THE FREE AND LIBERAL VENTILATION OF SEWERS In its relation to the sanitation of our dwellings Rend by .Tlr BAII.LARO£ iN>rorc Section III of the Royal Society of Canada ut itfi silting of nay 31, 1M93, in tiie City of Ottawa* As every thing which has to do with the well being of the human race, must be a pertinent subject of enquiry by the section of sciences : physics and chemistry ; I propose to arguo the question of the hygiene of our habitations as affected by the ventilation of the city sewers. " The plan of ventilation now most approved, says the writer T. A. E. of the article " Sewerage " at page 74, vol. XXI of the last edition of the Encyclopedia Britannica, is the very " simple one of making openings from the sewer to the surface of the street at short distances — " generally shafts built of brick and cement — and covering them with metallic gratings." Mr. Keating, city engineer of Duluth, Minn., formerly of Halifax, N. S., introduced the system in the latter city, and it has been carried out elsewhe?:e ; but sanitarians are prejudiced against such a mode of ventilation, I, ouring as thi-y do under the false impression that openings of the sort immediately over the sewers and along tbi centre of thj roadway, must of necessity give rise to odors and exhaltations more or less disagreeable and injurious to health. One must under such circumstances allow for a tendency to imaginary evils, as when two or three years ago, on complaint to me that a drain had burst in Montcarmel street, Qudbec and that the liquid sewage running from it emitted the most offensive smell, likely to breed sick- ness, it was found upon examination to be a stream of the purest water running from an aqueduct service pijie to the gardner's residence on Laporte street. Now, it is the very promoters themselves of sanitation carried to extremes, who, not understanding the question at issue, are the principal enemies of the proposed system. I soy " carried to extremes " and to proof : a host of unemplojed would-be-scientisto in each city, are constituted a "Board of Health ", elect a President, Vice-Presidents, Secretaries, Treasurers ; appoint health officers, insjectors, etc., and this galaxy of hygienists, to give themselves an air of p>iblic usefulness, prove over ztalous in clamoring against the falsification of alimen- tary substances, in advocating the filtering of water, in conjuring up microbes, bacteria and coa- tagious diseases, in battling for vaccination, disenfection, ventilation and the like. They fancy they are serious and in the end become so, and would convi:iC3 f)eople that a thousand precau. tiouary measures are at present indispensable, of which no one ever dreamed in the past, and with- out in any way suffering therefrom. All these subjects, no doubt, have there importance ; but with due regard to common sense ; and what is to be avoided is going to extremes. The human race has already existed for thousand of years, and longevity was at least as prolonged in times gone by as it is at present. Ventilation was an unknown sciences and people did not die the quicker for it. Unfiltered water was the common beverage ; and of our days, the boatmen of the Missisippi will tell you, as many of them have said to me, that they drink the un- filtered water of this river of ihree thousand miles in length, which every year c.irries down and deposits at its delta in the gulf of Mexico a hundred million tons of detritus and dirt. At the present time, we are told that an adult should have 1000 cubic feet of fresh air to breath per hour, and some would have it as much as 2000, even three; but it is admitted . that for chililrer. at school, from 400 to 600 cubic feet suffice. It is nevertheless true that one can thrive on half and even on a 4Uarter of the quantity ; for at study, respiration is quiescent, and it is so very little active during sleep, that a man is not at all the worse of having had but one tenth the quantity set forth, or ,as much for a whole night's rest as required during a single hour of active service— to wit: the contents of a room full, of 10 x 10 x 10 feet. But the thing explains itself when it is considered tliat the carbonic acid gas which man expires during day time or while waking, at the rate of 6^10 of a cublic foot per hour and which becomes absorbed by vegetable nature and the atmosphere, is produced at night in the pro- portion only of the ten times less active breathing of th° iiu'.iviiUial. And thit it is not so poi- sonous as one might imagine : witness the fact that infants and others breathe and rebieathe it while mi fHed up for hours, without the least inconvenience. t It can be shown by Herse's plan of slowly passinj^ a given quantity of atmosphoTic air throngh a tube of which the interior is coated with beef jelly, and to which passing micro- organisms become attached and in a few days, give rise, each of them to the formation of a new colony; that ordinary atmospheric air contains some 30 germs to the cubic foot; a ventilated room not less than 30 to 900 in an equal space, and that in au unventilatcd school room can be counted as many ab 18000 to the cubic fool— see under this head the researches of Carnelly, HaUane and Anderson at page 61 of vol. 17C of the London Philosophical Transactions for 1887 — and no one will or does pretend that these microscopic organisms have not always existed or deny that they have been breathed, inspired, taken into the lungs without the least attendant danger. I^rge cities date not only from to-day. The Romans, throu<;h sewers or conduits often open to the atmosphere, sent their excreta to the Sua, and they coulil inhale their exhalations with impunity, diluted and rendered innocuous as they were by the floods of water poured into them from their abundant aqueducts. And let me say in one word, to have done with these preliminaries, and shew that in many cases, the evil is not nearly as great as it is said to be, that while we are crying out for venti- lation, nine tenths of the human race do without it and appear to be none the worse for igiiorin» it. A thousand precautions are sought to be enforced in the drainage of our houses. Thou- sands of towns and villages, the wide world over, ignore the thing entirely and live quite as long as those who at great cost give themselves the luxury of sanitary modes of removing their excreta ; and during epidemics, as during normal times, there is no more, no less sicicness, there are no fewer, no less deaths in the one case than in the other. -411 this on my part is to bring about the conclusion that there is not in the proposed system of free and liberal ventilation of our sewers the danger that hygienists apprehend in its bearings on the sanitation of our cities. The advocates of sanitation, nowadays, go too fiir in demanding the ventilation of sewers by such expensive processes as the erection of tall chimneys here and there, and the estiiblishiuent of fires or of foci of heat and suction at numerous points ia every city of the old and new worlds ; and the last scheme in this direction is that of MM. Peek & Hall who in a 17 page article pub- lished in the " Contemporary Review of London " for February 1892, are trying to convince the peopli', the authorities, that they must of necessity tax themselves to erect expensive towers here and there, wherewith to create the necessary draught a-; in coal mines, to ventilate the London sewers, and thus as they pretend, e'.iminate thp deleterious qualities of the Londou fog made nocuous by the emanations from them ; notwithstanding that these fogs have existed from time imme- morial, and are no doubt due to atmospheric causes with which the warm sea breezes from the " Gulf Stream " may in some way be connected. With regard to mines, and coal mines more especially, where so many dangerous and explosive gases are in constant process of formation, the thing is most essential and absolutely in- dispensable, and even with every possible precaution accidents do happen and will persistently continue to do so : but a sewer is quite another thing : it is u!ider the street or roadw.iy, not far from the surfar-e, between which it suffices to practice openings at distances apart of some two to three hundred feet, to get rid of all the gases real or imaginary which the sewers give rise to ; such ventilation having to be established, and naturally enough so, at every intersecting sewer, change of direction and difference of level of the entire system of city drainage : vertical conduits of brick woik built in cement, of the full width of the sewer, by a length of say one and a half times their breadth, and being enlarged or gathered in at top or at the level of the roadway, so that each opening may when necessity dictates be used as a man- hole by which to enter the sewer, visit and scour it out as may be required ; each chimney or shaft terminating at the street level in a heavy cast iron frame, rebated to receive a perforated cover of sulhcient strength to allow of the heaviest traffic passing over it. These spiracles or breathers can not be too numerous, and at 150 ft. apart the ven- tilation would but be the better for it, the more readily to bring about the oxydation and disin- fection of the gases escaping f-om the .sewer into the atmosphere. It might seem at first sight that it were necessary to remove such emanations by con- duits reaching above all habitations, as proposed by some sanitarians, and this would be necessary were the gases half as poisonous or pestiferous as asserted. No, these emanations from the sewers, are by no means as noxious as they are said to be, and to proof : there are those who, so to say, inhabit them and pass their lives in cleaning, scouring and emptying them. — 3 — See the Paris Sewers : I have been in and through them on a viait of inspection lasting an hour or more, and that, in the company of a party of ladies and gentlemen from England Germany and elsewhere. The Paris sewers can be thus visited once a month under a permit to be obtained on applicmtion at the "Prefecture de la Seine ", and if it does not take place oftener, except on special permission to some person of rank or who can only make a short sojourn in -the city, it is that too frequent interruptions of the kind would materially interfere with th-; duties of those who are charged with their daily scouring out ana cleaning. Triip, the cess-pool system holds in Paris, and night soil or excreta do not find their way into the ditiins, boaiuse as an economical fcMtuie ihoy are retained to be utilized for manuring puri'oses, and nre during the dead of night punip«-d by suction into large cylindrical receptacles on four wheel tniiks ntiy the double 4 f et cut stone side walks on which two men on either side trot along and thus by means of a projecting bar propel the boats containing the excurtiouists. The sewers of secondary size, which empty their contents into that just described are only 10 fi-et in width, with a six feet thuunel between sidewalks two feet wide, and on either side thereof is laid a rail along which a series of cirs, again propelled by hand by men told off for the purpose, one on each side the channel, ride smoothly along above the flowing waters. The sewers, third in poini of size are six feet wide with a fide walk on one side only ; and one and all of them are thioi ghly lighted up with gas or oil and will now shortly be, if not already done, by incaa- desceut electricity. The quantity of water in the sewers i.s such as to dilute, in the ratio of say 100 or 1000 10 1 every piirticle of absolute sewage or excreta passing through them and which might otherwise irove noxious ; and they are absolutely without danger to the host of employees who may be said to pass their lives within them \ Fifty or a hundred years ago I would not have suggested wh it I now favor for cities and towns in general ; but where at present is the community of any importance in the old or new world, which has not its aqueduct, its abundant supply of water ; and in such abundance as to be in bulk a thousand or ten thousand times that of all the filth T,o be removed and such as to render it abso- lutely inoffensive, as far as any smell or noxious gases from it are concerned. Like Don Qui.\ote who created wind mills, then to war against them ; it is that terrible word " sewer gas" which after thus wrongly styling it, we are afraid of and endeavour to combat by the most expensive means, in no way called for and out of all proportion with the evil to be done uway with. " Sewer gas " is nothing more than ordinary atmospheric air slightly contaminated by its adniixturt with iVe gnses which are forrned liy the decomposition of the scwnge iiialtef, sis well hy the orgnnic gernn which these matters hold in 8us|<«>n«ion : microlK's and Itacteria, etc. It is equally certain tluil the would l)c-(Linj,'Tiins charact<'r of these gases, is n-diicod if not entirely eliniiniited by their free ex|iosuro to th • oxydi/ing action of the air. A more serious danger is that in certain cases of sickness, these products are elmrged with specific gcrins, and re- quire to Ik? promptly destroyed or removed hy gruvitition after being siifliciently diluted with water. The gas called " Sewer gas " has no existence, or ut least it noes not necessarily exist or in sj ite of oui endeavours to prevent it ; and if it does exist, it is because wo wil^ it so, since it is 80 easy to get rid of it, or rather to prevent its formation by conducting it imuiediately and continuously into the atmosphere by the proposed vcnlilutors along tlu^ centre of each street and as already slated directly over tlie, sewers to be desiufectcl. (Imcu more this g.is is noiliiiig b it :ii. niospheric air whit-h under itt normal and ever aetive pressure, penetrates thy sewers as it lioes oar houses am! our lungs. I have just said that the liquid and solid e>creta, when fre.sly produced and undec im- posed are absohitely inoffensive, with the exception of tho-e of certain disease^, but which nu\edwiih normal excreta or of p<'rsons in health, rarely count t'>r more than one in a ihousan I or even in leu thou.-iaud, as at present in Quebec for instance whrre th -re are, or were at tliti time of wiitiug this, eight cai^es of diptheria to a |opulation of SO.OiM) souls. The.«e excreta, I repeat, are inodorou', innoxious while in the water in which tlioy were deposited, and continuing their course infnll water towards the si'W.us and in full water ihrouL^h the sewers and until their expulsion into the river, lake or sea, as the case may be, and the time of this trajectory or pusi-Hge to an outing, not generally more than an lioirortwo in riparian cities like Toronto, Montreal, Qiub.'C, Ottawa, Hamilton, etc., or cities through which rivers pass as iu the ca>e of London or Paris, etc. ; decomposition dix-s not set in durin-at a head or depth as possible, and with an inclination proportiond to the depth of water; siudi sewers can be vent'lated in the way set forth, without giving rise to emanations in the slighte-.t degree anti-hygieiiie, or even more pestiferous, than those uf every day life which we cannot escape, as of the excreta of horses and the like. ' ' ' It is moreover known that a rapid or active run of water in a sewer, creates a friction at "ts surface which drags along with it a certain stialuin of air, which iu its turn gives motion in the same direction to a second stratum, this to a third and so on until the whole body of air above the water in the sewer is set in motion towaids the outlets of the system and thus expelled ; con- iribuiing thereby in a considerable degree to effect the ventilation of the conduits. ' But if I thus insist on the ventilation of sewers, it is not so niiieh on account of the sewers themselves, and of those who have to attend to them, as for the purpo-ij of thereby renderinji our habitation* safe from what might become •' sewer gas " in unventilated sewers; for no other odors, no other gases can find their way into our houses, than from the public drains ; and notwithstanding every | recaution to the contrary, the barriers will be some times broken, and contaminated air will jump the seal under tlft; pressure of waves and wind and rising tide at the outlets, or sucked into the house by partial vacuum due to the heat of the interior ; or again a plenum state of the air in the sewer will exist and therefore an increased pie.ssure, or greater than that of the air wiihin, and such pressure will overcome the slight head of water in the trap and penetrate beyond. It must be remembered that it requires quite a trifle to force the seal of the S pipe or double siphon, or of the trap so called. Generally th>jre is but a depth of from one to three inches u( water to be ovircouiu. A [iressuri; of only 4^10 of ao ounce will tlierefore suffice to force the inch of water, 1 1/5 ounce the 3 inches, and if iiny one will take the trouble to look at a barometer an>l si'e the three inch [.lay of nifrcnry allowocl for — I J lb. in the presbure or J lb. below the normal and 3 lb. above —and consider that one cm hiirdly aj>j.reciate or feel the difference; an idea will be h id of the iinpercei'tibility to our senses of the very slight increase in pressure capable of forcing' the 4eal of tho valve or air trap. And ihut t) V siiisea are too blunt to appreciate such slight differences of ftlmospheri c pressure is also made evileul by the fact that it ison'y when G.iy Lussac and Biot & Ara>?<» attained in their ballooiiii g p.xpcditions sich a ludght ns to have Itft iilino>t one half of the total weight of the atmosphere bem alh iheni ; only then it was thnt they became somewhat jiainfully aware of the diflercnce of pu'ssurc wiiiiin thcni and without, ;itid in the same way aj^ain as men can work under a pressure of >i-vci;il atmospheres, and p:Hs from the plenum to ili • outtf air, or vice versa, as from a comparative vacuum to a plenum, through the iutermediary of an air loi k with a simple tap at top and bottom to gra 1 lally bring about liie ciiauge of pressiire. But th' Mul in air traps jiives way before oilier causes than that of differeiise of pressure on opposite sides Of it ; as by capillarity when the fibres — so many minute conduits — of a I'iig or fraj^iueiit of a towel aire^-'ted on its w.iy and bending over the lip or crest of the cliim while reaching,' icp below ihe dipih of s( a! on one side and to a dejuh a little greater on the lower side, grailually dr.. w oil' the water fuuu the trap and leave tlin siphon open to the passage of the gases. It also happens that during v;ictlion, with the family in the country and the house shut, the w.iter in tho trap becomes ev iponited and thus agiin allows the foul air to pass from the sewer to the home; or it m.iy be a sudd m flush of w.iter, wliich momentarily held in suspension by an obstruciion, as of papi r, in ihe soil ] i|'e, when the chokiige gives w,iy In-fore the piessure of the eoliim, so suddenly pncipitates itself iuto and through the trap that with ilw vis viva of ih'j velocity acquired, it j' mps the boundary without leaving any of itself behind, or if any, too little to reach the ii[(e.\ of the d.iui or high enough to seal the siphon. Whence it is evident that the most perfect seal of the so called air-trap or barrier between the lious'' and drainage is but an inadequate mode of .sli itting out the atuiosphere of sewers. And it is because this fouler atmosphere of drains can not fail now and then to force the seal and find its wiy into the house or dwelling, ihit I favor the scheme of the free and liberal veiitiliition of these conduits of excreta, their direct communication wiih the outer air to prevent the forujation of gases whirh otherwise acquiring intensity with age, would or might become and under the pr.'seut unventilated .'system, do become noxious and |K)ssibly even jioisonous and there- fore destructive of health and happiiies within the dwelling. For with all ih • precautions of house-wives, and in many cases due to their very negli- g.'nee and more espii;ially iu pauper tenements, or in tho^e run up by th<^ dozin by pircimfjiiious lamll'irds an I where sanitary apfili.inces are wanting, vegetable and animiil matter may an 1 do find their way to ih'! si Wor> ; ihat is to say putrescent matter or subject to putrefaction, th? hydrogens fiom which, amonias and arids forming but slowly can not acquire undue intensity when by the vcnti'ntioii pro| o>i'd, these gases escape aiid liecouie mixed wilh, diffused in the outer atmosphcrr, before they acqiiiri' luiy smell or odor of a nature to cause them to l)e pronounced, not poisonous but even as niiuh as only slighily disagreeable to ihe most sensitive organs of smell. I have said that the .sewers should be made of ovoid section or pointed, wilh *ho n^irrow end down, and this holds especially where but little water passes, so that this w.iter may attain as great a height as possible in the sewer, which will float the soli'ls, hasten them along and scour out ihe jiipe continually. Moreover, the solids decompose more slowly when in water or if they do the contraiy, the w iter imbibes the gases and renders them harmless. This f|uestioii of the depth of w.iter in ratio to its width of stream in the conduit, make.s it imperative also that for house diainage and other, the pipes be of the sraalle.st diameter possible. This has long been fixed for .service or soil pipes from w.iter closets at 4 inches in the interior of houses; not does it require to be of any greater size without, or between the house and street sewer : for while the scouring water, which runs through the pipe at each flushing of the pan, fills the 4 inch pipe to a depth sutlicient to remove the solid excreta, it is evident that in a pipe of greater diameter, as 6 or 8 inches, the .'■auie quantity of water, and it cannot be any more abun- dant, coining as it does from a vessel of fixed cipaciiy — the 3 to 4 gallon service box or cistern as it is called— cannot wet the bottom of the larger pipe to such a depth ; or to much more than half the depth it does in the narrower pipe ; which rendering the flow or current less rapid, from the — 6 — broudiT friction area, the suliiU insteittl of tloatiii^ ut the surfitcu iis in tliu 4 " [>i(H', touch und drag tht! Uiltom and coining iu contact with, for initiince, hii excrescence of cement forced from tl>e joint by driving home the jiijie, adhere lo it, become dry uud h.ird before a new Hush follows to fiflp reiiiovo the oli>tiu",le ami during; »iich sojourn of i-xcreta in ihn pipe, eenit ^hhk-^ which with age become deleterion-*, if even they do not in course of timo ciuse ih.! coiniili'tn obnir iction of the • Te, as often hapi)ens iiud thereby grave inconveniences, itm>eJiments to saiiimtion and witlial, the exptn''e of a plumber to remedy the evil. It ihiiifore pertains lo sanitariain andoth rs to cotnb.it this erroneous idea on the part (if proprietor* and ignorant architects who believe in and aiivooate tlu' use or the absence of any such [ire- ventive apparatus, into the interior where the uir rarefied as it gener.dly is by a teriiper.iture nbove that of the o iter air or sewer, produces a partial vacuum and with it a sucti(ju inward of the emanations mentioned. [ may say and as bearing on the subject at issue :ui 1 th- sanitation of houses, tint, in any building the closets should as much as possible be place I one aliove the other in the ditferent ll.its, so as to ilisthaige immediately into a vertical conduit, rising directly from the cellar pipe to the very summit of the house or edifice and through the roof thereof. This pipe, the higher the better above the rnof, .-lioiild terminate in a cdwI of a shape to allow the wind iu its generally horizontal motion to cr.aie therein by suction a parti il vacuuiu an I tlu'iefnie a risint; current; most iH'ective in the eliiiiinuiion of such gases as may arise from excreM on their w.iy to the .sew.r and from as far down as the air trap Ijetween the house and outer drain ; while not, forgetting neiih ^r that one of the advantages of such a pipe discharging high into the atniosphere, is, sh )ul 1 th ; seal of the air trap fail Itelow, while that of the traps beneath each basin icinain nnbrok-n, to allow the sewer gases a mode of escipe through the roof without in any way endangering the well being or comfort of the inmates. I have already said th it tlu' water in motion in a sew t, that is by the friction at its surface, causes a current of air, or rather sets in motion by dragging wi'h it the air within the sewer, a fact well known to tho.se who have to do with these undergroimd conduits and which may be noticed at the outlets. In the same way, when other means are wanting, can a draught U^ created in a ventilating pipe or conduit, or a tine, precisely as with the " Injecteiir (iiflard" a jet of steam can be made to drag along with it a current of watei into u steam boiler to reiilenish the supply. There can be no spontaneois ventilation, no current, no motion in ihe absence of .some stimulating process : some, heat, force, or friction to bring about the same, and that, notwith^taiuling all the possible conduits and however well disposed to the effect desired ; anh;et iro:i suitably dis- posed to etlcct the desirable object, or in a flue adjoining, or the more expedious, though possibly more costly method of one or more jets of gas, or even a coal oil lamp set iu a flue and left to burn therein while at the tame time through an open and glazed aperture doing duty as a light iu the apanment. And if the burning jet of gas or lamp be overhead and intended to ventilate the room where it is doing duty, it sould be disposed beneath a funnel like cowl which will collect the vitia- ted air and through a tube of proper size convey it to thj flue or conduit for expulsion. To, 80 to 8ny, exhaust the Huhject of aerating, airing, vuntilatiiij^' and tliough it have no direct bearing on sewor ventilation ; hut as a mode of arriving at one of the efTects of ventila- tion, viz. Uie freshening or cooling of iIid iiir wiilim a building; I may suy ihat in ihu same way aa the sprinkling of slri'et», that i«, of the roadway and sidew.ilk^, brings alwut a mark'id recluctioa of the icuipjraturL', under iho aclion of ev.ijMjr.uiou oF ihu waler whii-h to becoiuj v.ipor robs llio air of and thus lessens it's heat ; in ihu haiue way can wu cool our houses by allowing a stream of water to flow by gravitation through a pipe to ihe summit of the roof wluiiico it am be by a perforated tube made to run like rain fro.-u th ; rid^e or saddle of ihu roof, down ihi siduj and theuco fall from the oaves. This artiUcial r.iin Would in its tt^ndency to evaporate, rob the air of its excessive h?at iiiid thu8 rtduce its temperaturo, or a current of waiin air flowing or blowing towards the house, with a tendency to ent'-r, would tlius at tiui thrt'sliDld of a door or window h- cooled down b'fore it renched a jtcrson sitting in the interior, in the same way as during a summer sliower the air whii h reaches one on a veranda feels most agreeably cooled down by the phenomenon ; and in the same way also as a Wiirm breeze reaching one after passing over and lickifig the surface of the ico in the family supi'ly van as it goes alom^ the street from door to door, deliclously fans tho face of any one encountering it, and suggests the idea of how a similar result can te bought about at home by so disposing a set of perforated shelves covered wi h ice, or a set of pi()es filled with ice cold water in a gallery along which the outer air can be made to tmvel and cool itself before entering the house, or by a series of jets of water so disposed as to cool the air by evaporation as already stated. To return now to my subject of the ventilation of sewers as affecting the hygiene of oui hiibit^itioU'!, I have to say that an additional and pertinent reason for ridding them of their vitiated air and thus debarring the latter from penetrating to the interior, is that of preventing the c tmpressiou of the air in the sewers, as often happens during the year, by sudden gusts of wind, or by persistent winds blowing up the sewors, or by the impulse or sudden action of waves, as w.dl by the rising of the tide and the conseijuent closing of the outlets ; and it is then especially, a thing of every day and of twice a day in tidal waters, that the great advantage of the proposed ventilating shafts bui'omes apparent, acting as they do as so many safety valves by which the comi)ressed air can escape into the outing, thus preventing it from increasing its pressure in a way to force the seal and get withing the building. The fiee and liberal ventilation of our sewers would therefore have the efl"ect not only of ridding them of their gases diu such exist ; but, if any such were formed, of not giving them the time to intensify and become noxious before being expelled into the ocean of air which envelops the Kurth to a depth of may-be 5(1 miles and of which the volume if it were reduced by pressure from above to th.it which would give it the .same weight per cubic foot throughout (say about au ounce at sea level) would still be some fifty times that of all the seas and ocean.=t, lakes and rivers of the world, and which under such a volume would more surely and abundantly dilute the gaseous emanations from the sewers, than can the less abundant waters of the earth dilute and render harmless the li(iuids and solids, the whole body of sewage which ceaselesly pours into them and has being doing so since man is man. I would also remark that exhaust steam from engines, boilers and the lika should not be discharged into the city sewers, as it not only ciuses the rapid destruction of thj brick work or masonry thereof by constant alternation of heat and cold ; but has also the injurious effect of hastening and aiding the formation of miasmatic gases by accelerating decomposition of putrescent substances, and by so increasing the pressure of the air within the sewers as to enhance the risk of forcing the seal of air traps in a way to give passage of the vitiated air to th^ interior. The author of the article on " Ventilation " in the Bristish Encyclopedia, and to which I have already referred, alludes but briefly to the ventilation of sewers, but at sufficient length to say that the free and liberal ventilation of sewers, by a system of air shafts ut short distanced along the line, is admitted to be the system most in favor now with engineers of experience, and I hope I have demonstrated to the satisfaction of all, and of even every sanitaiian, that the system is the only one which can cope with every difficulty and conjure all objections, all the danger presently existing of the irruption of miasma into our houses, accompanied as they may be by microbes, bacteria and other organic germs of such zymotic and contagious diseases as small-pox, typhoid, diptheria etc.