prove injurious to health by lowering the vitality of the human system and so pre- disposing to disease; hence the importance of keeping the air from sewers and drains out of inhabited rooms, both by adopting sound sanitary arrangements and also by thoroughly ventilating dwellings by making provision for a constant circulation and change of air. One of the most effectual means of keeping the air of sewers as pure as possible consists in laying the sewers at self-cleansing velocities, and in maintaining a clean and smooth bore. In this way the sewage passing through them away to the outfall expeditiously minimises the opportunities for decomposition, and the sewers are kept free from bad air. As soon as septic action sets in offensive gases are evolved, and the air of sewers becomes very foul. The principal methods which have been adopted for the ventilation of sewers may be shortly summarised as follows :— (a) Natural ventilation by the aid of open surface gratings at the road level, assisted by iron ventilating columns erected along the line of sewers, or by carrying ventilating shafts up the flank walls of buildings and other avail- able places. (b) Mechanical ventilation, by means of powerful fans. (c) Heat extraction, such as by— (1) Connecting sewers with chimney shafts. (2) Connecting with iron on other shafts erected along the lines of sewers, each of such being provided with heat either by a gas- burner in the base of the column or by means ENCYCLOPADIA OF VEN of a gas jet at the top—the object being to create an upward draught. (d) Deodorisation of the sewage and sewer air by the addition of disinfectants, chemicals, &e. Natura Ventitation of sewers depends upon the same laws as those which govern the circulation of air in buildings, and is the system most generally relied upon. Movement of the air depends upon the differences of tempera- ture between the inside and outside of the sewers, upon the outside wind currents setting up aspirating or extractive effects by blowing across the tops of ventilating columns, man- holes, and other openings, also upon the variations of flow in sewers and the conse- quent displacement of air. The conditions of the atmosphere, wind, &c., largely influence the working of natural systems of ventilation, hence it is frequently found that columns, unaided by heat or other artificial force, are inoperative, and occasionally observed to be passing a current of air in the reverse direc- tion to that intended. Ventilation shafts, when sufficiently numerous, afford useful points of relief of pressure within the sewers, especially in hilly districts where the sewers become rapidly charged and either force through or siphon out the traps on house drainage systems. Street columns are usually spaced from 100 to 200 yards apart and especially at the high or dead ends of sewers where they give the best effect. The shafts should be from 20 to 30 ft. in height, and preferably not less than 9 in. in diameter, to prove of any considerable ventilating efficiency. Shafts placed up the side walls of houses are usually much less effective owing to the num- ber of bends occasioned in the fixing, and to the occasional overshadowing of the tops of the shafts by roofs of surrounding properties. Every right-angled bend reduces the venti- lating effect by about one-fourth. Rust and dirt also accumulates at the bends, which in time seriously reduces the efficiency of the ventilator. The thorough ventilation of large mileages of sewers is a matter of some con- siderable difficulty, and whatever system is 494 VEN adopted, it should be simple and free from all complicated apparatus and independent, as far as possible, of mechanical aid. This simpli- fication is necessary in order that the cost of installation and of annual maintenance may be confined to within moderate limits, other- wise the system could not be reasonably extended over large areas. The direction of sewer air-currents varies with the position and direction of the lines of sewers with relation to the prevailing winds. In hilly districts the sewer gases tend to accumulate in the higher parts, unless checked in short sections, as is sometimes the case, by means of ramps or drop pipes fitted with flaps, so that any gases accumulating in each section may be separately dealt with, instead of traversing the whole length and rise of the sewer. The accumu- lation of sewer gases at the upper, or their fall to the lower, parts of a sewerage system necessarily varies from time to time according to the relative specific gravities of the gases or air currents which obtain at any given moment. Heat Extraction of sewer gases is a good method of ventilation if employed under proper safeguards, and when it can be in- stalled without involving an excessive initial outlay and subsequent heavy maintenance costs. The use of gas-heated ventilation columns involves a heavy annual expense amounting, very usually, to from £12 to £15 per year, and, as the number of such columns in even a medium-sized town may need to be over a hundred it will be seen that a serious yearly expense is entailed. It should also be remembered that accidents occasionally arise in the combustion of sewer gases, which some- times contain explosive mixtures, such, for example, as when a leakage of coal gas gains access to the sewers. The connection of sewer ventilation pipes to tall chimney shafts also involves considerable risk of dangerous ex- plosions, and so is now seldom adopted. MecHaNIcaL VENTILATION has been tried in many different forms, principally by the application of fans, but the effect of these is discernible only over very short lengths of MUNICIPAL AND SANITARY ENGINEERING. - VEN sewer, and, moreover, is readily overpowered and counteracted by wind currents and natural differences of temperature. Heavy initial outlay, running, and maintenance charges are an effectual bar to the wide adoption of this means of ventilation. In deep sewers it is frequently necessary to propel air into the sewer at one end and to extract vitiated air from the other by means of large fans driven by motive power. Deoporisation is not properly speaking a system of ventilation, inasmuch as it does not . remove the foul and introduce fresh air, but simply relies upon the covering, disinfection, and deodorisation of offensive gases emanating from sewage. Care is required as to the kind of deodorants or chemicals used as their employ- ment affects the final treatment of the sewage at the outfall works. The cost of chemicals and the necessary attention to their applica- _ tion renders the process too expensive for wide application, although it may be useful in certain special cases. Examination AND Entry oF Sewers.—The condition of the air in sewers requires careful testing, especially in the case of deep sewers, before workmen should be allowed to enter. This is most conveniently done by first lowering a lighted candle; if the light goes out or burns dimly the sewers should not be entered until thorough ventilation and change of air has been effected, and the conditions of the atmos- phere of the sewer again tested by means of a light. Should there be any sign of explosive gases, “safety lamps” should be used. In the present days of the very general employ- ment of motor-cars and the consequent ex- tended use of petrol, it is found, as a matter of experience, that this inflammable liquid often gains access to the sewers, by accident or otherwise, so that increased care of entry and the use of covered lights is essential. W. H. M. Venturi Meter.—This is a very useful apparatus for the measurement of large volumes of water, such as are passed through a rising main, leading supply pipe, or delivery 495 VIT pipe from filter beds. The meter consists of two parts, the tube and the recording appar- atus. The tube is fixed within and forms a part of the ordinary pipe line, and only differs from it by presenting for a short distance a truncated reducing cone coupled by a throat- piece to a similar expanding cone (see Figure). These reducing cones form the Venturi tube, and there are thus no moving parts in contact with the water. The measurement is obtained by the application of the Venturi law, that water flowing through a pipe of diminishing area loses lateral pressure as it gains in velocity. The difference in pressure thus obtained between the up-stream end of the reducing cone and the “‘ throat’ is termed the ‘Venturi head,” and, as the velocity in the pipe is proportional to the square root of this reduction of pressure, the velocity and thence Connections with ene nr ENCYCLOPADIA OF VIT with the view of grouping them into different classes according to certain definite characters they possess. These dividing characters must be constant, and must be definite. The uses of vital statistics are to obtain information as to the health of the people, as to the various diseases from which they suffer, to assist in the study of the good and evil con- ditions affecting humanity, and to furnish the necessary data for life assurance. For the purposes of vital statistics it is necessary to have a correct enumeration of the popu- lation (see ‘‘ PopuLation, ENUMERATION OF), and a complete and accurate registration of births and deaths; and when conclusions are formed and comparisons made it must be borne in mind that the likelihood of accuracy increases as the square root of the number of units dealt with. Annual death-rates, birth- rates, and marriage-rates are gene- rally expressed as so many deaths, births, or marriages among every 1,000 of the living population; they are, therefore, obtained by multi- v Venturi Meter. the rate at which the water is delivered through the pipe is inferred as a question of hydrodynamics. The observed reduction of pressure caused by the contraction of the pipe is conveyed by two small tubes (shown in Figure) to the recording apparatus which may be fixed anywhere within 1,000 ft. of the tube, or, if so desired, the registration may be conveyed electrically to any dis- tance. The recorder is a somewhat com- plicated apparatus, consisting broadly of a mercurial U tube receiving and embodying the element of the Venturi head, and of appropriate clockwork and gear which sup- plies the element of time, for the purpose of automatically recording the rate of flow upon a revolving diagram and exhibiting upon a counter the total quantity of water passed. Vital Statistics.— The science of statistics involves the collection of individual facts, plying the number of births, deaths, or marriages during the year, by 1,000, and then dividing by the number of the population. If the period for which a birth or death-rate is calcu- lated is less than a year, the rate then in- dicates the number of births or deaths per 1,000 of the population that would take place in the year if the proportion of births or deaths recorded during these shorter periods were maintained throughout the year. Thus a monthly death-rate would be calculated by taking the deaths registered during four weeks, multiplying these by the thirteen four-weekly periods in the year, and then multiplying by 1,000 and dividing by the number of the population. Now the proportions of children, middle-aged persons, and old people to the total population may vary in different communities, and as the death-rate varies at different ages of life, and even between males and females at the same ages, a correction must be made for any differences in the age and sex distribution before it is fair to com- 496 VIT pare the general death-rates of two towns. The means of obtaining the factor or ‘‘ figure for correction’’ is fully described in the Annual Summary of the Registrar-General for the year 1883, and the lengthy procedure is outlined in most text-books of hygiene and public health. The multiplication of the recorded death-rate of the district by this factor gives the death-rate which would obtain in that district if the sex and age dis- tribution of the population of the district were in the same proportion as it is in the country as a whole — thus eliminating the accidental differences due to sex and age, and affording a fair means of comparison of the healthiness of the district. It is obvious that the factor for correction can only be calcu- lated when the precise age and sex distribution of the population has been recently revealed by a census. There are other precautions which must be taken in order to avoid un- founded and erroneous statistical deductions. The number of deaths, for instance, at a cer- tain age-period must be expressed as the proportion of the number living at the age in question, this number as we have seen varying considerablyin different communities ; moreover, a special disease may be one mainly affecting certain age-periods, and a like error will be involved if the rate is not expressed as per 1,000 of the population living at the same ages, and of the same sex, as those attacked. Therefore it is a general rule in calculating death-rates that when the disease affects only a particular section of the community it should be expressed as the rate of mortality to every 1,000 of those who are liable to contract the disease. A good illustration of the application of this principle is to be found in the puerperal fever death- rate, which is taken as the ratio of the deaths from puerperal fever to every 1,000 registered births, since only those females who have recently been delivered of a child are liable to die from this complaint. Mild winters and cool summers favour a low death-rate from the lessened mortality from respiratory diseases and _ certain M.S.E- MUNICIPAL AND SANITARY ENGINEERING. 497 VIT intestinal diseases. The best statistical evidence of the health of the community is furnished by the corrected death-rate, although a sick-rate, were it available, would furnish still better evidence. ‘I'he zymotic death- rate also affords valuable evidence of the sanitary circumstances of a community. The zymotie death-rate represents the proportion of deaths from the seven principal zymotic diseases to every 1,000 of the population. The seven zymotic diseases recognised by the Registrar-General are:—Small-pox, measles, scarlet fever, diphtheria, whooping-cough, ‘fever’ (namely, typhus, enteric, and simple continued fevers), and diarrhea. Of these enteric fever and diarrhoea are more particu- larly associated with insanitary surroundings. The death-rate from consumption is also evidence of certain insanitary conditions of housing and of occiipation; and the rate of infantile mortality also ranks high as evidence of the health of the community. With refer- ence to this latter rate it must be pointed out that an infant is taken to be a child under one year of age, and the rate is therefore expressed as the proportion of deaths under one year of age to every 1,000 registered births. A life-table is a very valuable means of comparing the vitality of a community at one period with that of another period or with that of another community. By furnishing, by the law of probability, the expectation of life of the different members of the com- munity, it supplies a valuable comparative figure for statistical purposes, and one which, by enabling us to measure the probability of life and death, affords a scientific basis on which the calculations for life assurance are based. A life-table represents a generation .of individuals passing through life to extinc- tion; and the calculations of a life-table relate to an arbitrary number of individuals supposed to be born simultaneously, and to exist under the same conditions as those which apply to a general community. Usually the population is assumed to start with 1,000,000 births, and these are divided into males and females in proportion to the actual number of births of KK WAN either sex that have occurred in the given com- munity during an inter-censal period of 10 years. The mathematical probability of survival of every individual for each year of life is then calculated from data obtained from the actual community, and thus the hypo- thetical life-table population becomes the medium for the record of facts concerning the vitality of a given population. By the English table for 1881—90 the expectation of life at birth, for males, is 48°66 years; whereas amongst females the expectation of life is 47°18. For the purposes of comparing occupa- tional mortality, the death-rates amongst those employed in different occupations must be severally compared with the death-rate for England and Wales for the corresponding age periods and sex. In that way ‘“‘a comparative mortality rate” can be obtained. Tue Culer VitTat STatistics oF ENGLAND AND WALES FOR THE YEAR 1907. The general death-rate 15°0* per 1,000 per annum. The marriage-rate 158 “5 59 The birth-rate 26°3* sig 3 The phthisis death-rate 1:14 3 + The zymotic death-rate 1:26 35 85 The scarlet fever death- rate .. ae 0:092* ,, as The enteric fever aise rate .. 0:067* __,, 34 The aiattheries, dasth. rate .. 0°164 Pe “i The measles deaths rata 0°361 a 4 The whooping - cee death-rate .. 0:298 5h ts Diarrheal diseases death-rate .. 0°305* The rate of sntentile mortality was 118* per 1,000 registered births. * The lowest on record. H. R. K. Wanklyn & Cooper’s System of Sewage Purification was proposed in 1899, and consists of a system of aération with continuous flow through a series of tanks. The aération is aimed at by the application of means for continually removing the top layer of liquid and placing that layer down at the bottom of the next tank in the series. The ENCYCLOPADIA OF WAS sewage has to be elevated to givea fall of 7 ft., thus providing for a drop of about 4 in. between cach of the series of tanks. Waring System of Sewage Treatment. —Colonel George Waring obtained permission in 1894 to treat a portion of the sewage of Newport, Rhode Island, and there conducted experiments with the view of dealing with a large volume of sewage with a given tank capacity by means of a continuous system of working assisted by forced aération. The Waring system differs from Lowcock’s method (see Lowcocx’s Fiurers) principally in regard to the separate treatment of the sewage sludge by the employment of aérators. The sewage first passed a settling chamber for the removal of road grit, thence through a shallow bed of coarse broken stone to take out the coarser solids, and following this through “ straining tanks” containing stones and gravel with the object of effecting a mechanical sedimentation. The sludge from the latter when requiring emptying passed into a separate aérating tank again containing stones and gravel, where air was constantly forced through the material and the sludge dissolved by bacterial action. The straining tank was also rendered fit for re-use by forcing air through. Since the first experimental work there have been alterations of detail, and installations have been carried out at Willow Grove Park, Philadelphia, East Cleveland, Ohio, and many other places in the United States. Wash-Houses, Public.—Acrs or Parnia- mENnt.—Power to erect Public Wash-houses is contained in the Baths and Wash-houses Act, 1846, and the subsequent Amendments of 1847 and 1882. These sections also provide that the proportion of second-class washing accommodation shall be equal to twice the accommodation of the first-class (if any), and the maximum scale of charges are also set forth. GENHRAL ConsipERATION.—When consider- ing the question of a Public Wash-house, account must be taken of the neighbourhood, 498 WAS whether it is advisable to combine this pro- vision along with the swimming and slipper baths. Should the locality where the swim- ming baths, &c., are to be provided be some- what of a superior character it may be desir- able to build the wash-house separate and erect it in an industrial locality. An isolated building will be much more expensive to administer, but may be more convenient to the users. If the wash-house is erected along with the whole system of the baths, the entrance should be set in aside or back street so as to be away from the traffic and not interfere with the main entrance to the swim- ming and slipper baths. Entrances, &c.—Immediately inside the entrance door there should be a way into a covered forecourt where the women may leave their perambulators, mailcarts, &c., used for carrying their washing, until they return home. Arrangements should then be made for the washers to pass a barrier with their bundles, obtain their tickets from the office, and await their turn in a waiting room. Trcxet Orrice.—This should be so arranged that the clerk may control the women’s second, (and perhaps the first) class slipper baths, if possible, at the same time as the wash-house. In this case the first-class bathers would pass on one side of the office and the second-class and the women washers on the other. This will depend, however, on the amount of business done—should the number of washers be large it may result in a ticket office being required exclusively for the wash-house. Waritixe Room.—The waiting room should have lockers for the women, and a table, &c., for partaking of refreshments, as well as an open fireplace where water may be boiled. Wasuinc Room.—The washing compart- ments, which generally number about 50, should be arranged on either side of a central division with the supply pipes running over the partition. All iron should be galvanised. There should be three troughs, one each for boiling, washing, and rinsing or blueing, and a shelf on top for soap, &c. The troughs are generally of iron, but occasionally are of 499 MUNICIPAL AND SANITARY ENGINEERING. WAS porcelain. In the former case they are removable for cleansing purposes. If the compartments are arranged on either side of a central division and the washers in two rows side by side, each compartment will occupy a space 4 ft. long by 3 ft. 6 in. deep. The compartments are, however, sometimes ranged on either side of a central division, but the troughs are placed in pairs at right angles to the partition. This is a much moré expensive method, but it allows the drying horse to be arranged parallel to the. system, and permits each washer to see her clothes horse. The partitions between each compartment are about 5 ft. high and are: solid only down to within 2 ft. of the ground. Ample space must be allowed for washing down by the staff and the free use of a broom. A continuous slatted foot-board should be provided for the women to stand on while washing. Particular attention must be given to the question of drainage, so that the waste water may be quickly carried off and any stoppage readily removed. In the same room and in close proximity to the drying horses there should be two or three hydro extractors which answer the same purpose as @ wringing machine. Care must be taken to make the belting safe so as to avoid accident. There should be a folding table in the wash- house, also hat and coat pegs for the women. The drying horses should be placed at right angles to the troughs so that each woman may be able to stand sideways to and watch for the safety of her cluthes when they are in the drying horse. There should be at least one horse for every washing compartment, and, if possible, one or two to spare in case of a breakdown. The horses are generally 6 ft. 6 in. long by 6 ft. 6 in. high and 12 in. on face, hung entirely from a top rail so as to avoid grooves in the floor. Each horse should have four or five pairs of clothes rails, and there should also be a thin sheet iron plate dividing one horse from another as it prevents a recently wet article communicat- ing its dampness to an almost dry garment. It also prevents theft by transferring articles KK 2 WAS from one horse to another when one of the horses is partly withdrawn. The heat is conveyed from a small coil chamber and driven forward by a fan along a 1 ft. 6 in. by 9 in. iron duct, having an outlet hole over each compartment, the hole being auto- matically closed when the horse is withdrawn. The horse has also a door at the back, corresponding to the front one, to close the chamber when the horses are out, and so prevent the hot air from escaping. There should be plenty of top light and a Blackman fan in the gable to extract the steam which usually fills the room. W. C. accommodation should be provided immediately out of the wash-house room. Adjoining the washing room and near the waiting room and entrance there should be placed the mangling and ironing room, fitted with ironing and folding tables, stove, and one or two box mangles, mechanically and continuously worked. These mangles usually measure 10 ft. by 4 ft. ArtiriciaL Licutine.—The artificial light- ing of the premises should be by electricity, if possible, but a light should always be placed in front of each trough. R. J. A. Waste-Pipes. (See ‘‘ Prumpine.”’) Waste Preventers.—Cisterns for flush- ing closets and other sanitary fittings, arranged to discharge a limited quanity of water at each flush. The quantity of water permitted to be used by the majority of water com- panies is 2 gallons for each discharge. Where no such restrictions apply a 38- gallon flush is desirable. Flushing cisterns of this nature are generally actuated by a chain, which when pulled either admits water to the long leg of the siphon in the cistern or forces a body of water over the bend of the siphon and brings about the discharge of the cistern. The details of construction in the working parts of the cisterns vary greatly, but all depend upon one of these two principles; simplicity of mechanism is always an advantage. ENCYCLOP.EDIA OF WAT Water Analysis.—Microscopical Examina- tion—Chemical Examination—Chlorides—Hard- ness—Ammonia—Oxidised Nitrogen—Nitrites— Poisonous Metals—Phosphates—Organic Matter —lInterpretation of Analysis —Water is usually analysed to ascertain its fitness for drinking and other domestic purposes. It is also examined to determine its suitability for use in steam boilers, and for special manufacturing purposes. In the sanitary analysis of water a point of great importance frequently lost sight of is that the analyst is, except in the comparatively rare cases where the water contains a poisonous metal, not engaged in seeking for the actual substance that may do harm to the consumer of the water, but in estimating small quantities of substances that are found by experience to be the usual con- comitants of polluting matter which may contain harmful bacteria. Such substances are present in varying amount in drinking water from most sources, and if an analyst is examining a water for the first time, and without any knowledge of its derivation or surroundings he cannot so surely certify its purity as when he possesses such information. It is by the periodical examination of a water that the most useful information can be obtained, as any influx of polluting matter is almost sure to be detected by a careful microscopical, chemical, and bacteriological examination. Sometimes, from motives of economy, water supplies, whether public or private, are examined very seldom, or not at all. In other cases periodical examinations are made and the more frequently and minutely this is done the sooner any varia- tion in the water will be detected and the cause ascertained. It is highly desirable that all waters should be submitted to all three methods of examination. The microscopical examination possesses the advantage of rapidity, and in some cases the actual cause of trouble and the spot where it takes place can be ascertained more quickly than by any other means. ‘The chemical examination has the great advantage that it is less liable to accidental fluctuations than the bacterial con- 500 WAT tents of a water, and that the chemical bodies that accompany or are generated by pollution remain to some extent in the water and indicate that undesirable miatters can gain access to the water, even if the bacteria which accompanied them are no_ longer present. The chemical data yielded by a water are governed by the strata through which or over which the water flows, whether the gathering ground is cultivated or not, by the rainfall and the temperature. Thus water collected from chalk or limestone will contain carbonate of calcium; water from a ferru- ginous formation may contain iron, and waters from peaty ground vegetable acids. The bacteriological examination of a water has the advantage of affording a test which in many cases is of greater delicacy than chemical analysis. It has repeatedly been shown that an exceedingly small quantity of polluting material (sewage for example) may be added to an otherwise pure water, which, though incapable of detection by chemical means, can be detected with ease and certainty by a bacteriological examination. The fact that it is not often possible to detect specific bacteria, such as the bacillus of typhoid fever in an actual water supply, does not detract seriously from the usefulness of a routine bacteriological examination, when we are able to detect variations in the number and character of the bacterial population, which are greater than can be accounted for by any alterations of temperature or other normal causes. (See also ‘‘ Warer, SaMpPLiInG oF.”) Tue MicroscopicaL HxaMINATION OF WaTER. —It is necessary in the first place to draw a distinction between waters that have been filtered; either naturally or artificially, and those that have not. For instance, an upland water that has been artificially filtered through sand, or a chalk water that has been naturally filtered, ought both to be almost entirely free from visibly suspended matters, while an unfiltered river water of good potable charac- ter may contain a considerable number and variety of organisms and other sus- pended matters without any suspicion being MUNICIPAL AND SANITARY ENGINEERING. WAT thereby caused. The various organisms found in waters are usually shown in text- books on water analysis. Many of them have no hygienic significance at all, and simply afford evidence that the water has been exposed to air and sunlight and are found in pure mountain streams—some of them when present in quantity may produce an unpleasant smell or taste in the water, or may tend to act on the mains, or even produce such prolific growth as to diminish their capacity. On the other hand, microscopic examination may reveal the presence of starch granules, undigested muscular fibre, epithelial scales, fibres of paper, or fibres of clothing. The presence of these would naturally require explanation, and would cast grave suspicion on the water. In addition to the above the presence of such organisms as the sewage fungus (Beggiatoa alba), rotifers, or paramcecia would be regarded as suspicious. To examine a water for suspended matter it is usually customary to invert the bottle containing the sample in a conical medicine glass and allow the suspended matter to settle as far as possible in the bottom of the glass, from which it is subsequently drawn up by a pipette in a few drops of water and examined on a slide under the microscope. Most of the objects likely to be present can be discerned without staining; but after an examination it is advisable to add a little solution of iodine in order to decide whether any starch granules are present or not. The slide or slides should be examined under a $ in. and also under a % in. objectives. With the latter it is frequently possible to see bacteria, particularly the motile forms, without having recourse to staining. Some of the suspended matters commonly found in water do not readily settle to the bottom, and a good plan is to employ a method of filtration such as that proposed by Dibdin, or the original method of Sedgwick and Rafter, or its modifications. By means such as these it is possible to obtain a more or less accurate idea of the quantity of suspended matter present, as well as to ascertain its character. In the physical examination of a 501 WAT water, particularly when periodical examina- tions are to be made, it is an advantage to record its colour. This can be conveniently judged and recorded by using Lovibond’s tintometer—an apparatus in which a definite depth of the water is examined in a tube and its tint imitated by comparing it with slips of colour-glass of standard tints. The tinted glass slips are numbered, and in this way a definite record in figures of the tint can be obtained for future comparison. Since any variation in the composition of a water is very likely to be accompanied by a change of colour capable of detection by this apparatus, it is deserving of more extended use. Such an apparatus if regularly employed to make a daily test at a waterworks would be a useful means of giving an immediate warning of a change in the water that might otherwise escape notice. Generally speaking, the purest waters possess a faint blue colour. River waters and upland waters may have a greenish tint, while a yellowish colour would be sus- picious, though peaty waters may have a brownish tint. The standard glass slips of the Lovibond tintometer are coloured red, blue, and yellow and hence not only can any tint be matched by the use of the various glasses, but the degree of turbidity can also be recorded. The smell of a water is usually recorded as “normal” or “abnormal.” In some cases the growth of various alge may produce a noticeable smell; but it is very unusual to find any water otherwise fit to drink possessing any distinct odour. The only exception to this rule is the case of some peaty waters. The best way to ascertain whether a water has smell is to place about 200 c.c. in a stoppered bottle, warm up to about 65° C., shake, and then remove the stopper, and smell immediately. CHemicaL Examination or Water. — The general method of procedure adopted by most analysts in this country is modified to suit individual cases; but the ordinary practice is to determine the following items, viz., the solid residue left on evaporation, and its “ loss on ignition,” the chlorine, nitrates, saline “ce ENCYCLOP.EDIA OF WAT and albuminoid ammonias, the oxygen con- suming power, the hardness, temporary and permanent, and the presence of nitrites and phosphates. These data are usually sufficient in the case of a potable water. In the case of water for steam-raising, it is necessary to perform a mineral analysis of the solids because on the amount and character of these will depend the quantity and character of the “scale” likely to be formed in the boilers. The total solid residue is estimated by evaporating a known quantity of water in a platinum dish, over a small naked flame to a low bulk, then finishing the evaporation on a water-bath, and finally drying till constant in weight in an air- oven at 105° C. As the solids absorb moisture very readily they must be dried with care, cooled in a desiccator, and weighed quickly. After weighing, it is customary to ignite the solids carefully by heating them in the same dish. Very useful information can often be obtained by the appearance and smell of these solids on ignition. Distinct odours of either vegetable or animal matters are often obvious, or a perceptible darkening owing to the carbonising of organic matter may be noticed. The ignition should be carried to such a point that all organic matter is burnt off, but at a sufficiently low tem- perature as not to cause the volatilisation of chlorides. After ignition the solids are moistened with a strong solution of ammonium carbonate and again very gently ignited. This re-converts the calcium carbonate that may have been rendered caustic by the first ignition into carbonate again. The weight of the ignited solids subtracted from the total solids is reported as “loss on ignition.” The amount of total solids varies from a grain or two per gallon in rain-water up to 80 or 100 grains in some waters which are fit to drink. River waters may contain from 5 to 30 grains per gallon; chalk waters from 20 to 40, and upland waters from 10 to 20. Cutoripes.—A very low figure for chlorides is good evidence of the purity of a water, for the reason that sewage contains urine which 502 WAT itself contains a constant amount of sodium chloride. On the other hand a water may contain several grains of chlorine per gallon and be perfectly free from pollution, the chlorine being derived from the geological formation. As might be expected, wells near the sea are often high in chlorides. If the figure representing chlorine is known for the particular formation from which a water under examination is derived, then any increase on this would be highly suspicious. In countries where the geological structure is continuous over wide areas, it has been found useful to prepare maps indicating the distribution of chlorine (isochlors) and though in small insular countries like England this plan cannot be adopted over large areas, there are districts where the purest waters give a constant figure. The estimation of chlorides is carried out by titrating a measured quantity of the water with a standard solution of silver nitrate, using potassium chromate as an indicator. It is necessary that the water should not be acid. Tue Harpvess of a water, or its soap-destroy- ing power is due principally to the lime-salts it carries in solution. The hardness of a water is composed partially of salts precipitated by boiling (temporary bardness) and of others which are not so removed (permanent hard- ness). ‘The temporary hardness is due to calcium carbonate, held in solution by dissolved carbon dioxide, and is nearly all removed by boiling, which by driving off the carbon dioxide causes precipitation of nearly all the calcium carbonate. Water derived from chalk and limestone naturally contains calcium carbonate, while in water from the green- sand calcium sulphate predominates. Water containing calcium carbonate is softened on the large scale by adding known quantities of milk of lime, sufficient to neutralise the dis- solved carbon dioxide. This produces a precipitate of calcium carbonate, which in many cases is dried and sold if of good colour. The precipitate is allowed to subside, or the treated water is filtered through cloth and comes out clear and brilliant. Permanent MUNICIPAL AND SANITARY ENGINEERING. WAT hardness is not affected by the addition of milk of lime, or may be slightly increased if the lime used contains any sulphates. There are a variety of patterns of self-acting appara- tus sold for the purpose of adding regulated quantities of milk of lime to the water to be softened. The milk of lime must not be in excess, and it is customary to test the purified water with a solution of silver nitrate, which yields a brownish tint if too much lime has been added. The hardness of a water may not be entirely due to the carbonate or sulphate of calcium, as calcium nitrate or magnesium salts may also be present. In the laboratory the hardness of a water is usually ascertained by the use of soap-solution. This is prepared by dissolving 10 grammes of Castile soap in methylated spirit and making up to 1 litre. This solution is then standardised against a standard solution of calcium chloride made by dissolving 1 gramme of Iceland spar in as little hydrochloric acid as possible and carefully evaporating twice to dryness, afterwards dissolving in distilled water and diluting to 1 litre. The soap solution is either diluted with more spirit or strengthened (by adding more soap), until 11 c¢.c. of soap produce a lather lasting about 2 minutes, with 10 c.c. of the standard calcium solution, when diluted with 60 c.c. of distilled water. The mode of using the soap solution is as follows :—70 c.e. of the water to be tested is placed in a bottle capable of holding about 200 c.c. and soap solution is run in from a burette about a c.c. at a time, with occasional shaking. As soon as there is any appearance of a froth forming, half a ¢.c. is added at a time, and when a lather forms that lasts about 2 minutes the volume of soap solution used is noted, and 1 e.c. is deducted for the amount of soap that would have been required to make a lather if there had been no hardness at all. Ammonia.—In all natural waters a certain amount of ammonia is found, and in almost all polluted waters the amount is sufficient to enable it to be estimated. In rain-water the ammonia is derived from the traces existing in the atmosphere; in upland waters 503 WAT it is due also to the decay of vegetation or to the manuring of cultivated ground, or to the presence of animals. Ammonia exists in water in two conditions which are known as “free ” (or saline) and ‘‘albuminoid ”’ ammonia respectively. These are both estimated, the estimations being performed on the same quantity of water. The process followed is that of Wanklyn: A retort or flask of 1 litre capacity is connected to a condenser and water is distilled in the apparatus until the distillate is free from ammonia. Then into the cleaned flask are placed 500 c.c. of the sample, a few pieces of ignited pumice to prevent “bumping,” and about one-third gramme of ignited sodium carbonate. The apparatus being connected, the distillation is started and four separate lots of distillate, each of 50 ¢.¢., are collected in Nessler cylinders. To each of these cylinders is added 2 c.c. of Nessler solution, when, after standing for a few minutes, those containing ammonia show a yellow colour the depth of which depends on the amount present. The amount of ammonia present in each Nessler cylinder is found by running known amounts of ammonium chloride solution (each ¢.c. = 0°01 milli- gramme ammonia) into other cylinders, filling to the 50 ¢.c. mark with ammonia-free water, adding 2 c.c. of Nessler, and, after waiting till the colour has properly developed, com- paring the colours with those obtained as distillates. When correct matches have thus been made the total of cc. of ammonium chloride solution used multiplied by 0°01 will give the amount of free ammonia-in milli- grammes in 500 c¢.c. of sample. This, when divided by 500 and multiplied by 70, will give the amount in grains per gallon. To the 300 c.c. of water left in the distillate flask 40 c.c. of alkaline permanganate solution is added, and the distillation continued ; four further amounts of 50 c.c. each are collected which, when Nesslerised andthe tints compared with standard ammonium chloride solution as above described, will give the amount of albuminoid ammonia. Should the last cylinder collected show signs of ammonia, a quantity ENCYCLOPADIA OF WAT of ammonia-free water should be added to the distillation flask, and the distillation continued until all the albuminoid ammonia has come over. In the case of a water containing a very excessive quantity of ammonia, the colour obtained on Nesslerisation is too dense to allow of accurate comparison. Such a water must be suitably diluted with ammonia-free water and the distillation repeated. It is not possible to lay down any rules as to the amounts of saline and albuminoid ammonia which should not be exceeded in potable waters, beyond stating that most pure waters contain but little of either, so that if any appreciable quantity is found, more especially if the amounts present exceed what has previously been found in the same water, the cause should be sought for. Saline ammonia is sometimes found in perfectly pure chalk waters ; albumi- noid ammonia is found in peaty waters (owing to vegetation). Where there are a number of wells sunk in similar strata, if the results are compared, it will be found that any which are characterised by higher figures for ammonia than the rest will be found to show other abnormal figures,and an examination of the surroundings of the well will in most cases. give a clue to the cause ofthe pollution. Various causes may give rise to the presence of ammonia other than pollution. A water containing nitrates (as many pure waters do) may, on passing through a galvanised pipe, have some portion of the nitrates reduced to ammonia. Ammonia has also been found in waters owing to leakages of liquor from gas works ; in this case it is probable that traces of sulpho- cyanides would also be detected. OxipisED Nirrogen.—This exists almost always in the form of nitrates (of calcium or sodium), but nitrites are also, though very rarely, found. Nitrates are characteristic of chalk waters, but are generally found in vary- ing amounts in most waters. Upland waters, peaty waters, pure lake waters, rain-water, and pure river waters contain very little, while polluted river waters and polluted wells may contain large amounts. Here again no hard and fast rule can be laid down, and the analyst 504 WAT must toa considerable extent be guided by comparisons. If a shallow well-water, con- cerning the surroundings of which no information can be obtained, and nothing is known as to the nature of the soil, contains more than °5 of a grain per gallon it would be regarded as suspicious, and if the chlorine figure were also high (i.e., above 8 grains to the gallon, reckoned as chlorine) these figures would lead to suspicion. If the figure for saline ammonia is very low, it would show that a considerable amount of oxidation had taken place, which is more or less correctly termed “ past pollution,’ while if it is also high, present or recent pollution is suggested. Nitrates when once formed are not very liable to further alteration, except that they may be withdrawn by the various organisms that are natural to some waters, or, in the case of surface waters, they may be assimi- lated by growing plants. They therefore form a more or less permanent record of pollution in those cases where they cannot be produced by the geological conditions. There are three or four methods in use for the estimation of nitrates, the two most generally employed are as follows:—(1) The reduction of the nitrates by the copper-couple method, or by aluminium foil and soda. The copper- couple is prepared as follows: take a piece of thin zine sheet about 2in. by 4in., clean it with hydrochloric acid and immerse it for 3 minutes in a 8 °%/, solution of copper sulphate. Copper will be deposited on the zine as a blackish coating. Wash the coated zine with distilled water, place it in a wide- mouthed bottle holding about 200 c.c., and rinse it with the water to be tested and then fill up with the water and leave in the dark for 24 hours. At the end of this time the nitrates (and nitrites, if present) will be all converted into ammonia. When the reaction is complete, take out 10 cc. by a pippette and, after diluting with ammonia- free water, distil as in the estimation of saline ammonia, Nesslerising as previously described. (2) The other method in common use is the phenyl-sulphate method, which, though MUNICIPAL AND SANITARY ENGINEERING. WAT possibly not quite so accurate, has the merit of quickness. Evaporate 70 c.c. of the sample to be tested in a porcelain dish, finishing the evaporation over a water-bath. At the same time evaporate 5 cc. of a standard solu- tion of potassium nitrate, made by dissolving 722 of a gramme of potassium nitrate in a litre of distilled water. Each ec.c. of this standard solution will be equivalent to ‘0001 gramme of nitrogen. When the two evapora- tions above-mentioned are complete, 2 c¢.c. of phenyl-sulphate is added to the dried residue in each dish. It must be stirred so as to mix with every part of the dried residue and the dishes should be warmed (but not heated beyond a steam heat) for 3 minutes. The phenyl-sulphate is made by mixing 18°5 e.c. of strong sulphuric acid, 1°5 c.c. of water, and 3 grammes of phenol. When the mixture of phenyl-sulphate and residue has been well mixed and warmed it is diluted with 10 or 20 c.c. of distilled water, poured into a Nessler cylinder, made distinctly alkaline with ammonia, and diluted to exactly 100 e.c. in each case. It will be found thatthe standard, as soon asit has been made distinctly alkaline, assumes a clear yellow colour. The sample, if nitrates are present, will also show a yellowish tint which corresponds to the amount of nitrates present. Ifthe liquid is clear, nothing more is required except to make a quantitative comparison of the tint with that of the standard. If on the other hand it is cloudy, it needs filtering. The comparison is made as follows :—Place the two cylinders side by side on a sheet of white paper by the window, hold one vertically in each hand, and look down through the liquids at the paper. If the two tints are the same colour, the sample contains a precisely equal amount of nitrates to the standard, and as 70 «ec. were taken, the amount would in this case be ‘0005 gramme of nitrogen per 70 c.c., or "5 grains per gallon. If on the other hand the tints are not equal, pour out from the deeper of the two into a graduated (100 c.c.) cylinder, until the liquid left in the Nessler glass matches the other. Then reckon how many ¢.c. are required to do 505 WAT this, by subtracting the number of c.c. poured out from 100. For instance if the sample was the deeper and the tints matched after pouring out 20 c.e., the 80 c.c. left, being equal in tint to the standard, the sample must contain more nitrogen than the standard, the calculation being: 100 Sample = 60 per gallon of nitrogen. It sometimes (though very rarely) happens that an impure water will produce instead of a pure yellow tint, a greenish or brownish-yellow ; in such a case this process cannot be relied on, as unless the tints are similar in character it is impossible to compare them with accuracy. Nirrires.— As mentioned above, nitrites are very seldom found in potable waters, but as their presence is universally regarded as a suspicious sign, it is customary to test for them. The two tests usually employed are the iodide test and Gries’s test. The iodide test is performed as follows: — To 20 c.c. of the sample, add a few drops of pure sulphuric acid, a crystal of potassium iodide free from iodine, and a few drops of chloroform. Shake up, and then allow the chloroform globules to coalesce, when they will have a pink tint if nitrites are present. A “blank’’ using distilled water must be made and should show no pink colour what- ever. The Gries’s test is performed by adding a few drops of sulphuric acid to 20 c.c. of the water and then a little solution of metapheny- lene-diamine hydrochloride. If nitrites are present an orange-yellow tint will appear. This may be compared against a standard made from nitrite of silver. Standard solu- tions cannot be accurately prepared from sodium or potassium nitrites, on account of the instability of these salts. Potsonous Metaus.—The chief poisonous metal to be sought for in water is lead, though it is customary also to test for copper and iron and sometimes zinc. Lead is sometimes found in water owing to the action of soft water or water containing vegetable acid on lead pipes. It is a disputed point as to xX 5 = °62 grains ENCYCLOPADIA OF WAT what quantity of lead in a water should cause its absolute condemnation, but all authorities are agreed that even very small quantities are highly objectionable. As lead is a cumulative poison thereshould not be morethan one-fiftieth of a grain per gallon in drinking water, and it is believed that even this small quantity may have prejudicial results. To test a drinking water for lead 100 cc. may be placed in a Nessler cylinder, 1 drop of acetic acid added, and then a few drops of a clear, freshly made solution ofsulphuretted hydrogen. On standing forafew minutes, if lead is present, a darkening corresponding in intensity to the amount of lead present will be seen on holding the cylinder above a sheet of white paper. A similar tint is then prepared by taking various exact amounts of a dilute standard solution of acetate of lead and treating them in the same way, until a tint is obtained which matches the sample. As copper might be present (though it is rarely found) it is necessary to carry out a confirmatory test for lead which may be done by placing 100 c.c. of water in a Nessler glass and adding two or three crystals of potassium bichromate, together with a drop of nitric acid. After stirring up and allowing to stand for 5 minutes a yellowish turbidity will make its appearance. This turbidity can be compared more or less quantitatively, but if a large quantity of the sample water is available, say several litres, it may be evaporated to a small bulk and the precipitated bichromate of lead filtered off and weighed. PuospHates.—Many waters may be tested for phosphates with advantage. If they are present in marked quantity they must be regarded as evidence of pollution, more par- ticularly if they occur in conjunction with high nitrates and high chlorides. On the other hand their absence cannot be regarded as any proof of purity, as in a water contain- ing much calcium carbonate phosphates might be precipitated and filtered out by the strata from which the water is being derived. In unpolluted water probably only traces of phosphates will be found, but in polluted 506 WAT waters a sufficient quantity is often obtainable from 2 litres to admit of weighing the pre- cipitate. Evaporate 2 litres to10c.c. Add afew drops of nitric acid until faintly acid, warm to 80° C., and add 2 or 8 ee. of ammonium molybdate solution, warm and stir for 5 minutes. The precipitate (if phos- phates are present) is of a canary yellow colour. It may be filtered off and weighed. The weight multiplied by -0374 gives the amount of Pe: Os present in the quantity operated on. Oreanic Matrer in Water.—In addition to the various suspended solids in water men- tioned under the microscopic examination of water, there is always a certain amount of organic matter in solution. This is usually low in pure water, and high in polluted waters. The organic carbon and nitrogen were formerly ascertained by Frankland’s combustion process. This is but seldom performed nowadays, as the estimation of the free and albuminoid ammonias allow an arrival at the same conclusion in a more expeditious fashion. Organic matter (whether nitrogenous or otherwise) is determined by one or otber of the ‘‘ Moist Combustion ” pro- cesses. ‘The method in general use in this country consists in treating the water to be tested with an acid solution of potassium permanganate. The organic matter in solution which is present in a suitable state absorbs oxygen from the permanganate, and the excess of permanganate not used in oxidation is esti- mated by titration at the end of a stated time. The process, originally due to Forchammer, has been modified in various ways, so that figures by different observers should not be expected to compare, unless they employ the same details of procedure. Different workers also perform their moist combustion tests at different temperatures, causing a divergence of results. The consequence is that the figure is often of no significance to any one besides the analyst. In some waters much of the organic matter present is in an insoluble con- dition, and therefore has but little action on the permanganate. The following method is one that is frequently employed :—Place MUNICIPAL AND SANITARY ENGINEERING. WAT 250 c.c. of the sample of water in an absolutely clean 500 c.c. flask and a similar quantity of distilled water free from oxidisable matter in another flask. Warm both flasks on a water- bath to 80° F., add to both 10 c.c. of standard permanganate solution (each c.c. of which contains 0°1 milligramme of available oxygen), and 10 ¢.c. of 25 °/, sulphuric acid. Keep the flasks warmed to 80° F. If the colour becomes sensibly paler in the sample, add 10 c.c. more of the permanganate solution to both flasks. At the end of 15 minutes (or 4 hours) cool both flasks, and add to each one or two erystals of potassium iodide. The pink colour will turn to a yellow, due to the liberation of iodine by the reaction of the permanganate with theiodide. The liberated iodine dissolves in the excess of potassium iodide. The con- tents of each flask are then titrated with a standard solution of sodium hyposulphite, finishing the titration in presence of a few drops of starch solution. The standard solution of permanganate employed contains °395 grammes of potassium permanganate in a litre of water; the ‘hyposulphite ’ solution should contain about 1 gramme to the litre; and the special sulphuric acid is made by adding 1 volume of acid to 8 of water and then adding small quantities of permanganate solution until a very faint pink colour remains. Specimen calculations of this method and the others mentioned in these articles will be found in “The Chemical and _ Biological Examination of Water” (Pearmain & Moor). INTERPRETATION OF THE ResuLts YIELDED BY Anatysis.— The general conclusions to be drawn from the various methods that are employed in water analysis have been dealt with under each individual process. It remains only to add that it is impossible to generalise to the extent of laying down hard and fast figures for the purpose of designating ‘‘ pure or impure’’ waters. All the different features must be considered, and while it is often possible to class one water as pure and another as certainly polluted, there: remain a considerable proportion which must be regarded as falling into an intermediate class, namely, 507 WAT doubtful, or only to be used with caution. In some cases a doubtful water is the only avail- able one, and as it is quite useless to prescribe boiling because it will not be effectively or continuously carried out, the only alternative is to provide efficient filter beds for large supplies, and an efficient filter as well in the consumers’ houses (sec “‘ Domestic Fitters”). GC. G. M. Water, Bacteriology of.— Origin of Bacteria in Water and Influences Affecting them—Bacterial Indicators of Pollution—Enumeration of Bacteria —Detection and Estimation of B. Coli Communis —The Streptococci—B. Welchii—The Typhoid Bacillus—The Comma Bacillus—The Preparation of Media.—The nature and number of bacteria in water vary enormously. From a sanitary standpoint the actual number of organisms is secondary in importance to their origin. While some bacteria may be regarded as natural to water, others are washed in from the soil, and in a sewage polluted water organisms of excretal origin will be found. Provided the soil be unpolluted the bacteria derived from it do not affect the purity of a water. Should, however, the soil be contaminated with excre- ment, the purification of water percolating through it is materially dependent on two factors. The bacteria natural to soil have a strong antagonism for foreign bacteria, with the result that organisms of fecal origin more or less rapidly disappear, which dis- appearance is hastened by the temperature and medium not being conducive to their multiplication. In the absence of fissures the soil has a pronounced filtering property which precludes the passage of bacteria through more than a certain thickness. The depth necessary to prevent pollution varies with the nature of the soil, the amount of polluted matter, the rate of flow of water, and the exist- ence of defects allowing freer passage of water. The variation in the number of organisms present in a water is governed by conditions which operate by either increasing or decreas- ing them. During a shower the rain-drops carry down the aérial bacteria; as the shower ENCYCLOP-EDIA OF WAT continues the content of bacteria in’ the rain diminishes. This number of organisms is generally small, and pollution from this source can be regarded as immaterial. Aftera heavy rain, however, the bacteria in bodies of water may be decreased owing to dilution, or increased through the washing in of soil organisms. The lowering of the plane of saturation by excessive pumping from a well, through draining a larger area, may bring a polluted soil within the drainage area. An open well will ceteris paribus contain more organisms than a closed one (Savage). When flowing at a slow rate, or when stationary, the mineral and vegetable particles to which some of the organisms adhere subside, and the bacteria may also congregate together to form zooglea, in which case they will settle more rapidly than when isolated. This “sedi- mentation’’ constitutes the most important factor in the self-purification of water. In the clarification of water with alum, &c., and in softening by the addition of lime water, as in Clark’s process, bacteria are mechanically carried down. Bacrerrat Inpicators or Pottution.—The pollution of water with sewage naturally increases the content of bacteria, and a large number of organisms would appear suspicious. This presumption is strengthened if a large proportion of the bacteria will grow at blood heat, and if the count on gelatine (grown at 18° to 22° C.) contains an excessive proportion of organisms liquefying gelatine. Some of the bacteria found in pure waters, however, liquefy gelatine, others grow at blood heat, while the mere enumeration of organisms often does not give positive evidence of the purity. Itis, there- fore, necessary to search for certain bacteria which are normal to feces, and which, for a time at any rate, are capable of leading a saprophytic existence in water. Should these be found in appreciable numbers a conclusion is generally justified that the water is unfit for use. The organisms generally sought for are the Bacillus coli communis, streptococci and Bacillus Welchii (Bacillus enteritidis sporogenes). These exist in large numbers in human feces, 508 WAT but they, or organisms possessing very similar characters which do not admit of ready diffe- rentiation, are also found in the excreta of animals and birds, and thus do not necessarily indicate alvine pollution of human origin. Pollution with animal matter of any. kind, however, seriously discounts the suitability of a water for drinking purposes. BacrerioLocicaL ExaMInatTIoN oF WaTER.— A committee of the Royal Institute of Public Health formulated a scheme for the bacterio- logical examination of water to which English workers generally adhere. The committee give as the minimal number of procedures: (a) Enumeration of the bacteria present on a medium incubated at room temperature (18° to 22° C.); (b) Search for Bacillus coli and identification and enumeration of the organism if present. In addition the majority of the committee recommend: (c) Enumera- tion of the bacteria present on a medium incubated at blood heat (86° to 38° C.); (d) Search for and enumeration of streptococct. Asa routine procedure the search for B. Welchii is considered unnecessary. Unless the neces- sary inoculations into media can be made within 38 hours of collection, the sample must be packed in ice, but even then the examination should be commenced as soon as possible, as even ice packing does not prevent an alteration in the bacterial character of a water. The recommendations of the Royal Institute of Public Health committee are mainly followed in the following analytical scheme, and the composition of the media used are given at the end. Envumeration.—For organisms developing at room temperature nutrient gelatine or dis- tilled water gelatine may be used. With a polluted water the former allows more organisms to grow than the latter, while with a pure water a larger count is generally obtained with distilled water gelatine. The use of both media, therefore, affords useful information ; but when only one gelatine is used the “ nutrient” form should be employed. With a pure water the number of organisms developing on gelatine is generally more than MUNICIPAL AND SANITARY ENGINEERING. WAT ten times the number of those growing on agar at blood heat. In the case of a polluted water this ratio of organisms developing on gelatine to those developing on agar may become 10:2, or even less. With a polluted water the colonies liquefying gelatine may increase to more than one-tenth the total number on gelatine. For the counts on gelatine three tubes of nutrient gelatine are melted in a water bath at 40° C. Then three sterile Petri dishes are inoculated respectively with 0°5 ¢e.c., 0°3 ee¢., and 0°2 ce. of the sample run in from a sterile graduated pipette. The tubes of gelatine are taken from the water bath one by one, the plugs removed, the mouths singed in a Bunsen flame, and poured one into each dish. By tilting the Petri dishes several times the water is mixed with the liquefied gelatine. The Petri dishes are placed on a flat surface to solidify, and then incubated at from 18° to 22° C. The number of organisms on the gelatine plates is counted with the naked eye at the end of 72 hours, any doubtful colony being deter- mined with the aid of a lens. It is, how- ever, necessary to inspect the plates daily, as sometimes the number of liquefying colonies renders an earlier count necessary. ‘he counting is best done against a black back- ground, and when the colonies on a plate are very numerous a Pakes’s disc may be used to lessen the labour of counting. The total number on the three plates will give the number in 1 ¢.c. For the enumeration of organisms growing at blood heat, two tubes of agar are melted ina water bath at 100° C., cooled to 40° or 45° C., and the contents run, with the usual precautions, into separate sterile Petri dishes containing 1:0 and 0°1 ¢.c. of the sample. Expedition ig necessary, or the pre- paration will go “lumpy.” The plates are put in the blood-heat incubator and counted at the end of 40 to 48 hours. For con- taminated waters it may be necessary to dilute the water ten or one-hundredfold in order to render the individual colonies sufficiently discrete to be counted. All the foregoing experiments should be done in duplicate. 509 WAT The organisms developing aérobically on gelatine at room temperature may be as few as five or ten per c.c. in a water from a deep well or spring, and do not usually exceed 100 to 150 in a good water. A count of 500 per c.c. is sometimes obtained in surface waters free from pollution, but anything over this should raise suspicions. A thousand organisms per c.c. will generally condemn a sample. Detection anp Estimation or Baciiius Coul Communis.—Two single-strength tubes of MacConkey’s medium, preferably made with lactose instead of glucose, are inoculated with Ol cc. and 1:0 c.c. of the water. One double-strength tube is inoculated with 10 c.c. of the water, and two (in the case of a deep well water, five) other double-strensth tubes with quantities of 20¢.c. each. (The tubes for the reception of the quantities of 20 e.c.’s should contain 20 ¢.c. of the double strength medium, so that it is not diluted with more than itsown bulk of water.) The tubes are incubated at 37°C. (or better at 42° C.) for 2 days. The reddening of the medium showing the production of acid and the col- lection of gas in the inner tube afford pre- sumptive evidence of B. coli. Other organisms, chiefly of alvine origin, however, ferment MacConkey’s medium with the production of acid and gas, and it is, therefore, necessary to isolate and identify the colon bacillus. For this purpose the tube containing the smallest quantity of the sample which shows the reaction is used to inoculate solid media for the isolation of individual organisms. To effect this isolation two good loopfuls of the reddened MacConkey medium are inoculated into a suitable quantity of sterile water for dilution, and some of this is smeared over the surface of several sloped gelatine tubes. Or the suspected medium may be smeared over plates of Conradi-Drigalski agar. After pouring the Conradi-Drigalsk agari into the sterile Petri dishes, these should be placed in the blood-heat incubator, with the lids tilted to allow escape of moisture, for 2 hours. This partial drying is necessary to prevent ENCYCLOPADIA OF WAT colonies running together. (These can be incubated at blood heat, and thus save time.) Any colon bacilli will appear as large red colonies. Several suspicious colonies are inoculated into separate broth tubes, incu- bated for 12 to 24 hours at blood heat, and then examined in the fresh condition to ascertain motility, while a cover-glass prepara- tion of the broth is made and stained by Gram’s method.! B. coli is Gram-negative, and feebly motile. Occasionally the motility is not apparent. Its presence is, however, a guide as to the best tube to select for further work. Subsequent procedure depends on what attributes are regarded as typical of the colon bacillus. Houston considers that the term should only be applied to “ flaginac’’ organ- isms, i.e., those producing fluorescence in neutral red glucose-peptone water, acid and gas in MacConkey’s glucose medium, indole in peptone water, and acid and curd in milk. The Royal Institute of Public Health com- mittee give the following as characteristic of typical B. coli: A small, motile, non- sporing bacillus, growing at 87° C., as well as at room temperature, which is decolourised by Gram’s method, does not liquefy gelatine, and in a gelatine stab grows well to the bottom of the stab (facultative anaérobe). It pro- duces permanent acidity in milk, curdling the same within 7 days at blood heat, ferments glucose and lactose with production of both acid and gas. It is also desirable to show the production of indole, the change 1 Gram’s MetHop.—Some of the culture is smeared over a cover-glass, dried, fixed, and stained with anilin gentian violet solution (saturated alcoholic solution of gentian violet, 30 c.c.; anilin water, 100 c.c.) for 5 minutes; then immersed in iodine solution (iodine, 1 part; potassium iodide, 2 parts; distilled water, 300 parts) for one half to 2 minutes, when the film should have the colour of a used tea- leaf. The cover-glass is removed from the iodine solution, drained, and immersed in methylated spirit until the gentian violet colour no longer comes away from the preparation. The preparation may be washed and counter-stained with eosin, or after wash- ing it may be dried, mounted, and examined straight away. (N.B.—Anilin gentian violet solution does not keep for long.) 510 WAT in Grubler’s neutral red, and the yellowish brown growth on potato. Both Savage and Hewlett agree in the main with these characters. Therefore the pure culture in a broth tube which is Gram-negative and feebly motile should be inoculated into the following media: (a) gelatine, both in stab and surface cultures; this can conveniently be done in the same tube. A pearly white growth appears along the streak, which does not liquefy the gelatine. This tube should be observed for 10 days to exclude a liquefying organism. If a gelatine shake culture be also made, bubbles of gas will be produced in the medium. Gas bubbles may also be observed along the stab inthe stabculture. (b) Litmus milk incubated at blood heat will be reddened and curdled. (c) Neutral red glucose peptone water—a yellow colour with green fluorescence —is produced. (d) Peptone water. Indole is produced in 2 days.’ (e) Various sugar media, especially lactose and glucose media, both of which are fermented with production of acid and gas. Organisms differing from the typical colon bacillus in one or more respects are fre- quently met with, which are known as “atypical.” The precise significance to be attached to them is uncertain; but at the same time the probability that they were originally derived from excreta must not be overlooked. Savage is of opinion that ‘“ the nearer these glucose fermenting coli-like bacilli approach typical B. coli in their characters, the more nearly are our numerical standards for that organism applicable to them, while if they lack essential characters a propor- 1 The Indole Reaction is obtained by adding to 10 c.c. of the peptone water culture of the organism lec. of a01 % solution of sodium nitrite, and then allowing a few drops of concentrated sulphuric acid to trickle slowly down the side of the test tube. It is placed in the incubator for half an hour to render the pink or deep red colour more plain. A blank should be performed and the suitability of the peptone for the purpose proved. (n.B.—The cholera spirillum produces a nitrite in the culture medium and gives the reaction on the addition of acid alone.) 511 MUNICIPAL AND SANITARY ENGINEERING. WAT tionately greater number must be present to justify an adverse opinion.” Should typical B. coli be isolated in this way, it was obviously present in the amount of water inoculated into the original MacConkey tube from which the subcultures were made, and is duly reported as present in this quantity. This particular datum is by far the most important of the whole of the ordinary examination; but, like the other data, requires a very wide and comprehensive experience for its correct interpretation. Several ‘‘ working standards ”’ have been pro- posed for B. coli. Savage considers that its presence in 100 e.c., or less, of deep well or spring water, or in 10 c.c., or less, of shallow well water justifies an attitude of great sus- picion. Pakes suggests the condemnation of water containing the organism in 20 c.c., or less. In upland surface waters the signifi- cance of the colon bacillus is less certain owing to the probability of its derivation from the excreta of grazing animals, and Savage is of opinion that its presence in even 2 or 1 «ec. ‘means contamination, but not necessarily a contamination which it is essential to prevent.” Srreprococci.—Proof of the presence of these organisms affords a valuable confirma- tion of other results pointing to pollution, but less significance can be attached to their absence. The medium used in the prelimi- nary detection of coli (MacConkey’s lactose bile-salé medium) favours the growth of streptococci, and they should be looked for in hanging drops. Our knowledge of the subject does not at present allow any decided opinion on the significance of different species of streptococci, and they are only looked for as a class. It is uncertain whether they are capable of a saprophytic existence for longer or shorter periods than B. coli. Savage, after referring to the inapplicability of arbi- trary standards to streptococci, suggests that similar standards to those he has advocated for B. coli may be provisionally used. Bacituus Wecui (this name is applied by Chester to the organism or class of organisms WAT originally described by Welch and Nuttall, which Hewlett believes to be identical with the B. enteritidis sporogenes of Klein).—This organism is regarded as of less importance as an index of pollution than formerly, though Thresh attaches considerable importance to it. It has to be sought for in large quantities of water, the usual method being to pass 500 c.c. of the sample through a Pasteur-Chamberland candle, suspend the deposit in 5 ¢.c. of sterile water, and inoculate three milk tubes with 3 c¢c., 1 c.c., and 1 cc. of this concentrated water respectively. Hewlett’s method of con- ducting the test, though cumbersome, is much more satisfactory: Ten large boiling tubes, each containing 50 cc. of sterile milk, are inoculated with equal amounts of the water ; melted vaseline is poured on the surface of the milk to exclude the air, and the tubes heated to 80° C. for 15 minutes. After 2 days’ incubation at blood heat, B. Welchii produces a clear whey and a honeycombed mass of casein, while the gas produced is shown by a bubble under the vaseline plug. The B. butyricus, which is regarded by some as a non-pathogenic form of B. Welchti, gives a similar reaction, and the only satisfactory means of differentiation is to inject 2 c.c. of the whey subcutaneously into a guinea-pig of about 200 grammes weight, when B. J¥elchii will kill the animal in 48 hours. Tue Derection or THz TypHorp Baciuuvs. —This organism is seldom looked for except when an epidemic is in progress. Allow- ing 10 or 12 days as the incubation period, and a few subsequent days for the prob- ability of an epidemic to be appreciated, a sufficient time may have elapsed before the water is suspected to allow the organ- ism time to die out. This, coupled with the difficulty of its detection in water, accounts for the extreme rarity with which it is found in water. » head of cattle . » 8 4, » 9» sheep or pig : ® falgl pf » » 2-wheel carriage . » 8 5 » 9» 4-wheel 1 > oe ER ys » oo Square yard of garden. Of ,, For fire-extinguishing purposes, 200 gallons per minute for 30 minutes. According to Dr. Parkes, the amount of water used per head in a family of fairly cleanly people is as follows :— 517 WAT Cooking . 0°75 gallons. Fluid as drink Co ater, tea, coffee, &e.) . : O33 a Ablution, including a “daily sponge bath, taking 24 to 3 gallons 50, Share of utensil anid page washing : » BO iy Share of clothes (laundry) washing : . 30 ,, Total, say 12 gallons. With fixed baths and water-closets this is insufficient, and 25 gallons must be allowed as & minimum. The materials of the piping used for the conveyance of water through the house must be chosen with due regard to its nature, more especially when the water is such as will act upon lead. Lead is the chief mineral impurity to be guarded against in a domestic water supply, and certainly the most dangerous. It has a cumulative poisonous action, and when taken continuously, even in minute quantities, accumulates in the system and remains in the body until serious illness, and frequently fatal consequences, ensue. Amongst others of the troubles which may be ascribed to lead poisoning are: anemia, constipation, “‘plumbism”’ or lead colic, and local paralysis. The capacity of waters for dissolving lead and their rapidity of action varies considerably. Asarule the softer and purer the water the greater the danger of that kind. Cases have occurred in which the action has been so great and rapid that standing all night in the lead service pipes has been sufficient to deter- mine the presence of lead in poisonous quantities in the water in the morning. On the other hand, certain soft waters which might be expected to dissolve lead have little or no action upon that metal. Other waters, owing doubtless to seasonable variations, are operative upon lead at one time although inoperative at others. The action of water upon lead is of two kinds: the one leading to a solution of the lead, the other to its erosion and deposit in a loose powdery form, which is ENCYCLOPEDIA OF WAT readily swept away by the flow of water and conveyed to the consumer. When water is known or suspected to have a plumbo-solvent action, wrought iron, tin-lined or block-tin piping should be employed for its conveyance. Wrought-iron pipes have the disadvantage, however, that they rapidly corrode in the interior if of small bore, and that they also suffer considerably from outward corrosion. The water flowing through them is also apt to become discoloured by rust, which, though perhaps harmless in itself and only tem- porary in many cases, is nevertheless notice- able and objectionable to taste and sight. If iron pipes are used they should be lined with a continuous tube of tin. Tin-lined tees, bends, connectors, and other fittings are avail- able, and should be used in connection with them. Galvanised wrought-iron piping is unsuitable for the conveyance of potable water, as almost all waters—both soft and hard—have a solvent action upon the zine coating of the pipes; and all zinc salts are poisonous. Zinc poisoning, although occa- sionally fatal, is not, however, as serious as lead poisoning, nor are its effects cumulative. Block-tin pipes, although in most respects the most satisfactory, are, perhaps, too costly for use in all cases. A cheaper piping is lead- incased tin piping, which consists of an internal pipe of tin, varying from one-thirty- second to one-sixteenth of an inch in thickness, covered by an outer pipe of lead. Such pipes are made in all the usual sizes and strengths. Great care is necessary in their selection, as seams or blisters on the inner surfaces of the pipes and other faults in the tin lining occur. The continuity of the tin lining must be preserved, so that no lead is brought in contact with the water. Great care is neces- sary in making joints on this kind of piping, as the tin melts inside the pipe unless the joints are made with great dexterity. Nor is there any method of preventing a shrinkage of the tin on applying the heat necessary for making a joint on the lead pipe, even if the molten tin is prevented from blocking the pipe. So liable are joints on lead-incased tin 518 WAT pipes to prove unsatisfactory, that it is well to join the pipes in all cases by means of the special connectors made for the purpose. These are made on the principle of a cap and lining connection, and join the pipes without the use of solder or heat. When water is not lead-solvent, lead piping may be safely made use of, and will prove the most convenient to handle and fix, as it may be taken in all directions without the use of special bends. The water com- panies’ regulations as to strength must, how- ever be complied with. As will be seen from the following table, the requirements vary greatly in different districts :— Weiecuts oF Service Piers, in Las. per Linea Yarp, RequireD By Various Water ComPANIEs :— Diameter of Pipe in Inches. Name of Water Company. B)] 4) 8] #] 1) London .. 5 |6 | 74] 9/12] 16 Manchester Corporation —/|6 |—J| 9] 12] 16 Glasgow (Loch ces) —|7 |—|10/14/ 18 Sheffield. . 51/7 |9 | 11} 16 |} 22 Norwich. . 5/7 |9 11 | 16 | oat Nottingham bs ..[— | 7 | —] 11} 16 | 22 Market Hestereuey ..| 5 |6 | 74 | 11] 16 | 20 Kent --|5 | 7 9/12] — West Surrey 4)5$|]—|} 9} 14] 20 Caterham 5 |6 |8 | 10) 14] — Colne Valley .. 5/7 |9 | 11] 16] — Sevenoaks and Tonbridge —|5 |7 9 | 12 | 15 Water pipes, whatever the material of which they are made, should be carefully fixed to avoid air-locking, which is especially frequent in the case of lead pipes that have not been sufficiently supported and which have in con- sequence sagged. The pipes should all be fixed with a fall, so that the entire system may be emptied through taps, should that be necessary. The pipes should also invariably be fixed on inner walls to protect them from frost, and where this is impossible special provision should be made to prevent freezing (see ‘*Frost”). A stop-cock should be pro- vided at the point where the main enters the house, and other stop-cocks so placed that each section of the water supply system may MUNICIPAL AND SANITARY ENGINEERING. WAT be shut off for repairs if necessary without entirely cutting off the water supply of the house. While soft water may be dangerous, excessively hard water frequently proves a nuisance, by reason that it produces soap curds, and causes deposits and incrustations in boilers and hot water pipes. Soap curds form a greasy, slimy deposit in sinks and other sanitary fittings, and in waste pipes and drains, and these partly block the pipes and frequently become highly offensive, besides forming one of the minor difficulties of sewage disposal. Incrustations in boilers, hot water pipes and kettles increase the consumption of fuel and tend to block the pipes, which may sooner or later have to be taken out and cleaned or renewed. They are also liable to become a source of danger by causing boiler explosions, either through the blockage of the circulation pipes or by the cracking of the crust within the boiler, which would permit cold water to come into sudden contact with the highly heated iron of the boiler. In certain cases it is, therefore, desirable to partly soften the water before use by removing: the temporary hardness. This, indeed, is the only portion of the hardness which can be conveniently removed, as permanent hardness can only be eliminated by the introduction of substances which would render the water unfit for diet- etic purposes. Temporary hardness may be removed by Dr. Clark’s well-known process, which consists of the addition of 1 cz. of quicklime for each degree of hardness to every 700 gallons of water. This lime, by combin- ing with the bicarbonate held in solution in the water, reduces the latter to the form of a carbonate, which, being insoluble in water, is precipitated. Continuously working apparatus for the purpose are made by various makers, and answer the purpose well if attended to periodically. Impurities in suspension, if they exist in water in a building, can do so only as the result of shortcomings on the part of the authority supplying the water or of the house- holder. The impurities are various, and may 519 WAT range from particles of dust to small fish. Nevertheless, even where, as doubtless in most cases, the filtration of the public water supply is carefully attended to, it must be remembered that there are times at which filtration is not perfect. Such, for instance, would be the case during,severe frosts and during the first day or two on which a filter bed isused. Nor are filters always effective in removing bac- teria. All natural water contains them, in common with air, food, and even our tissues, . and the vast majority of them are harmless or even beneficial. The danger lies in the few bacteria which are branded as “ disease germs,” which (though as a rule absent) may at any moment be found in drinking water. To remove these and any suspended impurities which might be present in domestic drinking water, it is a wise precaution to resort to household filtration in almost all cases, pro- vided, of course, such a process is properly carried out and regularly attended to. Whilst it is desirable that water should be rendered clear and sparkling, the most impor- tant functions to be expected from a domestic filter are :— 1. That it should prevent the passage of pathogenic or disease-producing bacteria; and 2. That it must add no fresh impurity or bacteria to the filtrate. In these two all-important requirements many of the filters now upon the market utterly fail. Their filtering mediums, so far from being capable of arresting bacteria, rather favour their propagation and multi- plication by providing a suitable nidus for their development. Water passed through such a filter, if this has not been frequently cleaned and sterilised, is apt to be far more dangerous than unfiltered water. In order to gain some knowledge as to the relative efficiency of filters, Drs. Sims Woodhead and Cartwright Wood some years ago carried out a series of valuable experiments by sub- jecting all known filters to stringent tests by passing pathogenic organisms through them. As a result of these experiments, which con- firmed previous investigations by continental ENCYCLOPAEDIA OF WAT authorities, the investigators gave it as their opinion that the only forms of filters which did not admit the passage of disease germs were the candle filters known as the “ Pasteur- Chamberland,” the ‘“ Berkefeld,” the “ Aéri- Filtre Mallié,” the “ Pukall” filter, Slack & Brownlow’s, and Duff’s Patent Germ-Proof filters. All these filters are fixed to the mains and the water drawn through them. They need only be made use of for drinking water. For information on the sources and con- struction of works of water supply see “‘ WaTER Suppiy.” G.J.G. J. Water Supply (General),—Rainfall — Evaporation and Percolation—Classification of Sources of Supply—Springs and Deep Well Water—Upland Surface Waters—Surface Water from Cultivated Land—River Water—Quantity of Water per Head of Population—Character of Water and Causes of Impurity—Physical Characteristics—Action of Water on Lead— Construction of Waterworks—Catchment Areas and Storage—Compensation Water—Gravitation Supplies—Waste Weir, &c.—Outlets and Valve Towers—Siphon Outlets—Creeping Flange— Aqueducts—Service Reservoirs—Distribution of Water—Intermittent and Constant Supplies— —FPrevention of Waste—Fire — Pipes — Dual Supplies—Water Main Scraping. Water Suppiy (Grnerat).—According to the census of 1901 the population of England and Wales was about 324 millions of people. This involves a water consumption of, approximately, 1,000 million gallons per day, calculating upon the basis of 30 gallons per head per day. At 6d. per 1,000 gallons, this volume of water represents an annual value of over £9,000,000. It will be seen, therefore, that the collection, treatment, and distribution of so large a quantity of water is, necessarily, a work of very consider- able importance, especially having regard to the fact that the business of obtaining reliable sources of supply to meet the continual growth of population is a matter of ever-increasing difficulty, particularly in droughty periods, 520 WAT such as were experienced during the years 1900 to 1902. Ratnratu: Sources of Water Suppry.— All supplies of fresh water come primarily from rainfall, although collected under varying circumstances from river, lake, underground basins, or other sources. Water is obtained in its purest form by distillation. The heat of the sun is continually drawing up large quantities of moisture from the surface of both land and sea, thus forming clouds, which, in due course, return their water to the earth in a purified form. The water supply of any district therefore depends primarily upon the rainfall of the locality, and the extent and character of the gathering ground or “ catch- ment area.” The average rainfall of the whole of England and Wales is about 33 to 34 in. per annum, but varies considerably according to local circumstances. The fall in any given district depends largely upon its geographical position, the direction of the prevailing winds, and the distribution of hills, mountain ranges, forests, &c. That in the western and southern parts of this country is considerably in excess of the fall in the eastern counties. The rainfall on the western coast varies from 40 to 70 in. per annum, and as an exceptional instance, 190°28 in. were registered at Stye, in Cumberland, in 1888. On the eastern coast from 20 to 80 in. may be taken as the average, but in the year 1901, which, for England and Wales, showed an average deficiency of more than 138 °/, there were several places recorded in the county of Essex with rainfalls of between 14 and 15 in. only. The year 1901 was followed by an even drier year which resulted in a cumulative deficiency’ for the two years in England and Wales of 31 °/,, and over the British Isles as a whole there was a deficiency of rainfall in these two years equal to a quarter of one year’s fall. In many parts this caused something approaching a water famine, and gave great anxiety to those responsible for the management of water supplies. This 1 Below the 380-years’ average, 1870—99, which for England and Wales, was 34°28 in. MUNICIPAL AND SANITARY ENGINEERING. WAT dry period was followed by one of exceptional humidity—the percentage of excess of rainfall in 1903 (above the average 1870—1899) being approximately 28 °/,in England, and 33 °/, in Wales. For water supply purposes it is the minimum rainfall upon which all calculations must be based, and the late Mr. G. J. Symons, F.R.S., has given the following limits of fluctuation, based upon the results of a large number of observations extending over many years, which are believed to be within 7 °/, of the actual fall, viz. :— The wettest year will be 45 °/, more than the average. The driest year 33 °/, less than the average. The driest two consecutive years 26 °/, less than the average. And the driest three consecutive years 21°/, less than the average. In providing “storage”’ for water supply purposes it is found to be useless to atterapt to equalise supply over a longer period than three consecutive dry years, as by so doing there would be many years when the storage reservoirs would not get filled. It would be no use, for example, to provide sufficient storage to prevent over- flow during the year of greatest rainfall, or even the mean of a 10, 15, or 20-year period, because the daily addition this would make to the yield during dry years would not be com- mensurate with the cost of the additional storage capacity. The water which falls in the form of rain is ultimately disposed of in several ways. That which runs off the surface, generally spoken of as “surface water,” eventu- ally joins the neighbouring streams and rivers, unless intercepted and impounded in some storage reservoir, as, for example, at Vyrnwy, in North Wales, by the Corporation of Liverpool, and at the Elan Valley (Mid- Wales) by the Corporation of Birmingham. It frequently happens that surface water flowing from a watershed or catchment area consisting largely of cultivated lands, and containing a considerable population, becomes seriously polluted, as is the case with waters of this class coming from the watershed of the river Thames. 521 WAT Evaporation AND PeErcotation. — Another part of the rainfall is lost by evaporation, or is absorbed by trees and plants to form part of their tissues; and a third part percolates into the earth and ultimately joins the store of underground water recoverable for use by pumping, or part of which may reappear in the form of ‘‘ springs,”’ possibly at very distant points. The relative amounts of water dis- appearing in the above ways vary according to the nature of the soil, the contour of the land, and the season of the year. Rain falling upon a highly porous material, like gravel, sand or chalk, will rapidly disappear by sinking into the ground; but, if the district be largely composed of hard rock or stiff clay very little will percolate into the subsoil. The district around Brighton, consisting as it does of chalk, is almost wholly devoid of streams or surface water of any kind, the whole per- colating into the porous chalk and thus feeding the underground sources from which the town derives its entire supply. Of the total rainfall during any year, the most important is that falling during the winter half; it is this which replenishes the sources of water supply depleted during the summer. That falling during the warm season has but comparatively little effect owing to the large amount drawn off by evaporation. Summer rain, however, reduces the demand upon the waterworks as, of course, the daily consumption by the town is less during showery or dull weather. It is clear, therefore, that the period of the year in which the rain falls is of more importance than the total fall of the year, and a shortage is more likely to result from a dry winter than from a dry summer. In managing storage water it is very desirable not to draw upon it, if possible, until late in the summer season, as any deficiency in the supply is generally felt towards the close of the year. Hvapora- tion is hastened by the rain falling in numerous separate showers, and upon an impermeable soil; forests and vegetation afford considerable shelter to the ground and largely protect it from the influence of evaporation. In this connection it may be ENCYCLOP.ZDIA OF WAT noted that the Departmental Committee appointed in 1902 by the President of the Board of Agriculture recommended in their report “that the attention of corporations and municipalities be drawn to the desirability of planting with trees the catchment areas of their water supply.” The percolation of rainfall into the surface of the ground depends largely upon the geological and physical con- ditions which obtain. It depends upon the amount of rainfall, the porosity of the surface strata, and the slope and extent of the per- meable surface. It varies inversely as the evaporation is greatest in the winter season or during long and heavy rains, and least in warm and showery weather. The question of the degree of percolation has a direct bearing upon that of the level of water in wells and borings, and of ground-water in general—the annual rise and fall of which is frequently termed “ seasonal variation.” CLASSIFICATION OF SourcES oF SuPPLY.— The different sources from which supplies may be obtained have been classified by the Rivers Pollution Commissioners in their sixth report in the following manner :— 1. Spring water .. .. ) Very Wholesome 2. Deep well water... palatable. 3. Upland surface water ) Moderately 4. Stored rain water .. palatable. Suspicious ; 5. Surface water from ( cultivated land .. ,6. River water to which 7 Palatable. Dangerous sewage gains access ( 7. Shallow well water .. | Springs aNnD Drse WeLL Waters, where available in sufficient quantity, as a rule afford excellent supplies, but in some cases yield water of exceptional hardness, or occasionally it may be highly impregnated with salt, iron, or other constituents which render it unfit for domestic and trade purposes. (See articles “ Sprines,” ‘‘ WELLS,” and “‘ UNDERGROUND Warter.’’) Urtanp Surrace Warers.—These waters are collected from the high rocky mountainous districts of Wales and the north of England, and Scotland, which afford excellent sources 522 WAT for the water supply of large towns where the appropriate works for their collection, storage, and in some cases filtration, have been carried out. They must be clearly distinguished from the waters flowing from low-level catchment areas, consisting of cultivated lands with farm- steads, villages, and the usual rural popula- tion, such as in the valley of the Thames, where much of the water reaching the river becomes more or less polluted almost at its very source. For the supply of many large towns in this country, upland surface water flowing from watersheds consisting of the older geological formations such as granite, the Silurian and Devonian strata, mountain limestone, &c., is impounded by means of large earthen or masonry dams built across the valleys of the upper reaches of mountain streams. Birmingham has carried out a large scheme of this description at Elan Valley (Mid- Wales) to supply that city with 75,000,000 gallons of water per day. This is conveyed to the inhabitants by an aqueduct 78 miles in length. Similar water undertakings have been carried out by the Liverpool Corporation at Vyrnwy in North Wales, by Bradford in the Upper Nidd Valley (Yorkshire), by Manchester at Lake Thirlmere (Cumberland), by Glasgow at Loch Katrine (Perthshire), and many other towns in the north. A large gravitation scheme for the utilisation of the waters of the Upper Wye and Usk (Mid-Wales) has also been seriously proposed for the better supply of London. Upland surface waters of this character are usually almost free from animal impurities, - are peculiarly soft, but sometimes contain much vegetable or peaty matter. Ina series of some 200 analyses by the Rivers Commis- sion, the amount of dissolved solids in upland surface water from the igneous rocks was ascertained to vary from about 13 to 38 parts per 100,000, about 15 parts from sandstones and shales, and as high as 77°5 parts in water from the chalk and limestone watersheds. There was an almost entire absence of nitrates and chlorides, and a small amount only of organic nitrogen, showing the organic matter MUNICIPAL AND SANITARY ENGINEERING. WAT present to be of vegetable origin and to be derived from uncultivated lands. The larger authorities deriving supplies from upland catchment areas usually seek either to purchase the watersheds or to obtain certain rights and means of control of the contributory areas, in order that the necessary precautions may be observed and a systematic inspection instituted, to safeguard the water supply from possible pollution. Rain Warer.—In rural districts, where better means of supply are unattainable, the collection and storage of rain water falling on the roofs of buildings forms a valuable source of supply. Some of the disadvantages in connection with its utilisation, however, are the many precautions necessary to prevent its pollution, the uncertainty of the rainfall, the length of the dry season from year to year, and the large size of the reservoirs necessary to equalise yield and supply. Rain water is very soft and well aérated, and when not contaminated during its pre- cipitation, or by imperfect methods of collection and storage, is the purest of all natural waters. In the immediate neighbourhood of towns, however, it receives many impurities from the atmosphere, including organic matters, germs, sulphurous and sulphuric acids, which give it an acid reaction, and large quantities of tarry and carbonaceous matter derived from the combustion of coal. In an examination of London rain water, Angus Smith found 2 parts per 100,000 of sulphuric acid; 4 to 5 parts in Manchester rain water ; and in Glasgow water 8 parts. It therefore happens that when such water falls on the roofs of buildings it dissolves lime, iron, lead, zinc, &c., from the lead and zine flats, walls, gutters and pipes, and also con- tains much soct and foreign matters settled upon the roof, and may thus become very hard and impure. Where rain water is used for domestic purposes, the roofs, gutters, &c., should be kept quite clean and free from dust, soot, bird droppings, cats, leaves, and other polluting factors. If it is desired to use the whole available rainfall the roofs should be 523 WAT high-pitched and covered with an impervious material, such as good Bangor slates, so that there may be a minimum of loss from evapora- tion and absorption. he quantity of water to be obtained from any given roof or other catchment area for rain water will depend principally upon the average rainfall of the district and the area of the roofing. There will, of course, be small losses from evapora- tion and other causes to be deducted from the total. Where rainfall statistics are not obtainable the figure must be obtained by means of a rain-gauge in a similar manner to that followed in ascertaining the fall on a large catchment area for a gravitation scheme of supply. In this connection the “ Rules for Rainfall Observers,” issued by the “ British Rainfall Organisation,” founded by the late G. J. Symons, F.R.S. should be followed. For use in ordinary localities the ‘“‘ Snowdon rain-gauge”’ is recommended. It is 3 in. in diameter and easily fixed by four stakes driven into the ground. The glass measuring jar when filled to the top division holds half an inch, and each division on the scale marked thereon denotes one-hundredth of an inch of rain. The rain is conducted by a funnel to a bottle within the gauge, and the previous day’s fall should be measured each morning in the graduated glass and duly recorded. To find the quantity of water falling upon any roof area, the following formula may be applied :— A xX R_ (Number of gallons received 277274 | by the roof ina year. Where 4 = the area of roof in square inches ; and & = average annual rainfall in inches; and 277°274 = cubic inches in 1 gallon of water. Or for practical purposes, the calculation may be made by multiplying the roof area in square feet by the annual rainfall in inches and then by °52. This is practically equal to multiplying the roof area by half the rainfall, and in this simplified form the rule is within 4% of the true quantity. In calculating roof area the horizontal area must be used, not the area as taken on the slope. In ENCYCLOPAIDIA OF WAT England the average amount of roof area per person has been put at 60 sq. ft., and if we take 80 in. as the average annual rainfall, this gives a yield per person of 985 gallons, or 2°5 gallons per day, that is assuming there is no loss from evaporation. It may also be useful to note that 1 in. of rain gives 4°673 gallons per square yard of surface, or 22,617 gallons (equal to 101 tons) of water to the acre. In estimating the annual yield of water from. rainfall the average fall of the three driest years is a safe basis to calculate upon. Asa useful practical rule for ascertain- ing the requisite amount of storage for a rain- water tank, it may be noted that the minimum tank capacity to be provided should be at least capable of holding one-fourth the annual rainfall. Rain water may be stored in brick or slate storage tanks, built either above or below ground. Fig. 1 shows details of a suitable tank, built underground, in either brick or concrete, the inside being rendered in cement. The incoming rain water passes through a fine copper wire screen fixed at A to intercept leaves and other débris, through a sand or polarite filter at B, before passing into the storage tank, and the suction of the pump is protected with a fine copper gauze shield at C. Surrace WaTER FRoM CuutivaTeD Lanp.— This as a source of supply can only at best be looked upon with suspicion, being open at all times to dangerous pollution. It should not be used except under extreme necessity. ‘The impurities consist largely of organic pollution from the manuring of lands, animals, and human wastes. Any such waters employed for domestic use would require thorough subsidence in storage reservoirs and efficient filtration under watchful management before being delivered for public supply. There are many towns, however, that still take their supplies from rivers and streams which con- sist very largely of water of this class, whilst many others, owing to the growth of popula- tion and increasing pollution of the water- courses, have had to abandon their river supplies altogether or extract the water at a 524 WAT point nearer the source of the stream before pollution has taken place. The river Tame was originally the main supply to Birming- ham, but in 1869 it had become so polluted that it was abandoned for domestic use, and many other similar instances may be cited. River Water.—Much that has been said of “surface water from cultivated land” applies equally to river waters: On the use of river water subjected to human and other forms of pollution there is, however, considerable ‘diversity of opinion as to how far it is safe for large populations to depend thereon for domestic purposes ; but with respect to these sources of supply, it may be said that the bulk of medical and scientific opinion agrees | | Sill: I ARH NS = A LA i LLL Fic. 1.—Rain-water Storage Tank. that the drinking water of a large town ought not to be obtained from rivers and streams passing. through cultivated and inhabited lands. Works that deal with this class of water have usually been long established, and, since their construction, the water- courses drawn upon have as a rule gradually become more and more polluted, until. ulti- mately their abandonment will doubtless become a necessity. The possible means of pollution of a stream flowing through culti- vated lands are so very numerous that the river usually becomes in effect the common sink for the drainage and wastes of the water- shed through which it flows. The Rivers Pollution Prevention Acts and the work of River Conservancy Boards have minimised the evil, but much remains to be done. The opinion of the Royal Commissioners on Water Supply (1892) in regard to the use of MUNICIPAL AND SANITARY ENGINEERING. WAT the Thames, which receives a considerable amount of pollution and is subject to frequent and heavy floods, is of interest in this con- nection. The Commissioners reported :— “We are strongly of opinion that the water, as supplied to the consumer in London, is of a very high standard of excellence and of purity, and that it is suitable in quality for all household purposes. We are well aware that a certain prejudice exists against the. use of drinking water derived from the Thames and Lea because these rivers are. liable to pollution, however perfect the subse- quent purification, either by natural or artifi- ‘cial means, may be; but having regard to the experience of London during the last 30: years and to the evidence given to us on the. subject, we do not believe that any danger exists of the spread of disease by the use of this water, provided that there is adequate. storage, and that the water is efficiently filtered before delivery to the consumers.” In the same year (1892), however, occurred the very severe epidemic of cholera in Ham-. burg, which admits of no doubt as to the agency of water in propagating disease. The. cities of Hamburg and Altona both take their water supplies from the River Elbe—Altona. from a point some 7 miles below the discharge of the sewage of both cities, and Hamburg from about 7 miles above. In the latter instance the water taken was simply passed through ponds or settling tanks, but, owing to the increase in the demand for water it was. pumped through too rapidly to permit of much improvement by subsidence. At Altona, a little lower down the river but. continuous with Hamburg, the water was filtered through sand. The condition of the. raw water was even worse than that at Ham- burg, yet in Altona only 328 persons died, against 8,605 in Hamburg. The boundary line between the water areas of Hamburg and. Altona was clearly marked out in places by the cases of cholera; in some streets, for example, with one side supplied by Hamburg and the other side by Altona, the cholera stopped at the dividing line. A scheme of 525 WAT filter beds was rapidly pushed forward by Hamburg and brought into use the following year, when the city had equal immunity from the disease except for a short period when there was a sudden but limited rush of cases which were found to be due to a defect in the masonry which allowed unfiltered Elbe water to pass into the supply. The beneficial effects of the new Hamburg filters and of those at Altona which protected that city from a cholera epidemic in 1892 are thus demon- strated in a most practical and instructive manner, which applies also to the 6 millions of people in ‘* Water London.” Amongst other large centres of population depending upon river supplies may be mentioned Berlin, New York, Chicago, Boston, and Philadelphia. The natural organic purification of rivers during their flow is a subject which has received much attention, but is one upon which great difference of opinion exists. It was contended by the late Dr. Tidy that water containing 20°/, sewage would, in the course of a 10 or 12 miles flow, become purified by natural oxidation, whilst, on the other hand, Dr. E. Frankland, by experiments on the rivers Irwell and Thames, arrived at the opinion that a 200 miles flow would be insufficient for the purpose. After exhaustive inquiries the Royal Commission on River Pollution of 1868 arrived at the conclusion that ‘‘there is no river in the United Kingdom long enough to effect the destruction by oxidation of sewage put into it at its source.’ The principal enactments, other than local special Acts, dealing with the pollution of streams and watercourses are: The Public Health Act, 1875; the Rivers Pollution Prevention Acts, 1876 and 1893; the Waterworks Clauses Act, 1847 ; the Public Health Acts Amendment Act, 1890; the Local Government Act, 1888; and the Public Health (London) Act, 1891. Quantiry of Water RequirED PER Heap or Poputation.—The quantity of water that must be provided per head of the population is a fluctuating amount depending largely ENCYCLOPASDIA OF WAT upon local habits and conditions. It will vary (1) according to the nature of the locality, whether residential or manufacturing in character; (2) the method of drainage of the town, whether upon the “ water-carriage ”’ system or “conservative ’’ system; (3) the amount required for trade purposes, garden purposes, carriage-washing, &c.; (4) for municipal purposes, such as sewer flushing, street watering, public conveniences, washing streets and pavements, &c.; (5) the percen- tage of waste from mains and fittings. The total quantity of water supplied for all purposes will vary from about 20 gallons per head per day in residential towns up to 30 or 35 gallons per head in manufacturing towns, and in exceptional cases even the latter figure may be exceeded. The actual quantity supplied day by day will also vary according to the season of the year, whether summer or winter, whether wet or dry. The con- sumption is usually greater during frosty weather, owing to waste from burst pipes and mains, also to householders allowing their taps to “‘run’’ during the night with the view of preventing the water freezing in the pipes. The actual flow through the town mains will also vary considerably during different hours of the day. The maximum draught on the distribution mains may occur at any time between the hours of 8 a.m. and 5 p.M., and is frequently at its highest between the hours of 9 a.m. and noon. ‘The mains must, of course, be capable of passing water at the maximum rate without undue loss of “head” or pressure. As an approximation, the maximum rate of draught may be taken at twice the average consumption in the 24 hours. In regard to the rate of flow in the water mains, a well-established empirical rule fixing the velocity at 3 ft. per second has been laid down as suitable for fairly large mains. CHaRAcTER OF WatTeR From DirreRENtT SouRcEs anp Causes oF Impurriry.—Water, though pure at its source, may receive impuri- ties in a variety of ways before it reaches the consumer. As met with in nature it owes its characteristics largely to the geological 526 WAT strata or other physical conditions with which it has come into contact. Water derived from the older formations, as igneous rocks, granite, or millstone grit, is usually very pure, contains only a small quantity of minerals in solution, and a very insignificant amount of organic matter. Waters from limestone and dolomite are clear and bright in appearance, but contain sulphates of calcium and magne- sium in large quantities, and consequently have a high degree of permanent hardness. These waters are not good for manufacturing purposes and should not be used for domestic supply if a softer water can be obtained. A considerable number of towns in the Midlands and North of England are supplied from wells sunk in the New Red Sandstone formation, which yields a large quantity of water, usually of a good class well suited for public supplies. The towns of Birkenhead, Nottingham, Wolverhampton, St. Helens, and many others draw supplies from this strata. Birmingham and Liverpool have also in the past taken large quantities from the same source. The water at Nottingham and Wolver- hampton is between 8° and 10° of hardness, whilst at St. Helens it is 23° before the softening treatment and 10° after. Bristol is supplied from springs in the limestone conglomerate, and deep wells in the new red sandstone, and the water has a hardness of about 18°. The chalk is one of the most important of water-bearing strata and yields water of excel- lent and wholesome quality. It is always sparkling and agreeable to the palate on account of the large quantity of carbonic acid in solution ; it contains calcic carbonate, often in large quantities, and is therefore hard, but softens considerably upon boiling. A large number of towns in the south and east of England are supplied from this source, as well as a considerable part of London. The hardness may amount to 16° or 18°, whilst that from the lower greensand, below the chalk, is frequently much less, the ‘ Mid- Kent” supply from this source being about 10°. MUNICIPAL AND SANITARY ENGINEERING. WAT Traces of iron are to be found in practically all waters, and it is often met with in natural spring or deep well waters to an extent suffi- cient to render the water unfit for use and of a very disagreeable taste. This is frequently the case with water derived from sandstones, such, for example, as the Ashdown sands, or any strata largely impregnated with iron. The small quantity of one-fifth of a grain per gallon of water will impart an unpleasant chalybeate taste to the water. Iron is remov- able by precipitation with lime and oxidation. It may frequently be removed from deep well waters by thorough aération, time being allowed for precipitation. It is, however, much more expeditiously and conveniently removed by a system of forced aération under pressure in mechanical filters, the suspended oxide being afterwards filtered out (see ‘* MecuanicaL Fintration’’). Surface and subsoil waters present many variations in composition according to the nature of the ground where they are collected. The surface water from the millstone grit, Silurian and Devonian formations, from heaths, moorlands, and uncultivated lands, is usually pure, but if the catchment area con- tains much peat it will be of a brownish colour and occasionally acid in reaction. From cultivated and manured lands consider- able quantities of organic matter may be found in solution, and even in the absence of organic matter nitrates, nitrites, chlorides, and phosphates are sure to be present, indi- cating some previous contamination with animal matter. The water from graveyards and marshes must always be regarded as dangerous sup- plies; they contain organic matter in suspen- sion or solution in addition to nitrates and nitrites. Rain water, although a useful source in rural districts if properly collected, cannot be utilised in towns owing to the many impurities taken up from the atmosphere and the roofs of houses. Other means of contamination of water supplies may occur from the washing of large quantities of délris and decaying vegetable 527 WAT matter into open water conduits. If the water is collected from land dotted over with dwellings, farmsteads, agricultural buildings, xke., sewage may find its way into the water conduit, springs, or wells, and if such sewage contamination carry the specific poison of any disease, such as typhoid or cholera, it may thus speedily contaminate large quantities of water, including the rivers or streams into which it ultimately flows. Trade refuse, such as the effluents from a dye works, gas, brick, or chemical works, would seriously pollute a water supply if allowed to percolate into a porous strata and tlius reach the well, conduit, or stream from or Fic. 2. by which water is derived or conveyed. In rural districts the fouling of water chiefly arises from the proximity of dwellings, cess- pools, stables, or pig-styes to the well or other source of supply. Fig. 2 illustrates how impurities may readily reach a well sunk in a porous strata. If in such a case there had been an impermeable bed of clay (A B) over- lying the rock, and the well properly lined with iron tubes or brickwork from the ground surface to the rock in such a way as to com- pletely exclude the top waters, a good and pure supply might have been obtainable from the rock below if of a porous and permeable nature. PHysicaL CHARACTERISTICS OF Goop DRINKING Water.—It will be convenient here to briefly summarise a few of the leading physical characteristics of a good drinking water. It must be clear and entirely free from sediment or suspended matter. Ordinary printed matter should be clearly read through at least 18 in. ENCYCLOP.EDIA OF WAT depth of water. It should be colourless or bluish if looked at through a depth of 2 or 3 ft., and should be bright and sparkling showing that it is well charged with air and carbonic acid. ‘The water should have the pleasant sparkling taste of good water, and be free from brackish or other unpleasant or peculiar taste. There must be no smell other than the peculiar indescribable smell which fresh spring-water yields. It should be soft to the touch and dissolve soap easily. Hardness of water is that property which causes it to decompose a certain quantity of soap before a lather can be formed. It is usually expressed in degrees upon what is known as Clarke’s scale, in which one degree of hardness implies one grain of bicarbonate or sulphate of lime in each gallon of water. Water at and below about 6° of hard- ness is considered “soft”? water, and above this range it would be styled “ hard.” Hardness is of two kinds—(1) temporary or removable hardness, (2) permanent or irre- movable. Temporary hardness depends upon the presence of calcic and magnesic carbonates held in solution by carbonic acid (COs), with which it is loosely combined. When the COs is drawn off, as it can be by boiling, the carbonates are precipitated and form a white deposit, giving rise to the “fur” found lining the interior of kettles and boilers. Another method of precipitating the car- bonates is the addition of such an amount of lime-water as will combine with all the COz in solution, and so throw down both the car- bonates originally contained in the water, and those formed by the union of the CO: and the added lime-water. Permanent hardness is due to the presence of the sulphates of calcium and magnesium, and chlorides; also, in a minor degree, to iron, alumina, and free acid. Hardness of this kind cannot be removed by boiling One grain of chalk (calcic carbonate) wastes 8 grains of soap, so that the total annual waste of soap for any given population using water of known hardness may be readily 528 WAT calculated. In this way it has been estimated that the City of Glasgow saved something like £36,000 annually in soap by the introduction of the very soft water from Loch Katrine in the place of its former harder supply. The hardness of the water supplied to various towns differs very widely. The Glasgow (Loch Katrine) water is under one degree of hardness, that supplied to London about 16°, and that of the small town of Wellingborough (Northants) as much as 45° hardness. The water here is softened by Atkin’s process. Tue Sorrentnc Process by the addition of lime water indicated above was introduced by Dr. T. Clarke of Aberdeen in 1841; upon this principle the more recent methods are based, Among the towns using softening processes for their supplies may be mentioned South- ampton, St. Helens, Stroud, Wellingborough, Saffron Walden, and others. ‘The cost of softening varies from 3d. to 3?d. per 1,000 gallons, and from 10° to 24° of hard- ness are removed. In the modified process known as the Porter-Clark method the lime is mixed with water by paddles and is then passed through filter presses of cloth, insuring a clear product and saving time and space. This process is specially adapted for waters of a high temporary hardness like those of London from thechalk. The following forma- tions as a rule yield hard waters—Chalk, Upper Greensand, Oolites, Lias, Mountain Limestone, Coal Measures, and Devonian. Soft waters are obtained from the Bagshot Beds, Lower Greensand, Silurian, Metamorphic, and Igneous rocks. Action oF WartserR vron Lrap.—The ill- effects of the action of some waters upon lead are now well known, and great trouble has resulted from this cause in connection with many water supplies, especially in the North of England. Lead possesses a cumulative poisonous action by which small quantities accumulate through the daily use of waters so tainted, until serious illness ultimately ensues. A blue line around the gums is an important characteristic symptom of lead colic or “plumbism” as it is called. It is M.S.E. MUNICIPAL AND SANITARY ENGINEERING. 529 WAT very seldom that water in its natural state is tainted with lead, but it becomes so polluted in the course of distribution by contact with lead pipes, cisterns, &c. The soft moorland water of the Vartry attacked lead so readily that tin- lined pipes were used when the new supply was introduced in Dublin. At Sheffield, too, a similar difficulty was experienced with a part of the supply where the water was peaty and of an acid character. The soft waters of Loch Katrine, however, gave little or no trouble in Glasgow. The waters which act most on lead are: (1) The purest and most highly oxygenated, such as rain-water, and the moorland waters of up- land streams; (2) Those containing organic matter, nitrates, nitrites,and chlorides, such as water contaminated with sewage; (8) Waters containing a free acid, soft peaty waters as supplied to many towns in the North of England. Among those waters which act least upon lead are, hard waters containing carbonates, phosphates, and sulphates, espe- cially carbonate of lime. Such waters soon deposit a protective coating on the lead sur- faces. There are many other circumstances influencing the action of water on lead pipes. (1) It is affected by the length of time water is left to stand in the service pipes; (2) By the temperature of the water and the pressure under which it exists in the pipes, an increase of either favours the solution of the metal ; (8) New lead piping is more easily dissolved than that which has been in use for any length of time; (4) The lead is more readily acted on if other metals, as iron, zine, or tin, are in con- tact therewith, as galvanic action may be set up; (5) Bending a pipe against the grain and so exposing the structure of the metal increases the risk of solution; (6) Zine pipes, into the composition of which lead often enters, yield lead in large quantities to the water. Water which has been standing in a lead service for a considerable time should be first drawn off before taking a supply for drinking purposes, should there be any danger from lead-poisoning. Filtration of the water through animal charcoal is a good plan to MM WAT insure freedom from lead. The charcoal, however, will require to be regularly renewed. New and bright lead is at first acted on by most waters until a protective coating has been formed on the surface. In cleaning out a cistern this coating should not be removed, neither should cleansing with acids be resorted to. The best material for a water cistern is slate. Both zinc and galvanised iron are affected, especially the former. The lead from the paint of internally painted cisterns is sometimes dissolved by the water. Portland cement makes a good surface, but is nota convenient material to use for household pur- poses. To detect lead in water a test may be made by putting one drop of sulphide of ammonium in a wine-glass full of water and stirring with a glass rod. The water will immediately discolour (black) if lead is present. In a valuable report by Dr. Houston on ‘‘ Moorland waters in regard to their action on lead,” submitted to the Local Government Board, and published in 1903, the whole question has received very exhaustive treat- ment. It isof great public importance having regard to the large proportion of the popula- tion of this country receiving water supplies from upland gathering grounds liable to yield waters of plumbo-solvent or erosive tendencies. THe ConstRucTION oF WATERWORKS. — Systems oF Suppity.—The system of works upon which towns are supplied with water are usually classified either as “ gravitation ” works or “pumping”’ works; not infrequently it may be a combination or modification of both. In a gravitation supply, the water is usually obtained from a surface gathering ground, or catchment area, situate a consider- able distance from the town to be supplied, and at such an elevation as will admit of the water derived therefrom being collected in an impounding or storage reservoir from which it may gravitate through perhaps several miles of pipe-line or aqueduct to a service reservoir situated near the town. The latter reservoir must also, in turn, be at such an altitude as will insure the supply being ENCYCLOP.EDIA OF WAT delivered to the tops of all the various build- ings within the area of supply after having made satisfactory allowance for frictional losses of head in the distributing mains during times of heaviest draught. The general arrangement of such a system is shown diagrammatically in Fig. 8, in which the section from A to £ illustrates the supply collected from the gathering ground 4, into a storage reservoir B, passing, if necessary, through the filter beds and clear water tank below, and then gravitating through a pipe- line or aqueduct to the service reservoirs D, which are at a sufficient elevation to supply the town situated at FE. It frequently happens, however, that small outlying parts of a water area may rise to a height above the top water line of the service reservoirs, and in such case the water for these limited districts must be pumped through this additional height, usually over a “stand-pipe”’ or into an elevated water-tank or tower situated upon the highest ground available, so as to com- mand the tops of the highest houses within this area. In gravitation supplies, the works involved usually consist of any necessary preparation of the gathering ground such as the removal of dwellings, farmsteads, &c., where they may be likely to cause pollution, the formation of impounding or storage reservoirs in the lowest suitable part of the catchment area by the building of large earthen or masonry dams across the valley, the diversion into the main watershed of water from adjoining areas by means of pipe- lines or tunnels, the construction of the main aqueduct from the storage reservoir to the service reservoirs which should be placed near the town, and numerous accessory works incidental to the foregoing. The North and West of England and the country of Wales have excellent gathering grounds situate at high altitudes and subject to great rainfall. A great many towns in these parts have therefore naturally availed themselves of this excellent means of supply. Glasgow receives its supply from Lochs Katrine and Arklet, Manchester from Lake Thirlmere, Liverpool 530 WAT MUNICIPAL AND from Lake Vyrnwy (North Wales), Bradford from Nidd Valley, and Birmingham from the Elan Valley in Mid-Wales. In the east and south-east of England such gathering grounds are not available, and the supplies are derived either from rivers, springs, or deep wells, sources which are, as a rule, at a low level with respect to the district to be supplied, and the waterworks therefore necessarily becomes a ‘pumping scheme.” Referring again to Fig. 8 it will be seen that if the ground rises from the point F' in the section instead of descending, as in the gravitation section A to H, pumping will be necessary to raise the water the required “lift” through lines of rising main into high SANITARY ENGINEERING. WAT but, on the other hand, against this is to be set the permanent annual expenditure of a pumping works. So that in cases where an ample supply of equal purity upon either system may be secured the question of cost will usually be the deciding factor. The water supply of the Metropolis affords the largest example in the world of systems of pumping works, the water being derived from the Thames and Lea and deep wells in the chalk. CaTcCHMENT AREAS AND Srorace. — The extent of catchment area and storage capacity required for the supply of a town will depend mainly upon the quantity of water required daily, the amount of the annual rainfall and oo Collection ----- MR ercer a oe and Distribution ----- Saal 1 ! (ir 8 ! . 1 p s | | Gathering Bo IBS % Service \ ee EB i ies - vor | Top WeterLine __| 1 7 75 Moi Vp oS nn 1 ' % s 3 5 Bist 7 IG yen Dise,. Ton i gH | Pil yy ! Cuting Mair PUMPING i | ee Be ges Dip +Service a Sehene ! ! GL, op EP — — eeservorr Top Water Line _\ 1 | ' 1 1 pS Pr — — EO ! ' i = ; \ Pt {D ° Town 1 | icy ca | iE Gravirariow i i \ 7, ScHeme | 1 ! \ \ ! ! ! , 4 ' ; foot ! \ Sa eran og ee ee oe ET Fic. 3.—Diagram Illustrating Principle of Gravitation and Pumping Schemes. service reservoirs to supply the town at H. Other parts of the system such as storage reservoirs, filters, and clear water tanks may remain the same in either case. In a pumping scheme there is usually less of what may be called heavy engineering work involved in the collection, storage, and con- veyance of the water, but a large outlay is necessary in the provision of pumping machinery and buildings. The question of choice between gravitation and pumping schemes of supply often arises in practice. It will be obvious that no general statement of preference for one or the other could be made, as their relative merits will depend upon local conditions and the capital and working costs of each scheme. Generally speaking, the initial cost of a gravitation supply is greatest, 531 evaporation over that area, and the physical nature of the ground surfaces. It will be obvious that a much larger proportion of the total rainfall may be collected from a rocky and precipitous area than from one of a less hilly description or where a large amount of percolation may take place. Generally speak- ing, it has been found in England that the supply which can be relied upon from any definite gathering ground may be calculated by the formula :— Q = 62:15 A (3-2), where, @ = the daily supply in gallons. A= catchment area in acres. Jt = average annual rainfall in inches. E = loss of rainfall by evaporation in inches. MM 2 WAT In England, the loss by evaporation amounts to from 10 to 18 in. in the year according to circumstances. Where no natural lake is available, as in the case of the Glasgow supply from Loch Katrine or the Manchester supply from Thirlmere, the water flowing from a gathering ground is stored up in the rainy season for use during the dry period, by forming an artificial lake or reservoir. This is done by constructing a masonry or earthen dam across the lower part of the valley of a mountain water- course. In providing such storage it is found to be unnecessary to thus attempt to equalise supply over a longer period than a consecutive three dry years’ term, as by so doing there would be many years when the reservoirs would not get filled. The storage will also be regulated by the number of consecutive days in a dry time during which the supply might have to be drawn from the reservoir without any addition thereto. This period varies con- siderably in different districts, and depends upon the fluctuations of rainfall, the usual length of periods of drought, the amounts of percolation and evaporation, and other con- ditions, so that a much smaller storage would suffice in a wet district than in a dry one. For these reasons the storage provided may vary from about 70 to as much as 300 days’ supply, but in England will mostly lie between a minimum of 100 days in wet districts and a maximum of 250 days in very dry districts. CompEnsaTION Warter.—In addition to the water obtained from a catchment area and stored in reservoirs, it is necessary to consider the question of compensation, payable only in water, to parties lower down the streams affected, in consideration of the flood water abstracted for purposes of supply to some distant town. To insure that the flow of the streams shall never be less than a certain stipulated amount, the daily flow of “compen- sation water ” is fixed by the Act of Parliament authorising the construction of the works. It is clear that damage may result from such abstraction of water from streams, but, on the other hand, it is also equally certain that con- siderable benefit must accrue to riparian ENCYCLOPAEDIA OF WAT owners from the construction of impounding reservoirs mitigating the damaging effects of floods and equalising the flow of the streams throughout the year. In practice, where the entire catchment area of a stream has been appropriated for the supply of an impounding reservoir, the amount of compensation water has been fixed at one- third of the average yield of the gathering ground in question. Formerly the proportion of an ordinary stream available for useful purposes appears to have been much over- estimated, and the conditions imposed in regard to compensation water were more onerous than are now proved to be necessary. Thus, in 1847, Liverpool was required to deliver one-half of the available yield from the Rivington watershed as compensation, and Manchester, in 1848, delivered two-fifths of the yield from the Longdendale area into the river Etherow. These have since both been reduced to about one-third of the avail- able yield. The compensation water delivered by the Liverpool Corporation into the river Vyrnwy (Act, 1880) amounts to only about one-fourth of the yield of the catchment area, whilst that from the Thirlmere Works (Act, 1879) is only about one-tenth of the available annual yield of the gathering ground. Leaping FeaTuRES oF soME LARGE GRavI- TATION SUPPLIES. — Manchester, in appro- priating Lake Thirlmere for the purposes of supply, took powers to raise its natural level 50 ft., by building a concrete dam, faced with masonry, across its outlet, from the solid rock below up to a height of 57 ft. above the former level of the lake. By this means the area of the lake was increased from 8284 acres to 793 acres, and a total volume of about 8,131 million gallons of water was impounded at a low cost. The storage is equal to a quantity of 82°6 in. over the whole catchment area, and is able to afford a supply of 50 million gallons a day for a period of 160 days. It is important, in this case, to have ample storage, as the total catchment area only amounts to 11,000 acres, or about 220 acres per million gallons daily supply. The rainfall, however, 532 WAT in this district is large, amounting on the average of 18 years’ gaugings to 85 in.; whilst the fall for three consecutive dry years is as much as 71 in. Owing to the steep rocky nature of the hill slopes the proportion of the rainfall reaching the lake is also large. The compensation water to be discharged amounts to 54 million gallons a day. An aqueduct about 96 miles in length, and 7 ft. 1 in. wide by 7 ft. high where in tunnel, with pipe-lines where the invert falls below the hydraulic grade line, conveys the supply to the Prestwich reservoir, Manchester. Liverpool had not the advantages of a natural lake at Vyrnwy, but by. the con- struction of a concrete and masonry dam about 85 ft. high, above the river bed, across that river, impounded a storage of 18,000 million gallons for the supply of that city with a total daily quantity of 40 million gallons. A compensation water of 184 million gallons a day, or one-third of the supply, was also pro- ‘vided. This was more than five times the dry weather flow of the rivers. The reservoir affords sufficient storage for about 220 days. The catchment area is 28,500 acres, or 588 acres per million gallons daily supply. The mean yearly rainfall for a term of 20 years from a large number of gauges was found to be 65°16 in., and the average fall of three dry years (1887-89) amounted to 54°58 in. The supply is conveyed to Liverpool by means of an aqueduct, 7 ft. in diameter in the tunnels and about 684 miles in length, discharging into the service reservoirs at Prescot. Bradford.— The new Nidd Valley works for Bradford provide an additional supply of 20 million gallons a day for that city, by impounding on the Upper Nidd a quantity of 2,596 million gallons from a catchment area of 18,200 acres. This gives a catchment area of 910 acres per million gallons daily supply. There is also a further gathering ground of 9,900 acres for compensation purposes. The rainfall, based on a 12 years’ average, is 48 in. The dam forming the Gouthwaite compensation reservoir is of cyclopean rubble masonry in cement, and has a maximum depth MUNICIPAL AND SANITARY ENGINEERING. residuum lodges WAT from top water level to the foundations of 105 ft. Its thickness at the base is 70 ft. The water is conveyed from the Nidd Valley to the Chellow Heights service reservoir, a distance of 82 miles, in an aqueduct 5 ft. 6 in. wide by 6 ft. 8 in. high, with pipes across the valleys below the hydraulic grade line. Birmingham.—One of the largest schemes of late years is that for the supply of Birmingham from the Elan Valley, in Mid- Wales. Here six large reservoirs are contem- plated, having an aggregate storage capacity of 18,000 million gallons, capable of giving, for a period of 180 days, a supply of 75 million gallons a day to Birmingham, and a compensation water of 27 million gallons a day, or rather more than a third of the supply. The catchment area is 45,560 acres, or 608 acres per million gallons daily supply, and the average rainfall over a long term is about 70 in. The mean of three dry years is 56 in. ‘The dams are of masonry and vary in height from 98 ft. to 122 ft. above the river bed. The aqueduct is 74 miles long and delivers into the Frankley reservoir, to the west of Birmingham. Reservotrk Dams for impounding storage water are constructed of masonry, concrete, or earth, and are dealt with under article “Dams, EarrHen anp Masonry.” Waste Weir, Bye-CHaNnNnEL, AND Resipuum Lopars.—The respective positions and func- tions of waste weirs, bye-channels, and are illustrated in the accompanying Fig. 4. A waste weir forms a very important accessory to every reservoir, and should be provided at a suitable place at ~ the side of the reservoir. The sill of the weir should be at a slightly lower level than the highest proposed water level in the reservoir, so that any surplus water discharging into a full reservoir in flood time may escape over the weir and away through the waste water course to the natural stream below. The length of weir required in any given case will depend upon what depth of water it may be considered safe to pass over it, which should ordinarily not exceed from 1 ft. to 533 WAT 18 in., otherwise the safety of the embank- ment may be endangered. The weir should therefore be made long enough to dis- charge the full quantity of flood water which the catchment area is calculated to send down, so that this influx may be readily conveyed away down the waste water course without raising the top water level of the reservoir above the limit proposed in the design of the embankment or dam. The length of weir in practice is very generally made from 24 ft. to 4 ft. per 100 acres of drainage area, varying according to the locality and \STREAM RESIDUUM > = — es ENCYCLOPADIA OF WAT of flat steps, not exceeding 1 ft. rise with 8 ft. tread, into the upper part of the waste water course. , THe Waste Water Course is designed to carry all the water flowing over the weir or coming down the bye-channel safely into the natural stream below. It therefore has a fall equal to the greatest depth of water in the ~- > reservoir, and, as the shortest route is usually selected for reasons of economy, its inclination frequently becomes very considerable. The waste water, therefore, must not flow down at such a velocity as will injure the stability of BYE \CHANNE, Fic. 4.—Plan of Reservoir, showing Waste Weir, Bye-Channels, and Residuum Lodges. rainfall of the district. In the case of an earthen embankment the waste weir should be formed in the solid ground at one of the extremities of the dam and not passed over any of the made earthwork of the bank. If the configuration of the ground is favourable the weir may sometimes be formed, with slight cutting, through some depression at the side of the reservoir and the flood waters thus removed as far as possible from the made bank. In order to secure the greatest length of weir, and to reduce the amount of cutting, the weir is often formed curved in plan—the water, after passing over, falling by a series the work, although on grounds of safety and economy it is desirable to discharge it as quickly as possible. To check the velocity of flow a good plan is to form the waste water channel in a series of long shallow steps so constructed as to retain a pool of water on the top of each step, thus resembling a series of small weirs separated by pools, which have the effect of breaking up the impact of the falling stream. The steps shown in Figs. 5 and 6 are curved in plan with the view of increasing the stability of the work and the discharging power. In the case of masonry dams the waste may flow over a portion of the dam itself by 534 WAT terminating its crest at the top water level. The Vyrnwy dam is a good instance of this form of waste weir, and for this purpose the spaces under the 19 central arches between the piers carrying the roadway over the dam have been adapted, form- ing a weir 456 ft. in length. The surplus water thus falls down the outer face of the dam, which has been given a curved section to receive the shock of the falling water. A Bysz-Cuanneu formed in cutting around the side of a reservoir, as illustrated in Fig. 4, is a necessary accessory MUNICIPAL AND SANITARY ENGINEERING. WAT in order to avoid leakage of the water under pressure and consequent damage to the embankment or other permanent works. Outlet culverts at one time were commonly laid through the base of the dam, atits lowest part, and thus afforded a convenient means of draining off the water coming down during the construction of the dam. Outlets so placed are, however, liable to be damaged by the unequal settlement of the embankment, especially at the point of passing through the puddle wall, and leakage of water under pres- sure is almost certain to result, leading to work for the purpose of carrying away the flood discharge of the stream feeding the reservoir and for diverting the turbid and dis- coloured waters into the stream below the dam. It is also a great LL) ir Pool convenience as a by-pass during the construction of an earthen embankment. These bye-channels are controlled by gates or sluices, and are lined along their sides and bed with _— PLAN puddle, concrete, or masonry, as circumstances may require, in order to prevent the erosion of the stratum through which they may be formed. At the head of these bye-channels are formed small settling reservoirs termed “residuum lodges” or ponds (see Fig. 4) in which the sediment brought down by the flood waters is caught and deposited before the water passes on to the bye-channel or to the storage reservoir. These are provided with sluices or pipes for empty- ing them, and with movable shutters for diverting the water either into the bye- channel or reservoir, as desired. OuTLETs FRom Reservorrs: Vatve Towers. —Suitable means must be provided for draw- ing off the water stored in a reservoir for purposes of supply, and also for compensation, and as a-considerable head of water has usually to be dealt with the treatment of the “outlet” requires to be carefully considered 585 SECTION Fries. 5 and 6.—Waste Water Course, with Pools. subsidence and ultimately to the destruction of the dam. The prospect of failure is even greater when the valves controlling the dis- charge are placed at the outer end of the out- let, or in the centre of the embankment pre- venting access to the culvert for repairs. The outlet, whether consisting of a culvert or pipe, should be controlled throughout its length by a valve tower placed at its inner end within the reservoir. The safest though most costly plan, where a reservoir is formed of an earthen embank- ment, is to carry the culvert through a tunnel round the end of the embankment, or through the side of the valley into another watershed WAT if the conditions are favourable, and to control the discharge by a valve tower within the reservoir, having inlets at different levels so that the water may be drawn off at various depths as desired. In the Villar masonry dam on the Lozoya for the supply of Madrid, and in the New Croton dam (New York), the outlets are carried through the dams at a low level with the valve chambers formed in the dam. A better plan, however, is to carry the culvert in a tunnel at one side of the valley beyond the dam, as done in the case of the Vyrnwy reservoir, where the flow is controlled and strained through copper wire gauze in a masonry tower built in the reservoir. The compensation water here is discharged by means of a culvert carried through the dam direct into the river below. The proper arrangement of the outlet is a very important part of the design of a dam, and serious failures have resulted from unequal settlement near the culvert and infiltration of pressure water into the bank. The bursting of the Dale Dike embankment, near Sheffield, in 1864, on the occasion of the first filling of the reservoir was attributed to the unequal settlement and cracking of the puddle wall over the trench excavated in the rock in which the outlet pipes had been laid. Other causes contributing to this failure were the defective material used for the bank and the rough way in which it was raised, also the rapid filling of the reservoir. The em- bankment was 95 ft. high and the reservoir had a capacity of 114 million cubic feet. Another instance of failure was the embank- ment across the Lynde Brook, Worcester, Mass., which burst in 1876 and released a reservoir of 110 million cubic feet capacity, owing to the gradual percolation of the water under pressure along the line of outlet pipes. Vatve Tower.—The outlet culvert from a reservoir is usually connected at its inner or upstream end with a “valve tower” which contains the supply and scour pipes, straining screens, and valves for working the outlet works of the reservoir. The tower is also provided with a vertical cast-iron pipe (an extension of ENCYCLOPADIA OF WAT the outlet pipe through the culvert) into which branches, controlled by valves worked from the valve chamber just above top water level, are connected in a manner enabling the water to be drawn off at different levels as may be required. The tower is usually circular in plan and is built of masonry, brickwork, con- crete, or cast iron. SrpHon Ovutters.—Where a reservoir does not exceed about 25 ft. in depth, the water Air outlet, provision =< for charging ete. Fic. 7.—Siphon Outlet from Reservoir. may be drawn off by a siphon pipe placed as shown in Fig. 7; that is, carried up the inner slopes of the dam, over the top, and down the outer slope to a lower level than the bottom of the reservoir. There must, of course, be sufficient difference of head between the two legs of the siphon to overcome friction and to give the required discharge. Water may be drawn off at any level by means of valves suitably placed on the inner slope as illus- strated. To start the siphon the valves at both ends are closed and the pipe filled with water from the top of the embankment where a charging valve and air-vessel are placed. The discharge will be started by closing the valve at the top of the siphon and opening the others, but the summit must be kept free of air which will accumulate there and throttle the flow unless means are provided for its removal. The siphon may also be started by exhausting the air from the summit valve by means of an air-pump. Siphon outlets have the advantage of not interfering with the embankment below high water mark, but they usually require a good deal of attention and are not generally satisfactory. CREEPING FLANGE orn PuppiLe Cotiar.—The outlet culvert from a reservoir is stopped at some point in its length by a plug of concrete 536 WAT or brickwork, through which the outlet pipe passes. ‘he main passing through this plug should have cast upon it, or bolted around it, a deep projecting flange known as a “ puddle plate ” or creeping flange (Fig. 8) to prevent the leakage of water along the pipe. Leaping on Separatine Wetrs are employed for the purpose of automatically rejecting flood waters from a collecting conduit. (See article “ Leaping WErR.’’) Agquepvucts.—In a gravitation scheme the water is usually stored in a lake or reservoir formed in a valley situate in hilly ground ata considerable elevation above sea level, and also usually at a distance of many miles from the town to be supplied. The supply has, there- fore, to be conveyed by means of an ‘“‘aque- duct”’ to the service reservoirs in the imme- diate vicinity of the town, whence the water again flows by gravitation into the distributing mains, and is delivered at a pressure (depend- ing on the relative heights of the service reservoir and of the area of distribution) sufficient to reach the uppermost storeys of the highest houses. As formerly applied, the term ‘‘ aqueduct”’ related more particularly to structures like the bold masonry bridges erected by the Romans for the conveyance of water across deep valleys, and to similar channels for purposes of irrigation and navigation. In its present Calvert t : Oullel pipe J tp Creeping flange LH, WY Ui pp aa Fic. 8.—Creeping Flange, or Puddle Collar. and more extended sense an aqueduct com- prises, in addition to bridges, open or covered channels or conduits, tunnels, and metal pipe lines, now largely employed upon gravitation schemes of water supply. The internal sectional dimensions of an aqueduct for the conveyance of a given volume of water will depend principally upon the “hydraulic gradient” which can be given to MUNICIPAL AND SANITARY ENGINEERING. WAT the conduit. The hydraulic gradient is expressed in feet or inches of fall per mile of length, and is the vertical fall between any two points on the line of aqueduct divided by the length. The hydraulic gradient may be maintained throughout if the aqueduct is con- structed of the same cross section along its whole length, but it is frequently desirable to vary the gradient at different parts, on grounds of economy in construction, in order that the level of the work may be more nearly adjusted to the configuration of the ground or that the section of the tunnel, conduit, or pipes may be reduced in places. An outline section ofa modern aqueduct as constructed for a gravitation water supply scheme is given in Fig. 9, which represents the profile of the ground surface along the line of the aqueduct from Lake Vyrnwy to Liverpool. Such aqueducts consist of a channel con- structed to the inclination of the hydraulic gradient, and carried through hills or rising ground in tunnel; contouring hillside slopes or passing through fairly level ground in open cutting or cut-and-cover work; or, where the ground suddenly dips below the hydraulic gradient as shown at many places in the figure, the form of the aqueduct changes to a series of iron pipes laid side by side and following the contour of the ground surface with no greater depth of cover than is needed for protection against damage, instead of bridging the valley by means ofa huge arched bridge following the hydraulic gradient asin the early Roman works. The pipe lines are of cast iron or riveted wrought steel tubes and form large inverted siphons, often many miles in length, through which the water flows under a pressure depending upon the depth at which they are laid below the hydraulic grade line. The form of aqueduct at various points along the line will depend upon the con- figuration of the ground. Where this is fairly uniform, the hydraulic gradient will be followed by contouring the slopes in a more or less circuitous route, and the high ridges will be pierced by tunnelling, pipes 537 WAT being resorted to only when a deep valley has to be crossed. In the case of the above aqueduct it will be seen that the land mostly lies below the ENCYCLOPEDIA OF WAT straight course, except at the points where the level rises above the hydraulic gradient (above which the aqueduct must not rise), and here tunnelling is resorted to and the invert of the a of sae pean simtgomesecee ns ft e HYOQRAULIC_GRADIENT ; fre sce s ern edn eae aera aes tae eee meets e HORIZONTAL SCALE 4g 2 0 1 1 Ie % 2 p MILES VERTICAL SCALE 1000 1000 2000 FEET Fic. 9.—Vyrnwy Aqueduct. Longitudinal Section. hydraulic grade line shortly after leaving the lake except at a point just before reaching Oswestry. In such a case the aqueduct con- sists mostly of pipes following the irregulari- ties of the ground and following a fairly aqueduct coincides with the hydraulic gradient. The hydraulic gradient is also reached (see Fig. 9) at several points on the pipe line where “ balancing reservoirs” are introduced for the purpose of reducing the pressure of 538 WAT the water on the lowest part of the pipes by thus breaking up the fall of the aqueduct into independent sections. The plan of following the hydraulic gradient usually involves a large amount of cutting for the conduit, and it frequently becomes neces- sary to follow a more circuitous route by contouring the hill slopes to avoid sudden changes of level in the ground, but balancing reservoirs are not required upon this method of constructing an aqueduct. Where a pipe line is adopted, a straighter and shorter course is obtainable and the available gradient is consequently greater. There is, however, a greater loss of head owing to the frictional resistance in the pipes, and a greater water section is therefore required for the same amount of discharge. In a pipe line, also, the pressure at the lowest point may become unduly great if not relieved by balancing reservoirs at suitable intervals. Some of the most important aqueducts in this country for water supply purposes are the two from Loch Katrine to Glasgow (24 miles), from Thirlmere to Manchester (96 miles), from Nidd Valley to Bradford (82 miles), from Lake Vyrnwy to Liverpool (683 miles), from Elan Valley to Birmingham (74 miles), and from Derwent Valley to Leicester (about 72 miles). The Thirlmere aqueduct contains about 142 miles of tunnels, 36°75 miles of covered conduit, and about 45 miles of 48 in., 40 in., and 86 in. cast-iron pipes, laid as inverted siphons through the valleys. The siphon across the valley of the Ribble is 94 miles long, and that across the valley of the river Lune has a dip giving a maximum head of water of 427 ft., equal to a pressure of about 186 lbs. to the square inch. The pipes are mostly carried over the rivers at the bottom of the valleys on bridges, so that they are readily accessible for inspection and repairs. For about 88 miles from Thirlmere a hydraulic gradient of 20 in. per mile is maintained, but in the remaining 132 miles there is an avail- MUNICIPAL AND SANITARY ENGINEERING. Service B Reservoir WAT able fall of about 82 in. per mile, and the diameter of this line of piping is consequently reduced to 36 in. The siphons connect with the conduits through rectangular chambers formed at each end, and an automatic valve shuts off the supply in the event of the bursting of a pipe in the line of siphon. The conduits are about 7 ft. by 7 ft. internal dimensions, and are formed of concrete on the cut-and-cover system with the portions in tunnel lined with concrete. The aqueduct is carried across small streams on masonry bridges, and a uniform gradient of 20 in. per mile is maintained. The Vyrnwy aqueduct is divided into six sections by “balancing reservoirs” con- structed on sites where the land attains the Fic. 10.—Hydraulic Gradient of Pipe Line. level of the hydraulic gradient. It happened, however, that there was no land along the last 204 miles of the aqueduct of a sufficient height to reach the hydraulic gradient, and it thus became necessary, in order to make a break in the long line of pipes under pressure between the Cotebrook Balancing Reservoir and the Prescot Service Reservoirs, to form a “ balanc- ing reservoir’ on the top of a high tower, shown in the section (Fig. 9), on the summit of Norton Hill, situate about 3 miles to the east of Runcorn between the valleys of the rivers Weaver and Mersey. By this means the reservoir is raised to the hydraulic gradient, which at that point is 110 ft. above the sur- face of the ground. The reservoir consists of a circular basin 80 ft. in diameter, formed of steel plates, and having a central depth of 31 ft. The hydraulic gradient on this aque- duct varies from 2 ft. per mile in the tunnels 5389 WAT to 6°87 ft. per mile in the long siphon between the Oswestry reservoir and the Malpas tank. The pipe line will ultimately consist of three lines of pipes, and their diameters range from 32 in. to 42 in., according to the amount of fall available in the different sections. In the case of a burst pipe, automatic valves worked by the fall of a float gradually shut off the supply, and air valves fixed at all the summits of the siphons are provided for the escape of the air which otherwise accumulates in the mains at the high points and throttles the flow of the water. The aqueduct from Elan Valley to Birming- ham has a hydraulic yradient of only 15°84 in. per mile in the tunnels and conduits, but in the siphons the gradient is increased to 86 in. per mile, and will consist of six lines of 42 in. metal pipes. The total ultimate supply through this aqueduct is to be 75,000,000 gallons per day; that through the Vyrnwy aqueduct is 40,000,000 per day, and 50,000,000 from Thirlmere to Manchester. On the Elan aqueduct the longest siphon is 17 miles in length, and the greatest dip of the pipe line is 550 ft. below the hydraulic gradient, where the Severn is crossed by a bridge near Bewdley. Service Reservorrs.—As mentionedalready, the service reservoir is usually situate in the immediate vicinity of the town supplied, and is constructed upon the best available site of such an elevation as will be capable of deliver- ing a supply of water by gravitation to the highest houses within the water area. Wherea town consists of widely varying levels it is well to divide the water area into various high, middle, and low-level districts, or ‘‘ zones”’ of supply, and to provide a separate reservoir for each if the conditions render such a system economical. By this means the cost of pump- ing to unnecessary heights will be avoided, as also the excessive pressures otherwise obtained in the lower parts of the town, which often cause much waste of water through weak or defective fittings. The main objects of a service reservoir are, (2) to maintain a small storage of water near the town to provide against irregularities of ENCYCLOPADIA OF WAT consumption and to form a reserve to be drawn upon in cases of sudden demand, as the outbreak of fire, or to meet an emergency, such as the bursting of a rising main, the failure of an aqueduct, or of the pumping machinery delivering to the reservoir; (b) to give a fairly constant head on the supply mains, thus equalising the pressure therein, which cannot be secured by pumping directly into the mains; (c) to enable the pumping machinery to work at a fairly uniform and economical rate, and to avoid night pumping. The rate of consumption of water varies according to the requirements of the town supplied and the extent to which trade and municipal supplies are connected to the system, but the demand is usually largest during the morning hours, commencing to increase at about 6 a.m., and reaching a maximum somewhere near 10 a.m. There will be various fluctuations during the re- mainder of the day, and the minimum supply will pass out during the night or early morn- ing from 1 amto4a.m. By making a careful comparison of the quantity given out during these 4 hours a good idea of the percentage and variations in the daily waste may be obtained. On the average it is found that rather more than twice as much water is consumed between the hours of 6 a.m. and 6 p.m. as between 6 p.m. and 6 a.m. A service reservoir should hold from 1 to 8 days’ ordinary supply, or more if for any local circumstance the conveyance of water to the reservoir is liable to interruption. The reservoir is usually formed by excavating and building about half its depth below the ground surface and embanking the upper half above the ground line with the excavated material. The walls are built of concrete or brickwork, sometimes backed with clay puddle, and rendered internally with cement or bitu- minous sheeting. Seeing that the situation of service reservoirs is close to inhabited areas, they should nearly always be covered to prevent pollution of the water by dust, soot, or other objectionable matter, and the water is thus kept at a more uniform temperature, 540 WAT cooler in summer, and less liable to frost in winter. The depth of the water therein should be not less than from 12 ft. to 15 ft., sufficient to impede the growth of animal and vegetable life. There are many ways of covering reservoirs, amongst which may be mentioned a wood roof, with slates, concrete arches and piers, concrete arches or slabs carried by girders and joists, girders and jack arches, corrugated iron on light iron trusses, and expanded metal and concrete carried by girders and iron columns. The various accessory details connected with a service reservoir include an inlet, out- let, overflow, scour or wash-out pipe, access ladder, manholes and ventilators, and water- level indicator. A good plan is to surround the inlet by a dwarf wall to retain a small quantity of water which will act as a cushion for the incoming water to fall upon. The outlet should be a few inches above the level of the floor and guarded by a close wire sereen. Manholes for access and light during cleaning and repairs should be provided, and the reservoir should be well ventilated. The water level in the reservoir is now very generally recorded by means of an electric water-level indicator connected direct with the pumping station or the water engineer’s office. It is a good plan to have a large reservoir divided by means of a dwarf wall so that one- half may be used for maintaining a constant head on the supply mains whilst the other half is under repair or being cleaned. Circular reservoirs are more economical to construct than rectangular ones, as the thick- ness of the walls may be much reduced. Taking the thickness of straight walls in rectangular service reservoirs as varying between one- fourth and two-fifths of the depth, those of circular reservoirs have been found strong enough with a thickness of from one-sixth to one-tenth of the depth. In construction, circular reservoirs will be found to be from 20 to 40% cheaper than those of a rectangular design, but are not, of course, so economical in ground space. The cost of a covered service reservoir MUNICIPAL AND SANITARY ENGINEERING. WAT varies from about £2 up to as much as £10 per 1,000 gallons capacity, depending very largely upon local circumstances and the size of the reservoir. About £5 per 1,000 gallons may be taken as a fair average price under ordinary conditions. Concrete, when made of good clean materials, is a very useful material for the construction of aservice reservoir. A circular reservoir of 550,000 gallons available capacity formed of this material at Upwey for the Portland Urban District Council was built entirely of concrete composed of 6 parts Moreton gravel to 1 part of Portland cement. The reservoir is 90ft. internal diameter with a depth of water of 16 ft. The external wall is 3 ft. thick, and the floor, which slopes towards a wash-out pipe, is 1 ft. in thickness. The roof is of concrete arches of 8 ft. clear span and 1 ft. thick, and is carried by eight cross walls 1 ft. 6 in. thick pierced with openings 10 ft. by 8 ft. The internal surfaces are rendered with two aoe of Portland cement mortar, the first coat, ? in. thick, being com- posed of 1 part sommes to 2 parts sand; and the second coat 4 in. thick, of 1 part cement to 1 part sand, and trowelled to a hard smooth surface. The reservoir is well ventilated, and lighted from the crown of the arches, and a valve chamber is formed outside the reservoir through which passes the rising and delivery mains. Water is admitted to and flows from the reservoir by a floating arm, and is thus always drawn from about 9 in. below the surface so that no sediment or floating matter can enter the supply mains. A Jennings’ patent electrical mechanical indicator and recorder is fixed at the pumping station, and is elec- trically connected with the reservoir, so that the quantity of water in the reservoir is always known to the man in charge at the pumping station. This reservoir cost £2,270, or £4 2s. 6d. per 1,000 gallons. Distrisution or Water.—A water supply, having been delivered to a service reservoir of sufficient elevation to command the area of supply, is distributed by means of cast-iron lead-jointed mains throughout the water area. 541 WAT The first consideration is to decide upon the best routes and determine the requisite sizes of the leading trunk mains, having due regard to the elevation of the various streets to be supplied, and the present and future popula- tion to be connected thereto. For branch mains supplying a single street, 8 in., 4 in., or 5 in. diameter pipes will usually be sufficient, but the sizes of leading mains will vary considerably according to the districts fed by them, and each case will involve special investigation. Where there is no special provision in the way of a subway under a street, a good position for the water main is in the roadway at a distance of about 3 ft. from the curbing. The mains should be laid with a minimum of 2 ft. 6in. or 8 ft. of cover as a protection against frost and damage from heavy traffic, and the pipes should be thoroughly well coated with Dr. Angus Smith’s solution or other like preservative and have a thickness of metal adequate for the water pressure to which the pipes will be subjected. Whilst some distinction might be made in the thicknesses of metal between two entirely separate zones of supply having widely varying pressures, it will be unwise to attempt to differentiate between the pressures of the same area, otherwise great confusion may easily arise for the want of standard sizes in the spigots and sockets of pipes, and thus lead to much inconvenience and delay in the execution of repairs. Another objection to reducing the standard thicknesses is that water at a higher pressure may upon an emergency, such as a fire, require to be turned into the low pressure district. In very wide streets with much traffic it is not unusual to have a large leading main near the centre of the roadway with smaller tapping mains on each side in or near the footpath, to which are connected the house supplies, thus leaving the trunk main exclusively for the supply to districts beyond. The pressure in the leading main is thus maintained and the inconvenience and cost of crossing the street to make house connections is avoided. ENCYCLOPADIA OF WAT In laying out a distribution system it is important to provide adequate main capacity, bearing in mind that it is the maximum summer supply during any hour of the day which must be provided for and not the average of the year, month, or week. The maximum rate of draught may be taken approximately at double the average consump- tion of 24 hours, and mains must be of sufficient capacity to deliver the requisite quantity at the required pressure during all periods of the day. In long lengths of small-sized mains the frictional losses at the time of heaviest draught will be considerable, and the size of the mains should be such that not more than about one- fourth of the available statical head should be consumed in overcoming friction. In addition to the ordinary supply it must be remembered that a heavy draught will also be made at times for street watering purposes and that this usually occurs at the time when domestic supplies are at a maximum. It is necessary, therefore, that the pressure should at all times be sufficient to reach the highest storeys of premises within the distribution area. In districts where there is great variation of levels it usually becomes necessary to divide the area into separate districts or ‘‘ zones of supply”? so as to maintain pressures in the mains suited to these different areas, otherwise an excessive pressure will obtain in the lower areas. As a maximum pressure a head of about 200 ft., equivalent to 86 lbs. to the square inch, may be adopted. Water fittings in general use will not satisfactorily withstand a head much beyond this figure under ordinary working conditions without great waste of water. The different zones of a district, usually designated ‘high-level,’ ‘ middle,” and “low-level” according to circumstances, are supplied by means of service reservoirs, water-towers, and stand-pipes suitably placed to command the various levels. A “‘stand-pipe ” supply is given by placing a vertical pipe (in the form of an inverted U) in the line of rising main, and the water is pumped against the additional head due to the height of the stand-pipe, and a corresponding 542 WAT increase of pressure is thus afforded for houses lying at a greater elevation than the service reservoir. The surplus water passing over the top of the stand-pipe falls through the down leg and enters the service reservoir. Where a considerable area at the higher level has to be supplied it is preferable to have more high-level storage than is afforded by a stand-pipe, and for this purpose a ‘water- tower” is substituted (see ‘“Stanp-Pipz anp Arr- VESSEL ”’). By zoning a district in this way the cost of raising the whole supply to one high-level reservoir is avoided, and the pressures are maintained more uniformly throughout, but some additional complication and expense may be involved in the daily working of the different levels, so that it becomes desirable to confine the number of zones within the limits of absolute necessity. Tn laying out a pipeline, care should be taken that no part of the line rises above the mean hydraulic gradient or the discharge will be impaired or perhaps be nil. The hydraulic gradient is represented by a straight line drawn from the point where the water enters the pipe line (as B.; Fig. 10) to the termination of the line at its point of discharge, C. When the pipe line is below the hydraulic gradient the discharge at C will be that due to the hydraulic gradient BC. If, however, the ground rises to a point such as at A, the hydraulic gradient BC will no longer govern the discharge, which will be limited to that due to the flatter gradient BA. The remaining and steeper portion A C of the pipe line B AC may therefore be of a less diameter than that from B to A to give an equal dis- charge. It is therefore readily seen that the section of a line of main should be plotted and the hydraulic gradients obtainable well considered before the sizes of the different sections of a pipe line are finally decided upon, otherwise an insufficient discharge may result or an unnecessary expense may be incurred by continuing a main of large diameter when one of a smaller section would have proved adequate. MUNICIPAL AND SANITARY ENGINEERING. WAT The delivery of water mains of various sizes and hydraulic gradients is obtained in practice from hydraulic tables based on the results calculated from empirical formule arrived at by various experimenters in hydraulic science. Space will not permit of more than a mere mention of the subject here, but reference should be made to works specially devoted thereto.1_ The formula now commonly used is Herr Kutter’s, which gives more correct results than the older formule and takes into account the degree of roughness of the internal walls of the pipes. Speaking generally, the difference between Kutter’s and the older formule is that it gives smaller discharges for small diameters, and larger discharges for large diameters. Intermittent Suppiy.— Water supplies were formerly delivered to consumers at short intermittent periods of the day, during which the storage cisterns of dwelling-houses were filled for the use of the household until a further supply from the main was again avail- able. The object of the system was to prevent waste and to economise water, but there were many drawbacks to this method, particularly from a sanitary point of view, and it has now become almost obsolete. The principal objec- tions to an intermittent service are—(1) the storage of considerable quantities of drinking water oftentimes in more or less unsuitable and dirty receptacles ; (2) the risk of pollution of the water owing to the mains and service pipes being alternately empty and charged, thus producing at times an inward suction in the case of leaky pipes. The intermittent system is seldom resorted to at the present day except under absolute necessity during periods of shortage of water. Constant Suppry.—The efforts of water 1“ Water-pipe Discharge Diagrams” (Kutter’s formula), by E. B. & G. M. Taylor, Civil Engineers (published by B. T. Batsford). ‘‘ Hydraulic Tables,”’ by P. J. Flynn, Civil Engineer (E. & F. N. Spon), “Practical Hydraulics,” by Thomas Box (EH. & F. Ns Spon). ‘Tables for the Solution of Ganguillet and Kutter’s formula,” by Col. E. C. 8. Moore, R.E. (B. T. Batsford). 548 WAT authorities are now invariably directed to the maintenance of a “constant supply’ of water in the mains at a good pressure, so that water may be drawn by the consumer direct from the main. Occasional temporary interruption under this system occurs only during acci- dental bursting of a main, repairs, or altera- tions. To meet such emergencies it is advisable that the consumer should be provided with a small storage in well-covered cisterns made of slate, galvanised iron, or other suitable material. Cisterns should, however, be placed in a position readily accessible for in- spection and cleansing. In addition to taps drawing from storage cisterns, each consumer should also be provided with a tap for general use, taking its supply direct from the main. The introduction of a constant water supply service at good pressures has involved the necessity for superior types of water fittings in order to prevent waste and misuse of water. All such fittings should be subject to the approval of the water authority, and be tested and stamped before being passed for use. Prevention oF Waste.—The extent to which expense may be usefully incurred in the prevention and detection of waste is a problem requiring the careful consideration of the waterworks engineer. The value of the water thus lost must be balanced against the cost of the detection and prevention of the waste. Where the first cost of the water is considerable, or the quantity limited, the introduction of means to prevent waste will be well repaid by the saving thus achieved, as leakage and careless waste, if unattended to, are liable to become so serious in the aggregate as to materially increase the annual cost of supply, particularly where the water has to be pumped. Moreover, the saving of waste enables the supply to be extended to a larger area, and tends to defer the time when it will be necessary to expend further capital in augmenting the sources of supply. One of the principal means of detecting and localising waste is by the application of Deacon’s waste- water meter system, first introduced at Liver- pool in 1873-75. In this system the distribu- ENCYCLOPZDIA OF WAT tion area is subdivided into small districts containing from 2,000 to 3,000 consumers, and a waste-water meter fixed in a by-pass pipe on the distributing main supplying this district at a point where this branch main leaves the primary main, so as to isolate the supply to the sub- district by passing it through the meter. The meter contains a revolving drum upon which is automatically recorded the quantity of water passing into the district. If, during some portion of the night or during the small hours of the morning, the consumption so recorded is larger than is reasonable for that period of the 24 hours, it may be safely inferred that some unusual draught is taking place either through waste in the main itself or in household fittings. The investiga- tion is then followed up by an examination of the sub-district during the night, and each stop-cock to the separate premises supplied is sounded by using the valve-keys as stetho- scopes, and any sound indicating passage of water is carefully noted and traced to its origin as far as possible. Premises into which water is thus noted to be passing are examined internally on the following day, and by these means the location of waste is speedily effected. Much time is thus saved in house-to-house inspection, as the diagrams from many of the sub-districts of a large town may show the conditions to be normal and that no material waste is taking place, thereby enabling the time of the inspectors to be concentrated upon those areas in which the waste is shown to be greatest. Fire.—The demand upon the water dis- tributing system for fire purposes is a very variable and uncertain one. Much depends upon the class and density of the property to be served. In the case of fully-built-up dis- tricts in a crowded city with high buildings, offices, and warehouses containing more or less inflammable stock, a liberal allowance in main room capacity must be made. Consideration must be given to the elevation of the property served with relation to the level of the service reservoir and the pressure available at the fire hydrants when discharging through the 544 WAT requisite length of hosing. It is also impor- tant to have regard to the probable maximum number of hydrants likely to be in use at the same time, and the main room provided should be such that the water pressures will be well maintained when the maximum number of hydrants is in use. For fire purposes 24 in. diameter canvas hosing is commonly employed, and the loss of pressure due to friction in traversing long lengths is very marked. In cases of large and important buildings, especially where there are a large number of occupants, several hydrants will necessarily be in use at the same time, and if a satisfactory supply is to be afforded, the volume of the main must be increased to meet such an emergency. In elevated situations where the ordinary pressures in the mains is insufficient to throw a jet of water to the top of a building, the water may usually be more advantageously used through a fire engine, and the capacity of the mains should be adjusted to meet such a demand. In districts where the water is pumped direct into the distributing system, ample stand-by power should be provided, and the fire brigade headquarters should be in direct telephonic communication with the pumping station so that immediate notification of the outbreak of. fire can be transmitted thereto by the fire authorities. The spacing of hydrants will require consideration in regard to the properties to be served; thus in busy town centres they are often placed from 50 to 100 yards apart, and from 100 to 150 yards in residential quarters. Important corners and cross-roads will require special provision according to circumstances. Cast-Iron Pipes for water supply purposes are usually made in 6 ft. lengths for 2 in. and 24 in. diameters, 9 ft. lengths for 3 in. to 10 in. diameters, and 12 ft. lengths for 11 in. diameter and upwards. The pipes should be suitable for a working pressure of about 300 ft. head of water, and should be tested to a proof strain of not less than 600 ft. This margin is necessary owing to the varying pressure to which the pipes are liable during their life- time, such as sudden shocks and “ water M.S.E. MUNICIPAL AND SANITARY ENGINEERING. 545 WAT hammer,” as may be caused by turning the water off too suddenly or by air in the pipes giving rise to concussion. For these pressures the thicknesses of metal for 2 in., 8 in., and 4 in. should be 2 in., for 6 in. diameter pipes z in., for 9 in. diameter 3% in., and for 12 in. diameter 2 in. Ample initial strength is also necessary owing to the deterioration of the pipes after being laid in the ground, where they are liable to decay and oxidation, thus, in the course of years, materially reducing their thickness. Carbonaceous matter, such as cinders, will, with moisture, eat into or “ pit” the surface of the pipes laid in this material. Very soft waters also tend to cause deteriora- tion by oxidation and inerustation. Cast-iron pipes should be tested to the pressures above named before leaving the foundry, and should sustain the test for several minutes, being struck at the same time with a hammer so as to produce a strong vibration. Specimen test bars and rods of the metal employed in the casting of the pipes are also very usually required to be submitted by the founders for testing the transverse and tensile strengths. The straight pipes are cast in sand moulds placed vertically, and the special castings in close boxes. The thickness of the metal should be as uniform as possible and the weights of the pipes in the small diameters should not vary more than from 83 to 4°/,. As soon as the pipes have been proved, and before they are attacked by rust, they should be coated externally and internally with a preservative composition such as Dr. Angus Smith’s solution. The pipes are heated to from 800° to 400° F. and dipped in a mixture of the composition approaching boiling point, thus forming a _ protective coating on the metal. Water mains should be jointed with the best soft blue pig lead and well caulked. The joint should be run in one running so as to insure the whole joint being homogeneous. To prevent the lead passing into the insides of the pipes, and to economise the quantity of lead used, the joint is first caulked with NW WAT yarn, then run with lead, and afterwards set up. On all distributing mains a very important fitting for the proper control of the supply is the sluice valve, of which a large number are always required. These valves should be double faced, having two gun-metal faces on the body of the valve and two on the valve door. The valve spindle and nut are also of gun-metal, and the gland and stuffing-box bushed with gun-metal. In a district of supply it is Important that all the valves should open the same way, as if some are left-handed and others right-handed trouble will arise through the valves being shut by mistake. All valves should be subjected to a hydro- static pressure of 600 ft. of water as a test before use, and should be coated similar to the cast-iron mains described above. Screw- down valves have the advantage of shutting off the main gradually and preventing con- cussions. A plug-cock should not be inserted in a water main, as its sudden closing would have a very damaging effect. Large sluice valves on leading mains should be provided with indicating wheel gearing to show when full, half open, or closed. It is difficult to start opening the door of a large valve when the pressure is on one side only, and to over- come this trouble a small by-pass pipe with valve or stop-cock is provided, communicating with each side of the large valve for the pur- pose of charging up the main before opening the larger valve. Leading supply mains and pumping mains should be titted with self- acting air escape valves placed at every high point on the line of main for the escape of air which otherwise accumulates at these points. Air pipes of about 2 in. diameter con- trolled by a full-way cock are also sometimes provided for releasing large quantities of air when a main is being re-charged after empty- ing. But little difficulty is experienced from the accumulation of air in the branch supply mains as a rule, as the continual draught on these mains by the house services allows of the ready escape of air. Other varieties of waterworks apparatus ENCYCLOPADIA OF WAT and fittings in general use for the distri- bution of water include different classes of fire hydrants, stand-pipes, street watering posts, drilling apparatus for connecting to mains, tapping ferrules, stop-cocks, bib-taps, ball valves, bath and lavatory fittings, flushing cisterns to w.c.’s, automatic flush tanks, and surface boxes for hydrants, meters, &c. Of these it may be said, generally, that the best types are usually those which are the simplest and strongest in design and construction, and that whilst a very good idea of their great variety and design may be gathered from an inspection of the various makers’ catalogues, experience in their use under ordinary every- day conditions is the best means of finding out what good points of design are to be looked for and what weak points are to be avoided in the selection of fittings of this kind. Water Service Pipes communicating be- tween the supply main and the premises to be supplied should not be less than ? in. internal diameter, and should be made of strong well-galvanised iron piping, or, in the case of a hard water, they may safely be of lead. The pipes must be capable of with- standing an internal pressure of from 400 ft. to 600 ft. head of water, and should be laid in the ground with not less than 2 ft. of cover so as to protect them from damage by frost or other cause. Every house should be provided with a separate service pipe, which should be connected with the main by means of a brass screw stop ferrule. A stop-cock is inserted in the service pipe near the point of entrance to the premises supplied and on the footpath wherever possible. A tap should also be inserted in the service pipe for the purpose of completely emptying the pipes in case of frost or repairs. The drawing and stop- cocks should be of the screw-down pattern, of the best make, and be tested and stamped by the water authority before use. All soldered joints on lead pipes should be of the kind known as “ plumbers’” or ‘“‘ wiped” joints. Overflow or “‘ warning pipes” from cisterns 546 WAT should be so placed that the overflow may be readily detected and should not be discharged into gutters, rain-water pipes, lead flats or roofs, otherwise a waste of water may be allowed to continue for a considerable time before being remedied. The regulations of water authorities usually stipulate that w.c.’s., urinals, and boilers should not be supplied direct from the mains, but from separate cisterns. Water-waste preventers attached to w.c.’s and urinals should be capable of discharging 2 gallons of water in each complete flushing operation in 15 seconds. Such apparatus should be of a type approved by the water authority, and should be capable of discharging their contents rapidly and with certainty, so as to secure the full benefit to be derived from the effect of the flush. A continuous running dribble of water is of no practical use for flushing pur- poses, and is extravagant and wasteful. To prevent waste, baths should be fitted with a water-tight plug outlet attached to a chain. Ball-taps for cisterns should be tested and proved water-tight under a pressure of, say, 300 Ibs. to the square inch, or according to the maximum pressures likely to be experi- enced from the mains. With proper regula- tions and adequate supervision, water authori- ties are enabled to check much waste and misuse of water, such as frequently arise from the employment of inferior fittings. Dvuat Supriigs or Water.—The difficulties of obtaining within a reasonable distance suitable supplies of pure water (in sufficient quantity) is yearly increasing with the growth of population, and the question is often dis- cussed as to the advisability of introducing dual supplies of water, using the purer sources for all dietetic purposes, and employing a less pure and cheaper water for street watering, sewer and drain flushing, and certain trade purposes. Several seaside towns in this country have installed plants and mains for the use of sea-water for municipal and other purposes, but the results, speaking generally, can scarcely be considered a success, and in some cases the system has been abandoned 547 MUNICIPAL AND SANITARY ENGINEERING. WAT altogether. The dual system of supply has been followed out to a considerable extent in Paris, where the water for domestic purposes is drawn from natural springs in the chalk in the basin of the Seine and brought to the city in three closed aqueducts, viz., the Dhuis, the Vanne, and the Avre, and discharged into covered service reservoirs; whilst the supply for the streets, gardens, stables, yards, and trade purposes is obtained from the river ‘Seine, the Marne, and the canal of the Oureq, and other sources, including artesian wells. The double system is, however, not favourably reported upon. The use of two waters obviously involves the laying down of a double set of distributing mains, thus greatly increasing the cost to the water undertaking, and also greatly adding to the complications of the supply and increasing the risk of mistakes in making connections with the mains. When the increased initial cost is taken into consideration, together with the annual expenses of the upkeep of two supplies, the advantage of such a system is very doubtful, unless some purely local con- ditions in a given case operate powerfully in its favour. Warer Main Scrapinc.—Mains which have become much reduced in discharging capacity are sometimes cleansed by introducing a “scraper” into the main through special “‘hatch-boxes ” provided thereon, and forcing the same forward by applying water pressure behind it. The process, however, is frequently a troublesome operation, owing to the scraper occasionally becoming fixed at a bad joint or bend in the main, involving, in some cases, the cutting of the main in order to remove it. Scraping is not often attempted on mains less than 6 in. in diameter. The average cost of scraping appears to be about ‘75d. per yard per inch of diameter of main, including wages, lead, yarn, hatch-boxes, and scraper, but the plant having once been purchased, subsequent scraping costs should be com- paratively small. For further information upon “water supply,” reference should also be made to the NN2 WAT following articles :—‘“ Abyssinian Wells” ; ‘“Alge in Water Supplies”; ‘Artesian Wells”; ‘ Bacteriology of London Water Supply’; ‘ Bore-wells”; ‘ Catchwater Drain” ; “Cholera”; “Dams’’; ‘‘ Effluents”’; ‘Filters (domestic) ’’; ‘‘ Filtration (mecha- nical)” ; “ Filtration (through sand)”; ‘‘ Fish Life in Streams”; ‘Frost (effect on water fittings)’; “Gauging of Streams”; ‘“‘ Head’ of Pressure, loss of’; ‘Hydraulic Memo- randa”’; ‘“ Hydrostatic Head”; “ Intake’; “Lateral Water Filtration”; ‘‘ Leaping Weirs”’; ‘Local Government Board Require- ments (water supply)”; ‘‘ London Water Supply”; ‘‘ Meteorology” ; “ Micro-organisms in Water”; “Ozone”; “Pipes, Cast-iron, &e.”; “Plumbing”; “ Pumps and Pumping Machinery”; “Rainfall”; ‘“ Rain-gauge’’; “* Rising Mains”; ‘“ River Boards”’; ‘‘ Rivers, Purification of”; “ ‘Separator’ for Rain Water”; “Siphon”; ‘‘ Stand-pipe and Air- vessel’; ‘“ Sterilisation of Water”; ‘Suction of Pumps”; ‘“ Typhoid”; ‘‘ Underground Water’; “Valves (water supply)”; ‘ Ven- turi Meter’; “‘ Water, Analysis of”; “‘ Water, Odours and Tastes”; ‘‘ Water Meters ” ; “Watershed”; “ Water, Sampling of”; “Water Supply (domestic) ”’; ‘ Water Supply, Royal Commissions-on”’; ‘‘ Wells.” W. H.M. Water Supply, Royal Commissions on. —During the past 40 years the question of water supply has been under consideration by a number of Royal Commissions, Select Committees, and others. ‘The following are the dates of the appointment of the various Commissions, and of their reports :—1866, Royal Commission on Water Supply: Chair- man, the Duke of Richmond, K.G.: reported 1869; 1868, Rivers Pollution Commission (replacing Commission issued in 1865): reported 1874; 1872, reports by Mr. William Pole, “‘On the Constant Service System of Water Supply”; 1879, Parliamentary ‘‘ Re- turn showing the means by which drinkable water is supplied to every Urban Sanitary District in England and Wales”; 1880, ENCYCLOPEDIA OF WAT Select Committee on London Water Supply ; 1884-5, Select Committee of House of Lords on Water Companies; 1892, Royal Commis- sion on Metropolitan Water Supply: Chair- man, Lord Balfour of Burleigh: reported 1898; 1897, Royal Commission on Water Supply within the Limits of the Metropolitan Water Companies: Chairman, Lord Llandaff: reported 1898 and 1899; 1900, Select Com- mittee on Local Authorities’ Reproductive Undertakings. The question has also been dealt with on several occasions in connection with Bills for the water supply of the Metropolis and other towns. Duxe or Ricumonp’s Commission, 1866.— The Commissioners were directed to ascertain what supply of unpolluted and wholesome water could be obtained by collection and storage in the high grounds of England and Wales, either by the aid of natural lakes or by artificial reservoirs, at a sufficient elevation for the supply of the large towns, and to inquire into the existing water supply to the Metropolis. They soon found that an inquiry into the supply of the provincial towns would be one of great magnitude and would pro- bably occupy several years. They therefore confined their attention almost exclusively to the more pressing question of the supply to London. After considering various proposals to bring water from Wales, the Lake District, and Derbyshire, they expressed the opinion that the water from the rivers Thames and Lea, together with that obtainable from the chalk and lower greensand, would suffice to supply any probable increase of the Metro- politan population ; that there was no evidence to lead to the belief that the water supplied by the companies was not generally good and wholesome; that its quality depended on perfect filtration ; and that artificial softening did not appear to be applicable to the Thames water. They expressed strong opinions in favour of the system of constant supply, and of the control of water undertakings by local authorities. Doubts are cast on the reliability of gravitation supplies to large towns from catchment reservoirs in hilly districts, and it 548 WAT is strongly recommended that no town or district should be allowed to appropriate a source of supply which naturally and geo- graphically belongs to another. This report was issued on 9th June, 1869. Rivers Pouuution Commissron, 1868.— Meanwhile the question of water supply was also being considered by the Rivers Pollution Commissioners, Dr. Edward Frankland and Mr. John Chalmers Morton, having been entrusted to the original Commissioners in an instruction dated 7th July, 1865. Their sixth and final report, issued 30th June, 1874, deals exclusively with this question, and constitutes a most valuable and exhaustive review both of the existing supplies and of the available sources throughout the country. The following is their classification of waters in order of merit :— 1. Spring water (5)... ..) Very 2. Deep well water (6) ..} palatable. 3. Upland surface water (2)) Moderately 4 5 . Stored rain water (1) .. palatable. Suspicious <5. Surface water from culti- 6. River water to which}Palatable. Dangerous Monette vated Jand (8).. sms sewage gains access (4) 7. Shallow well water (7) .. The numbers in brackets give the positions of the various waters in order of softness. Ex- cessive hardness is condemned, and, for waters possessing it, artificial softening is recom- mended. Soft and moderately hard waters are referred to as equally wholesome. The Commissioners state emphatically that no river in the United Kingdom is long enough to secure the oxidation of sewage which may be discharged into it, and that no process which had been proposed down to that time could be relied on to purify polluted water. The protection afforded by sand filtration against the propagation of epidemic diseases by water is characterised as “feeble.” The Commissioners therefore recommend the early abandonment of the Thames and Lea as sources of water for domestic purposes in the Metropolis, and the exclusive use of spring and deep-well waters from the London basin MUNICIPAL AND SANITARY ENGINEERING. WAT softened with lime. Whenever circumstances compel the taking of a water supply from a polluted river, storage reservoirs are recom- mended of sufficient capacity to render unnecessary the intake of water during floods. The water supplies of the Royal residences are specially reported on. Royan Commisston on Merropouitan WaTER Suprry, 1892.—Lord Balfour’s Commission reversed the finding of its predecessors recommending the abandonment of the Thames and Lea, and expressed a strong opinion that the water supplied to London was “of a very high standard of excellence and of purity, and ... suitable in quality for all household purposes.” With regard to the prejudice which exists against these waters on the ground of sewage pollution they observe: ‘‘ We do not believe that any danger exists of the spread of disease by the use of this water, provided that there is adequate storage, and that the water is sufficiently filtered before delivery to the consumers.” They were also of opinion that a sufficient supply for the wants of the Metropolis might be found within the valleys of the Thames and Lea for a long time to come. They recommended the exercise of all possible vigilance to prevent unnecessary contamination of these rivérs and their tribu- taries, the construction of adequate storage reservoirs, and the keeping of accurate observations on the effect of pumping from the chalk upon the water levels in the wells in that formation. Royvaa Commission oN Water Svuppiy WITHIN THE Limits oF THE METROPOLITAN Water Companies, 1897.—The first report of Lord Llandaff’s Commission dealt exclusively with the question of intercommunication between the systems of the different Metro- politan water companies. Their second and final report was of a more general character. In the latter they expressed a general ap- proval of the findings of Lord Balfour’s Commission as regards the suitability and adequacy of the existing sources of supply to London. They examined the proposals 549 WAT brought forward by the London County Council for obtaining a supply from Wales and dismissed it as costly and unnecessary. They expressed a strong opinion in favour of constituting a public authority to acquire and manage the undertakings of the London water companies, and outlined the constitu- tion of the suggested authority and the powers which should be entrusted to it. A. J. M. Water Supplies (Odours and Tastes in). —The causes of odours and tastes in water supplies and the methods of prevention have Free- Fic. 1.—Synura, magnified 500 dia. swimming colony of from 10 to 40 biciliated individuals. not generally received the full amount of attention the importance of the subject deserves. Many engineers in charge of the working of water supply systems are familiar with complaints from consumers in regard to smells from the water supplied, especially when heated, or in respect of unusual tastes occasionally noticeable in the same. Such complaints often occur at intermittent periods, and, in many cases, no proper explanation has been forthcoming owing to the difficulty of precisely identifying the true cause. Of recent years much light has been thrown upon the subject by a more systematic study of the microscopy of drinking waters, and it is now known that such odours and tastes are very frequently due to the periodic growth of ENCYCLOPEDIA OF WAT minute vegetable and animal life in the water at its source. These periodic odours and tastes are to be distinguished from those which constantly obtain in a water, and which may be due to its geological source or 1 § 4 yo ) V4 a0 Ae n AG mee a K % Q Uroglena, showing a single cell magnified 1,000 dia. the dissolved mineral constituents it contains— for example, as in the case of brackish, chaly- beate or mineral waters, such as those of Bath, Harrogate, and others. Chemically pure water is free from both odour and taste, but is not met with in nature. Many under- ground waters have either a saline or inky taste, and some a decidedly sulphurous odour, and gases may be given off in very perceptible quantities. Water from swampy ground or from thickly wooded catchment areas may yield a somewhat mouldy, woody, and unpleasant taste. Nearly all waters have some odour, though oftentimes it is too faint to be observed by the ordinary consumer. Roughly speaking, such odours may be due to the presence of organic matter other than living organisms, to the decomposition of organic 550 WAT matter, or to the growth of living organisms, both animal and vegetable, in the water. Odours derived from organic matter other than living organisms are in general of a vegetable origin, and are variously described by different observers as marshy, peaty, straw-like, woody, and such like. Heating the water generally intensifies the smell. When vegetable or animal matter in water begins to decay very unpleasant odours are sometimes produced. These are commonly described as mouldy, fishy, musty, and so forth. Of all the odours occurring in water supplies the most important are those due to the development of living organisms owing to their nature being oftentimes very offensive, and also to the fact that they frequently seriously affect large quantities of water, rendering it quite unsuited for public supply. In the writer’s experience the rapid development of the diatom asterionella in a large open storage reservoir, in which a mixed supply of spring and underground water was unavoidably stored, rendered a large body of otherwise excellent water totally unfit for public supply, and also proved to be so prolific that the surface of sand filter beds became effectually blocked with the diatoms in the course of about 8 days’ working. The surface film on the sand could then be rolled off like a carpet. Fic. 3.—Volvox, magnified 80 dia. Like most animals, different kinds of living organisms in water each have a natural characteristic smell, so much so, that experi- enced observers are able at once to identify the organism by the smell of the water. In MUNICIPAL AND SANITARY ENGINEERING. WAT a great many cases, and perhaps in all, the odour is due to the existence within the cells of the organism of minute oil globules, or compounds analogous to the essential oils, which are to be distinctly observed under Fic. 4.—Rivularia, magnified about 500 dia. suitable powers of the microscope. The oils are produced during the growth of the organism, are generally most numerous in mature forms, and oftentimes particularly so immediately preceding sporulation or encyst- ment. The odour is intensified by any process Fic. 5.—Anabena, magnified 500 dia. tending to break up the organism, such as mechanical agitation, increased pressure, pumping, or heating the water, as the “ oils” thereby become liberated and dispersed throughout the water. This natural odour of the oil globules of the organism, the 551 WAT production of which represents a kind of stor- ing up of energy, is to be clearly distinguished from the disagreeable odours produced by their decomposition. The organisms develop most luxuriantly in quiet reservoirs, ponds, or back- waters, and are oftentimes attached in great quantities to the vegetation contained in the reservoir. The odours commonly met with in water supplies are very variable and are difficult to describe. A few of those which are fairly well defined together with the organism causing them are :-— Description of Natural Odour. Organism Causing the Odour. Ripe cucumber odour with bitter taste .. bd Synura. Fishy and oily odour .. Uroglena. Fishy .. 2 Us .. | Volvox. Mouldy and like freshly cut grass .. 23 aH .. | Rivularia. Mouldy and_ grassy — like nasturtiums .. bg .. | Anabena. First aromatic—geraniums— and with larger numbers of organisms strongly fishy .. | Asterionella. A water may be odourless although contain- ing large numbers of organisms. Most of the organisms produce oil at some stage of their growth, but the oils in some cases may be odourless. The aromatic odours are mostly Fic. 6.—Asterione/la, magnified 500 dia. due to the diatomaceex, the strongest smell being that derived from asterionella above referred to. Uroglena gives a very unpleasant odour ; it is quite common, and water impreg- nated with this organism smells fishy and something like cod-liver oil. The fishy odours ENCYCLOPADIA OF WAT are generally produced by organisms belonging to the animal kingdom. The question naturally arises as to whether the drinking of water containing large quan- tities of living organisms is injurious to health. This is a matter which cannot be very defi- nitely answered, but from present information it is generally believed that such organisms are not injurious. At the same time, how- ever, if appears more than probable that a change from the drinking of pure water to the use of one highly charged with micro- scopic growths may at least give rise to tem- porary intestinal disorders, especially in the case of invalids and young children. The question of the removal of micro- organisms from large quantities of drinking waters is a matter of some difficulty, and, in many cases, of almost impossibility except by the slow operation of the ordinary processes of nature. Ordinary sand filtration is not always successful, as the odour-producing substances may sometimes pass through the filters unchanged. Also, large quantities of microscopic material rapidly accumulates by deposit and by increased growth upon the surface of the filter beds, causing prohibitive expense in cleansing the same. The best course to adopt, wherever possible, is to take steps to prevent the development of such growths by avoiding the conditions which have proved favourable to the multiplication of the organisms. For example, in the writer’s experience, the open storage of deep well or underground water together with surface or spring waters produces at certain periods very troublesome growths of asterionella which may seriously interrupt the entire town supply. This has been completely over- come by the installation of mechanical filters to deal direct with the underground water (which, in the case in point, contains iron in solution), and storing the top waters only in open reservoirs pending sand filtration in the ordinary way. W. H. M. Water-Wheels.— Water-wheels areseldom installed now, but so many remain in use and 552 WAT they are so well suited for driving pumps, without the intervention of gearing, that the main features of the various types may be shortly considered. These may be broadly classed as ‘“undershot,’’ “overshot,” and “* breast ’’—terms derived from the manner in which the water is applied to them. The undershot wheel is driven by the impulse of the water upon “floats” or paddles radiating from its circumference. Such wheels were originally placed in mid-stream with their floats dipping into it. An improvement con- sisted in damming the stream and providing a sluice at the bottom, through which the water issued and impinged upon the floats with a velocity proportionate to the“ head” behind the dam. By setting the floats at a tangent to the circumference better results were obtained, but the greatest advance was made by Poncelet, who curved the floats and wheel- race and thereby realised about 60 °/, of the theoretical power of the waterfall, and effi- ciency of twice that of the common undershot wheel. The “‘Poncelet” (which is strictly speaking a kind of ‘‘impulse” turbine) is a very suitable water-wheel for falls up to about 6 ft. In the overshot wheel the water is carried over the top by a ‘“ pentrough” from the open end of which it discharges into buckets placed around the circumference of the wheel. An overshot wheel thus acts entirely by gravity, the unbalanced weight of the water in the descending buckets causing @ preponderance on that side of the wheel and consequently its rotation. The chief sources of loss are due to the fact that the wheel, in order to clear the bottom of the pentrough and back-water in the tail race, must be less in diameter than the height of the fall, and also that the buckets are emptied before they have completed their descent. The highest efficiency obtainable is about 70 °/.. In the “pitchback’”’ wheel the diameter exceeds the height of the fall, and the pen- trough, instead of being taken over the wheel, discharges the water on to its shoulder ; the leverage at the commencement is, there- fore, more advantageous than with an MUNICIPAL AND SANITARY ENGINEERING. WEB overshot wheel, but the slight gain involves a larger and more expensive wheel. With the old form of breast wheel the water acts both by impulse and gravity. In construe- tion it differs from the undershot in not having wide open spaces between the floats on the circumference of the framing; in fact, the floats serve as buckets, the water being retained in them by the walls between which the wheel works and the concave “breasting’’ (of brickwork or masonry) embracing a portion of the periphery, until its escape into the tail race is permitted. It is now usual to fit buckets similar to those of an overshot wheel. The “hatch” or sluice by which the supply is regulated is now so arranged that the water flows over instead of under it as formerly; by this means every inch of “‘ head ”’ is utilised, and the water, act- ing entirely by gravity, is used to better advantage. Breast wheels may be classed as ‘“‘high”’ or “low,’’ according to whether the water is applied above or below the horizontal centre line of the wheel. Until the advent of the turbine, the breast wheel was the most efficient for utilising falls of moderate head. These conditions so often exist in this country that breast wheels have received a great deal of attention and have been brought to a high degree of efficiency. This varies from 55 °/, for the low breast up to 70°/,, and in some cases 75 °/,, for the high breast. The large size of a water-wheel in relation to the power developed renders the first cost high; this is also increased by the massive gearing neces- sary to impart the requisite speed to the machinery. Further they are seriously affected by floods, as the floats or buckets have to be driven through the back-water. (See “ Warer Power,” ‘‘ Tursines.’’) E. L. B. Webster’s Process of Sewage Purifica- tion by “ Electrolysis.—The precipitation of sewage by “‘ electrolysis” has been success- fully tried at Crossness, near the southern out- fall of the Metropolitan sewage. By this system 553 WEL the sewage is passed through channels between iron electrodes, whereby the chlorides are electrolysed and the sewage is deodorised by the chlorine and oxygen set free at the positive pole of the electrode, and the iron salts formed also assist in the purification of the sewage. It appears that the treatment produces a reduction in the oxidable matter in the sewage of from 60 to 80 °/,. A risk of a direct process such as electrolysis would seem to be that the effective action may be only local, and that sewage may pass between the electrodes without much purification. Wells and Well Supplies.— Wells of different kinds are named according to their depth, size, mode of sinking, and so forth, e.g., shallow wells, subsoil wells, dip-wells and draw-wells, deep wells, Abyssinian or tube wells, and artesian wells or borings. SHaLtow WELLS are those entirely contained in a superficial bed of gravel or sand, and fed by land soakage and surface springs, which may fail in dry weather. ‘I'he water is either dipped, raised by hand or by a suction pump. In the sixth report of the Rivers Pollution Commissioners, the shallow wells examined were under 50 ft. in depth, and the deep wells generally over 100 ft. deep; nevertheless, a well completely contained in a superficial stratum of sand or gravel may be actually deeper than a so-called “deep” well, which has pierced a regular geological stratum such as the chalk or new red sandstone. Deep well water is generally looked upon as one of the purest waters obtainable for public supply, except when containing mineral salts in objectionable quantities. The salts present will depend more upon the strata through which the water has percolated than upon its original source. Deep well waters often con- tain a large amount of iron and are frequently somewhat deficient in aération. In such a case the water should be discharged in a cascade over a bell-mouth pipe, or down a series of steps in order to effect a thorough aération, and so hasten the precipitation of the iron. It may also be treated for the ENCYCLOPADIA OF WEL removal of iron by means of the Candy oxidising pressure filters (see ‘‘ MEcHaNicaL Finrration ”’). Excellent deep well supplies have been obtained from the new red sand- stone by Birmingham, Liverpool, and many other towns, and from the chalk by Brighton, Margate, Eastbourne, and other places. Hastings obtains its deep well supplies from the Ashdown Sands, the water there being highly impregnated with iron. The chalk supplies are obtained by large wells some 10 or 12 ft. in diameter sunk in the chalk, and having “adits” or headings driven in different directions from the base of the well so as to intercept the water-bearing fissures and create a large reserve of under- ground storage. Derr Borines in the new red sandstone, Ashdown sands, and other strata are fre- quently drilled through the rock to consider- able depths by special boring machines, and are lined as sunk with lengths of steel tubing screwed together, the lower lengths of tubing having a large number of perforations for the admission of the water. Such wells are bored to almost any requisite depth, from 3 in. up to 30 in. in diameter, and the water is often tapped under an artesian head, as, for example, is the case with many borings within the London basin. When a deep boring is sunk through the London clay to the lower Tertiary sands or deeper into the underlying chalk, the water rises in the borehole, and, in some cases, even reaches the surface and overflows. The conditions under which such a circumstance arises will be apparent from an examination of Fig. 1, which is a geological section across the Thames basin, north to south, from the Chiltern Hills to the North Downs and Weald of Kent. Ifthe water is tapped in low-lying ground as at A in the figure, which is in the hollow of the London basin, it is necessarily much below the level of the outcrop of the water- bearing strata at Band C, and the water will consequently be forced up the boring to its rest-level approximating to that in the surrounding strata. In some districts the 554 WEL pressure of the underground water is such that it not only rises and overflows at the surface, but is forced into the air many feet, thus producing what is termed an “ Artesian well”’ (see “Artesian Wetts”). One of the most interesting of such wells is that at Bourn, in Lincolnshire, which supplies the town of Spalding. It was bored by C. Isler & Co., Southwark, in the Oolitic beds, and at the depth of 100 ft. it yielded a flow of 1,800 gallons per minute at a'pressure of 10 lbs. to the squareinch, reaching the ground surface with a rush. On sinking a further 34 ft. the flow was increased to 3,480 gallons per minute. In another boring (6 in. in diameter) by the same firm at 4 i xz 2 pe yo Sp cro iw MUNICIPAL AND SANITARY ENGINEERING. LONDON WEL lation of fresh supplies, to gradually deplete the storage of subterranean water. In England the most favourable strata for deep wells are the chalk, oolites, new red sandstone, and the lower greensand. The yield will depend on the extent of the under- ground reservoir, the area of the outcrop of the water-bearing strata, its porosity or degree to which it admits of percolation of rainfall, and other considerations (sce ‘‘ UNDERGROUND Warter’’). SHaLLtow Wetis.—In rural districts good water may oftentimes be obtained from a shallow well, provided the requisite precau- tions are taken in the construction to insure Fic. 1.—Geological Section across the Thames Basin from the Chiltern Hills to the Weald of Kent. Keighley, Yorkshire, sunk in the upper beds of the millstone grit, a supply of 15,000 gallons per hour was tapped, and the water rose to a height of 40 ft. above the surface. In the London basin the general rule is that in borings 400 ft. deep the water level is 100 to 200 ft. from the surface. The fountains in Trafalgar Square are supplied from an artesian well penetrating to a depth of about 390 ft. below the surface; and numerous private supplies to breweries and other manufacturing establishments, as well as part of the supplies of some of the London water under- takings, are derived from the chalk underlying London. The effect of continually drawing large supplies from borings of this description is to lower the general level of underground water, and, unless adequately fed by the downward perco- SEEN ESSENSE AE A protection from contamination and _ surface washings. The sides of such a well should be lined with brickwork set in cement, outside of which should be a thickness of impervious clay puddle extending downwards for about two- thirds of the depth of the well, or as circum- stances may require. The brick lining should 555 WEL also be carried up 2 or 8 ft. above the adjoining ground surface and fitted with a good cover, to prevent rubbish, animals, &c., from falling into the well. The ground around the well should also be paved with some impervious paving, as asphalte or concrete, and sloped away as shown in Fig. 2, so that no top soakage may gain access. For drawing the water a pump is much to be preferred to the old-fashioned bucket and windlass, as the well can be kept permanently covered SS { 'y fF eS eases a 1 ae D ress 1 ! ings sof Safa" | SECTION ' ' 1 1 1 1 I 1 ' 1 t | eee Wee: fe et fe ' / { ! x ' ( 7 \ | \ LP eee if \ ‘ . \ ' ‘I | / “I \ uv Well M \ 4B C4 tee @—--+2_---Z}_ PLan \ \ / ' ‘ Sy ge I : ‘NS 7 / Ra ae et ay - ‘ Ss, x XN N ’ ‘ , i showing e.xctent of influence of pumping for a depression AB in the well Fie. 3. and the water is not disturbed and exposed to pollution to the same extent. In spite of precautions, however, all wells may at times become polluted if situate near cesspools or other accumulations of filth. Much depends on the direction of flow of the ground water. If this becomes polluted by leakage from adefective cesspool or drain and the ground water flows in the direction of a well, the water therein will naturally acquire dangerous properties, and in this way the germs of typhoid, for example, may be conveyed from cesspool to well, and the disease thus rapidly spread throughout the area supplied from this source. ENCYCLOPADIA OF WHI Numerous cases of this kind have been met with in practice. The risks of such pollution are always greatest after heavy rainfalls, when the level of the ground water is high and more likely to be brought into immediate contact with leakage from cesspools, &c. Pumping from a well draws down the level of the underground water around the site of the well somewhat in the manner illustrated in Fig. 8, where A B is assumed to be the extent of the depression from ‘“‘rest level.” This influence is communicated in all direc- tions from the site, and the slope of the lines of depression BC E and BDE will depend largely upon the porosity or permeability of the surrounding strata. The distances from which underground water is thus drawn often extend to many miles radius, and are expressed in terms of the depression. In chalk the dis- tance may amount to 57 times the depression of the water level in the well, and in coarse gravel the distance affected is as much as 160 times the depression. Very much will depend, however, on the nature of the strata in any individual case. (For further information see also articles “‘ ARTESIAN WELLS,” ‘‘ ABYSSINIAN Wetus,” “ Warer Suprpry,’’ and ‘ UnpsR- GROUND WaTER.’’) W. H. M. White Lead.—This is hydrocarbonate of lead made by exposing metallic lead to the fumes of carbonic acid gas and acetic acid. The ancient “stack ’’ process is usually recog- nised as yielding the best results, notwith- standing all attempts at improvement. The metallic lead is cast in the form of wickets not unlike a miniature gate in shape. Pots con- taining acetic acid are arranged close together on a platform covered with spent tan, and these wickets are strewn indiscriminately upon the pots. A second platform is built imme- diately above, and upon it the pots and wickets are placed, and so on until the top of the chamber is reached. The chamber is then closed in so that the fumes cannot escape, and after a period of three months the metal wickets are converted into a white lead. These are then taken out, passed through mills, 556 WHI washed, ground and dried, and finally again ground in oil, when the white lead is ready for painters’ use. English white lead is probably the best in the world. There is a good deal of white lead made abroad coarsely ground and brought to this country and ground here and then sold as ‘English manufacture.” In specifying white lead it is advisable, therefore, . to state that it is to be “ English corroded.” Adulterated white lead is either marked “reduced,” or No. 1, No. 2, &c. Pure lead is always marked ‘“ Genuine,” and if contained in an unbroken package one may be reason- ably sure the contents are as represented. Whittaker & Bryant Filter—The Whittaker & Bryant “thermal aérobic filter ’’ was introduced at Accrington in 1898. Septic tank liquor was distributed over a filter consisting of 1 ft. of limestone chippings at the top, 6 ft. of gas coke, and 2 ft. broken stone by means of a revolving distributor. A distinctive feature of the system consists in the use of a steam pipe in the delivery of the sprinkler. A small jet of steam is injected into the sewage as it arrives at the distributor with the object of raising the temperature of the sewage and filter generally to a suitable degree for rapid bacterial action. The arti- ficial heatis also intended to induce air currents through the filter and thus create better aération. Filters of this description have also been successfully tried at Leeds. Wind Force.—The force of the wind is usually estimated without instruments accord- ing to Admiral Beaufort’s scale. This scale, with the generally accepted equivalent velocity in miles per hour, is as follows :— Scale. Description of Wind. Equivalent Velocity. O Calm. O miles per hour 1 Light air 1—3 _,, 5 2 Light breeze AF 55 is 3 Gentle ,, 8—12 _,, i. 4 Moderate,, 18—18 ,, ‘ 5 Fresh ,, 19—24 ,, 5 6 Strong ,, 25—81 ,, a 7 Moderate gale 32—38 ,, +5 MUNICIPAL AND SANITARY ENGINEERING. WIN Scale. Description of Wind. Equivalent Velocity. 8 Fresh gale 39—46 miles per hour 9 Strong ,, 47— 54 ,, 3 10 Whole ,, 55—63 _,, i 11 Storm 64—75 ,, 5% 12 Hurricane above75_,, es The best instrument for recording the force of the wind is Dines’ Pressure-tube Anemometer. In this advantage is taken of the fact that the air, in blowing over an obstacle, produces small differences of pressure on various sides of the obstacle, which are capable of exact measurement, and afford information of the velocity of the wind. The “‘ head”’ consists of a piece of tube open at one end, which end is kept facing the wind by a vane. The wind blowing into the tube produces an excess of pressure within it. There is also a piece of tube placed vertically and pierced by a ring of small holes. The wind blowing over these holes produces a slight decrease of pressure inside. These differences of pressure are com- municated by composition tubing, which may be of any length, to the place where the recording part of the instrument is placed. The registration is produced by means of a bell-shaped vessel which floats inverted in water in a closedchamber. ‘The pressure tube, i.c., the tube coming from the “head” in which there is an excess of pressure, opens above the water-level inside the inverted floating vessel, and the other tube, i.e., that in which there is a decrease of pressure, com- municates with the sealed chamber. Very trifling differences of pressure are sufficient to alter the level at which the inverted vessel floats, and a pen rigidly attached to the vessel makes a continuous record on a clock drum in the usual way. The charts are arranged to give both the wind velocity in miles per hour and the wind pressure in pounds per square foot. In the Osler Anemometer the pressure of the wind in pounds per square foot is recorded by its action on a circular plate mounted on spiral springs and kept facing the wind by the vane. During gales the wind attains a high velocity, the greatest recorded in 1 hour being between 77 and 80 miles at 557 WIN Fleetwood. In gusts, however, the velocity of the wind may momentarily exceed the rate of 100 miles an hour. W. M. Wind Motors. —Although the familiar four-armed windmill is becoming a thing of the past, employment of the wind as a motive power for pumping, &c., is extending. At exposed sites in this country, a wind of not less than 15 miles an hour may generally be expected to prevail for about one-third of the year, whilst for about half the year it will be 10 miles and over; but it is often below the latter velocity for from 8 to 5 days, and occasionally a week. These points, how- ever, can only be satisfactorily elucidated by local observations. Wind engines, when lightly loaded, will run with a breeze of less than 10 mailes an hour, but as the power of wind varies as the cube of its velocity, their performance would be exceedingly small. For the same reason the great increase of power due to winds of a higher velocity than about 20 miles an hour has usually to be run to waste. The modern wind engine has, relatively, more than twice as much sail area as a four-armed windmill, but it only runs at about half the speed, so that the surface is used to less advantage. Owing, however, to its low speed, the vanes of a wind wheel may be set at a much greater angle with the plane of its revolution, and this, coupled with the large sail area, gives it a much higher starting “torque,” and enables it to work in lighter winds than would suffice for the old-fashioned mill. In a good breeze, the power of either type, diameter for diameter, is much the same. The proportions of four-armed wind- mills vary considerably, but the following represents good practice. The breadth of the sweep is usually about one-fifth of its radius, which is commonly from 80 ft. to 40 ft.; the sail surface, in the direction of its length, is generally divided in the proportion of three to one by the “whip” or radial arm, the narrow portion moving foremost. The “ weather’? angle of the inner end of the wide part varies from 20° to 25° with the ENCYCLOPADIA OF ZIN plane of motion according to the length of the sail; in some cases the angle gradually diminishes until it becomes about 7° at the outer extremity, but with cloth sails, to avoid flapping (and often with shuttered sweeps), the tip is made to coincide with the plane of motion. In this case tha sail rapidly hollows inwards from the tip in order that an effective angle may be reached as soon as possible. The “lead,” or narrow portion of the sail, usually preserves throughout its length the same angle as the inner end of the sail. The best tip speed is about two-and- a-half times that of the wind, and in a 15 mile wind each 75 ft. of sail surface should give about 1 h.p. actual, and assuming that the speed ratio of the sails to the wind may remain constant, the power will increase nearly as the cube of the wind velocity. The wind wheel has its vanes arranged in an annulus, and their combined area is generally from 60 to 70 °/, of the total disc surface. The weather angle of the vanes varies from 30° to 40°, and is often uniform throughout their length. To produce 1 h.p. in a 15 mile wind from 110 ft. to 130 ft. of sail surface is required according to the design and size of the mill—the larger sizes being less efficient. The usual method of speed control is to allow the wheel to turn more or less obliquely to the wind according to its pressure; this is accomplished by a hinged rudder or tail vane which is maintained at right angles to the plane of the wheel by a weighted lever or spring. The axis of the wheel is parallel to, but not in line with, the rudder, so that, but for the action of the weighted lever, the wheel would throw out of the wind. Large wheels are usually regulated by altering the weather- ing of the vanes, automatically or otherwise, which are hinged for that purpose. (See “ ANEMOMETER.’’) E. L. B. Zinc.—Zinc is one of the metallic chemical elements, found to a limited extent in England as zine sulphide, called ‘zine blende” or “black jack.’ The metal is usually extracted by the Belgian process as follows: — The 558 ZIN mixed ore and coal are put into fireclay cylinders of about 8 in. diameter and 3 ft. long, closed at one end; from 40 to 80 of these cylinders are ranged in a furnace like gas retorts. The carbon of the coal unites with the oxide of the zinc and escapes as carbonic oxide, leaving the metallic zine to come off as a dense vapour. This is con- densed in cast-iron conical tubes, from which it is raked out into a large iron ladle; the zine is then skimmed from the dross and cast into ingots of 70 lbs. to 80 lbs. each. Zine is pliable and moderately soft ; at a temperature of 200° to 250° F. it is rendered malleable, and may be rolled into thin sheets. For this purpose the crude ingots are re-melted and cast into purer ingots of convenient size for rolling and passed between cast-iron rolls. Sheet zinc is extensively employed for cheap gutters, small rain-water pipes, lining wood cisterns, and covering flat roofs. It resists the action of pure air and moisture, but the air of towns, being heavily charged with acids, acts freely upon it and destroys it rapidly. It has one serious defect for roofs, a3 it blazes fiercely under the action of fire. Zine, although supposed to be very light, weighs the same as cast iron—a square foot 1 in. thick weighs 374 lbs. There is a zinc gauge differ- ing from the standard gauge, and still some- times used: No. 12 Z.G., °025 in. thick, is used for flashings ; No. 14, ‘031 in. thick, for dormers and flats; No. 16, :041 in. thick, for gutters. Zine when alloyed with twice its weight of copper forms yellow brass, but zine enters into the composition of many alloys in the bronze series as well as the brass series. The terms ‘“‘ higher ’’ and “ lower” applied to brass express the greater or less quantity of zine in the composition. The effect of zinc in an alloy in small quantity is to increase the fusibility without reducing the hardness, in larger quantity it increases the malleability when cold, but entirely prevents forging when hot; 1 to 2°/, of zine enables sounder cast- ings to bemade. Zinc is brittle when cold, and again at 400° F., but it is malleable at 212° F. Galvanised iron is sheet iron, corrugated MUNICIPAL AND SANITARY ENGINEERING. ; ZYM or plain, coated with zinc by immersing it, when thoroughly cleansed, into a bath of melted zine covered with powdered sal ammoniac. Galvanised iron forms a cheap covering for the sides and roofs of sheds, and is very largely used in new countries. The sheets are 6 or 8 ft. long, 8 ft. 2 in. wide before corrugation, 2 ft. 6 in. wide with 5 in. corrugations, and the depth of corrugation is a quarter of the width. It is laid with 6 in. laps when on the slope, 3 in. when vertical. No. 16 standard gauge .is the thickness used where great strength is required, 17 to 19 for first-class work generally, 20 to 22 for ordinary work, 23 to 26 with 3 in. flutes for shipping abroad. Hi. A. Zine Oxide (known as Zine White).—A valuable pigment used in paint. It owes its increasing use to the fact that it is non-toxic and is not susceptible to the influence of sulphur compounds, as white lead is. It isa pure white, is very durable, and has a large covering d¢apacity when ground in oil. (See “ Pants AND PaINTING.’’) Zones of Supply.—A term used to indicate different levels or areas of pressure in the distribution of water. In districts of a very undulating character it sometimes becomes necessary to limit the water pressures in the supply mains in the lower parts of the town and at the same time to adopt means of augmenting those in the more elevated areas, thus creating “‘ zones of pressure or supply,” each being adjusted to the requirements of the portion of the district served. (See “ Warr Suppty.”’) Zymotic Diseases.—After Pasteur’s dis- covery of the anthrax bacillus, and his demonstration that it was the specific cause. of anthrax in man and animals, bacteriologists directed attention to certain other diseases, and it has since been ascertained that many of these are due to the infection of the system by micro-organisms. There are still others so elosely allied in character to those known to 559 ZYM be caused by bacteria that there can be little doubt that they are due to a similar cause, but as yet the specific germ has not been discovered. Originally all such diseases were termed ‘‘zymotic,” but of recent years there has been a tendency to abandon the term altogether or to restrict its use to the more acute specific fevers. The zymotic death-rate is still recorded by medical officers of health, and signifies the annual number of deaths per 1,000 population from the seven principal zymotic diseases, which are small-pox, diph- theria, scarlet fever, measles, whooping cough, typhoid (gq. v.), and allied fevers and epidemic diarrhea. Other zymotic diseases are cholera (¢. v.), influenza, plague, cerebro-spinal fever, German measles, mumps, erysipelas, yellow fever, tetanus, glanders, syphilis, gonorrhea, leprosy, pneumonia, and tuberculosis. There are many others, such as rheumatic fever, which are almost certainly due to infec- tion by micro-organisms, though absolute proofs are yet wanting. Certain of these diseases are notifiable. The Infectious Disease (Notification) Act, 1889, imposes an obligation upon medical men to notify to the local medical officer of health certain cases of infectious disease which occur in his practice as soon as he becomes aware that the patient is suffering from such disease. The diseases so notifiable are scarlet fever, diphtheria, small- pox, cholera, fevers (typhoid, typhus, continued and puerperal), and erysipelas; but measles, chicken-pox, phthisis, and other diseases may be scheduled by a local authority after certain formalities and with the consent of the Local Government Board. It is now fully recog- nised that these diseases are not caused by insanitary conditions. Such conditions greatly predispose persons living within their sphere of influence to attack, by reducing the vitality or disease-resisting power of the system, but unless the specific germ of a disease is present and in some way gains an entrance into the system that disease will not supervene. Where filth is prevalent, where overcrowding abounds, and especially where these are ENCYCLOPEDIA OF ZYM associated with poverty, the possibility of the germs of disease gaining access to the system is enormously increased, and it is the preva- lence of zymotic diseases under such condi- tions that has led many to conclude that they are the only condition necessary for the causation of certain fevers. The subjoined table gives the death-rates per 1,000 popula- tion from all causes and from the principal zymotic diseases, including phthisis, for the last three completed decennia :— 1861-70. | 1871-81. | 1881-91. |1891-1900. All causes 22:4 | 21°38 | 19.1 18°2 Small-pox 16 | = °23 04 “006 Measles “44 39 44 41 Scarlet fever .. “98 “72 83 16 Diphtheria ae 18 12 16 26 Whooping cough ... 53 ‘51 °45 88 Fevers re Hs 88 ‘48 24 25 Typhoid fever — 82 ‘20 ‘17 Diarrhceal diseases .. 1:06 94 67 ‘73 Phthisis 2°5 2:1 14 It will be observed that measles and diph- theria show no signs of decreasing ; obviously, therefore, sanitary improvements have had no influence upon them, or if there has been any effect it is so masked by the other factors, such as enforced school attendance, as to be unrecognisable. The decreased prevalence of small-pox is chiefly attributable to the con- tinued practice of vaccination. Scarlet fever mortality has decreased so rapidly and steadily that we might conclude improved sanitary conditions and the provision of isolation hospitals have had a most marked effect, but there are reasons for doubting whether such is the case. The type of the disease has been undergoing a continuous diminution in viru- lency, so that, although as many cases occur as heretofore, the mortality has fallenenormously. It is possible, however, that the more clean con- ditions which obtain and the isolation of the more severe cases have had a share in diminishing the virulency. That fevers have decreased to one-fourth is due to the greater attention paid to supplies of milk, water, and articles of food, to the diminution of 560 ZYM overcrowding, the demolition of slums, and the erection of workmen’s dwellings, and to im- proved methods of sewerage and drainage. The reduction in the death-rate from diarrhoeal diseases may be due to the same causes, but as very young children are the chief sufferers, and the mortality varies very largely from year to year according to the earth-temperature in the autumn, itis obvious that there are conditions, of which we are as yet ignorant, which influence the mortality from these diseases. The cause of the great and continuous decrease in the mortality from phthisis is one of the enigmas of public health. The drying of the subsoil by the sewerage of towns, the prevention of damp in houses by enforcing proper building by-laws, are possibly important factors. Small-pox, measles, scarlet fever, diphtheria, whooping cough, and typhus fever are diseases which are spread by the inhalation of the breath of infected persons and by the inhalation of minute particles of sputum discharged by infected persons when coughing. The infec- tion of typhus fever and small-pox also appears to be capable of being given off from the skin. Obviously, therefore, there is less danger of these diseases being disseminated in roomy and well ventilated houses than in small badly ventilated and overcrowded dwellings. Outbreaks of scarlet fever, typhoid fever, and diphtheria have frequently been traced to milk, though how the milk became infected has not always been discovered. Generally, however, it has been found that some person suffering from one of these diseases has been employed in the cowsheds or dairy from which the implicated milk was derived. M.S.E. MUNICIPAL AND SANITARY ENGINEERING. 561 ZYM Typhoid fever and cholera are chiefly water- borne diseases, but any article of food may become infected, and convey the diseases. The germs of these diseases are chiefly voided in the stools, and in typhoid fever the patient’s urine often swarms with the specific bacteria. Hence the great danger arising from the use of privies and pail closets, of water-closets without proper flushing apparatus, from accumulation of house refuse and from defec- tive paving around yard gullies. Infection under such circumstances may easily be conveyed by flies or by wind to exposed articles of food, and spread of the disease results. It is fortunate for the human race that the mere presence of a few of these germs in the system rarely suffices to set up disease, otherwise man would have been exterminated long ago. The blood possesses certain germicidal powers, and when vitality is unimpaired, germs entering the system, if not in excessive number, may be destroyed. Where it is necessary for the microbes to gain access to the blood stream before they can produce any evil effects it is quite possible for them to pass through the alimentary canal and fail to enter the system. The blood also possesses to some extent the power of destroying the toxins or poisonous bodies formed during the growth of disease-producing bacteria. These properties explain why, when large numbers of persons partake of specifically infected water or milk, only a small propor- tion, as a rule, are actually attacked by disease. (Vide ‘‘Gurms or Diszass.’’) J.C. T, 00 A LIST OF BOOKS ON Sewerage and Sewage Disposal. ADAMS, JULIUS W. Sewers and Drains for Populous Districts with Rules and Formulas for the Determination of their Dimensions under All Circumstances. Ninth Edition. Mlustrated. 8vo., cloth, 236 pp: New Yorks. 1902.0. sscig ce sages de see ecaan teermtnn ease $2.50 BAKER, M. N. British Sewage Works and Notes on the Sewage Farms of Paris and on Two German Works. 8vo., cloth, 150 pp. New SEO DOA ce cocaine cae ec reagan tn alegre inne i $2.00 Sewerage and Sewage Purification. Fourth Edition, revised and enlarged. 16mo., boards, 161 pp. (Van Nostrand Science Series No. 18.) New York, 1907... 0.0.0.2... . cee e cece e eee 50 cents BARWISE, SIDNEY. The Purification of Sewage. Beinga Brief Account of the Scientific Principles of Sewage Purification and Their Appli- cation. Second Edition, revised. Illustrated. 8vo., cloth, 220 pp. NeW YOrk, L904 Sic sscieansinn in Re tac inant pum macinmie bach ay Net, $3.50 DIBDIN, W. J. The Purification of Sewage and Water. Third Edition, revised and enlarged. Illustrated. 8vo., cloth, 415 pp. New WOODS LQG cee ic deca dalanas ial beg: dushe aheaa paar uae ORE Syren dona Deneraeacaaaa $6.50 DUNBAR, Dr. Principles of Sewage Treatment. Translated by H. T. Calvert, 147 Illustrations. 8vo., cloth, 304 pp. London FOLWELL, A. PRESCOTT. The Designing, Construction, and Mainte- nance of Sewerage Systems. J ifth Edition, revised and enlarged. Illustrated. 8vo., cloth, 469 pp. New York, 1908........ $3.00 FOWLER, GILBERT J. Sewage Works Analysis. Illustrated. 12mo., cloth, 148 pp. New York, 1902............. ese eee eee $2.00, GERHARD, W. P. The Disposal of Household Wastes. Second Edition: Illustrated. 16mo., boards, 195 pp. (Van Nostrand Science Series No. 97.) New York, 1904.................000-- 50 cents —— The Sanitation, Water Supply, and Sewage Disposal of Country Heuses. Illustrated. 12mo., cloth, 346 pp. New York VQOD ssisnanice x Sachs Scares esd a a nrc orlarecarseins eta i tielav snags 9.404 Net, $2.00 MARTIN, ARTHUR J. TheSewage Problem: A Review of the Evidence Collected by the Royal Commission on Sewage Disposal. 12mo., cloth, 379 pp. London,1905................0 202s Net, $3.50 MERRIMAN, M. Elements of Sanitary Engineering. Third Edition, re- vised. and enlarged. Illustrated. 8vo., cloth, 250 pp. New MOrk 1906s cisicsciaa ais ee wed zie ss ete Oiaie Gitta dea wesw Net, $2.00 MOORE, E. C. S. and SILCOCK, E. J. Sanitary Engineering. Third Edition, revised and rewritten. Two volumes. 920 illustrations. 8vo., cloth, 900 pp Philadelphia, 1910.............. Net $14.00 OGDEN, H. N. Sewer Construction. 192 Illustrations. 8vo., cloth, 347 pp. New York, 1908; ..ccsccceccse terse vedesecen es $3.00 Sewer Design. 54 Illustrations. 5 Plates. 12mo., cloth, 245 pp. a New: VOrk; 1907026 ue coc cease asl ay hen RaNe eyes $2.00 RAFTER, GEORGE W. The Treatment of Septic Sewage. Second Edition. 16mo., boards, 140 pp. (Van Nostrand Science Series No. 118.) New. York? 1907230 ccisadaadaecaa me teiae sae ens eee ee 50 cents RAFTER, G. W., and BAKER, M. N. Sewage Disposal in the United States. 116 Illustrations. 8vo., cloth, 598 pp. New York. .$6.00 RAIKES, HUGH P. The Design, Construction, and Maintenance of Sew- age Disposal Works. Being a Practical Guide to Modern Methods of Sewage Purification. 72 Illustrations. 8vo., cloth, 430 pp. New Yorks, 1908%....3 pete ccucscceais ccs tinned wat Saas ema Net, $4.00 RIDEAL, SAMUEL. Sewage and Bacterial Purification of Sewage. Third Edition, enlarged. 58 Illustrations. 8vo., cloth, 367 pp. New York, 1907. cscs da'sc maedv gina aids Wane Valeo Sa Gea $4.00 SCOBLE, HERBERT T. Land Treatment of Sewage: A Digest of the Reports made to the Royal Commission on Sewage Disposal by their Specially-appointed Officers. 4to., cloth, 80 pp. London and; New York, 1908 )0. edis aa eviedonanepecciievrna wae dare etd es $2.00 SLATER, J. W. Sewage Treatment, Purification and Utilization. Illus- "trated. 8vo., cloth, 270 pp. London, 1897............... $2.25 STALEY, C., and PIERSON, G. S. The Separate System of Sewerage: Its Theory and Construction. Third Edition, revised and enlarged, with a chapter on Sewage Disposal. Illustrated. 8vo., cloth, 336 pp. New Work 18 99 soa, «shag sauce caus emer nud bate Hoanneanemuers $3.00 THUDICHUM, G. Simple Methods of Testing Sewage Effluents for Works Managers, Surveyors, and Others. 16mo., cloth, 60 pp. London, T9086 decreed rssh sane aeaantaish as eeaae NEw «lend nace Jadubaaai Said Net, $1.00 VENABLE, W. M. Methods and Devices for Bacterial Treatment of Sew- age. 43 Illustrations. 8vo., cloth, 242pp. New York, 1908. .$3.00 VERNON-HARCOURT, L. F. Sanitary Engineering with Respect to Water Supply and Sewage Disposal. 287 Illustrations. 8vo., cloth, 419 pp. New York, 1907................ Memman Aoianwew alae $4.50 WANKLYN, J. A., and COOPER, W. J. Sewage ‘Analysis. A Practical Treatise on the Examination of Sewage and the Effluents from Sew- age. Illustrated. 12mo., cloth, 230 pp. London, 1899. . Net, $2.00 WARING, GEO. E. Modern Methods of Sewage Disposal for Towns, Pub- lic Institutions and Isolated Houses. Third Edition. Illustrated. 12mo., cloth, 259 pp. New York, 1903......--..--.----- $2.00 ——— Sewage and Land Drainage. fourth Edition. Illustrated. 4to., cloth, 400 pp. New York....... 00... ce eee eee eens $6.00 Any book in this list will be sent postpaid to any part of the world on receipt of price, by D. Van Nostrand Company, Publishers and Booksellers, 23 Murray and 27 Warren Streets, NEW YORK. Fifteenth Edition, Revised, Enlarged and New Tables and illustratisns added, J Vol., octavo, 644 pp., 200 Illustrations, fine Cloth binding, $5.00 A PRACTICAL TREATISE ON Hydraulic and Water-Supply Engineering: RELATING TO Hydrology, Hydrodynamics, and to the Practical Construction of Water-Works, in North America. WITH NUMEROUS Tables and Illustrations. BY J. T. FANNING, C. E., MEMBER OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS. CONTENTS. SECTION I.—Collection and Storage of Water, and its Impurities. Chapter I.—Introductory, Chap. II.—Quantity of Water Required. Chap, Ill.—Rainfall. Chap. IV.—Flow of Streams. Chap. V.—Storage and Evaporation of Water. Chap. VI.— Supplying Capacity of Watersheds. Chap. VII.—Springs and Wells. Chap. VII.—Impurities of Water. Chap. [X.— Well, Spring, Lake, and River Supplies. SECTION II.—Flow of Water through Sluices, Pipes, and Channels. Chap. X.— Weight, Pressure, and Motion of Water. Chap. XI—Flow of Water through Orifices. Chap. XII.—Flow of Water through Short Tubes. Chap. XII.—Flow of Water through Pipes under Pressure. Chap. XIV.—Measuring Weirs and Weir Guaging. Chap. XV.— Flow of Water in Open Channels, SECTION III.—Practical Construction of Water-Works, Chap. XVI.—Reservoir Embankments and Chambers. Chap. XVII.—Open Canals, Chap. XVII.—Waste Weirs. Chap. XIX.—Partitions and Retaining Walls. Chap. XX.—Masonry Conduits. Chap, XXI.—Mains and Distribution Pipes. Chap. XXII.—Distribution Systems, and Appendages. Chap. XXIII.—Clarification of Water. Chap. XXIV.—Pumping of Water Chap. XXV.—Tank Stand Pipes. Chap. XXVI.—Systems of Water Supply. Appendix.— Miscellaneous Memoranda. INDEX. , ~D. VAN NOSTRAND COPIPANY, Publishers and Booksellers, 23 MURRAY AND 27 WARREN STREETS, NEW YORK. eel — === IMPORTANT NEW BOOK ——= 6x9 In. Cloth 429 Pages 72 Illustrations $4.00 Net ———) SewaceE DisposaL Works By HUGH P. RAIKES Assoc. [. Am. S. C. E., Assoc. [1. I. C. E. Contents Alternative Methods of Treatment and Preliminary Considera- tions Affecting the Design and Construction of Works. Diffusion in Tidal Waters. Irrigation and Land Filtration. Removal of Matters in Suspension by Screening and Treatment in Tanks. Chemical Precipitants and the Disposal of Sewage Sludge. Filtering Media for Bacteria Beds. Contact Beds and their Operation. Percolating Filters, Alternative Methods of Construction and Working. Distri- bution over Percolating Filters. The Separation and Disposal of Storm Water. Purification of Trade Wastes. Maintenance and Management of Sewage Disposal Works. Index. N view of the fact that many millions of dollars are spent annually on Sewage Disposal Works, it is obviously a matter of the greatest importance, in the interests both of economy and of public health, that those who are entrusted with the design and construction of such works, or with the expenditure of public money upon them, should not only clearly understand the essential principles involved, but should also have at their disposal the latest results of contemporary experience to guide them in the practical application of those principles. Although the chemical‘and biological aspects of Sewage Disposal have been very fully dealt with by a number of whriters, there is no up-to-date book from which equally full and reliable information can be obtained regarding the more practical side of the question, considered from the point of view of the engineer. In attempting to make good this deficiency, the author of the present book has presented an impartial review of the modem methods of sewage purification, on the practical application of which he has been engaged for the past fifteen years. We can, without hesitation, highly recommend this book to all engineers interested in this important and timely subject. D. VAN NOSTRAND COMPANY PUBLISHERS AND BOOKSELLERS 23 Murray and 27 Warren Streets : NEW YORK o 5 THIRD EDITION Revised and Enlarged a 8 Wo. Cloth, Illustrated. 379 Pages. Price, $6.50 PURIFICATION SEWAGE AND WATER W. J. DIBDIN, F.I.C., F. C- S. CONTENTS Preface. Introduction. Chapter 1I.—General Considerations. Chapter II.—Antiseptics, or Preservation for Limited Periods. Bacter- jological Methods. Chapter III.—Precipitation. Chapter IV.—Experi- ments at Massachusetts and London, Chapter V.—Sutton Experi- ments. Chapter VI.—The Septic Tank and Other Systems. Chapter VII.—Land Treatment Versus Bacteria Beds. Chapter VIII.—Manches- ter Experiments. Chapter IX._Leeds Experiments. Chapter X.—The Bacterial Treatment of Factory Refuse. Chapter XI —Screening. Chapter XII.—The Purification of the Thames. Chapter XIII.—The Discharge of Sewage into Sea-Water. Chapter XIV.—The Filtration of Potable Water. Chapter XV.—Systematic Examination of Potable Water. Chapter XVI.—The Character of the London Water Supply. Chapter XVII.—The Action of Soft Water upon Lead. Chapter XVII.—The Absorption of Atmospheric Oxygen by Water. Chapter XIX.—Analyses and their Interpretation. Chapter XX.—Ventilation and Deodorisation of Sewers. Chapter XX!I.—The Royal Commission on Sewage Disposal. Appendix I.—Examination for Matters in Supension. Appendix II.—Dissolved Oxygen. Index.—List of Illus- trations, Diagrams and Tables. —— D. VAN NOSTRAND COMPANY, Publishers and Booksellers. 23 MURRAY AND 27 WARREN STREET, NEW YORK. Seoond Edition, Revised and Enlarged. 8vo., Clotn. 220 pp., with numerous Illustrations and Diagrams. Price $3.50 Net. THE PURIFIGATION OF SEWAGE BEING A Brief Account of the Scientific Principles of Sewage Purification and their Practical Application BY SIDNEY BARWISE, M. D. (Lond.) B. Sc. M.R.C.S., D.P.H. (Cams.) Fellow of the Sanitary Institute, Medical Officer of Health, Derbyshire County Council, With an Appendix on the Analysis of Sewage and Sewage Eifiluents, CONTENTS. CHAPTER I.—Sewage; Its Nature and Composition. CHAP. II1.—The Chemistry of Sewage. CHAP. IIl,—Varieties of Sewage and the Changes it Undergoes. CHAP. IV.—River Pollution and its Effects. CHAP. V.—The Land Treatment of Sewage. CHAP. VI.—Precipitation, Precipitants, and Tanks. CHAP. VII—The Liquefaction of Sewage. CHAP. VIII.—Principles Involved on the Oxidation of Sewage. CHAP. IX.—Artificial Processes of Purification. CHAP. X.—Automatic Distributors and Special Filters. CHAP, XI.—Conelusion. APPENDIX. ON THE ANALYSIS OF SEWAGE AND SEWAGE EFFLUENTS, Cuap,. 1.— The Apparatus Required for Sewage Analysis. Cuap. Il.—Standard Solutions Used in and Methods of Sewage Analysis. INDEX. D. Van Nostrand Company Publishers and Booksellers 23 Murray and 27 Warren Streets New York WORKS BY WM, PAUL GERHARD, 6. E, HOUSE DRAINAGE AND SANITARY PLUMBING. ‘Twelfth Edition, 1908. Illustrated. 231 pages. 18mo. Price, bound in boards, 50 cents. (Science Series No. 63). * Eminently practical and comprehends more valuable information on the _ subject than we have seen in any other work of the same size.”—Journal of the Franklin Institute. “Tt is one of the best summaries of house drainage and sanitary plumbing hitherto published." — The Sanitarian. RECENT PRACTICE IN THE SANITARY DRAINAGE OF BUILDINGS. Second Edition, 1890. 175 pages. 18mo. Price bound in boards, 50 cents. (Science Series No. 93.) Forms Supplement to No, 63. Contains Maxims of Plumbing and House Drainage, a Complete Plumbing Specification, also Memoranda on the Cost of Plumbing Work and Sugges- tions for a Sanitary Code. THE DISPOSAL OF HOUSEHOLD WASTES. Second Edition. 1904. Illustrated. 195 pages. 18mo. Bound in boards, price, 50 cents. (Science Series No. 97). A discussion of the best methods of treatment of the sewage of farm houses, isolated country houses, suburban dwellings, houses in villages and small towns, and of institutions, such as hospitals, asylums, prisons, hotels, etc., also of modes of removal and disposal of garbage, ashes and other house refuse. GAS LIGHTING AND GAS FITTING. Third Edition,1904. 190 pages. 18mo. Bound in boards, price 50 cents. (Science Series No 111.) A Pocketbook for Gas Companies, Gas Engineers, Gas Fitters, Manufac- turers of Gas Appliances, Gas Consumers, Builders, Architects, and Munici- pal Inspectors. Contains Hints to Gas Consumers. THE SANITATION, WATER SUPPLY, AND SEWAGE DISPOSAL OF COUNTRY HOUSES. With- 114 illustrations. 12mo. Cloth. 348 pages. Price, Net $2.00. D. VAN NOSTRAND COMPANY, Publishers and Booksellers, 23 MURRAY AND 27 WARREN STREET, NEW YORK. ieee by Microsotte