UMASS/AMHERST # 315DtitiD05E13D57 \. * %r Am' $r ..-^. ^ »-' ^ %: 1 ■■>= •:'•;_■. LIBRARY OF THE MASSACHUSETTS AGRICULTURAL COLLEGE No._±tk XD ( 512 Source^ P6R6 This book may be kept out TWO WEEKS only, and is subject to a fine of TWO CENTS a day thereafter. It will be due on the day indicated below. 4 2, S, 1, T7 I ( 109 ) II. — The Paris Seicage Irrigation at Gennevilliers. Bj F. R. DE LA Tr:6honnais. [With a Map.] The village of Gennevilliers, notwithstanding- its close vicinity to the gay city of Paris, never was a lively spot. Its very name was scarcely known but a few years ago ; and very scanty are, even now, the visitors who bend their way to its barren solitude. But the tide of progress has lately reached that lonely suburb ; and what pleasure-seeking and merry throngs have done for the fame and prosperity of its near neighbour, Asnieres^ sewage has accomplished at last for Gennevilliers. The Paris sewers, whose turgid streams have been directed round about the all but deserted village, and made to pour their noxious filth over its sandy waste, have brought fertility to its natural barrenness, and, as if with a magic wand, changed its desert-like wilderness into luxuriant fields, teeming with verdure and plenty. But, alas ! prosperity and fame — as frequently is the wont of those two goals of human ambition — have lately brought discord and strife in their train. A recent debate in the Legislative Assembly of Versailles has divulged the existence of a serious quarrel between two parties of the inhabitants of the district, and between one of these parties and the city of Paris — the bone of contention being the disputed advantages of sewage as applied to the Gennevilliers fields and market-gardens. As the question at issue forms one of the most interesting chapters of my subject, some further reference to it will be made hereafter. Here the question will naturally be asked, whereabouts is Gennevilliers ? Before I fully enter into my sewage narrative^ I think it expedient to answer that pertinent question. Visitors to Paris have no doubt observed those remarkable meanderings of the River Seine, which occur immediately after its effluence from the city. The first bend of the stream takes place just above St. Cloud. There the river turns sharply to the right, reflecting from its clear surface, formerly the splendour, now the blackened ruins of the royal village. Retracing its course, as it were, the Seine then skirts the base of the frowning height upon which sits the fortress of Mont Valerien. Farther on, it hugs closer still the very outskirts of Paris, and soon in- verts in its yet clear waters the Longchamps racecourse, and the green plantations of the Bois de Boulogne. Then come Neuilly on the right, Courbevoie and Asnieres on the left bank, and then at last, not far from the line of fortifications, Clichy is reached. It is at that spot that the first outlet of the Paris sewage disgorges its black stream into the River Seine. Up to that spot the river is as clear as a mountain torrent. Its pas- 110 The Paris Sewage Irrigation at Gennevilliers. ^age througli tlie city has scarcely tainted its pellucid trans- parence. Confined between stately quays, spanned by a long succession of monumental bridges, uncontaminated by the outlet of any sewer, its bright stream only adds freshness and beauty to the splendour of the scene, and it issues from the city nearly as pure as it entered it. Even at Clichy the line of the sewage remains well defined, as if the pure water of the river recoiled from the foulness of the invader. On the left bank, skirting the plain of Gennevilliers, the water preserves its purity until it reaches St. Ouen, where another outlet disgorges a new supply of sewage, and fouls the river altogether. Further on, St. Denis is reached ; and there the northern sewer, together with the outflow of the Bondy jpoudrette manufactory, turn the poor river into a huge open sewer, the foulness of which is more easily imagined than de- scribed. It is at St. Denis that the apex of the first bend of the Seine is reached. At that spot, frightened, as it were, at the mass of filthiness that pollutes its waters just at that point, the river turns sharply to the left, bending its course past Argenteuil and Bezons, towards St. Germain, Poissy, &c. The extreme end of the kind of peninsula enclosed within that first loop of the Seine is called the plain of Gennevilliers ; and it is opposite Clichy, on the southern reach, and Argenteuil on the northern, that the now famous village is situated. It would have been difficult to select a more eligible field for the disposal of the Paris sewage by absorption and cultivation than the plain of Gennevilliers. Its immediate vicinity to the principal outlets of St. Ouen, Clichy, and St. Denis, sparing the necessity of constructing any great length of costly mains, ren- dered it particularly adapted for the experiment of absorption. The loud and threatening complaints raised by the inhabitants on account of the foulness of the river, and the accumulation of putrid filth all along its banks, compelled the Paris municipal authorities to attempt this plan without delay. But it was not the proximity of its position alone which particularly fitted the plain of Gennevilliers for such a purpose. The porous character of its gravelly soil supplied a natural filter, both deodorising and disinfecting, whilst its utter barrenness offered an admirable field to test the fertilising powers of sewage. The plain of Gennevilliers consists of a gravelly drift several yards in thickness ; and before the contents of the Paris sewers were diverted to its surface, it was a perfect waste, chequered with pits and quarries ; and scarcely any attempt had ever been made to bring any portion of it under cultivation. Having described the position and nature of the place so happily selected by the Paris Commissioners to demonstrate the The Paris Sewage Irrigation at GenneviUiers. Ill efficacy of the agricultural system for thoroughly solving the sewage problem, I will now examine the economical principles upon which that system is based, and describe, with their re- sults, the processes resorted to by the Paris Sewage Commission. This will form, I hope, an interesting chapter in the history of sewage. An account of what has been done in this instance may be useful to other civic corporations, who are contemplating the application of the same system to the disposal of the sewage of their localities ; and it is with that view, although I may fall short of my purpose, that I have attempted the task of writing this paper. It may be said of the application of town-sewage to agricul- ture, that the thought of it arose more from the necessity of getting rid of a pestilential nuisance than from any want of fer- tilising matter felt by agricultural husbandry, or from a well- defined conviction that any great advantage would accrue there- from to the public weal, by promoting an extra growth of crops, or improving any large extent of unproductive land. The truth is, that so far as agriculture is generally concerned, the application of sewage is of slight interest ; not, indeed, in respect to its effects on land, which, it must be admitted, are very remarkable, but from the fact that the available supply is so limited, that the extent of land that might be benefited is comparatively very narrow. For instance, the whole of the land which the sewage of the city of Paris, however large its bulk may be, could effectually irrigate, does not exceed 12,000. acres, the produce of which, enhanced though it might be under the influence of such an irrigation, would barely provide for the food of one-fifth of the city's population. But if the sewage question is but of small import to agricul- ture, it possesses a paramount interest in respect to the health of towns, and lies heavy in the responsibilities of civic corporations. The necessity of disposing of the offals of human agglomera- tions is a charge, the whole burden of which must exclusively fall upon the cities themselves. Agriculture is willing enough to bear a helping hand in laying out her fields for the purification of town-sewage, and is even thankful for the benefit it will un- doubtedly derive from it ; but the costly process through which the supply is made available to agriculture must naturally be left to the charge of municipalities, the boon to husbandry not being adequate to so large an outlay. The great merit of the application of sewage, so far as agri- culture is concerned, consists, then, in its simplicity. The fer- tilising stream must be brought within the immediate reach of the land, at a level that will allow its flow and self-distribution 112 The Paris Sewage Irrigation at Gennevilliers. to proceed from natural gravity. It is only under such circum- stances that a farmer can lend his fields to the process of irriga- tion, which may now be admitted to be the most effectual means that can be devised for disposing of town-sewage, without nui- sance to man or beast, and with great advantage to the produc- tion of food. This is a modern problem which has been forcibly raised in our times, in consequence of our better understanding of the hygienic economy of towns ; and its solution has become an absolute necessity. The excreta of civilised communities must be effectually removed from the precincts of human dwellings ; not, indeed, by relieving one spot, only more effectually to poison another, through a mere local transfer of the pestilence ; for this would only spread the nuisance over an extended area^ and under aggravated circumstances ; but by a process of absorption, based upon the natural principle of transformation of organic matter within the soil. In that powerful chemical laboratory of Nature, sewage is not only bereft of its noxious effluvium, within the influence of which neither animal nor vegetable life can exist, but the very pestilential elements which make it a rank poison are converted into succulent food, A knowledge of that well-known chemical property of soils, than which there is no more powerful deodorising and disinfect- ing agent in Nature, naturally suggested to the minds of those interested in the solution of the sewage problem, to spread the contents of town-sewers over lands conveniently situated, instead of wasting their fertilising treasures into watercourses, thereby polluting rivers, destroying animal life within their bosom and vegetable life on their banks, and, moreover, fouling all the adjacent country's atmosphere, to the serious detriment of the health of its inhabitants. It is not long since the metropolis of France has enjoyed the sanitary advantages of sewers, and even now the system is still incomplete as compared, for instance, with that of London, inasmuch as nine-tenths of the cesspool-drainage are still with- out any direct communication with the sewers. The remaining tenth only communicates with the sewers so far as the liquid offal is concerned, the solid being confined within vessels called tinettes, which, when full, are periodically removed in vehicles, suited for that purpose, and replaced by empty ones. Thus the contents of nine-tenths of the Paris cesspools have to be periodically pumped up, and their contents removed to Bondy, where they undergo the process which converts them into pou- drette, or human guano. The tinette system, however, has been applied to all the newly- built houses, and is gradually extending. It consists of an iron The Paris Sewage Irrigation at Gennevilliers. 113 ^movable double cylinder, adapted to a pipe connected with the water-closets, &c. The inner cylinder is perforated, so as to allow the liquid to escape into the sewer. Only the solid .matter remains, and is taken away. With that sole exception, the sewers of Paris are well planned and substantially built ; and when their communication with all the cesspools is complete, Paris will have nothing to envy, even in London, with regard to that essential hygienic institution. The Paris sewers, in fact, have been raised to the distinction of one of the most interesting sights of the gay capital. Most illustrious strangers who visit Paris make it a point to ride in the sewers in carts, and to float down the subterranean stream in boats specially provided for that purpose ; and it is a feat that can be accomplished with the greatest ease and comfort, without any risk of contamination or offensive smell. In 1856 the total length of the Paris sewers did not exceed 160 kilometres, about 100 miles. In 1874, all branches included, -they had extended to a total length of 771 kilometres, a distance equivalent to nearly 500 miles. The connection with private houses and public establishments consists of a funnel-like orifice, into which the tinette, above described, is fitted ; and, as I have already explained, this tinette is connected by means of pipes with water-closets, back-kitchen sinks, and other receptacles, through which all domestic offals are got rid of, with the excep- tion of the sweepings, ashes, and other dry refuse, which are every morning deposited before the street-doors, and removed away in dust-carts. The streets are carefully cleansed every day with hand- and >^ horse-brooms ; and the dirt is swept into the sewers through apertures and gutters contrived under the curb-stones on each side of the streets. So it may be said of the Paris sewers that they provide infinitely better for the sewage of the streets than for that of the houses — a system which every hygienic economist must implicitly condemn, as altogether inadequate to the most elementary sanitary requirements of a town. The sharp bend in the River Seine which I have already described was a natural advantage of no mean importance, of which the Paris Board of Works did not fail to avail themselves. This bend, by bringing land at a lower level than that of the stream in its course through Paris, within an easy distance of the city, greatly facilitated the discharge of the sewage into the river itself at Clichy, St. Ouen, and St. Denis. This local advantage enabled the engineers to dispense with the costly construction of lengthy canals across and through valuable pro- perty, the expense of which would have laid a heavy burden upon their scheme. They had, however, taken for granted VOL. XII. — S. S. I 114 The Paris Sewage Irrigation at Gennevilliers. that the river — which, as I have described, conveniently retraces its course so as to skirt the northern line of the fortification, and actually forms a ditch into which the sewage could be readily discharged — would remove the sewage with sufficient rapidity to avoid stagnation, and consequent fermentation and putrefaction. But the result was most disappointing and em- barrassing. The rapidity of the current of the river, which is con-> siderable in its course through Paris, becomes greatly slackened immediately the river leaves the city, in consequence of the existence of those very meanderings. The pressure of so large an addition of foul liquid, holding in suspension a considerable amount of solid matter, impeded rather than accelerated the already sluggish flow of the river. The consequence was that a black putrescible mud was deposited by natural precipitation along the banks of the river, and in its very bed. The sewage- waters, owing to the rapidity of their underground flow, emit no smell whatever in the sewers, as may be experienced by a visit to them ; but no sooner do they emerge into the river than, becoming almost stagnant, they enter at once into rapid decom- position. All the oxygen which they naturally contain, or have acquired through being agitated during their rapid outfall, is soon expended in the process of decomposition of the organic matter they contain ; and the water of the river soon becomes unfit to support animal life within itself, or vegetable life in its bed, and even along its banks. No sooner did the sewers disgorge their contents at Clichy,. than the fish swam away to purer reaches, or died when they were hopelessly overtaken by the foul stream ; and even the river- snails were seen to crawl out of the river. Along the banks all vestiges of vegetation disappeared ; and the River Seine, so beautiful and clear up to this spot, became at once the foul and putrid cloaca of the Paris sewage, similar to that de- scribed by Livy as existing in ancient Rome, flowing into the Tiber, and known under the name of Tarquin's Cloaca ; receptaculum omnium purgamentorum urbis* The chemical investigation which was rendered necessary by the alteration of the Seine waters through the admixture of the Paris sewage was the origin of the recognition, if not of the discovery, of this fact : that the degree of putrescible condition of water, and consequently of its unfitness to support organic life, may be expressed by its capacity to dissolve oxygen. In other words, the presence of a certain quantity of oxygen in water is^ indicative of its purity and fitness for domestic uses. * Hist., Lib. I. cap. Ivi. The Paris Sewage Irrigation at Gennevilliers. 115 In France, all hygienic chemists now employ no other method for testing the purity of water, than by ascertaining the quantity of oxygen it contains in solution, through a most simple and ready process invented by M. Gerardin, one of the hygienic inspectors of Paris. It is a remarkable fact that sewage, or even ordinary stagnant water, after having undergone rapid decomposition when in a state of repose, recovers a condition of comparative purity, after a while, under the action of air and light. Sewage-water when enclosed in a glass jar will soon decompose, and emit bad smells, but after some time it will gradually get clear, owing to the precipitation of the solid matter which it ^ held in sus- pension. One of the first tokens of this restoration of purity is the appearance of vegetable life in the shape of algae, such as Oscillaria viridis and Palmella. After a while, the noxious smell will disappear; and limpidity and purity are restored. M. Gerardin, on being invited by the Sewer Commissioners to make microscopic and chemical analyses of the Seine water fouled by the influx of the sewage, was led to abandon the long and tedious processes of the laboratory, and try if it were not possible to test the alteration of water by means of some che- mical reagent, such as permanganate of potash : a salt the use of which had often been recommended to that effect. It was in 1856 that M. Monnier first proposed the use of per- manganate of potash to test the presence of organic matter in water, relying on the property of that salt to get discoloured by substances having a great affinity for oxygen. In practising with this reagent, M. Gerardin met with two difficulties, which led him to give it up : — First, the solution of that salt is of a light pink colour, which it was impossible to distinguish in the turgid samples of water that were to be analysed. Secondly, permanganate of potash indicates the oxi- dising capability of organic matter, rather than the degree of its decomposition and its influence on the condition of water. However, the numerous experiments made with that reagent, led M. Gerardin to this important conclusion : that the discolo- ration of the solution of permanganate of potash was owing to its oxidising the organic matter in the water. That matter, whether in solution or suspension, has therefore more or less affinity for oxygen, and if so, it must easily absorb the oxygen dissolved in water. When water contains its normal quantity of dissolved oxygen, it may be considered pure, and capable of sustaining the life of fishes and plants. When the quantity of dissolved oxygen diminishes, fishes whose respiration is active can no longer live in such water, whilst those of a lower order, whose respiration is less active, can still exist. This is the reason whv I 2 116 The Paris Seicage Irrigation at Gennevilliers. eels, for instance, will live in water so foul as to kill other fish, and leeches will thrive where even eels cannot exist. Among fresh-water shells, Unio pictorum will die before Cyclas cornea or Bythinia impura. Physa fontinalis and Valvata piscinalis require aerated water, whilst Planorhis corneus thrives in impure water. The same rule obtains with vegetable life. Those algae pos- sessing a superior organisation, that is, being provided with chlorophjl, their cells being ramified and well articulated, are only found in well-aerated water ; they thrive only in rapid streams, close to waterfalls and other running waters, whose surface is constantly renewed by a quick motion. Unicellular algae, on the contrary, are found in stagnant water, which is partly deprived of its oxygen through the presence of organic matter in a state of decomposition. From those considerations, M. Gerardin sought first to ascer- tain whether there existed any dissolved oxygen in waters which are notoriously foul, such, for instance, as those which issue from factories and sewers ; and the result of his analyses was that no oxygen was to be found in them. Thus the conclu- sion which that eminent chemist came to is, that the salubrious or noxious quality of water is in direct ratio with the quantity of dissolved oxygen it contains. A comparison between the state of the Seine water above, at, and below the influx of the sewage, will best illustrate M. Gerardin's theory. Above Paris, the average amount of dissolved oxygen comes to 9 cubic centimetres per quart ; through Paris, the average is 7 ; below Paris, and up to Asnieres Bridge, it descends to 5*34. At St. Denis, after the whole of the sewage has been disgorged into the river, there is not a trace of oxygen ; but as the stream goes down, and the sewage gets rid of its organic matter by pre- cipitation and fermentation, oxygen reappears by degrees, viz. : — At Epinay, 1*05 ; at Bezons, 1-54 ; at Marly, 1-91 ; Maisons- Lafitte, 3-79 ; Poissy, 642 ; Mantes, 8-17 ; Rouen, 10-42. The quantity of nitrogen follows the same progression, but in an inverse ratio. So in those places where most oxygen is found, there is the least nitrogen, and vice versa. It would be highly interesting, no doubt, to develop here the practical purposes to which M. Gerardin has applied his sewage- water theory, especially as regards the refuse liquids from chemical factories, distilleries, fecula mills, &c. ; but it would extend this paper to an unreasonable length. Suffice it to say, that M. Gerardin has come to the conclusion that water that does not contain at least 8 cubic centimetres of dissolved oxygen per quart, is not fit for domestic uses. The Paris Sewage Irrigation at Gennevilliers. 117 The storm of angrj remonstrances that arose from the dwellers on the banks of the Seine, when the sluices of the Paris sewers were opened, can be easily imagined. Numerous petitions were signed, and threats of actions against the Paris munici- pality freely hurled, by the inhabitants of the affected suburbs, as well as by those interested in the navigation of the Seine, the course of which soon became impeded by the deposit of black mud along its banks and in its very channel. An idea may be formed of the extent to which the river soon became polluted by the fact of immense gaseous bubbles, several yards in diameter, rising to the surface, then bursting, and filling the atmosphere with a most offensive stench. Some of the chemists attached to the Paris Sewers Committee had the curiosity to analyse the gas which issued from these bubbles ; and they found it to consist chiefly of proto-carbonate of hy- drogen, burning with a blue flame.* In the first instance, the Paris authorities, with the view of remedying, to a certain extent, the evils so justly complained of, adopted no better expedient than that of constructing huge tanks, into which the contents of the sewers were first diverted, in order that they might undergo a preliminary purifying process previous to their being poured into the river. But these tanks were soon found inadequate to the influx of the sewage. However, the experiment was tried ; and at first the precipita- tion of the solid matter was effected by natural gravitation taking place, when the sewage was at rest in the tanks. The com- paratively clear liquid was then decanted back into the river, and the solid residue removed from the bottom of the tank, which was then immediately refilled. But this imperfect method only rendered the evil still more crying, inasmuch as no sooner was the liquid at rest, than it entered at once into active fermenta- tion and decomposition ; and the stench that arose from the tanks was most insufferable, especially in the summer months. Then purification by means of chemical action was tried. Sewage-water contains various mineral and organic matters, which impart to it an alkaline reaction, and is thus easily acted upon by chemical processes, of which these matters become themselves energetic elements. Numerous experiments were therefore made with a view to obtain more rapidly and more * The exact composition of that gas was as follows : — Proto-carbonated hydrogen . . . . 72 • 88 Carbonic acid 12 "30 Oxide of carbon .. 2*54 Sulphydric acid 6-70 Other substances 5*58 100-00 118 The Paris Sewage Irrigation at Gennemlliers. effectually a precipitation of the solid matters held in solution and suspension bj the sewage-water, by means of sulphate of alumina, lime, and other reagents, the use of which had been recommended in England and other countries ; and to that effect new tanks were constructed on a still larger scale on the Gennevilliers side of the river. The sulphate of alumina process seemed at first to give the most favourable results. Sulphate of alumina, after being decom- posed by the alkaline elements contained in the sewage, was transformed into alumina in the form of granulated gelatine. It then merely exercised a kind of mechanical action over the solid matters suspended in the sewage, precipitating them, along with itself, to the bottom of the tank. Under the action of that process the water was entirely clari- fied, and was decanted back into the river in a clear state ; but it was soon found that the purification was merely mechanical, and that the water, clear and pure though it might appear, re- tained all its noxious characters. Sulphate of alumina acts only on the matter suspended ; the water retains all the matters in solution, together with the organic elements liable to fermenta- tion. This was clearly demonstrated by chemical analysis, as the following Table will show : — Nitrogen Yolatile and combustible matters Mineral matters Sewage-water in its natural state. Water clarified with sulphate of alumina. Kilog. 0-037 0-729 2-038 Kilog. 2-804 021 240 724 985 The clarified water was thus found to contain two-thirds of the nitrogen of the sewage, and one-third of the volatile and combustible matters, which are for the most part organic. Besides this unsatisfactory result, the large amount of solid matter remained to be dealt with, after it had been removed from the bottom of the tanks. This had to be spread over a large area to undergo the necessary process of drying ; and when it is con- sidered that more than 200,000 tons would have had to be treated every year in that manner, it may be imagined what a mass of noxious gases would have arisen from such an accu- mulation of filth. It was, besides, calculated that the simple cost of the chemicals used would have been equal to the manuring value of the mud, and therefore its removal would have entailed an additional burden upon the ratepayers. The Paris Sewage Irrigation at Ge uievilliers. 119 It seems incredible that as the contents of the cesspools and the solid matter collected in the tinettes are not allowed to fall into the sewers — being carefully carted away to Bondj and other places — the Paris sewage should contain so large a quantity of solid matter both in solution and in suspension. From the withdrawal of all solid excremental matter, it might be inferred, on the contrary, that very little solid matter would be found. It has been ascertained, however, that no less than 15 lbs. of suspended solid matter is contained in 1000 gallons of the Paris sewage, besides 8 lbs. in solution, giving a total of 23 lbs. Some idea may then be formed of the extent to which the warping of the river was carried, and of the necessity, to which the municipal authorities were soon obliged to yield, of keeping steam-dredges at work along the reaches most affected by the sewage deposit. , At the outfall of St. Denis the quantity of solid matter amounts to as much as 35 lbs. per 1000 gallons ; and some idea of the jnanuring value of the solid part of the sewage at that spot may Joe gathered from the following analysis : — lbs. Nitrogen 1| Combustible and soluble matter ... .. 14 Mineral matter 19^ Total solid, per 1000 gallons ., 35 No wonder that the dwellers on the banks of the river, and the navigators upon it, so loudly complained. By means of the drags, a most costly process, no less than 82,000 cubic metres of putrescent mud were removed every year ; but this was only a mitigation of the evil, and by no means a cure, inasmuch as the stench emitted by the heaps of this black fatty silt, removed by the drags, was greatly increased in intensity by being exposed to the action of the air and of heat. The cost of the dragging opera- tions came to about 7000Z. a year. Owing to the limited quantity of sewage hitherto utilised by the Gennevilliers people, the drags are still at work ; but the still more costly and inadequate process of purification by sulphate of alumina has been altogether abandoned, to the great discom- fiture of the manufacturing chemist, whose factory was close at hand, in Gennevilliers itself, and who supplied the sulphate of alumina at no small profit to himself. The supply of that chemical alone would have cost 40,000/. a-year, if the process had been persisted in. In the meantime, the Sewers Commissioners, assisted by thosy eminent engineers, MM. Mille and Durand-Claye, were not idle in contriving other means of overcoming the huge diffi- 120 The Paris Sewage Irrigation at Gennevilliers. culties in whicli the Paris sewage question was involved. During' the years 1867—1868, sewage irrigation was tried on a piece- of waste ground at Clichy . The sewage-water was pumped up ' to that piece of land and made to percolate through 3 feet of soil. A drain was provided, and the filtered water collected and carefully analysed. It was found that so much as 80 per cent, of the carbonate of ammonia was retained by the soiL Sewage, containing 43 grammes of nitrogen per ton before its application to the land, when analysed after percolation through the soil, gave scarcely any trace of it in a decomposable state; Only 1*6 gramme of nitrogen in a state of mineral ammonia could be found. It was the same with the quantity of soluble oxygen. The sewage-water, when laid on the land, scarcely contained 2 cubic centimetres of oxygen per quart. On its effluence from the soil it was found to contain from 8 to 10, which is the unerring characteristic of healthy water. These satisfactory results, added to the success achieved in the agricultural part of the experiments, naturally pointed to the direct application of sewage to the land as the only effectual and^ practical means of solving the troublesome problem. In 1869 an announcement was made that sewage would be supplied gratis to any one who felt inclined to use it on the Gen- nevilliers territory for agricultural or market-gardening purposes. The response to that offer was sufficiently encouraging to in- duce the Commissioners to undertake at once the necessary works of delivery and distribution. To that effect, it was requisite, in the first place, to raise the sewage from the level of its outlet to a height of 11 metres, a little over 36 feet, so as to command the available area in the plain of Gennevilliers. A powerful pump, on the centrifugal principle, was first erected at Clichy. By means of this engine, the sewage is now raised so as to flow through an iron pipe which is laid underneath the footway of the Clichy bridge, and is thus carried over to the left bank of the river. Thence it is distributed all over the available space by means of open ditches, built in bricks and cement ; and, owing to the high level attained, it is calculated that at least 5000 acres can be irrigated in Gennevilliers alone. The quantity of sewage annually discharged from the Paris sewers cannot be estimated at less than 100,000,000 tons ; this gives a daily average of nearly 300,000 tons. Calculating 8000 tons as the average quantity which one acre of light gravelly soil can effectually absorb, it would require 12,500 acres to get rid of the Paris sewage ; but up to the end of 1875, the owners of only 350 acres had taken advantage of the boon so graciously proffered ; and even this small area is threatened to be greatly diminished, if not removed altogether.- The Paris Sewage Irrigation at Genyievilliers. 121 The manufacturing chemist who supplied the sulphate of alumina has lately been moved to enter public life ; and at the last election for municipal honours he managed so skilfully, that the old Corporation, who had authorised the City of Paris to lay their mains and distribution canals along the parish highways, were turned out of office, mayor and all, and the chemist was elected to the civic chair, where he now reigns supreme, surrounded by a council of his own choosing. Who would have thought that such a matter-of-fact question, as that of sewage could have arrayed in opposition to its peace- ful, if not over-fragrant, sway, so powerful a champion as universal suffrage ! One of the first deeds of the new municipality was to organise a most determined attack upon the whole scheme ; and one of the first steps taken was to denounce the contract which had been signed between the former Corporation and the City of Paris. Then a most vehement petition was sent to the Legis- lative Assembly, and it was discussed in the House at the sitting of the 18th of November last. I will not enter into the merits of this opposition, which mainly rests on grievances having but a temporary, I might say accidental, foundation, and the fons et origo of which lie in motives having a personal rather than a public interest. Suffice it to say, that the complaints preferred by the new municipality chiefly referred to the excessive use of the sewage, which had the effect of flooding the cellars of the village by raising the level of the subsoil-water. This grievance, as we shall see presently, is, to a certain extent, legitimate ; but as it can easily be remedied, it ought not to be alleged as a reason why the application of the system should be stopped altogether. Unfortunately for the cause of the complainants, another peti- tion, signed by a nearly equal number of landholders, but advocating a diametrically opposed scheme, was presented at the same time, contradicting the facts and arguments of the new Gennevilliers Corporation, and praying not only for the con- tinuance, but for the extension of the irrigation system. Another significant fact is that not one of the landholders who are using sewage on their fields has joined the dissentients. The Minister of Public Works, and the eminent Paris engi- neer, M. Krantz, had therefore no trouble in refuting the petition of the Gennevilliers Municipality ; and the whole matter was referred to the Minister, who in his speech had sufficiently foreshadowed his opinion to leave very little hope of success in the minds of the worthy mayor and his sympathetic coun- sellors. The total quantity of sewage that can be poured over Genne^ 122 The Paris Sewage Irrigation at Gennevilliers. -villiers from the two outlets of Clichj and St. Ouen may be computed at 44,000 tons from each, daily ; but only one-fourth of that quantity was used in 1874. The following Table shows the progressive rate of the quantities used since the commencement : — 1869 1870 1871 1872 1873 1874 1875 Number of Acres irrigated. 16 55 Quantities used. 650,000 Tons. 810,000 „ War and Commune. 128 221 289 314 1,500,000 7,200,000 8,000,000 The sewage, as already stated, is pumped up at Clichy to the Jevel of the Genevilliers' embankment by means of powerful pumping-engines of 150-horse power. From the higher level to which the sewage is pumped up, pipes, 4 feet in diameter, bring it along the Clichy Bridge to the plain. The sewage of St. Ouen, commanding a higher level, simply flows by its own gravitation through a main 2 miles in length, and directed to the extreme end of the peninsula. Both streams are then united in an open channel, built in bricks and cement, more than a mile in length, and 7 feet wide, running along the Genne- villiers and Asnieres embankment. From that main, subsidiary canals of various widths and lengths, complete the distributive network. Before we examine the agricultural results which have hitherto been obtained from the direct application of the Paris sewage to the land, it may be well to examine its chemical composition, in order to render possible a comparison with the sewage of English towns, and especially that of London. From the fact I have already stated, that the solid excre- mentitious matter is not allowed to pass into the sewers, it may be inferred at once that a notable difference may be expected between the sewage of both cities, especially as regards its manuring value. This difference exists to a remarkable degree between the Clichy and the St. Denis sewage-waters. At the latter place, where the great northern main discharges its contents, the refuse of the Bondy poudrette manufactory falls into the sewer, and the numerous manure-works of that neighbourhood send their con- tingent to the sewage ; and the consequence is that a much The Paris Sewage Irrigation at Gennevilliers. 123 larger quantity of nitrogen and combustible organic matter is found in the sewage at that spot than at Clichj. The sewage-water issuing at the latter outlet and at St. Denis respectively contain per ton : — Nitrogen Combustible or volatile organic matter Mineral matter CUchy. Grains. 61-73 10,185-45 21,605-50 31,852-68 St. Denis. Grains. 2,160-55 21,296-85 29,939-05 53,396-45 When the whole irrigation system is complete, and all the sewage from the three outlets is made to flow into one single channel, which will convey it in a flood over the proposed area, of sufficient extent to absorb one hundred million tons of sewage per annum, the average sewage will thus convey to the land no less than 200 grains of fertilising matter per gallon. As I have already stated, no better soil could have been selected to test the efficiency of the agricultural system, with the view of getting rid of the sewage nuisance, than the plain of Gennevilliers. Its immediate vicinity to the outlets, which saved the necessity of constructing any great length of costly mains ; its low level, which allowed the distribution of the sewage by gravitation, once it was raised up to the level of the river embankment ; the great depth of its gravelly subsoil, through which the water easily percolates to the water-bearing stratum, the level of which, from its direct communication with the river, never rises above it, except in case of great floods, when the natural drainage is taxed beyond its power of discharge ; — all these advantages and favourable circumstances, could not fail to help the experiment to a highly successful issue. As might have been expected, the water, after perco- lating through the gravelly soil, was found at its effluence into the river in as great a state of purity as could be desired. The soil acts as a natural filter of great power, through which the water becomes easily aerated and oxygenised. To those favourable elements must be added the utterly barren nature of the tract of waste land comprising the plain of Gen- nevilliers, to which, however, its proximity to the capital would give a very high value, if it could only be made productive. This transformation, sewage alone could accomplish ; and market- gardeners, nurserymen, and agriculturists, were not slow in accepting the proffered boon. Unfortunately the available area is by no means adequate to 124 The Paris Sewage Irrigation at Gennevilliers. receive the quantity of sewage which, sooner or later, must be diverted from the river ; and one of the legitimate causes of complaint alleged by the adverse petitioners, was the excess of flooding with sewage to which the Paris Commissioners were tempted, in their anxiety to get rid of their commodity. Flushed by their manifest success, they thought that the capacity of the land to absorb the sewage had no limits ; and we find that in the year 1874 some of the fields were favoured with no less than 40,000 tons of the liquor per acre. No wonder that the level of the water-bearing stratum was so raised as to flood some low-lying- cellars, and the bottoms of old gravel-pits. This was not ir- rigating the land, but flooding it with a vengeance. The Paris engineers had calculated that each acre could easily and profitably absorb some 82,000 gallons of sewage, calculating upon three crops a year, and a flood of 27,000 gallons for each crop. This is evidently excessive, for it would amount to the drainage of 360 inhabitants per acre ; whereas in England the drainage of 200 inhabitants is, I believe, found by practice to be the maximum that can be absorbed by an acre of land under active cultivation. On the sewage-farm at Croydon, the sewage from 165 inhabitants only is used for one acre. It must be admitted,, however, that the same rule does not obtain for all soils and climates. It is obvious that the hot and dry plain of Genne- villiers, especially during the summer season, can absorb a much larger quantity of sewage than any part of moist England. At all events, it plainly appears that the policy aimed at by the Paris. Sewage Commissioners was not so much to promote the proper growth of vegetable market-commodities, as to get rid of the largest possible quantity of their sewage ; and however little sympathy may be felt for the petitioners, it must be admitted that through the lavish supply of sewage, they had some reason to complain. The plain of Gennevilliers lies at the base of the high ground of the Mont Valerien and Buzenval districts, and receives all the rain that falls on that extensive watershed ; and although its alluvial gravel measures, in places, from 25 to 45 feet in depth j, yet when, in addition to natural drainage arising from the rainfall, it receives a dose of 40,000 tons of liquid in the course of a year, its absorbing capacity is evidently overtaxed, and the evils complained of are the result. Even in winter, when, the crops being all removed, the land remains idle, the sewage is nevertheless poured over the naked surface, leaving a black deposit intended to warp the soil and increase the depth of its crop-bearing stratum for the ensuing season. This is evidently wrong in practice. It has been^ demonstrated in England that, together with the soil, vegeta- tion is a most energetic deodorising and purifying agent, by The Paris Sewage Irrigation at Gennevilliers. 125 assimilating under some form or other, whether organic or mineral, all the fertilising matter contained in the sewage ; there- fore, if the purifying process by vegetable absorption be left out, and that duty exclusively apportioned to the action of the soil, at a time when it is saturated with the winter rainfall, it is obvious that failure must be the result. There can be no doubt that the comparative break-down of the system, as applied to Genne- villiers, must be ascribed to that cause, and that the adverse petition to the Legislative Assembly by some of the inhabitants rests upon some legitimate foundation. So far as agriculture is concerned, there is no gainsaying the fact that extraordinary success has been achieved at Gennevilliers. The principal crops grown under sewage-irrigation naturally belong more especially to market- and nursery-gardening than to ordinary farm-culture ; but it may be asserted that in no instance of sewage-irrigation has the application of the system been attended with greater success. • Last year a Committee was appointed by the Central Agri- cultural Society of France, at the request of the civic authorities, to examine the various plots of ground under sewage-treatment, with the view to determine the merits of the respective occupiers, and award prizes accordingly. The first prize, consisting of a work of art, was presented to M. Jolliclerc, whose plot of 20 acres deserves a special notice, owing to the great skill displayed in its management, and the systematic care with which all the operations connected with the application of sewage, in season and out of season, are carried out upon it. It was about the close of the year 1869 that M. Jolliclerc took a lease of about 20 acres of ground, which had been utterly abandoned owing to its barren nature. It was only in the month of June 1870, that sewage could be brought to it, so extensive had been the preparatory works of levelling the land for the proper distribution of the sewage and the construction of the canal connected with the main. Seeds of various vegetables, rsuited to the Paris market, were then sown, and the first crops were so abundant and so beautiful, that M. Jolliclerc succeeded in obtaining most favourable contracts to supply the ' Grand 'Hotel,' several hospitals, barracks, and other large establish- anents in the metropolis. The unfortunate events of the year 1870 and 1871 interrupted M. Jolliclerc's cultivation ; but at the termination of the Com- mune Civil War, his operations were actively resumed, and a visit to his sewage market-garden will amply repay the trouble of the journey. It is, indeed, difficult to imagine a more interesting picture of active and luxuriant vegetation. 126 Tke Paris Sewage Irrigation at Gennevilliers. Artichokes, beetroots, carrots, cabbages of all kinds, cucum- bers, melons, bulbous chervil, spinach, strawberries, beans, turnips, onions, parsnips, leeks, green-peas, potatoes, pumpkins, tomatoes, &c. — in fact, all the vegetables known to the Paris climate are cultivated in turn, each according to its proper season, with a success which, as regards size, flavour, and abundance,, has never been equalled in the neighbourhood of the capital. Having an unlimited supply of rich sewage at his command, M. Jolliclerc never allows his ground to remain fallow, except in the depth of winter, which, in that low and porous district, is always of exceessive rigour. The land is dug up with the spade and laid out in beds,, about 2 feet 6 inches in width. Each stetch is divided by a channel of equal width, which the sewage is allowed to flood after each crop, and in summer, several times, whenever the land gets dry. After each crop, the order of the stetches is inverted, the new bed intended to receive the fresh crop being raised where the former sewage-channel was laid. By means of this alternate rotation, half the space remains in bare fallow, and thus gets fer- tilised both from actual rest and direct absorption of sewage- water, whilst the crop growing on the adjacent bed derives from the right and from the left, all the moisture and nutrition it requires for its rapid growth and development. With this judicious system, it will be seen that the growings plants have no direct communication with the sewage, and no contact whatever with it, even through the leaves. Taking into consideration the barren nature of the ground where M. Joliclerc has laid out his market-garden, the bulk of the crops he obtains is considerable. The average quantities of various produce harvested from this sewage market-garden being as follows per acre : — carrots, 20 tons ; red beet-roots for salad, 35 tons ; French beans, 6 tons ; cabbages, 30 tons -^ spinach, 4 tons ; artichokes, about 40,000 heads. From 20 acres he had under cultivation at the outset of his operations in 1869, M. Jolliclerc has now increased his holdings to 300 acres, and is making arrangements to further increase it to 1000 acres. Besides market-gardening, there are also regular farming operations carried out at Gennevilliers under the sewage-system. From ground of the same description as that of M. Jolliclerc, M. Boismal succeeded in harvesting, in 1874, 50 tons of excellent mangolds, 32 bushels of wheat, and 56 bushels of oats per acre. Industrial crops of unusual bulk and quality have also been obtained from highly successful experiments. M. Auguste Royer has obtained 31 tons of mint out of 5 acres of irrigated land, of a The Paris Sewage Irrigation at Gennevilliers. 127 value equal to 40Z. per acre. Asparagus and potatoes grow also jnost luxuriantly and profitably. M. Tholomier took some old quarry-ground, measuring about 3J acres, at a rental of 6Z. in all, from which he has obtained an annual produce exceeding 160Z. in value. Nursery- and flower-gardening are also carried on most success- fully at Gennevilliers under the sewage system. All visitors to Paris are pleasantly struck with the beautiful display of cut and pot flowers gracing numerous open-air markets and shops all over the French capital. In fact, the flower-trade is one of great and still growing importance ; and the area of land devoted to that beautiful culture is greatly extending every year in the immediate neighbourhood of Paris. Several well-known nur- serymen and flower-growers have recently established gardens at Gennevilliers, specially devoted to that industry under the sewage- system ; and nothing can give an idea of the peculiar and extra- ordinary brilliancy of colour and fragrance of perfume pertaining to the various flowers grown from those sewage-irrigated beds. The growth of fruit-trees has also been attempted with won- derful success in point of rapidity of development in the trees, and the excellence and size of the fruit produced. Familiar as my English readers are with the good effects of the application of sewage in England, I doubt if they would be prepared to realise the wonderful results of that system under the Paris climate, and upon the sandy soil of the Gennevilliers plains, unless they saw it, and came to consider the local cir- cumstances which give to the application of sewage unusually favourable conditions. In the first place, the porous nature of the soil readily drains from the seed-bed the excess of moisture arising from an over- abundant flooding of sewage ; and, secondly, the large amount of caloric which readily accumulates in the gravelly subsoil from the exposure of the surface to the hot Paris sun during the summer season, acts as bottom heat ; and it is easy to imagine what energetic activity sewage-irrigation, under such climatic influences, must impart to vegetation. Already, as a natural consequence of the successful results, the rent-value of the land susceptible of being irrigated has risen considerably. Land which formerly could hardly com- mand 20s. an acre, is now readily let at 6/. IO5. The Munici- pality of Paris get now as much as 8Z. an acre for the land they possess in Gennevilliers, and the rate is still increasing. As another consequence of that prosperous state of the dis- trict, population is rapidly increasing, labour being in great demand, owing to the extensive market-gardens established upon every available spot of land within reach of the sewage. 128 The Paris Sewage Irrigation at Gennevilliers. New dwellings are being erected, and quite a new village, called Les Gresillons, has lately sprung up near the Clichj Bridge, and is chiefly inhabited by market-gardeners. Under these circumstances, it is but natural to find that the Paris municipal authorities, disregarding the petty opposition raised against the very existence of their scheme at Genne- villiers by a small knot of discontented or disappointed people, are pushing on their plans for the extension of their works of distribution, so as to dispose of the whole of the sewage. To that effect, they have applied for a declaration from the State that the scheme they have now selected to dispose of the Paris sewage through its absorption by the soil, is of utilite puhlique : a declaration which is equivalent to an Act of Parliament, autho- rising appropriations, and granting of all the powers, necessary to carry on works without any fear of individual opposition. The land available at Gennevilliers and Asnieres not being sufficient to absorb all the sewage, it is now intended to cross the river again at St. Germain, and irrigate all the land lying on the verge of the forest along the river, and if need be, pour whatever is not used for agricultural purposes into the forest itself. This seems to be the only practical way of dealing with the serious difficulties in which the question is involved ; and, from the pressing necessity of the solution of the problem, in that way and in no other, it must at last prevail. The late lamented M. Ducuing had prepared a scheme to take the Paris sewage to the sea at Havre, along the course of the river Seine, thus repeating the scheme recommended of old by Ovid. *• Dorice ab Iliaca placidus purgamina Yesta, Detulerit flavis in Mare Tibris aquis." But, on examination, that scheme was found impracticable, not only on account of the enormous expenditure of capital it would entail, but also on account of its engineering impossibilities. Such is the position of the sewage question in Paris. From what I have said, it may be fairly concluded that the happy solution of the grave difficulties in which the Paris Corporation found themselves involved when it turned out, against their fond expectation, that the River Seine did not remove the sewage along with its stream, but got helplessly fouled and poisoned, has at last reached a point beyond the stage of groping experi- ments. The issue is now close at hand, and there cannot be any apprehension about its successful and satisfactory character, when we consider, on the one hand, the crushing urgency of the want and the completeness of the remedy, and on the other the irresistible power wielded by the great city's corporation, which has determined to adopt that remedy. :^m\ %^<^' ^ ^>^ ^r^- .4 -^' > ■'■." '■■■^m W^ \ ' v':>*?^- Av