UC-NRLF THE MINERS' : - PQGKET-BOOK. LOCK, BDLLIYANT & CO. LTD. MANUFACTUKERS OF LIBRARY OF THE UNIVERSITY OF CALIFORNIA. Class AERIAL ROPEWAYS On all Systems TO CONVEY MATERIALS OF EVERY DESCRIPTION AND IN ANY QUANTITIES. Adaptable where no other form of transport can be used. Write for Illustrated Catalogues. Rcgd. Office, 72 MARK LANE, LONDON, B.C. Works, MILLWALL, E. THE PHOSPHOR BRONZE CO. LIMITED. Sole Makers of the following ALLOYS: PHOSPHOR BRONZE (" Cog Wheel" and "Yulcan" Brands). Ingots, Castings, Boiled Plates, Strip, Bars, and Tape. " DURO METAL " ( R tS e e red ) ALLOYS A & B. A Hard Bronze for Roll Bearings, Wagon Brasses, etc. PHOSPHOR TIN AND PHOSPHOR COPPER (" Cog Wheel " Brand). The best qualities made. ALUMINIUM AND MANGANESE BRONZE AND BRASS ("Yulcan" Brand). WHITE ANTIFRICTION ALLOYS, PLASTIC METAL. The Best Filling and Lining Metal in the Market. BABBITT'S METAL ("Yulcan" Brand). Made in Seven Grades. "WHITE ANT" ("TST*) Metal, No. 1. 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ELECTRIC SIGNALS and TELEPHONES. JEFFREY HEADERS. JEFFREY COAL AND ROCK DRILLS. Write for Catalogue No. 63. Eetabltebeb 1835. fourital The Oldest Mining Paper and the Pioneer of the Technical and Trade Press of the \Vorld for MINERS, METALLURGISTS, ENGINEERS, MANUFACTURERS,, CAPITALISTS & INVESTORS, EVERY SATURDAY PRICE 6>d. STJBSC :R,I:PT:IO w s (PAYABLE IN ADVANCE) MONTHS TWELVE. Six. THKEK. Inland 24/- 13/= 7/ Canada 26A 14/- 7/6 Rest of the World .. .. 30A 16/- 9/ Advertisement and Editorial Offices 46 QUEEN VICTORIA STREET, LONDON, E.G. THE MINERS' POCKET-BOOK A REFERENCE BOOK FOR ENGINEERS AND OTHERS ENGAGED IN METALLIFEROUS MINING BY C. G. WARNFORD-LOCK I/ M.INST.M.M., F.G.S. FIFTH EDITION, ENTIRELY REWRITTEN WITH NUMEROUS ILLUSTRATIONS ^ OF THE I UNIVERS of Xon&on : E. & F. N. SPON, LTD., 57 HAYMARKET mew Work: SPON & CHAMBERLAIN, 123 LIBERTY STREET 1908 te? INTRODUCTION TO FIFTH EDITION. THE fact that four long editions of this little volume have been exhausted, is in itself evidence that a measure of success has attended the author's effort to cater for the needs of his fellow- workers in the domain of metalliferous mining. It may truly be said that professional men of no other class are so often confronted by problems and difficulties, and have at the same time so little opportunity of accumulating books of reference or of gaining access to libraries. Hence a portable yet comprehensive means of refreshing the memory with facts, figures and formulae is very acceptable. It is not pretended that the whole education of a Mining Engineer can be achieved by reading a single book, or indeed any number of books ; but whatever his schooling and subsequent practical experience, no man can afford to neglect keeping him- self posted in what others are doing. The ultimate aim of all mining is financial gain, so that economic or commercial considerations are of primary import- ance. Lessening of costs means extension of the industry a consummation which must appeal strongly to us all. This has been kept prominently in view throughout the following pages. By entirely re-writing the present edition, it is hoped that its general utility has been increased. The deletion of matter possess- ing but limited interest has made room for a material expansion of the more important subjects connected with underground opera- tions. As before, the published and unpublished results of others work has been fully utilised, and the author takes this opportunity of expressing his indebtedness to the numerous writers and pub- lications quoted. Comments and criticisms will be gladly accepted for future editions, and may be addressed to the care of the publishers, i C. G. WARNFORD-LOCK. 182314 CONTENTS. PAGE POWER .. ... .. .. 1-83 Manpower .. .. .. .. .. .. .. 1 Animal power ,. .. .. .. .. .. 10 Wind power .. .. .. .. .. .. .. 13 Water power .. .. .. .. ... 16 Steam power .. .. .. .. .. .. .. 52 Electric power .. .. ... .. .. .. 67 Gas power .. .. .. .. .. .. .. 70 TRANSMITTING POWER .. .. .. .. .. 84-145 Belt driving 84 Rope driving .. .. .. .. .. .. .. 94 Hydraulic 109 Pneumatic .. 109 Steam .. .. .. .. 118 Electric transmission .. .. .. .. ..123 Systems compared .. .. .. .. .. .. 142 WEIGHTS AND MEASURES.. .. .. .. .. 146-155 Ores and rocks . . . . . . . . . . . . 146 Avoirdupois and Troy equivalents .. .. .. .. 147 Grains and dwt. in decimals of 1 oz. .. .. .. 147 Lb., qr., and cwt. in decimals of 1 ton .. .. .. 147 Mexican mining weights . . . . . . . . . . 148 Surveying measures . . . . . . . . . . . . 148 Areas of circles .. .. .. .. .. .. 149 Thermometer scales .. .. .. .. .. .. 150 Standard laboratory screens .. 152 152 153 154 155 Straits weights and measures Equivalent prices per kati and per Ib. Equivalent prices per pikul and per cwt. Russian mining weights and measures PROSPECTING .. .... .. . .. 156-177 Superficial deposits .. .. .. .. :. .. 156 Deep deposits .. .. .. .. .. .. .. 165 Diamond drilling .. .. .. .. .. .. 167 CONTENTS. PAGE MINE SURVEYING 178-197 Measuring inaccessible distances .. .. .. ..178 Shafts 180 Levels 184 Inclines .. .. .. .. .. .. .. 188 Latching or dialling .. .. .. .. -. 188 Dip, depth and thickness of beds Sampling and charting .. .. .. .. ..193 DRILLING 198-220 Bits 198 Power drills 201 Air-driven drills 204 Machines 206 Electrically-driven drills 208 Placing holes 210 Speed and cost .. .. .. .. .. .. 211 BLASTING 221-235 Charges 222 Precautions .. .. .. .. .. .. .. 223 Thawing explosives . . . . . . . . . . . . 224 Application 228 Cost 229 Electric firing 230 Explosives store . . . . . . . . . . . . 232 SHAFT-SINKING 236-286 Style and location 236 Shape and size 239 Excavation 242 Removing dirt . . . . . . . . . . . . 248 Lighting 249 Un watering .. .. .. .. .. .. .. 249 Timber 250 Timbering 253 Guides 261 Crib-setting 262 Concrete linings .. .. .. .. .. .. 264 Steel lining 268 Stations 269 Connections between vertical and underlay . . . . 270 Sumps and lodges .. .. .. .. .. .. 271 Kemoving timbers .. .. .. .. .. .. 271 Ladder-ways and ladders <,. .. 272 CONTENTS. PAGE Bad ground 273 Speed of sinking .. .. .. .. .. .. 279 Cost of sinking 280 DEVELOPING 287-300 Drives 287 Excavating .. .. .. .. .. .. .. 289 Timbering 291 Cost 294 Winzes and rises .. .. .. .. .. .. 295 General costs .. .. .. .. .. .. 298 MINING METHODS .. .. .. .. .. .. 301-415 Superficial 301 Dredging 337 Bucket dredger .. .. .. .. .. .. 337 Centrifugal pumps .. .. .. .. .. .. 349 Grab dredger 354 Beds 355 Coal 355 Iron .. .. .. .. .. .. .. .. 370 Petroleum 371 Phosphates 373 Pyrites 373 Salt 374 Sulphur 375 Talc 376 Tinstone 377 Veins 379 Timbering stopes . . . . . . . . . . . . 379 Renewing timbers .. .. .. .. ., .. 381 Overhead stoping .. .. .. .. .. .. 383 Underhand stoping . . . . . . . . . . . . 384 Combination stoping .. .. .. .. .. 386 Stoping practice . . . . . . . . . . . . 387 Slicing .. .. .. .. .. .. .. 389 Blocking 391 Pillaring f . 392 Square-set timbering .. .... .. .. 396 Rock-tilling 403 Pig-stying 409 Payment for stoping .. .. .. .. .. .. 409 Machine v. hand stoping .. .. .. .. ..411 Mining costs .. .. .. .. .. .. .. 412 CONTENTS. PAGE HAULING AND HOISTING .. .. ,, c .. .. 416-500 Surface transport .. .. .. .. .. .. 416 Underground haulage . . .* . . . . , . 429 Hoisting 454 UNWATERING .. .. .. .. .. .. 501-522 Pit draining .. .. .. .. .. .. .. 501 Water-lifting wheel ..501 Siphons .. .. .. 502 Hydraulic ejectors . . . . . . . . . . . . 503 Pneumatic ejectors .. .. .. .. .. .. 505 Baling-tanks 505 Pulsometers 506 Cornish pumps .. .. .. .. .. .. 507 Steam pumps.. .. .. .. .. .. .. 510 Compressed-air pumps .. .. .. .. ..513 Electric pumps .. .. .. .. .. .. 514 Centrifugal pumps .. .. .. .. .. .. 516 Sinking-pumps .. .. .. .. .. .. 518 Pump columns .. .. .. .. .. .. 518 Pumping costs .. .. .. .. .. .. 521 VENTILATION 523-526 SANITATION 527-528 LIGHTING .. 529-532 SIGNALLING 533-541 FELLOW AID IN MINING ACCIDENTS .. .. .. 542-553 MINERALS, ORES, AND METALS 554-597 LIST or USEFUL BOOKS 598 GLOSSARY .. 5 " INDEX .. .. 613 THE MINEES' POCKET-BOOK. POWER. Units. The unit of work, i.e. expended power, is the moment or effect of 1 Ib. through a distance of 1 ft., and is termed 1 foot- pound (ft.-lb.). Its metric equivalent is the kilogrammetre, or pressure of 1 kg. through a distance of 1 m., which = 7 '233 ft. -Ib. ; so that 1 ft.-lb. = -138 kg.-m. Horse-power. This is the usual measure of work performed, and 1 h.p. is computed to be equivalent to the raising of 33,000 Ib. 1 ft. high per minute, or 550 Ib. per second. But this is merely theoretical, as a horse can exert that force for only 6 hr. per day ; hence 1 work h.p, = the power of 4'5 horses at 3 miles per hr. The metric equivalent of this is 1 cheval or cheval-vapeur = 75 kg.-m. of work per sec., which (x 7 '233) - 542 '5 ft.-lb., or 1'37% less than 1 h.p. Then 1 h.p. = 1-013 chev.-vap. ; 1 chev.-vap. = -986 h.p. 1 cub. ft. per h.p. = 028 cub. m. per chev.-vap. 1 Ib. per h.p. '447 kg.-m. per chev.-vap. 1 cub. m. per chev.-vap. = 35*084 cub. ft. per h.p. MAN POWER. Theoretical. Various authorities fix the value of man power as follows : (a) Equal to raising 70 Ib. 1 ft. high, in 1 sec. for 10 hr. per diem = 4200 ft.-lb. per min. (Haswell). (6) Exerts a force of 30 Ib. for 10 hr. a day, with a velocity of 2*5 ft. per sec. = 4500 ft.-lb. per min. (c) Ordinary labourer at ordinary work = 3762 ft.-lb. per min. (Smeaton). Walking. A man can traverse 12*5 times the distance hori- zontally that he can vertically. Walking to and fro on a rocking beam, assuming his weight at 12 stone (168 Ib.), he can produce an effect of about 4,000,000 ft.-lb. in 10 hr. per day = 6666 ft.-lb. per min. He can average, without load, on level ground, 3 7 miles per hour for 8| hr. = 31 '45 miles a day. [The average Chinese coolie can cover 30 miles a day with a load of over 100 Ib. continuously for months !] Ascending slight elevations, unloaded, at 5 ft. per sec. for 8 hr. a day = 4290 ft.-lb. per min. Carrying. On short distances, returning unloaded, he can POWER MAN. carry (a) 135 Ib. for 7 miles a day; (6) 111 Ib. for 11 miles; (c) at !< 75 ft. per sec. for 6 hr. a day = 14,700 ft.-lb. per min. (Morin); ((7) at 2 -5 ft. per sec. for 7 hr. a day, always loaded = 13,200 ft.-lb. per min. (Morin). (e) carrying up slight elevation, returning unloaded, at '2 ft. per sec., for 6 hr. a day = 1680 ft.-lb. per min. (Morin). [The Chinese porters carrying tea and salt traverse 10 miles a day with a 200-lb. load, for weeks on end, much of the journey being at 7000 ft. elevation.] Pulling. (a) Hauling a boat in a canal, a man can transport 55 t. for a distance of 7 miles in a 10-hr, day; (6) at a velocity of 2 ft. per sec., for 8 hr. a day = 3120 ft.-lb. per min. Lifting. (a) Lifting with the hands, at '5 ft. per sec., for 6 hr. a day = 1320 ft.-lb. per min. ; (fc) pulling and pushing alternately in a vertical direction, at 2'5 ft. per sec., for 10 hr. a day = 1950 ft.-lb. per min. ; (c) by single pulley, he can lift 36 Ib. with a velocity of '8 ft. per sec., for 10 hr. a day ; (7. per t. (Scott); (/) The ordinary computation per 10 hr. shift in U.S. is 14, 16, 18, or 20 cub. yd. per man, according as the ground has been POWER MAN. previously loosened by plough or by pick, the handiness of the shovel, the surface shovelled ou, and the lift for loading (Gillette) ; (g) Shovelling alluvial wash containing big boulders, 2| cub. yd. per 10 hr. man ; wash 2 ft. deep, lift 9 ft., 3 cub. yd.; wash 4 ft., lift 6 ft., 5 cub. yd. ; wash 3 ft., lift 5 ft., 7J cub. yd. (Purington). Digging and Shovelling. (a) Digging and loading into barrow, per 10 hr. day, good average man (England), 8-10 cub. yd. earth, 6 cub. yd. firm gravel or tough clay, 3-5 cub. yd. picking ground (Fairley); (Z>) Chinese labour in Malayan tin mines, 2 men, 1 filling and 1 emptying baskets, with about 60 ft. carry, can excavate about 10 cub. yd. per diem 5 cub. yd. per man under best conditions. Ordinarily, the figures are 390-520 cub. yd. per man per aim. = (at 300 days) 1*3-1 '73 cub. yd. per man per diem, (c) Indian coolies in Malayan tin mines, using hoe and basket, carrying same distance, average about 2 cub. yd. Picking and Shovelling. (a) Picking alone in U.S. (wages 7%d. per hr.) varies from Id. to 6d. per cub. yd., the larger figure being for very tough clay or cemented gravel ; average ground is 2-3d = 2J-3| cub. yd. per hr. ; (6) Picking and shovelling combined (loading into wagons) costs in U.S. Q-2ld. per cub. yd. (wages 7$d. per hr.), according to ground as in (a) = J 1 cub. yd. per hr. (Gillette). Wheeling. (a) On short distances a man can barrow 150 Ib. 10 miles in a day ; (Z>) wheeling a loaded barrow up an incline of 1 in 12, at a velocity of 625 ft. per sec. (say J mile per hr.) = 4950 ft.- Ib. per min. ; (c) wheeling a load and returning empty, on the flat, at 1 ft. per sec. (say f mile per hr.) = 7920 ft.-lb. per min. (Morin) ; ((?) in ordinary contractors' work in the U.S. a man's max. capacity is 15 miles per 10 hr. with 250 Ib. (say 1 cub. yd.) load on level on grades, 1 50 Ib. load is enough ; including time lost in tipping and changing barrows, with a carry of 100 ft., a man can wheel per hr. about 30 loads, or, say 2-2J cub. yd., according to the grade. (Gillette.) Drilling. (a) Rand custom is 4 holes, 5J ft. deep, per machine per diem. Labour Economics. It is surely hardly necessary to insist on the advantages of contract work over day's pay. It is the only proper system, because it is the only fair one either to the employer or to the employed. Even in pre-Union days, when many men honestly tried to do a full day's work for a day's wage, it was not truly equitable to pay the same rate to the efficient and industrious as to the inefficient and lazy either one was underpaid or the other was overpaid ; while the refined arts of modern trades unionism and the cultivated loafing which now prevails among all kinds of workmen, have made any daily wage ridiculously unfair to the employer. A good deal of experience and judgment is necessary in fixing contract rates, to ensure that men may not earn an unduly hijrh pay for limited labour; but it must not be assumed that B 2 POWEE MAN. because labourers under contract earn more money per man per diem than they did under a daily wage, they are necessarily doing more costly work the converse will always be the case, unless extremely poor care has been exercised in determining the rate. To begin with, it tends to weed out the inferior workman, because it directly encourages the interest and attention and mental qualities of the operator ; the poor worker is stimulated to improve himself, or is shamed away from the job on comparing his low earnings with others' ; and as the efficiency of the worker is in- creased, the numbers employed may be decreased, and one natur- ally lets out the inferior man. This improvement in the work effects a further economy by lessening the need for supervision, and again another in the wear and tear on plant and tools, and the diminished waste of supplies. A single example may be quoted to illustrate the argument. It refers to the Center Star and War Eagle Mines, Kossland, B.C., and is based on about 2500 ft. of driv- ing and sinking, and over 60,000 t. of ore stoped (Davis, E. & M. Jl., 29/6/01). Development wages explosives total Contract, Daily Wage. Cost per ft. Cost per ft. 25s. 2d 34s. 10d. 11 5J 11 7 36*. 46*. 5d. Stoping wages explosives total .. Cost per t. 18'85(Z. 5-00 Cost per t. 37-50& 5-75 Advance per month driving 97 -5 ft. 50*8 ft. sinking 58ft. 27 -2 ft. Average daily wages earned 17s. 2d. 14s. 7<1. Another very important consideration embodies such matters as the duration of working hours, overtime, night work, and Sunday work. Where trades-unionism does not make it impossible, it will be found, in almost all cases, that a 10-hr, shift, with an allowance of even 1 hr. rest in the middle, will be much more economical than an 8-hr, shift with only 20 min. interval. It means 2 shifts only instead of 3 per 24 hr., thus lessening super- vision costs, and diminishing the time lost (and paid for) in men travelling to and from the face. All overtime is fundamentally and especially poor economy : the work is always inferior, and the wages paid for it are grossly in excess, Night work should always POWERMAN. be avoided as much as possible : men cannot and will not work as well at night as in day time ; their energy is actually impaired, for no man is able to recuperate in the same degree by day sleep as by night sleep. Tests have been actually made of pitting a .gang of superior men on night shift against a gang of inferior men on day, and always with the result that the latter's work was more satisfactory to the employer. Automatic machinery, will, of course, produce as much by night as by day, and there is distinct gain in uninterrupted running up to a certain point, while the labour of attendance is not so exacting but that it may be done with reasonable efficiency. Yet the experience of any mine manager will be that machinery breakdowns in mine and mill, and accidents of all kinds, occur most often at night, and especially during the first three hours after midnight, when the human system is physio- logically weakest. Sunday labour should always be restricted to the smallest limits. Not only is every man who puts in 6 days* real work all the better for a rest on Sundays, but it has been proved beyond cavil with railway locomotives that those running 6 days a week only outlasted by years those on 7-day duty, costing far less for repairs, doing better work, and giving a much higher return for the capital invested in them. Types and Efficiencies. While the qualities of labour of differ- ent racial types vary as greatly as the nationalities themselves, it must never be forgotten that the useful effect of any labour is almost as much dependent upon the manner in which it is con- trolled as upon its own inherent merits and demerits ; and before discussing the traits of some, of the principal classes of human labourer, a paragraph may be devoted to insisting on this very material fact. The real efficiency of a shift-boss or other foreman is to be reckoned far less by his own skill and knowledge of the work than by his ability to get the best possible results out of the men lie controls. It should not be necessary to insist on this, but in one's own experience and it must be the experience of most mining engineers who have managed enterprises in foreign countries there have been so many and such glaring instances of mis- handling of the local labour supply, to the exceeding detriment of the undertaking, by miners placed in immediate charge of gangs (excellent workmen though they were themselves), that special emphasis inust be laid on it. The average school-of-mines student, being of a class superior in breeding and education, is better equipped for the job than the practical miner, but even he, un- fortunately, gets no training in that direction, and often does not think it worth while to learn from his neighbour when he can. Yet the mines which have established the best records for econo- mical and good work can invariably trace much of their success to careful attention to this question. Thorough capability in handling men is much more essential than high technical qualifications to the junior members of the mine staff. During post-graduate POWER MAN. courses, students should be careful to cultivate the art most assiduously. The labour troubles of the Rand and Rhodesia have been largely due to ignorance and carelessness and worse in the management of both the Kaffir and the Chinaman ; no man, though he be black or yellow, will tamely submit to the senseless brutality of the average Cornish and Australian miner who is placed over him. White mine labour is familiar to most of .us, and does not need much description. For low-grade products, especially when in superficial deposits, the Staffordshire and Cleveland iron miners demand preference, followed by the Welsh quarry men. The Cornishrnan shines at timbering, but is very conservative and un- adaptable to strange conditions. The Basque of the Pyrenees is a born artist at hand-drilling, even in the hardest ground ; and the N. Italian is a very good all-round man. The American under- stands hard work, but commands huge pay, and the criminal records of the Western unions are a stain on civilisation. The mining laws of the Australian colonies are accountable for the average poor quality of the native-born mine labour, and for the insecurity of mining capital. In India, the best underground labour is furnished by the Moplahs, a fish-eating race from the W. coast. The Tamil, though much employed in excavating and other surface work, both in India and Malaya* is never a "hard-ground man. Burma and the Shan States, as well as Malaya (both insular and peninsular), really depend on the Chinaman. The cost of Moplah labour is about -^ that of English labour (Smyth). The Tamil's wages range com- monly between lOrL and Is. 3d. a shift. In some of the Malayan tin gravel mines the Tamil is distinctly superior to the Chinaman, because of his habit of carrying a load always on his head ; he is thus able to discharge into a full-sized (2 cub. yd.) truck without the need of any staging or plank, and this is of considerable ad- vantage. Also he tolerates scorching sun-heat better than any other race ; but he lacks stamina, and is often a drunkard. The Korean would be quite useful if he would emigrate. He is, perhaps, slightly less intelligent than a Chinaman, but he is a big strong fellow, and is less conservative and superstitious. Korean coolies earn about 7%d. a day; miners, Sd-ls. ; carpenters and blacksmiths, Is.-ls. 3d. Koreans become very fair engine drivers, whereas Chinese scarcely ever do. Japanese may easily be over-rated. Though intelligent, indus- trious, strong and enduring, they are very quarrelsome and difficult to manage, and have a very high opinion of themselves which one does not always share. They are prone to strikes and lawlessness. In Korea, Japanese fill most of the mechanics' places, and earn somewhat higher wages than either Koreans or Chinese, reaching as high as 3s. a day, and occasionally more. In Japan, at the principal gold mines, in 1903, wages ranged as follows (Weigall) : POWEE MAX. Women (ore-picking), od. ; boys, 6) A wheeled scraper will take a larger load, say -i- cub. yd., especially with the aid of a " snatch " team and extra labour, but the cost will not be lessened. (c) In Alaska, a team (2 horses and 1 man) will scrape, on soft schist bedrock, 30-40 cub. yd. ordinary small gravel, 25 yd., per diem. (Purington.) Mule. (a) The big S. American mule is equal to a horse in strength, and superior in endurance and cost of keep. (&) Underground colliery haulage in Illinois, by mules, on 275 working days per ann. (mules costing 45Z. ea., depreciation 20%, interest 6%, drivers 10-lls. a day), cost l-2r?. per t., as against electric haulage Id. (Peltier.) Ass. The powerful Syrian ass carries a huge load 450-550 lb. of grain; but ordinarily the ass is less than half as effective as a horse. On the other hand, he is far more cheaply fed, housed and tended, and is much hardier and more immune against epidemics. POWER WIND. 13 Ox. The 'working ox is not equivalent to more than J horse, but possesses a marked advantage in team work (oxen pulling so much better together) and in steady straining on the hauling where Jiorses would jerk ineffectively. Oxen should always be shod for road work. Llama. In the Andean country (S. Amer.), the llama is the only avail- able beast of burden. He is equal to a load of 100 Ib. at 10 miles a day for several consecutive days, and may be pushed to 20 miles in a single day, but will require a week's rest to recover. The llama thrives at 12,000 ft., costs about 11. per head, and is cheaply fed, thriving on the local grass. (Pearse, 1893.) WIND POWER. The altitude or head of the atmosphere at uniform density will be the altitude of a column of water 33 * 95 ft. divided by the sp. gr. of the air (-0012046), or, The velocity due to this head will be V = 8-02 V287183 = 1346-4 ft. per sec., the velocity with which the air will pass into a vacuum. When air passes into an air of less density, the velocity of its passage is measured by the difference of their density. H and h = density of air in inches of mercury ; t = temperature at time of passage ; and V = velocity of wind in ft. per sec. V = 1346-4 / H ~ fe (l + -00208 t\. The force of wind increases as the square of its velocity. a = area (sq. ft.) exposed at right angles to wind ; F = force of wind (Ib.) ; H = h.p. ; and v = velocity of plane a in direction of wind, + when it moves opposite, and when it moves with wind : F = -002288 a V 2 , when v = o. P =-002288 a (V .) H Ex. A train running E.N.E. 25 m. per hr. exposes a surface of 1000 sq. ft. to a pleasant brisk gale N.E. by E. Required resist- ance to train in the direction it moves, and h.p. lost : 14 POWER WIND. E.N.E. - N.E. by E. = 3 points = 33 45' ; V = 14 ft. per see., a brisk gale ; v 25 x 1 ' 467 = 36 6 ft. per sec., and F = 002288 sin. 2 33 45' x 1000 (14 + cos. 33 45' X 36 '6) 2 = 305 -lib. H = 305-1 x 36-6 550 = 20h.p. (Nystrom.) Horse-power and Sail-area. (Moles worth.) V = Velocity of wind in ft. per sec. A = Total area of sails in sq. ft. = 1,100,000 h.p. -j- V a . N = Number of sails, hp. = -00000091 A V 3 . Velocity of tips of sails = 2 6 V, nearly. Velocity and Force of Wind in Ih. per sq. in. (Nystrom.) Miles per Hour Ft. per Sec. Lb. per sq. ft. Common Appellations of Winds. Miles i per i Hour. Ft. per Sec. Lb. per sq. ft. Common Appellations of Winds. 1 1-47 0-005 ( Hardly I perceptible. 18 20 26-4 29-34 1-55 1-968 > Very brisk. 2 2-93 0-020 vJust 25 36-67 3 075 ) 3 4-4 0-044 j perceptible. 30 44-01 4-429 | 4 5-87 0-079 } ! 35 51-34 6-027 f High Wind. 5 7-33 0-123 1 Gentle 40 58-68 7-873 ) 6 8-8 G177 f pleasant wind. f 45 66-01 9-963J) 1 10-25 0-241 J 50 73-35 12-30 > Very High. 8 11-75 0-315 \ 55 80'7 14-9 ) 9 13-2 0'400 60 88-02 17-71 Storm. 10 ,.12 14 15 14-67 17-6 20-5 22-00 0-492 708 0-964 1-107 [pleasant brisk gale. 65 70 75 SO 95-4 20-85 102-5 24-1 110 27-7 117-36 31-49 i Great Storm, i Hurricane. 16 23-45 1-25 100 140-66 50 Tornado. Dimensions of Sails. (Molesworth.) Length of whip .. 30 ft. Breadth, base 12 in. Depth 9 Breadth, tip . .. .. 6 ,. Depth 4 Rule for Angles of Sails. (Molesworth.) A = Angle of sail with plane of motion at any part. K = Total radius of sail in ft. D = Distance of any part of sail from axis. 18 D 2 A = 23 - . B 2 POWER WIND. 15 If radius of windmill sails be divided into six equal parts, the angles at each part, reckoning from axis, will be : Distances from axis . . .'. $ 1 | i 4 tip. Angle of sail with axis 67 i 69 YH C T5 79* 85 Angle of sail with plane of motion . . 22* 21 18* 15 10* 5 In a windmill about 60 ft. diam., the diam. of middle point of arm. is 30 ft. ; circum. of circle in which that point revolves, 94 ft. ; number of rev. made a minute, with a 5 mile an hour wind *-, about 7. The speed of extremities of arms is 1320 ft. a min., or about 15 miles an hour, or 3 times that of the wind. Under ordinary circumstances, speed of outer extremities of arms ranges from 20 to 30 miles an hour, say 30 miles an hour when the wind blows at 10 miles with a pressure of about \ Ib. per sq. ft. The total surface of sails unfurled in a mill 60 ft. diam., is 1250 sq. ft. ; say half lost by furling = 625 sq. ft. effective. As the surface is set obliquely to the wind, pressure in direction of motion would be reduced from \ Ib. to about \ Ib., as a mean over the whole of the arms, giving a total pressure in direction of motion of about 90 Ib. The mean velocity of arms is half that of the extreme = 15 miles an hour, or 1320 ft. a min. Therefore 90 Ib. moving at 1320 ft. a min. = 90 x 1320 = 118,800 Ib. moving at 1 ft. a min. = about 3J h.p. By doubling diameter of a mill, its effective surface (i.e. its power) is quadrupled. Wind power, from its general distribution, is a more valuable auxiliary than tide or waves. The chief objections to it practically are its uncertainty in amount and the variable speed of the motor itself. But it may be profitable to employ a windmill where the work to be done admits of suspension during a calm or of storage of energy. The average velocity of the wind is low, in most places between 5 and 10 miles an hour, corresponding, respectively, to pressures of 2-8 oz. per sq. ft. At most inland places it may be taken as about 7J miles an hour ; but in some exposed situations, near the sea, it amounts to as much as 16f miles an hour. A speed of 10 miles is generally attained during 6-9 months per aim., according to locality, whilst a 16-mile wind may be expected, under favour- able conditions, for about 4 mos. There are few days without periods of brisk breezes (15-20 miles an hour), giving wind pres- sures of 1-2 Ib. per sq. ft. An effective wind motor should be able to work at good advan- tage up to, say, 5 Ib. per sq. ft. pressure at fairly uniform speed ; and should be strong enough to stand up against winds of 50-60 miles an hour. 16 POWER WATER. The work yielded by a mill constructed on the best principles should be '04 ft.-lb. per sq. ft. of sail surface, with a wind velocity of 3 '28 ft. per sec., and will increase with the cube of the speed of the wind, subject, of course, to limitations. WATER POWER. The natural power contained in a fall of water is equal to the weight of the quantity of water passing over per second, multiplied by the vertical space through which it falls. 1 cub. in. fresh water = '03621 Ib. ; cub. in. X '00360 = gal. (Eng.). 1 ft. =6'24 gal. (Eng.), or 6 '32 gal. (U.S), or 62-57 Ib., or '559 cwt., or '0312 ton (of 2000 Ib.), or '0278 t. (of 2240 Ib.). 1 cub. ft. sea water = 64*11 Ib. ; weight of sea water = 1*027 of fresh water. 1 ice = 57-31b. 1 yd. fresh water = 1682 5 Ib. 1 gal. (Eng.) = 10 Ib. or -16 cub. ft., or 4 '543 litres ; gal. x '16045 = cub. ft,, or x 277*274 = cub. in., or x '0044 = tons. 1 Ib. = -01607 cub. ft., or '1 gal. 1 cwt. 1 ton (2240 Ib.) , 1 (2000 Ib.), 1 litre = 1-8 cub. ft., or 11-2 gal. = 35-97 cub. ft., or 224 gal. = 32-11 cub. ft., or 200 gal. = 61 cub. in., or 0353 cub. ft., or 22 gal. 1 kilo = 2-2041b. 1 cub. metre ., = 1000 kilo., or 1000 litres, or 35-31 cub. ft., or 1 308 cub. yd., or 220 gal., or 1 ton approximately. Rainfall in in. x 2,323,200 = cub. ft. per sq. mile, or x 14 = millions of gal. per sq. mile. When p pressure (Ib. per sq. in.), h = head of water (ft.), v = theoretical velocity (ft. per sec.), and g = sp. gr. ; then p - h X -4335. h = p X 2-307. -.= '0155. * g Pressure per sq. ft. = -4335 X 144 = 62-424 Ib. = 32-2. 20 = 64-4. \/2^ = 8-025. = 8-025 V/r h = = " 155 v *' POWER WATER. 17 cot>ocor>coi>ocot>ocot>o:oi> GOSDiOCOrHCOCOOCOOOCOCO'OCOCO rHrHrHiMC^COCOCOl> 5t^coo^c5cct>c5i-otO'*cV:cqrHco rHCOiOt>C5rHCOOl>'QOI> rH rH i I rH rH CO a* ^ ^ ^ ^ ^ *? *? *? *? T 1 7* 7 1 J^ T 1 ^ f 5 I '"'" ^^^SrHrHlHrHCO O ^ *1 10 O O O O O O O O O O O O O rH COL-QHHt^LCpOQiOOiOOiOOO !f o . T 1 ....".*'...' . . T 1 ."..."... O O rH rH rH CO !> rH lO OK ^^ rH rH r- 10 5 O O O O C 5 O O O O : 5 CO l> 00 05- 18 POWER WATER. y Pressure, and Power, at 100 gal. per min. at 62 F. Head Ft. Pressure Lb. per sq. in. | Power, h.p. Head Ft. Pressure Lb. per sq. in. Power, h.p. Head Ft, Pressure 'i Lb. per sq. in. Power, h.p. 1 43 03 625 270-63 15-79 1825 790-23 46-13 2 87 05 650 281-45 16-42 1850 801-05 46-76 3 1-30 08 675 292-28 17-05 1875 811-88 47-39 4 1-73 10 700 303-10 17-68 1900 822-70 48-02 5 2-17 13 725 313-93 18-31 1925 833-53 48-65 6 2-60 15 750 324-75 18-95 1950 844-35 49-29- 7 3'03 18 775 335-58 19-58 1975 855-18 49 92 8 3-46 20 800 346-40 20-20 2000 866-00 50-55 9 3-90 23 825 357-23 20-85 2025 876-83 51-18 10 4-33 25 850 368-05 21-48 2050 887-65 51-81 11 4-76 28 I 875 378-88 22-11 1 2075 898-48 52-44 12 5-20 30 900 389-70 22-74 2100 909-30 53-07 13 5-63 33 925 400-53 23-38 2125 920-13 53-70 14 6-06 35 j 950 411-35 24-01 2150 930-95 54-33 15 6-50 38 975 422-18 24-64 2175 941-78 54-96 16 6-93 40 1000 433-00 25-27 220C 952-60 55-60 ir 7-36 43 1025 443-83 25-90 2225 963-43 56-23 18 7-79 46 1050 .454-65 26-53 2250 974=25 56-86 19 8-23 48 1075 465-48 27-17 2275 985-08 57-49 20 8'66 50 1100 476-30 27-80 2300 995-90 58-12 30 12-99 76 1125 487-13 28-43 2325 1006-73 58-75 40 17-32 1-01 1150 497-95 29-06 2350 1017-55 59-39 50 21-65 1-26 1175 508-78 29-69 2375 1028-38 60-02 60 25-98 1-52 1200 519'60 30-33 2400 1039-20 60-65 70 30-31 1-77 1225 530-43 30-96 2425 1050-03 61-28 80 34-64 2-02 1250 541'25 31-59 j 2450 1060-85 61-91 90 38-97 2-27 1275 552-08 32-23 j 2475 1071-68 62-55 100 43-30 2'53 1300 562-90 32*86 2500 1082-50 63-18 125 54-13 3-16 1325 573-73 33-49 2525 1093-33 63-81 150 64-95 3-79 1350 584-55 34-12 2550 1104-15 64-44 175 75-78 4-42 1375 595-38 34-75 2575 1114-98 65-07 200 86-60 5-05 1400 606-20 35-38 2600 1125-80 65-70 225 97-43 5'68 1425 617-03 36-01 2625 1136-63 66-34 250 108-25 6-31 1450 627-85 36-64 2650 1147-45 66-97 275 119-08 6-94 1475 638-68 37-28 2675 1158-28 67-60 300 129-90 7-57 1500 649-50 37-91 2700 1169-10 68-23 325 140-73 8-22 1525 660-33 38-54 2725 1179-93 68'85 350 351-55 8-85 1550 671-15 39-17 2750 1190-75 69-^9 375 162-38 9-48 1575 681-98 39-80 2775 1201-58 70-12 400 173-20 10-11 1600 692-80 40-44 2800 1212-40 70-75 425 184-03 10-74 1625 703-63 41-07 2825 1223-23 71-39 450 194-85 11-38 1650 714-45 41-70 2850 1234-05 72-02 475 205-68 12-01 1675 725-28 42-33 2875 1244-88 72-65 500 216-50 12-64 1700 736-10 42-96 2900 1255-70 73-28 525 227-33 13-27 1725 746-93 43-59 2925 1266-53 73-92 550 238-15 13-90 1750 757-75 44-22 2950 1277-35 74-55 575 248-98 14-53 1775 768-58 44-85 2975 ! 1288-18 75-18 600 259-80 15'16 1800 779-40 45-49 3000 1299-00 75-82 POWER WATER. 19 The Miners 1 "Inch." The miners' " inch " is an arbitrary measure of the quantity of water which will flow through a given space in a given time, adopted in the early days of American gold-mining, and established by the law of each miners' camp, without any attempt at a universal scale. Thus there are scarcely two localities where the miners' inch has the same signification, the size and shape of the outlet and the manner of discharging the water varying constantly. The most common basis of calculation is the volume which will pass through an opening 1 in. square in a plank 2 in. thick, with a pressure or head ranging from 4 to 11 in. above the centre of the orifice. But the shape of the aperture is a most inconstant figure, and this alone tends to make the computations inaccurate, besides which, the varying head is an even greater source of discrepancy. Thus the statute " inch " in B. Columbia is given as 1 68 cub. ft. of water per min., and this is defined as equivalent to that quantity which will pass through an orifice in. wide, 2 in. high, and 2 in. thick, with a constant head of 7 in. above the top of the orifice, and every additional " inch " shall mean so much as will pass through the said orifice " extended horizontally in." But actual measurements (Drummond) have proved (a) that the first-named orifice discharges 2 147 cub. ft. instead of 1 68, and (&) that widen- ing this orifice alters the coefficient of discharge. Standard '* inches " in various districts range all the way from 1 39 to 2 34 cub. ft. per min. The convenience of a definite figure has come to be recog- nised, and as heads much exceeding 6 in. are incompatible with most ditch and flume deliveries, a low figure is -desirable. The Institution of Mining and Metallurgy has adopted 1 5 cub. ft. per min. as its standard, and this conforms very closely with the recog- nised best practice in the United States, being in fact the actual " inch " as fixed by State law in California and Montana. Thus, 1 cub. ft. per sec. = 40 miners' " inches " ; or, cub. ft. per min. x | = miners' " inches." Another vague term, an outcome of what is considered the necessary flow for a first-class hydraulic under- taking, is the " head " or " sluice-head." This may really be anything: thus (a) "the flow necessary for a box 12 in. wide set in a grade of 8 in. per 12 ft., or 20 miners' * inches ' (= 30 cub. ft.) per min." ; (6) u equivalent to 60 miners' ' inches 'of 1-5 cub. ft." ; (c) " 200 inches " ; (tZ) " 600 gal. per min.," which is equiva- lent to about 95 cub. ft. per min. ; (e) " with a sluice-box set at about in. per ft., 45 cub. ft. or 30 ' inches ' per min. ; " (/) " as it became possible to set sluice-boxes on a steeper grade (9 in. per box of 12 ft.), the quantity increased to 100 cub. ft. or 67 * inches ' per min." Thus the expression is so inaccurate as to be worse than useless. Cost of Water Power. Theoretically, falling water can furnish the cheapest power, while it is also self-renewing, and requires no current expenditure c 2 20 Po WER WATER . beyond the wear of the transmitting machinery. In many cases, however, costly works are needed before the power can be used. Where the supply is variable, extensive reservoirs may be needed to regulate it and to prevent an excessive supply at certain seasons from becoming dangerous. There is no other source of power which needs such careful preliminary plans and estimates. At some installations in Switzerland and in Norway, power is obtained at a cost of only 17s. 9d. per h.p.-year. At many Calif ornian mines which are supplied with water power by " ditch companies," it is computed that pine-wood fuel at 21s. per cord affords steam power at about the same cost as water under a fall of 175 ft. at IQd. per miners' " inch," the " inch " being reckoned at 15,000 gal. per 24 hours (= 1'65 cub. ft. per min.). The usual selling price of water there is 7J to Wd. per " inch " ; and the cost of pine-wood is 16s. 8d. to 29s. per cord. Measuring Streams. The computation of the breadth, depth, and velocity (in ft. per min. as travelled by a float) of a stream is a very simple matter. The sectional area reduced to sq. ft. and x by the speed = cub. ft. per min., and this x f (or *66) = miners' "inches." It is neces- sary to select a portion of the stream having the most uniform cross section. Measure 120 ft. along the stream, and, at the extremities of this length, and at right angles across the stream, fix two straight cords ; then get a few floats of wood (so weighty that when placed in the water they will not project above it so as to be materially affected by the wind). Drop the floats lightly into the current at a little distance above the upper cord, and note the time by a stop-watch that they take to pass over the distance between the two cords. This should be repeated several times with floats both in the middle and near the sides of the stream ; the mean is then taken of the surface velocity of all the experi- ments. Having by these means found the several spaces run over in a given time, the mean proportion of all these trials is taken for the surface velocity of the water. Four-fifths of the surface velocity is a good approximation to take for the mean velocity of the stream, or the velocity it would have, supposing all the particles of the stream to move in every part of its channel with one uniform motion. Kegard the 120 ft. as 100 ft. only, so as to have a safe margin of speed. If the channel of the stream has a moderately even outline, measure its depth at regular intervals from shore to shore. Add all these depths together, and divide the sum by the number of soundings. An average depth is thus gained. Calcu- late then the area of the section by multiplying the average depth in ft. by the width in ft. To abridge calculation, the accompanying table (p. 21) shows POAVER WATER, 21 mean velocities corresponding to surface velocities from 120 to 800 ft. per inin. for ordinarily free-flowing streams. Multiply the area by the velocity, and the product will be the flow (in cub. ft. per min.). The test for velocity should be made at the same point where the measurements for depth are made, and a place on the stream should be selected for both where the banks are as nearly parallel as may be, and where the current and flow are the most tranquil. Ex. A stream is 24 ft. broad, and 10 soundings at every 2 ft. on a line from bank to bank give 2, 6, 8, 9, 7, 11, 11, 10, 9, and 2 in. as the depths. The average velocity as determined by float is 4 ft. per sec. What is the flow ? Ans. The sum of the 10 soundings is 75 in., which gives an average depth of 7*5 in., equal to "*625 ft. The section area then is 24 x 625 = 15 sq. ft. The velocity being 4 ft. per sec., the flow = 15 X 4 = 60 ft. per sec. If the stream runs over a bottom so irregular that an average depth cannot be gained, or an average velocity measured, there is no recourse but to construct an artificial channel, having no grade, into which it may be turned while measuring. Considerable allowance for retarded speed must be made when a stream has a very rocky or bouldery bed. Surface and Mean Velocities of Water (in ft. per min.}. Surface Velocity. Mean Velocity. Surface Velocity. Mean Velocity. Surface Velocity. Mean Velocity. 120 98-00 182-5 154-80 245 212-50 122-5 100-25 185 157'10 247-5 214-85 125 102-50 187-5 159-40 250 217-15 127-5 104-75 190 161-70 252'5 219-50 130 107-00 192-5 164-00 255 221-80 132-5 109-25 195 166-30 257-5 224-15 135 111-55 197-5 168-60 260 226-45 137-5 113-80 200 170-90 262-5 228-80 140 116-05 202-5 173-20 265 231-10 142-5 118-30 205 175-50 267-5 233-45 145 120-60 207-5 177-80 270 235-75 147-5 122-85 210 180-10 272-5 238 ' 10 150 125-15 212-5 182-40 275 240-45 152-5 127 40 215 184-75 277-5 242-75 155 129-65 217-5 187-05 280 245-10 157-5 131-95 220 189-35 282-5 247-45 160 134-20 222-5 191-65 285 249-75 162-5 136-50 225 193-95 287-5 252-10 165 138-80 227'5 196-30 290 254-45 167-5 141-05 230 198-60 292-5 256-75 170 143-35 232-5 200-90 295 259-10 172-5 145-65 235 203-25 297-5 261-45 175 147-95 237-5 205-55 300 263-75 177-5 150-20 240 207-85 305 268-40 180 152-50 242-5 210-20 310 273-10 22 POWER WATER. Surface and Mean Velocities of Water continued. Surface Velocity. Mean Velocity. Surface Velocity. Mean Velocity. Surface Velocity. Mean Velocity. 315 277-8 375 334-2 435 390-8 320 282-5 380 333-9 440 395-6 325 287-2 385 343-6 445 400-3 330 291-9 390 348-3 450 * 405-1 335 296-6 395 353'0 500 452-5 340 301-2 400 257-8 550 500-0 345 305-9 405 362-5 600 547-7 350 310-6 410 367-2 650 595-5 355 315-3 415 371-9* 700 643-3 360 320-1 420 3T6'7 750 691-2 365 324-8 ' 425 381'4 800 739-2 370 329-5 430 386-1 Dams, Reservoirs, and Penstocks. The utilisation of water for power purposes always involves the provision of some retaining structure through which the issue is controlled. The strength of such structures must be adapted to withstanding the pressure of the water, and it must be borne in mind that water at rest exerts pressure (i.e. its weight) equally in all directions the sides have to support exactly the same load as the bottom, no matter what the area may be. Depth, therefore/-is the sole factor of pressure, and is to be computed at 62 5 Ib. upon" every sq. ft. of surface (sides and bottom) for every 1 ft. in depth. In all water-power installations dependent upon a running stream provision must be made for dealing with two classes of foreign matter which every stream carries floating and non-floating bodies. Floating bodies may embrace logs, branches, leaves, ice, and fine silt. All but the last-named may be arrested by a hinged grid of iron bars, covered with wire netting if necessary, sloping against the stream. Screens may be conveniently made in sections not exceeding 7 ft. x 3 ft., mounted on angle-iron frames, and inter- changeable, some spares being available while cleaning is going on. No. 6 galvanised wire, J in. mesh, is good. It must not be forgotten that twigs and leaves sink when sodden, and a screen to be effect- ive must reach bottom. Silt may be best removed by settling pits (with conical bottoms if possible) furnished with a plugged drain and a powerful hose if pressure is available for hydraulically sluic- ing, them out. Non-floating impurities are the gravel which is brought down by heavy floods and by the operations of alluvial miners on the stream above. These are easily and effectively got rid of by a sand-drain in the deepest point of the dam wall, con- trolled by a rack and pinion gate. It should be in the most direct possible line of the greatest flow of the stream, while the supply POWER WATER. 23 for the flume or ditch is taken from slack water. Abundant by- pass for flood- waters is of course always essential. Channels. Artificial channels, either ditches, flumes, or pipes, have to be constructed for conveying the water to the point where it is to generate power, after due calculation of the relative proportions and dimensions of the area, the inclination, the volume, and the velocity necessary. Sectional Area. To find the sectional area of a channel (a) when sides are perpendicular: width of bottom (in.) x height of one side (in.) = area (sq. in.); this -i- 144 = area (sq. ft.). (6) when sides are sloping : width at top (in.) + width at bottom (in.) x depth (in.) -~ 2 = area (sq. in.); this -- 144 = area(sq. ft.). (c) when sides slope to a point : width (in.) x J depth (in.) = area (sq. in.) ; this -r- 144 = area (sq. ft.). Wet Perimeter. The "wet perimeter" of a channel is the transverse length of so much of the bottom and sides as is covered by water. The least wet perimeter necessary to accommodate a given volume is secured when the width of bottom is between If and 2 J times the depth of sides, and, needless to say, such peri- meter involves the least expenditure in excavation of ditch or con- struction of flume relatively to volume of water carried. But other considerations interpose. Thus evaporation which may easily account for a 10% loss on a great length is much more marked in shallow and in slow currents ; while in frosty regions, narrowness will help the formation of an ice-crust which may allow the flow to continue 4-6 weeks longer. Grade. To find what grade or fall must be given to a channel of uniform section to obtain a given discharge in a given time. Ke- quired discharge (cub. ft. per sec.) -s- sectional area (sq. ft.) = necessary velocity (ft. per sec.); multiply this by itself; multiply this product by wet perimeter (ft.), and multiply this product by 0001114; divide this product by sectional area (sq. ft.), and call result a. Then multiply velocity by wet perimeter and this product by -00002426; divide this by sectional area, and call result b. Then a + b = grade per ft. (in decimals of a ft.) required. Ex. Required grade per ft. for flume 20 in. wide and sides 11 in. high to deliver 28 cub. ft. per sec. Ans. [Sectional area = 220 sq. in. (say 1 528 sq. ft.) ; wet perimeter = 42 in. = 3 5 ft.] Discharge (28) -r- sectional area (1-528) = velocity (18*32); this x itself - 335-622 x wet perimeter (3-5) = 1174-677 x '0001114 = -1308 -i- sectional area (1-528) = -0856 = a. Velocity (18-32) x wet perimeter (3-5) x '00002426= -001555, this -4- sectional area (1-528) = -001 = b. Then a (-0856) + b (-001) = -0866 ft. per ft. = 86-6 ft per 1000 ft. = 1-039 in. per ft. = 12-47 in. per 12-ft. box. 24 POWER WATER. Discharge. To compute discharge (cub. ft. per sec.). Multiply sectional area (sq. ft.) x grade (ft. per ft.) x 9000 -*- by wet peri- meter (ft.); extract square root of quotient and subtract '1089 ; result = mean velocity (ft. per sec.). This x sectional area (sq. ft.) = discharge (cub. ft. per sec.). Ex. Kequired discharge from flume 30 in. wide and sides 12 in. high having grade of 1 in 100 = -01 ft. per ft. Ans. Sectional area (2-5 sq. ft.) x grade (01) = -025 x 9000 = 225 -*- wet perimeter (4 -5 ft.) = 50, whose sq. root is 7 '0711, this -1089 = 6 -9622 = mean velocity (ft. per sec.) x sectional area (2 5) = 17 4 cub. ft. per sec. discharge. For the greater frictional loss in a ditch, deduct about 10%. Dimensions. To ascertain dimensions needed to afford a given discharge (cub. ft. per sec.) on given grade, the accompanying tables (pp. 25-27) may be used. They are computed on the assumption of smooth and straight channels. Ditches. Leakage occurs most extensively in gravelly soils ; 1-5 in. of surface per day are extreme losses, with an average, perhaps, of about 2 in., which it will be always safe to count on, except in old ditches. A high velocity decreases loss in this way, but is destruc- tive to the banks ; it should rarely exceed 200 ft. per min. Ditches should always have a uniform grade, otherwise there will be an accumulation at some points and a thinning-out at others, with deposits of sand and silt, and increased danger of breakage. It is also highly advantageous to have a complete system of waste- weirs to carry off surplus waters occasioned by floods, and to lessen the damage of breaks. These should be put in just below where- ever a new stream falls into the ditch, and just above those places where, by reason of a shelly or crumbly soil, the ditch is weak. At high altitudes, in the spring, difficulty occurs in starting the water, through accumulations of snow in the ditch ; it is best to flush out in short sections (a mile or so). Cut a hole in the bank a mile from the head, and when the water has soaked that far it will carry off the unmelted snow through this break with great rapidity. As soon as clear, that hole is mended and another is made a mile farther on. Damage and leakage from earth-slides, falling trees, roots, springs, animals (trampling and burrowing), and storms, must be provided against and allowed for in calculating capacity. Cost of Ditching. (a) When plough and scraper can be used, ditching can be done at 10f7. per cub. yd. If the soil is so rocky as to call for the pick and shovel, it will cost 15-20c7. A safe figure for a ditch 3 ft. wide at bottom, 4J ft. wide at top, and 18 in. deep is 158. 3fZ. per rod. (Californian rates.) (Z>) With labour at Qd. per hr., 48. per cub. yd. for rock, and 2s. 6r7. for gravel, earth, and clay. (Kirkpatrick.) (c) Peruvian labour on contract, 6d. per cub. yd. (Heath.) POWER WATER. POWEE WATER. EHCQQ # ^lNpi--*f-ai-lpNNrtlr-IOOCO^-F-<*.OOr-lpTj<^OiO | S ~ ] { SO** .2 ST "M*-W.t-ep<0O<**-.H.t-iO^-OOMOSOiCJaO'^l.-;O gp-ir- tc^c^oocoooco^Tji^^T^iotfSiaotfssosococDsocoa* i ^ ccc - -. ^^ Ti* O <0 O^ to TH rH C cc m ^ ^ ^_ , ^, ^ ^ w , wv ^^ w _ w ,,, UJ 4 , WJ _ _ r-lrH^-lNlMC^C^MfCMCOfOCOWCOM^^^^^^Th^ -r " 1 ^ MOOD . T ^*i-TjTj(ooir5ji-ii-iooi-io?o^HMcoi-i*'C^U5t.t^o HPQQ "" " ,-...-.,-,.,.-.." " """" 3 f i t l-.XOOI>.VOOO 5s 1* - a T H N S w c-5 c'p^*-COt-^' !Cf the old wooden flume. The life of such piping is unusually long, the ~ 36 POWER WATER. losses in friction are very small, and in large sizes the cost is much less than for steel. In a quite recent power plant at Pueblo (U.S.) use is made of a wooden stave pipe, 30 in. diam., the staves being secured by steel bands spaced at 2|-8 in. centres, according to the head, which, in passing depressions, reaches 215 ft. This pipe-line, 4 miles in length, is constructed through extremely rough country, some of the curves being of less than 100 ft. radius, and one compound curve is stated to have a radius of 35 ft. The pipe passes through a tunnel over 1500 ft. long, and a portion of it is suspended by cable. See Figs. 3, 4. Pipes, Iron and Steel. The pipe most generally in use, however, is made of wrought iron or steel. In fact, outside of the United States one could hardly find either suitable timber or the requisite mechanical skill for making wooden pipes. Strains. In practice it is rare tttat the pipe lies more than 20 ft. below the hydraulic grade-line, and consequently the pipe is not called on to withstand more than 10 Ib. per sq. in., which is within the strength of ordinary stove-pipe iron. On the other hand, occa- sionally the static head runs into high figures, examples in opera- Strengtli of Sheet-iron Piping. (Van Wagenen.) Head of Water, in ft. 100 150 | 200 250 300 400 500 600 800 100 Resulting Pressure against Sides of Pipe, in Ib. per sq. in. !> 43-4 i 65-1 Required Thickness of Pipe, in inches or decimals of an inch. 2 009 '013 018 022 027 036 '045 055 075 095 3 013 ! '020 026 033 040 054 068 082 112 143 4 017 '026 035 ; 045 053 072 090 110 149 191 5 022 ! -033 044 056 067 090 113 137 186 237 6 026 -040 053 067 080 108 136 165 224 287 7 030 j '046 062 078 093 126 159 193 261 333 8 034 -053 671 089 107 144 181 220 298 382 9 039 j -059 079 101 120 163 205 247 335 427 10 044 '066 089 112 134 181 -227 275 373 475 12 053 I -080 106 134 161 217 '273 330 448 575 14 061 -093 124 156 187 253 -318 387 523 666 16 069 '106 142 178 214 288 -363 1 -440 596 763 18 078 -120 159 201 242 326 -409 i -495 670 850 20 088 -132 177 223 267 361 '454 549 746 950 24 105 '159 213 268 321 433 '545 660 895 1*150 30 132 '198 267 336 402 543 ; '681 825 1-120 1-420 36 156 -238 318 402 483 651 *819 990 1-340 1'710 42 184 -279 372 469 562 759 955 1-160 1-570 2'000 48 210 -317 425 535 641 866 1-090 1-320 1-790 2 '290 POWER WATER. 37 Thickness and "Numbers" of Sheet Iron. No. 4 has a thickness of 250 in. 7 8 9 10 11 12 13 14 15 16 17 200 166 142 133 111 100 090 083 076 071 066 062 058 No. 18 has a thickness of 19 20 21 22 > 23 24 25 26 ,, 27 28 29 30 055 in. 052 ,, 050 047 ,. 045 044 041 040 038 037 035 034 033 Ordinary Dimensions of Pipe Lines. Diameter of Pipe. Pressure. No. of Iron. Thickness of Iron. in. ft. in. 22 150 16 0-060 22 150 to 250 14 0-078 22 250 to 310 12 0-098 30 150 14 0-078 30 150 to 275 12 0-098 40 160 0-236 1 tion reaching 940 lb., 1047 lb., and 1165 Ib. per sq. in. r the falls ranging between 2000 and 3000 ft. The annexed table shows the thickness of iron piping necessary to withstand given pressures. The iron used varies generally from No. 16 to No. 11, according to the pressure, the best iron only being employed. The size of the pipe will depend upon the supply of water; with 1500-2000 miners' *' inches " of water, a 22-in. pipe will suffice ; where the supply is 3000 " inches," a 30-in. pipe must be used, and so on. No. 14 iron will resist a pressure of 300 ft. head, or 130 lb. to the sq. in. ; and an 11-in. pipe of No. 16 iron, a pressure of 500 ft., or 217 lb. to the in. No. 14 iron is "083 in. thick, and weighs 3-35 lb. to the sq. ft. ; No. 16 is -065 in. thick and 2 '63 lb. to the ft. Persons having no practical experience generally make their pipes unnecessarily heavy. (Hep. State Mineralogist, Cali- fornia.) Eiveted pipes cause eddies and consequent loss of head, and are more liable to corrosion. The best system of riveting is Ferguson's spiral. Lap welding is ordinarily too costly. In the Ferguson locking-bar system, the joint is made in the cold by hydraulic pressure, and is superior to all others. Material economy may be secured by graduating the thickness 38 POWEK WATER. of the metal employed to the pressure which each section of say 100 ft. of the pipe will have to withstand. With a riveted pipe, it is necessary to bear in mind the shearing effect of the rivets, as well as the tensile strength of the metal. Every pipe should be submitted to hydraulic test at double the pressure which it will be called upon to bear in work, and be rejected for the least sign of weakness. In estimating the working pressure, it is not sufficient to calculate simply the Ib. per sq. in. represented by the column of water at rest ; a very wide margin must be allowed for pulsation and jar ordinarily not less than 50% extra, and in extreme cases as much as 150 to 200%. In this respect, the resisting strengths of cast iron, wrought iron and steel plate have been proved to be in the proportion of 1, 6, and 20, which fact should suffice to determine the selection of steel pipe under all circumstances. The strains which pipes of this nature have to stand are due to internal pressure, bending, expansion, sudden shocks, and possibly also to a crushing strain arising from the creation of a vacuum, The thickness of pipe to withstand the pressure due to any head can, of course, easily be determined ; but seeing that the sudden si locks which might arise from quick closing of valves and tardy action of safety appliances, cannot be ascertained with any degree of accuracy, it is well to err on the side of safety. All pipe lines should be fitted with several spring relief-valves, mainly for the purpose of relieving the almost instantaneous rise of pressure, and consequent shock, arising from the ram action that takes place when the water issuing from the nozzles is sud- denly arrested either entirely or partly. This is more likely to occur where small nozzles are used, because, however careful one may be in guarding against such an occurrence, it is almost impos- sible to prevent foreign substances, such as weeds, twigs, small stones, bits of wood, etc., accidentally getting into the pipe line at the reservoir end. Sometimes nozzles of only J-in. diam, are used, and of course a very small quantity of foreign matter would entirely or partly close the orifice. Expansion. One of the problems in connection with laying down steel-pipe lines for power purposes is expansion. For , example, with a difference of temperature of 100 F. a steel pipe 100 ft. long will lengthen f in., which means that a straight pipe a mile long will extend over 3 ft. When working under ordinary conditions, with the pipe full of water, the difference of tempera- ture is never likely to be so much as this, but 50 F. is not by any means unknown. If the pipe cannot be laid in a trench in the ground and covered with turfs (leaving only the joints exposed), it should be painted a dull white, to reflect the sun's rays, and dimin- ish the movement due to expansion and contraction. Some makers take up expansion in flanged-joint pipes by inserting at intervals short lengths of corrugated pipe, but these are not to be commended. An ingeniously simple and cheap expansion joint consists of a POWER WATER . 39 well-soaked leather washer between two gasket rings on this out- side of the pipe, and allowing this to play inside a 6 ft. length of larger pipe. Lengths. As to lengths, while 6-7 ft. of large cast-iron pipe is quite enough for convenient handling, 20-30 ft. of steel pipe of the same capacity can be easily manipulated, although it might not be desirable to have it all in such long sections. The fewer the lengths, the fewer the joints, and, as these are the most likely spots for leakage, a lessening of their number is advantageous. But excessive length anything beyond ordinary railway-wagon length, tor example would be most inconvenient, and liable to result in damage during transport. Joints. Joints are of three principal kinds flanged, screwed and independent. The first is the only feasible form for cast-iron pipes, the flanges being simply faced in some cases, with a plain leaden gasket ring, or an iron one and packing of tarred flannel; a 1 \ / a TW a ^m\ FIG. 0. FLANGED JOINT FOR PIPES. FIG. 6. BOLTED JOINT FOR PIPES. etc., between ; or one end may be recessed or grooved to receive a corresponding bevel or projection on the other, with round rubber packing. The best of these styles is shown in Fig. 5, which is that adopted by Armstrongs for withstanding 700 Ib. per sq. in. The flange is cast on the pipe, and is strengthened by brackets. Wrought-iron pipes may have a flanged joint, and be bolted together ; and the flange may be attached by screwing or riveting. With a flanged joint, there is often considerable difficulty in securing tightness; a screwed joint, on the other hand, is very costly, and can be applied only to welded pipe. Incomparably the best joint in the author's experience is the independent bolted joint shown in Fig. 6. It occupies no more space than flanges ; it can be made and unmade in a fraction of the time ; it is not affected by expansion or contraction of the pipes; it permits a faulty length of pipe to be removed and replaced most rapidly and simply, with a certainty that the new length will fit and make an 40 POWER WATEE. equally good joint ; and it allows of quite as much bend or depar- ture from a straight line as any pipe line should have. It is dependent upon the tarred-rope or rubber packing a being compressed into extremely close contact with the pipe-ends by means of the bolts fc, the shoulders c, and the cast-iron ring d. It is made by Mephan Ferguson, Footscray, Melbourne, Victoria, and has been widely applied throughout Australia. The author used it in a most trying situation, on a column of 10-in. x 18-gauge and 24-gauge steel pipe 600 ft. high, exposed to daily alternations of temperature amounting to over 50 F., and sometimes a severe " water-hammer," without a single joint even " weeping." Very similar is the " Acme " joint of Lewis & Sons, Wolverhampton, but it necessitates flanging the pipes. The socket or Kimberley joint is sealed with lead ; each pipe length then takes up its own expansion, and the joints can be caulked or re-made easily. These joints also enable the pipe to follow slight inequalities of the ground. To ensure efficiency with lead joints, it is best to lay the pipes straight from point to point, and, where sharp bends must be made, the angles should consist of strong junction-boxes secured on rigid foundations. Between these boxes the pipes act as columns in compression, and such columns being in unstable equilibrium, the pipe must be held in line by being clamped down to foundation blocks at frequent intervals. In this way, the end pressures are received entirely by the junction boxes, and the transverse pressures by the pipe clamps. In many cases, on small installations, the only joint needed is the slip or stove-pipe or telescope joint, as it is variously called. The larger or female end is slightly expanded by wrapping around it an absorbent material soaked in kerosene, and igniting it ; the heat slightly stretches the metal and softens the pitch coating, whereupon the male end can be driven home. With pipes of large diameter, the sections are faced together by using a set of triple blocks on each side, having 2 men operating each set of blocks, and a fifth man to guide the mnle end of the pipe and at the same time jar it to a tight fit by using a heavy hammer or beetle against a slab of wood on the end of the pipe. It is often practicable and desirable to divide the line into two or three different sizes. If shipped ' made-up," this permits of the pipe being stacked, one section inside of another, thus economising in freight. Or pipe of this character can be cut, punched, formed, and shipped nested at dead weight, and riveted up on the ground into a continuous line. This is sometimes less expensive than to ship the pipe made up. Pipe, Pressure in. Pressure (Ib.) = diam. (in.) squared x ' 341 X height (ft.). Ex. Required pressure in column of water 20 ft. high in pipe 12 in. diam. Ans. 12 (in. diam.) x 12 X "341 x 20 = 982'081b. POWEE WATEE. 41 Pipe, Contents. The square of the diam. (in.) gives the weight of water (Ib.) in 3 ft. length. Ex. Contents of a pipe 15 in. diam. and 9 ft. long = 15 x 15 X 3 = 675 Ib. Pipe, Discharge. To find pipe diam. required to effect given discharge at given speed Discharge (cub. ft.) x 144 -5- velocity (ft. per min.); divide result by '7854, and take out square root = diam. Pipe Velocity. To ascertain velocity required to discharge given volume in given time Multiply volume (cub. ft.) by 144 and divide product by pipe area (sq. in.). Water Wheels. There are various types of water-wheel, according as it is desired to make use of large or small volume and great or little fall. The height of fall (ft.) x volume (cub. ft. of water per min.) -*- 706 = actual brake h.p. The h.p required x 706 -r fall (ft.) = re- quired volume (cub. ft. per min.). Volume available and h.p. required being known, h.p. x 706 and -r- volume (cub. ft. per min.) = height (ft.) necessary to produce the h.p. These are all calcu- lated on 75% efficiency. With overshot wheels, the factor 706 must be increased to 815 ; this means only 65% efficiency, which is as much as can be relied on after allowing for loss of power in increasing speed through the medium of heavy gearing wheels. The old-fashioned water-wheel is, at best, clumsy and cumbrous, but in cases where the fall is less than 20-25 ft., it may be used, provided there is no scarcity of water, and that the cost of transit of so ponderous a machine is not serious ; but the danger of acci- dent to the gearing wheels, and the wear of bearings, render it out of place in most instances. It is very largely superseded by turbines, which are so much lighter, and which make so much better use of the water. A good turbine will give 80-90% efficiency, but not more than 80% should be reckoned on in any case. The four principal types of wheel and their applicability are: Undershot or breast wheels : max. head, 6 ft. ; efficiency, 25-50%. Overshot wheels : head, 5-50 ft. ; efficiency, 75%. Reaction wheels or turbines : head, 5-100 ft. ; efficiency, 80-90%. Tangential or impulse wheels, also known as Pelton wheels and "hurdy-gurdies" (U.S.) : head, 50-2000 ft. ; efficiency, 85-90%. Turbines. For making the most of the power contained in a stream of low fall there is no machine like a well-designed turbine. Generally, Po WEE WATER. where the fall is low it is also inconstant, the supply varying too. Such variations need special provision to get anything like satisfac- tory efficiency out of half-gate (or less) flows. Yet installations are not unknown where the fall is only 2 ft., and where excellent results are obtained from even quarter-gate volume. For greatly fluctuating falls, the most constant speed without sacrifice of effi- ciency is probably secured with the Jonval turbine. The annexed table, wherein efficiency is reckoned at 75%, is applicable to turbines : Water needed (cub. ft. per min.)for various powers under stated heads. Horse-Power. 8 10 15 20 30 40 50 60 70 80 h 3 ft. fall 1883 2353 3539 4 . 1412 1765 2648 3530 6 ,, 941 1176 1765 2353 3530 8 706 883 1324 1765 2648 3530 10 565 706 1059 1412 2118 2824 3530 12 471 588 883 1176 1765 2353 2940 3530 15 311 471 706 942 1412 1884 2353 2824 3295 20 282 353 530 706 1059 1412 1765 2118 2471 2824 25 1 226 282 424 565 847 1130 1412 1694 1977 2260 30 189 236 353 471 706 942 1176 1412 1648 1883 35 161 202 303 403 606 806 1010 1212 1412 1612 40 141 176 265 353 530 706 883 1059 1235 1412 45 125 157 235 314 471 628 784 941 1098 1255 50 113 141 212 282 423 565 706 S47 988 1130 60 94 118 176 235 353 471 588 706 824 942 TO 81 101 151 202 303 403 505 606 706 807 80 71 88 132 1 176 265 353 441 530 618 | 706 100 ., 56 71 | 106 ; 141 212 282 353 424 494 565 Turbines, proportions. (Cullen.) Q The quantity of water in cub. ft. per second. H The height of the waterfall in ft. P The H.P. of the water at 75 percent. .. = 700' d The inner diameter of the wheel N The number of buckets B The breadth of shrouding .. .. = d x 3 X 28. _ d X 55 POWER WATER. 43 T> 8 The shortest distance between two buckets = . D The external diameter to point of buckets = B x 2 + d. A The sectional area in inches between all) _ 'Q X 60 the buckets / ~~/s/Hx2'18 h The height of buckets = -^- , N fe 1) The breadth of rim for directors = S x 2*8. r The radius for centre of directing channels = D x 3*6. v The velocity of inner circumference for low) / falls .. I = ^H X 4-4. Y The velocity of inner circumference for) o high falls } = /Hx8-l. R The revolutions of wheel per minute .. TJ The diameter of turbine shaft in inches .. Note. A = -Tf= ~for high falls ; but A = nQ for VH x 2 '18 '0q falls under 38 ft. Power is gained by extending the shroud about | its breadth past the buckets when the water leaves" them. Ex. (a) Given 100 cub. ft. water per sec. in a waterfall 9 ft. high, required the proportions for a turbine to be driven by 50 cub. ft. per sec., and 25 cub. ft. occasionally, to yield at least 75% effi- ciency under either conditions. Ans. -,-= + -1 = 7*03 ft., the interior diameter. d X 3 + 28 = 49, nearest number of buckets. J5 = 7 89 in., breadth of shrouding to point of buckets. . B ^_^ = 1-753 in., shortest distance between two buckets. Bx2 + h. Calories. b.t.u. 97 8300 14,940 63 8400 12,120 94 8450 15,210 60 8200 14,760 90 8600 15,480 57 7900 14,220 87 8700 15,660 55 7700 13,860 80 8800 15,840 53 7400 13,320 -.2 8700 15,660 51 6900 12,420 68 860d 15,480 The relation between calorific power of a coal and its composi- tion as indicated by proximate analysis is very closely represented by the formula, P = 82 C 4- a V, in which P is the calorific power, C the percentage of fixed carbon, V the percentage of volatile matter and a is a variable coefficient, which is dependent upon the tenor V 1 in volatile matter of the pure fuel, that is, the fuel minus ash and moisture. (v 1 = 100 . The values of the coefficient a corresponding to different values of V 1 when plotted differ but little from a straight line, the values being as follows : V 1 5% 10% 15% 20% 25% 30% 35% 40% a 145 130 117 109 103 98 94 80 In the case of anthracite a = 100. The average calorific 54 POWER STEAM. power of anthracite is 8250 calories. The calorific power rises with the content of volatile matter to the maximum of about 8700 calories when V is between 10 and 30 %, and then falls as the per- centage of volatile matter increases further. The formula was deduced from calorific determinations of 600 coals of different kinds, and gives results which in nearly all cases agree within 1 %. (Goutal.) All coal, therefore, should be examined for carbon, ash, and volatile matter, and be purchased only on its heat value basis as determined by analysis. Coal invariably deteriorates by storing, especially if exposed to the weather. Good bituminous coal will lose 6 % by lying in the open air for 2 years. Some coals are liable to spontaneous com- bustion when wetted ; others " slack " or fall to powder under the influence of air ; and others again intumesce, forming channels and crusts, and cannot be used in gas producers. Sometimes, with coal producing an abundant ash, the ash carries much unburned coke, which may be jigged out, amounting to as much as 5 % ; this can be burned quite well with forced draught. Great saving may be effected in pulverising coal for mechanical stoking ; with equal evaporation it may reach 29 %, and with equal amounts of coal the increased evaporation may be 48 % in favour of pulverised coals. Coke. Coke should be tested for moisture, as well as for carbon, ash, and volatile matter ; also for sulphur, in some cases. Some coke is too dense, some too friable, and some too ashy (12-19 %). Wood. Perfectly dry wood, carrying only 2 % ash is valued at about 7800 b.t.u. ; wood with 25 % moisture = 5800 b.tu. Gener- ally it is computed that 2J t. dry wood = 1 t. coal; or '4 t. coal = 1 t. wood. Hard woods are generally superior to soft. The Cape Copper Co., in Namaqualand, use thorn (mimosa), costing 20-25s. per long ton, and the consumption averages 6 t. per 24 hr. for 80 h.p. = about 7 Ib. per h.p. per hr., or say 2 t. wood = 1 t. good coal. Fuels, Miscellaneous: Heating Values. b.t.u. Peat, completely dry, 4% ash 10,200 air-dried (25 % H;O), 4 % ash 7,400 Tan-bark, completely dry, 15 % ash 6,100 30% moisture 4,300 Straw, dry, 4 % ash .. 6,300. 10% moisture 5,450 Liquid hydrocarbons 18,000-20,000 Lignites 8,000-11,000 Wood charcoal 14,500 Hydrogen 82,000 Marsh gas 23,500 Olefiantgas 21,300 POWER STEAM. 55 Oil. The heating value of ordinary mineral oil (liquid hydro- carbons) is about 21,000 b.t.u. per Ib. (including the latent heat in the steam formed by burning the hydrogen), or about 45 % more than that of pure carbon. In ordinary locomotive boilers, 1 Ib. petroleum will evaporate 15 Ib. water (as against 1 Ib. coal = 7 Ib. water), and in special boilers as high as 18 '95 Ib. has been reached. For locomotive work, steam is more easily produced and is main- tained up the steepest gradients, and great economy is effected by reducing the supply of oil when descending or remaining stationary ; the life of the boilers is prolonged, inasmuch as the tubes do not foul ; the nuisance of smoke and the danger of sparks are entirely obviated. Most crude oils, having been obtained from wells, carry small proportions of water, as well as more or less sand or grit. The heavier and more viscous the oil, the greater the tendency there is to hold in suspension these deleterious substances. It can be assumed that no crude oil is perfectly clean. Therefore, in the installation of any oil-burning plant, special provision should be made for straining out all foreign matter. Arrangements should be provided for catching the water as it slowly settles to the bottom of the tanks. Sand increases the wear on the small annular nozzles of the burner, or, when using burners provided with specially small orifices, these may become altogether clogged. The gauze used for oil strainers should be formed of brass meshwork equal to about half the width of oil orifice in the burner. These strainers are not unusually placed on the oil pipe on each side of the pump, thus ensuring that no grit gets into the pump, and that any particles of old packing or other material from the pump cannot go to the burner through the last filter. A still more desirable plan is to have two strainers between the pump and the burners, so that, when one filter is being opened, the current of oil can be transferred by means of a pass-by valve through the other filter. There is no practical device that will directly separate the water from the oil, This can only be satisfactorily effected by allowing the water to settle to the bottom of the tanks by gravity. A thread of water blown into the oil burner effectually extinguishes the flame in the furnace, and, if the oil does not soon follow the water, there may be difficulty in relighting without introducing an outside flame. In order to ensure a supply of oil without admixture of water, the oil-suction pipe is caused to swing up or down in the oil tank to a level at which it is known that pure oil can always be obtained ; or the movable oil-suction pipe may be carried by a float. The suction tip is thus always maintained at a point within a few inches of the top of the oil. The tip is also surrounded by a steam-heating coil, the object of which is to slightly heat the oil in proximity to the inlet, thus increasing the fluidity of the oil, so that even in cold weather it may be readily 56 POWER STEAM. pumped. At the bottom of each tank there should always be pro- vided a cock for the purpose of blowing off any water which may have settled. Certain crude oils at the ordinary temperature of the atmos- phere are of great viscosity, which increases as the temperature gets lower. At 30 -40F., which is not an unusual outdoor temperature, the fluidity of the oil is so slight that it is almost impossible to pump it, or force it to the burner. It is therefore necessary in many regions that there should be means of heating the oil. In all pipes intended for transmission of crude oil, con- nections should be made to enable steam to be turned into them after shutting off the oil. They can be thus cleaned by the heat and the force of the blowing steam, and any deposited asphalts, paraffins or condensed hydrocarbons can be cleared out before the pipes become choked so as to impair their efficiency. The heating of the oil should never be carried to such a tem- perature as will cause decomposition of the hydrocarbons. With most burners it is desirable that a uniform pressure should be maintained on the oil circuit. A reliable plan is to pro- vide the oil chamber of the pump with what would correspond to an air chamber on a water pump, or to provide a separate tank or chamber in which a constant air pressure is maintained on top of the oil by additional means. In all oil installations, it is very important that the control of the oil and of the steam or compressed air should be so arranged that in case the delivery of any one is reduced or interrupted, a corresponding reduction or shutting off should be effected in the supply of the other elements. It is especially important that oil should in no case continue to be forced or pumped to the burners when the steam or air required for spraying is shut off, as in such an event the unsprayed oil is liable to flood in upon the hot brick- work, and a furnace explosion is likely to occur. Boilers. Duties. The practice of quoting boiler duties in " h.p. " is not sound, because the h.p. must depend on how the steam is utilised, i.e. in what kind of engine. It is much better to have a guarantee of its capacity in Ib. of steam raised per hr. at given pressure (say 70 Ib. per sq. in.) from stated fuel. The unit of commercial h.p. developed by a boiler is usually taken as 34J units of evaporation per hour; that is, 34| Ib. of water evaporated per hour from a feed- water temperature of 212 F. into dry steam of the same temperature. The standard is equivalent to 33,317 b.t.u. per hr. It is also practically equivalent to an evaporation of 30 Ib. of water from a feed-water temperature of 100 F. into steam at 70 Ib. gauge pressure. A boiler rated at any stated capacity should develop that POWEK STEAM. 57 capacity when using the best Coal ordinarily sold in the market where the boiler is located, while fired by an ordinary fireman, without forcing the fires, while exhibiting good economy. And further, the boiler should develop at least one-third more than the stated capacity when using the same fuel and operated by the same fireman, the full draft being employed and the fires being forced ; the available draft at the damper unless otherwise understood being not less than J in. water, column. The usual practice of boiler makers is to allow 10-12 sq. ft. heating surface and 33 sq. ft. grate surface to 1 h.p. The kind of fuel used would make an important difference as to grate surface. Many conditions modify calculations in determining the h.p. of a boiler, such as design, quality of material, facilities for cleaning, impurities in the water, calorific power of fuel used, attendance, and draught of chimney, etc. So also the factors of grate and heating surface, temperature of feed water, proper control of air to support combustion, steam and water space, circulation of water within the boiler, all vary with each type of boiler.used, and even with different proportions in the same type. Approximately the h.p., if externally fired, may be calculated thus circumference 'of shell (in.) X its length; then the pro- duct of the urea of all the tubes or flues x their length ; add these products together ~ 144 to find sq. ft. ; then 14 ; 144 represents the sq. ft. of heating surface in the shell, tube and flues, and 14 the sq. ft. of heating surface usually allowed per h.p. For internally fired boilers, the circumference or square of fur- nace (in.) x its height ; then the circumference of one tube x its length, and this product x the entire number of tubes, taking into account also the sq. in. of surface presented by the crown or tube sheet. Add these quantities together and -- 144 ; the quotient will be the heating surface in sq. ft. ; and this -- 14 = h.p. With a good draught for the furnace, 10 sq. ft. of heating sur- face, J sq. ft. of grate surface, 8 Ib. of good coal, and 1 cub. ft. of water evaporated per hr., may be estimated for each nom. h.p. that the boiler should develop. For cylindrical boilers, each nom. h.p. requires 1 cub. yd. capa- city, 1 sq. yd. heating surface, 1 sq. ft. grate-bar surface, 1 cub. ft. water evaporated per hr., and 28 sq. in. of flue area ; the area for entrance of air to ash pit should be J in. of grate area ; depth of ash pit, 18-30 in. The grate-bars should incline downward towards the front, lin. per ft. ; not over f in. thick and to ^ in. spaces between. The furnace should have at least 3 cub. ft. of space above each sq. ft. of grate surface. For horizontal tubular boilers, length of tubes should be 48 times the diarn. For soft coal, 4 in. diam. gives the best results, with 1 in. space between the tubes, and 2J-in. space between the 58 POWER S tubes and shell of boiler. Tubes should be set in vertical rows to facilitate cleaning. Firing. Furnace construction must be adapted to the fuel, and it is absurd to suppose that furnaces designed for burning anthra- cite or semi-anthracite fuel, will satisfactorily burn fuels containing 30 % or more of volatile matter. The percentage of volatile matter which a fuel gives off when heated is, in fact, a measure of the size of the chamber required for its complete combustion, and it is here that the laboratory examination of fuels yields results of the greatest value. Tn ordinary firing with any class of boiler, the air is for the most part admitted to the furnace through the air-spaces between the fire-bars. The layer of coal should be of uniform thickness and not too thick, and the clinker should not be allowed to obstruct the air-spaces. The fire should be fed at short intervals with corre- spondingly small quantities of coal, instead of allowing it to burn down low before throwing on a large quantity, thus lowering the furnace temperature by the abstraction of the heat required to gasify the volatile constituents of the new supply. The lowering of the temperature leads to a reduction of the chimney draught at the exact time when the highest temperature and the greatest admis- sion sire required to effect the combustion of the hydrogen, which, as a consequence, passes away unconsurned, having added nothing to the useful heat of the furnace. A portion of the carbon, also, which at the moment of throwing on fresh coal was floating about in the furnace at a high temperature in search of oxygen to com- bine with, is cooled down below the temperature necessary to its combustion, and passes wasted away into the atmosphere, either in the form of smoke or combined with the hydrogen as olefiant gas. The most important causes of low initial furnace temperature are excessive air supply to the furnaces, and too sudden contact of the half-burned gases with the water-cooled tubes or plates. Larger combustion chambers and refractory furnace linings are the proper remedy for the latter evil, and gas testing is the check and remedy for the former. If in an 8-ft. Lancashire boiler, 12 cwt. coal per hr. be used, it is obvious that J cwt. of this should be put in each flue every 5 min. If, as in hand firing, 3 times this amount be put on every 15 min., a very irregular production of steam is the result, and probably a very regular production of smoke, because 1J cwt. coal are put on a fire which has only the same amount of air going through the bars each minute, or, rather, somewhat less than it had before it received this charge of coal. It is more economical to work boilers at their full capacity and to have as few boilers at work as possible. Not only are radiation losses thus minimised, but the heat-absorbing powers of the re- maining boilers are improved. Incomplete combustion, radiation, and loss of heat in the chim- POWER STEAM. 59 ney are responsible for about 38% of the theoretical heat value in a boiler working alone. Lagging. Insufficiency or lack of boiler, steam-pipe and feed- water pipe covering is a fertile source of loss. Experiments have shown that each sq. ft. of uncovered steam or boil-er surface wastes on an average 10 cwt. coal per ann. An excellent lagging consists of chopped straw and clay or dung laid on 4-5 in. thick. A wrap- ping of old gunny bag will hold this on to pipes. Types. As to the best type of boiler for the economical produc- tion of steam, it may be taken for granted that all surviving well- known types of boilers are capable, each in its own way, and for its own purpose, of effective steam raising if properly handled. Of these, the principal in general use are the Lancashire (double-flued cylindrical) boiler, the Cornish (single-flued) ; the water-tube, in various forms ; the loco-type ; and the internally-fired, return-tube boiler. The smaller kinds of vertical boiler, and small boilers of any kind, as a rule, are installed with other objects than fuel economy. Externally-fired cylindrical boilers of all kinds are out of the running, on account of the inevitable deposit of scale on the bottom just where it is exposed to the greatest heat. The Lancashire boiler, with addition of a good steam dome as a preventive against priming, due to excessive water-feed by careless native stokers, is about the best all round for mine work. The old-fashioned return-tube boiler, for moderate pressures, and with the exercise of ordinary intelligence in the choice and care of its setting, grates, etc., will do just as good work as any water-tube boiler, and often better than many of them. No class of stationary boilers is operated uniformly under such high pressures as are loco-type boilers, nor do any boilers evaporate as much water. With the strong draught due to the exhaust steam entering the stack, a tremendously high rate of combustion is possible, and it. is customary to allow only 2-2 '5 sq. ft. of heating surface per h.p., while 10 sq. ft. is a moderate allowance for station- ary boilers. Water-tube boilers are not much used on mines, as the circum- stances are not very suitable to them. With high-speed engines and good water, they may be used in connection with mills and electric stations, but for winding purposes they are quite out of place. For mining work it pays in the end to have extra boilers, as a stand-by during cleaning and repairs, and for sudden emergencies in extra pumping or baling. No boiler should run more than 3 months without examination. Care of. Boilers should be tested to a pressure half as much again as that to which they are to be worked. Though hydraulic tests are m9re severe, even with warm water, than steam pressure tests, they are not sufficient by themselves to ensure against explo- sion, especially in the case of bricked-in boilers. They should be supplemented by thorough internal inspection, with plenty of 60 POWER STEAM. hammer testing for impoverished plates. Bottom shell plates beneath the fire box should be exceptionally carefully examined, owing to their liability to corrosion from moisture and leakages from gauge-cccks, etc. Ashes should not be piled in front of the boiler, as the gases thus produced are stated to be capable of de- stroying a in. plate in less than 18 months. Top blow-offs should be totally avoided, since they are likely to render new boilers dangerous through corrosion of the plates by the slime or silt, which is always left behind, and which accumulates round the bottom of the pipe if ending vertically, or along the sides of it if it is a perfo- rated longitudinal one. They should be replaced by a bottom blow-oif. The boiler should be blown out every 24 hr., and the water-gauge every hour. Safety-valves, owing to their being made of one pattern, and fitted to the boiler irrespective of the working pressure, are defective from the commencement, more often than not; they should not be set or checked by the pressure-gauge, since the latter Las always an error which fluctuates with the pressure. It ought to be the other way about, the gauge being checked by the valve, and annually tested against mercury. The valve should be lifted every 24 hr., and should dance on the cushion of steam before reseating itself after being released. Government boiler inspection is insisted on in some countries. and generally performed in the most perfunctory manner. Hence, the English system of an inquiry after an accident works better than any compulsory inspection by Government officials, and has made boiler owners careful. Mechanical Stokers. Frequently, cheap fuels, perhaps rather small, from one colliery, contain nearly, or quite, as much heat as other fuels of larger size and much more expensive, from another, or even from the same colliery. It makes little or no difference to a mechanical stoker what the size of the fuel may be it will burn one as efficiently as the other : in fact, it prefers fine coal. A few examples from English experience maybe given : (a) Rough slack used in hand firing contained 10,698 b.t.u. per Ib. and cost Ss. per ton ; fine slack, only possible in mechanical stoking, contained 12,070 b.t.u., and cost 6s. 9r?. economy 37 %. (6) Hand firing coal 10s. 6d. per ton : smudge burned mechanically, 4s. economy, 57 %. (c) Economy, 28*8%. (d) Economy, 23 %. In many situations it means permitting the local inferior fuel supply being availed of. as against importing English coal at great cost. On the other hand, mechanical stokers are costly at first, and are as liable as other machinery to suffer from careless handling, and they do not always pay to instal. A coal which cakes and arches, or which clinkers much, is apt to cause much trouble with them. Forced Draught. With some very low-class fuels, forced draught, by means of large slow-speed fans handling ample volumes of air at low pressure, is a necessity ; and when such fuel has a tendency to clinker, steam blowers may be used intermittently. POWER STEAM. 61 Forced draught, as opposed to natural (chimney) draught, per- mits an increased efficiency through diminished grate area and accelerated combustion, hence better economy. Liquid Fuel. To obtain the greatest efficiency from oil fuel, it should be burned in a confined combustion chamber, so as to obtain the highest possible temperature. To do this, the chamber must be of a refractory non-conducting substance, which soon becomes heated to incandescence ; and all gases, together with the incoming air, pass through this focus of heat. The heated brick-work is of still greater use in ensuring perfect continuity of the heat supply, especially when burners tend to act in gusts, as they often do under improper action of the pumps, or where there is dirt or water in the oil supply. When the oil is injected with a steam jet, better results are obtained than when air is used as the spraying medium; and the steam-injected oil seems to have a much softer flame, and to be easier on the furnace plates. Feed Water. Water is generally described as being soft or hard. It is called hard when it contains considerable quantities of the salts of calcium and magnesium in solution ; but when only a small quantity of these salts is present, it is called soft. The chlorides, sulphates, and nitrates of calcium and magnesium are easily dis- solved and maintained in solution by water, but the carbonates of these elements can only be maintained in solution by an excess of carbonic acid in the form of bi-carbonates. The following distinctions are made with regard to hard waters : (1) Temporary hardness, that is hardness caused by the bi- carboimtes of the alkaline earths, and which disappears in boiling. (2) Permanent hardness, that is, hardness caused by the chlorides, sulphates, and nitrates of the alkaline earths, which is not lessened by boiling. The sum of the tem- porary and permanent hardness is the total or aggregate hardness. In order to express the relative hardness of different waters, the following measurements have been adopted : England . . 1 grain of calcium carbonate (CaCO 3 ) per gallon of water. France .. 10 milligrams of calcium carbonate (CaCO 3 ) per litre of water. Germany . . 10 milligrams of calcium oxide (CaO) per litre of water. Calcium,' in the form of bi-carbonates and sulphates, is the chief constituent of the dissolved mineral matter in hard water, whilst it occurs also in small quantities as chlorides, nitrates, and 62 POWER STEAM. nitrites. Next in order conies magnesium in the same combination as calcium, The bi-carbouates of iron and manganese, and the car- bonates, chlorides, sulphates, nitrates, and silicates of sodium and potassium, are rarely absent, but seldom occur in large quantities. Water also absorbs oxygen, nitrogen, and carbonic acid, and occa- sionally sulphuretted hydrogen may be found in it. Organic matter occurs in some lake and river waters. Carbonic acid enables water to dissolve substances, such as the carbonates of calcium, magnesium, iron, and manganese (which pure cold water could only dissolve with great difficulty, in minute quantities, if at all), by converting the carbonates into bi-carbonates, the bi-carbonates being soluble in pure water. It has been found from experience that scale over the heating surfaces of a boiler to the thickness of ^ in. will cause a waste of about an eighth of the efficiency of the boiler, and the waste increases as the square of the thickness. The amount of incrustation varies considerably with the quality of water, and with the regularity with which the operations of blowing through and cleaning out are practised. Occasionally vegetable matter of a glutinous nature, held in suspension by the feed water and precipitated by heat or concentration, covers the heating surface with a thin coating almost impermeable to heat, and which hardens the mineral deposit, so that it is next to impos- sible to remove it, and hence causes over-heating. Softening. The Porter-Clark process is based on the following theory: When ordinary burnt lime or calcium oxide is added to water which contains the bi-carbonates of lime or manganese, the excess of carbonic acid necessary to keep the lime or magnesia in solution in the form of a bi-carbonate combines with the calcium oxide, forming insoluble carbonate of lime, both by the decomposi- tion of the bi-carbonate of lime, and by the combination of the excess of carbonic acid given off in decomposition with calcium oxide added to the water. In this reaction the carbonates only are precipitated. The sulphates are precipitated by using a small quantity of soda, Na 2 CO 3 . The sodium carbonate and calcium sulphate mutually exchange their acids, forming insoluble carbonate of lime and soluble sulphate of soda. The latter salt is so very soluble that it is not precipitated even after much concentration upon evapora- tion, and thus it flows out of the boiler when the mud-plugs are removed for washiug-out. A little alum is mixed with the soda to aid the precipitation ot solid matter held in suspension by the water; it also materially assists the precipitation of the salts in the precipitating tanks. The reaction is represented by the following equations : OaSO 4 + Na CO 3 = CaC0 8 + Na,SO 4 . H 2 Ca (C0 3 ) 2 +CaO = 2 CaC0 3 + H,O. HJVIg (CO 3 ) 2 + CaO = CaCO s + MgCO 3 + H a O. POWER STEAM. 63 The quantity of lime required to soften 1000 gal. of water is 2 '24 Ib. ; soda 4 '5 Ib. ; and alum '1 Ib. The above quantities give very satisfactory results. It is not found necessary to reduce the degree of hardness lower than 6 and 7, as the heating surfaces are kept practically clean when water of this degree of hardness is used. The water, after being softened, dislodges old incrusta- tions and deposits from boilers previously using hard water. (W. W. F. Fallen, Proc. Inst. C.E., xcvii. 354.) On the basis that 1 Ib. coal at 8s. per ton burnt in the furnace of the boiler will convert 9 Ib. water into steam, the cost of eva- porating 1000 gal. \vator would be 4s., whereas the cost of the water, even including softening, should not exceed 6d. per 1000 gal. As an average statement, it is safe to say that the use of water of 20 hardness will cause a loss of 15-20 % in fuel ; that is to say, the decrease in the efficiency of the boiler due to scale formation, more frequent blowing off, increased repairs, etc., will be about 20 %. This means an increase in the cost of evaporation of about Is. per 1000 gal., whereas the cost of softening (including interest on plant) should not, in an extreme case, exceed 3d. per 1000 gal. From the point of view of steam raising, the softening of water is thus well worth consideration. Various forms of apparatus are in the market. The combined purifier and filter made by the Humboldt Engineering Works is very good. The cost of installation may range from 20s. per h.p. (up to 1000 h.p.) down to 5s. per h.p. (in plants of 15,000 h.p.). Chemi- cals vary from JcZ. to 2|t?. per 1000 gal., according to hardness, and commonly are %-ld. Attendance and power should be almost nil. Economies resulting may reach as high as 56 % of the fuel bill. Heating. In the conditions of ordinary practice it is computed that a saving of 1 % in fuel is made for each increase of 11 F. in the temperature of the feed- water. The heating medium may be (a) live steam, taken direct from the boiler, or (6) exhaust steam, which might otherwise go to waste. At first glance, it would seem impossible to gain anything by taking steam from a boiler to heat the feed- water for that boiler, except in the matter of purification, and the prevention of stresses due to unequal expansion. The idea of a thermal gain, or saving of fuel, would seem preposterous, inasmuch as all the heat taken from the boiler would be returned thereto, neglecting radiation losses, leaving the heat balance just the same. Yet actual economy has been proved by the use of live-steam heaters. The explanation lies in the fact that the hot feed-water is better able to absorb heat rapidly than the colder water, while at the same time the circulation is augmented, which further tends to increase the rapidity of heat transmission. The prevention of heavy scale formations also facilitates the heating and reduces heat losses. A great consideration is safety. It is no longer a matter of 64 POWER STEAM. doubt as to what effect cold feed-water has upon a boiler, especially one carrying high steam pressure. Engineers have come to recognise the fact that it is extremely poor practice to introduce comparatively cold feed-water into a boiler whose plates are at a temperature of 100-200 higher than that of the water. The contraction and expansion set up by changes of temperature hasten the deterioration of the shell, and weaken it, by the well-known principle of fatigue of metals, and contrary to all ideas of safety. Koughly 1 Ib. of exhaust steam at atmospheric pressure possesses sufficient heat to raise the temperature of 6 Ib. of water from 50 F. up to 212 F. When this operation is performed in an open heater, the resultant is 7 Ib. of boiling hot water, because, in the open heater, the 1 Ib. of condensed steam is conserved and utilised as part of the boiler-feed supply. When the operation is undertaken in a closed heater, the resultant is only 6 Ib. of hot water for the boilers, because in a closed heater the condensation of the steam used in accomplishing the heating is wasted, as it is contaminated with oil. Therefore a given quantity of exhaust steam will heat more water to a given temperature in an open heater than in a closed heater ; or, with a limited supply of exhaust steam, the feed water can be heated to a higher tempera- ture in an open heater than in a closed heater, and consequently an open heater will give the greater fuel economy. Where the supply of water suitable for boiler-feed purposes is limited, or where the cost of pumping this water is high, it is im- portant that an open heater should be used, since the closed heater under ordinary conditions requires about J more fresh water to make up the supply required by the boilers. Again, an open heater will materially improve the quality of any boiler-feed supply, no matter how bad it may be, giving opportunities for purification that the closed heater cannot give. In an open heater, as already pointed out, i of the entire feed supply is made up of condensed steam. This is perfectly free from scale-forming impurities, and is itself an element of purification. Besides this, an open heater gives the opportunity for precipitating within the heater some of the most common and troublesome scale- forming impurities, such as the bicarbouates of lime and magnesia, because, being vented to the atmosphere, it permits the escape of the carbonic acid gases which are liberated when the water is heated to a temperature of 200 F. or over; and provision can e.asily be made in heaters of the open type for the detaining and removal of the resulting precipitates and other solid impurities (through sedimentation, filtration and flotation). To gain com- plete protection from the formation of scale in boilers, it; may also be necessary as when the water contains sulphates to employ chemical treatment in conjunction with special apparatus for the purpose. The use of an open heater also provides for driving off any air and free gases carried in the feed supply. POWER STEAM. None of these opportunities for purification is presented in the closed heater. Being operated under a pressure exceeding that of the boiler, it cannot be vented for the escape of the gases, thus making impossible any considerable precipitation of the soluble impurities ; nor can any effective provision be made for settling the solid impurities out of the water, because the water is kept in constant agitation. These advantages are sufficient to determine the use of open heaters in mining districts. The scant purification which is obtained in a closed heater is at the expense of heating efficiency, for the precipitated impurities build up a coating of scale on one side of the tubes or coils, while on the other side is collected the oil with which the exhaust steam is contaminated. Both materially hinder the transmission of heat, and cases are now on record of closed heaters which, when new and clean, gave temperatures of 200-210 F., but which, after a few months' service, would not raise the temperature of the water above 160-170. Again, an open heater is much easier to care for; there is free access to the interior, and it can be thoroughly cleaned without disturbing the pipe connections. An open heater can be made cheaply and easily on any mine, out of an old boiler shell, plated up at the ends, and passing the steam exhaust pipes through it. The absolute prevention of any grease or mineral oil entering the boiler is of vital importance. Even a coating of quite inappre- ciable thickness such as may be left after wiping off carefully all that can be seen will effectually prevent actual contact betwe.en the water and the boiler plates, and a temperature may thereby be induced in the latter of over 800 F., whereas all kinds of iron and inild steel are extraordinarily weakened and rendered brittle at about 630 F. Engines. Duty. Calculations of the duty or h.p. of an engine can only be approximate, as they are modified by such factors as the friction of the moving parts, the loss of steam at valves and joints, amount of condensation, quality of lubricants, amount of load, and so on ; but the following rules may be useful : (a) Piston area (sq. in.) x mean pressure (Ib. per sq. in.) on piston x piston speed (ft. per rain.) -4- 33,000 ft.-lb. = h.p. Ex. Find h.p. of engine whose piston is 12 in. diam., stroke 16 in., rev. 140 per min., steam pressure 30 Ib. Ans. Area = 12 in. x 12 in. = 144 sq. in. x -7854 = 113-0976 sq. in. of circular area x 30 Ib. pressure = 3392-928 Ib. x speed (16 in x 2 x 140) = 4480 in. = 373-3 ft. per rain. = 1,266,580 '0224 -- 33,000 = 38 '38 h.p. (6) Piston diam. (in.) squared x stroke (in.) x rev. per min. x 4. Cut off 5 figures from the right and x mean pressure (Ib.) = POWER STEAM. h.p. Ex. Diam. (12 in.) x 12 = 144 x stroke (16 in.) = 2304 x rev. per min. (140) = 322,560 x 4 = 1,290,240; remove 5 figures = 12-9 X pressure (30 Ib.) = 38- 7 h.p. Cost of Steam Power. Various estimates have been- made of costs of steam power under different conditions. (a) Generated in 1000-h.p. units, with coal at 16s. per ton (2000 Ib.) and allowing 5% interest, 3J% depreciation, 2% repairs and 1% insurance, and iaxes = 70s. 10 Year (300 working days of 10 hr.). Coal at per Cost per h.p. hour. (2000 Ib.). 31 4,b. 5lb. 6lb 71b. 81b. s d s. d. s. d. S. d. s. d s. d s. d. 8 4 37 6 50 62 6 75 87 6 100 10 5 46 10 62 6 78 1 93 9 109 4 125 12 6 56 5 75 93 9 112 6 131 3 150 14 7 65 7 87 6 103 1 131 3 154 2 175 16 8 75 100 125 150 175 200 18 9 84 4 112 6 140 7 168 9 197 11 225 20 10 93 9 125 156 3 187 6 ; 210 9 250 En. & M. Jl., Jan. 27, 06. (0) High-speed steam engine, with Lancashire boiler : 25 h.p. unit. 100 h.p. unit. Coal : 5 Ib. and 4 Ib. per b.h.p.-hr. respectively, at 12s. per ton .. Water: 4 gal. per b.h.p.-hr. at 9d. per 1000 gal Labour: 15s. and 27s. per week, respectively Interest, depreciation, etc. 10% 90 d. 289 5 d. 10 2 Cost per h.p. per ann. 37 10 35 173 6 18 40 67 10 100 496 15 4 19 4 POWER ELECTRIC. 67 (ft) Cost of fuel per h.p.-hr., with coal at per ton (2000 Ib.) as follows : Coal, Ib. per 4s. 2d. 8s. 4d. 12s Gd. ; 16s. 8d. 20S. lOd. 25s. Od. 29S. 2d. h.p.-hr. s. d. s. d. S. d. S. d. S. d. s. d. s. d. 4 10 1 8 2 6 3 4 4 2 5 5 10 5 1 0* 2 1 3 u ; 4 2 5 2* | 6 3 7 3* 6 1 32 6 3 9 5 6 3 7 6 8 9 7 1 5| 2 11 4 4* 1 5 10 7 3* [ 8 9 10 2f 8 1 8 ; 3 4 5 6 8 8 4 10 11 8 10 2 1 i 4 2 6 3 8 4 10 5 12 6 14 1 (i) Cost of fuel per h.p.-hr., with wood per cord (128 cub. ft. = 3000 Ib.) as follows : Wood, Ib. per i 8s. 4d. 12s. 6d. 16S. 8d. 20s. lOd. 25s. Od. 29s. 2d. 41s. 8d. h.p.-hr. s. d. s. d. s. d. s. d. . d. s. d. s. d. 10 2 9* 42 5 6* 6 Hi 8 4 9 8* 13 10i 12 3 4 50 68 84 10 11- 8 16 8 15 4 2 63 84 10 5 12 6 14 7 20 10 20 5 6i 84 11 li 13 10i 16 8 19 5* 21 9 (*> Engine. Fuel. Cost per Ton. Consump. per h.p.-hr. Cost per h.p.-hr. Cost per ann. (300 days at 10 hr.) per 100 h.p. s. d. Ib. d. s. d. Simple, non-conden. Bit. coal 12 6 5 334 418 2 2 Comp.-Conden. _ 12 6 3 201 251 10 Steam turbine . . " 12 6 3 201 251 10 ELECTRIC POWER. The ease with which electric power can be sub-divided and transmitted over great distances without excessive loss permits the establishment of large-scale generating stations whether from water or steam and the accompanying economy of large units. Of the two systems, continuous current and alternating current, 2 68 POWER ELECTEIC. the latter, especially on the triphase style, possesses several advan- tages. It is cheaper to instal, and admits of being generated and transmitted at a high voltage, at a relatively smaller cable cost. It can be transformed to any suitable working voltage in the neigh- bourhood of the motor, and the absence of a commutator on the motor considerably simplifies the working and attention required. Its chief disadvantage for economical working arises where regula- tion in the speed of a motor is required, as a regulator has not yet been invented which will do more than consume the surplus cur- rent beyond that required for the speed at which the motor is run- ning ; accordingly, the same amount of current is required for a motor running at half load as at full load, the surplus being wasted in the regulator as heat. A shunt-circuit continuous-current motor, on the other hand, can be regulated with very little loss of effi- ciency. The voltage used varies very much with the conditions : for tri- phase current it is not, as a rule, less than 1000 volts ; it is usually 2000-3000 volts, and sometimes 5000 volts, and, in the majority of cases, it is transformed down to 200-300 volts at the motor. The pressure of continuous current does not, as a rule, exceed 500 volts. When the power has got to be uniform, as in the case of stamp- batteries and compressors, the advantages of electric motors are pro- nounced ; but, where the load is not uniform, as in the case of haul- ing from deep shafts, the advantages over steam power are not so great. For triphase motors, no man of greater skill than an ordin- ary millwright is needed for their operation and handling ; for so long as there is oil in the bearings, and electric current is supplied, the work will go on. The oil in the bearings need not be replaced under ordinary circumstances oftener than once in 3 months ; and practically the only attention needed is to keep the machinery clean. In some cases, where with coloured labour there is much shirking on night shift, and stoking is slack, electric power may be of great advantage apart from economy. Thus at Kolar, India, it is found that 20 % more work is done, owing to the uniformity of power supplied. In all electric power installations, a small (5 h.p.) air compressor and necessary hose connections will be found invaluable for cleaning machinery. Pressure should be available at 100 Ib. per sq. in. Costs. (a) Coventry Corporation works report that on 51,114 units sold in 1896, the costs were 6 64d per unit, and the average selling price was 5'85