Return this book on or before the Latest Date stamped below. University of Illinois Library Mfl'i' 25 I9|!0 OCT 2 6 1976 L161— H41 (o 2 - ( (THE SEWERAGE OF PARIS. 'Sf GEO. E. WARING, Jr. gyjN important technical commission has been employed during the past year in considering the best manner for relieving the city of / Paris of its renowned odors — odors which prevail not only in the public streets, but almost universally within houses of all classes. The projects under investigation are of two classes : one proposing the entire removal of faecal matter and household and industrial wastes by sewers (tout a Vegout) ; the other proposing the emptying of vaults and cesspools by improved processes, or the removal, by the Beflier or Liernur systems, of foul wastes only, conveying these to suitable points without the city, and then converting their organic contents into arti- ficial products, to be used for agricultural or chemical purpoes. At O present every house has its cesspool or vault, in which all waste organic matter is retained for long periods, during which its fermenta- tion acts as a source of great contamination of the air, and, presum- *^ably, of a serious infection, originating epidemics of typhoid fever ‘iH and other zymotic diseases. The Liernur system of daily removal by pneumatic process would withhold from the vaults the solid matters of kitchen waste, and the total products of the water-closet, leaving the liquid kitchen wastes to flow to the present sewers. The Berber sys- tem would remove all household wastes, but the solid portions only after they had, through putrefaction, assumed a liquid form, r- T he discharge of all wastes directly to the sewers would lead to the entire suppression of vaults, cesspools, and other seats of deposit within the habitation. This complete removal receives the approval 0^ of the best authorities on the subject; but in Paris it is met with the 'difficulty that most of the sewers — all except the large collecting sewers — are so large, and carry such limited flow, as to cause depos- its and local putrefaction, which would only transfer to the sewer and to the street the offensiveness now originating in the house and in the cesspool. There is the further difficulty that only a relatively small portion of the rapidly growing city is now provided with sewers of I ^ THE SEWERAGE OF PARIS. any sort : a recent report of the Director of Works estimates the length ot unsewered streets at about 220 miles, requiring for construc-l tion, if the existing system should be extended, an outlay of seven million dollars. J These facts are now being carefully considered and discussed b the J echnical Commission, which has ordered the trial, on an exten sive scale, of the system of sewerage carried out in Memphis. Th( atest leature of the discussion, which has been going on actively sinct 1 ovember last, is a paper submitted by M. Vauthier, a member of the Commission, and also of the Municipal Council of Paris, read on the 28th of March, 1883, before the first Sub-Commission. Of this paper we furnish the following translation : — The exposition! made by M. Poutzen, C. E., on the 10th of last January before the Second Sub-Commission, on the subject of the system of removing water-closet matters and household wastes, that Mr. VV aring applied for the first time in the city of Memphis, United States, seems to offer a new solution of the question of the sanitary improvement of Paris {de V assainissement de Paris^, J he greatest difficulties that arise, not only from the universal dis- charge of water-closet matter into the sewers, but henceforth, also, in connection with the maintenance of the sewers in a proper state of I cleanliness, seem to relate chiefly to the primary sewers of the system ; that is, to those which begin in the streets in which they lie, and which ^ M. Hunil)lot, Engineer-in-Chief, calls the direct sewers. According to the ideas and mode of construction followed up to this time in^ Paris, these direct primary sewers are always of rather large dimensions. The invert has a width always of 40 centimetres, and lately we have had occasion to see, in a number of sewerage projects submitted to the Municipal Council, that the tendency is rather to augment than to diminish the size. In a great number of these pro- jects for primary sewers or for sub-main sewers having the same char- acter, the original ‘‘Type 12’’ has been supplanted by “ Type 13,” which carries the invert from 40 centimetres to 50 centimetres (16 inches to 20 inches). This tendency is understood if we consider the notion which has thus far controlled the establishment of large sewers {paleries degout). Indeed it seems to be economical reasons only that have ' prevented a further enlargement. These sewers are convenient sub- terranean passageways, where the hand of man is considered an in- dispensable auxiliary to cleansing, and where there may be placed ! the bundles of wires for telegraphs, telephones, etc., and pipes for the supply of water. For a long time the house branches have been con- | structed according to the same ideas, being intended to be utilized as i passageways in the emptying of vaults, etc. But the better these primary sewers satisfy the desiderata in view ' of which they have been constructed, the less are they adapted to receive, without inconvenience, faecal matter and household wastes. d he water used in washing the public streets — the only water on which we can depend for cleaning the sewers, in view of the intermit- ^ See American Architect for April 21, 188iJ. THE SEWERAGE OF PARIS. 3 ^ent character of the rain-fall — produces only a momentary current. Some portions of the sewers indeed escape even this street water and the rain-water — those parts which are above the first inlet of the sewer, when this is inclined in the same direction as the street, as is most frequently the case. It would doubtless be possible, by deliver- ing water into the sewer which had been used for washing the gutters, to remove this last objection ; but if it were proposed to change the present intermittent current to a continuous one, we should be obliged either to employ an exaggerated amount of water, or we should secure only an insignificant current. This vice of the primary sewers has already struck everybody. It has been proposed to correct it by establishing a reservoir at the head of each sewer ; but we are always met by the objection stated above : either we must use a great amount of water with this special object, or we shall have but an insufficient palliative. The defect indicated is fundamental. It depends essentially on the fact that the primary sewers are intended, as are the others, for pas- sageways for workmen — not only as channels for the removal of water. The invert is too large, and it is in vain to reduce it by adopting, as at Brussels and in London, the oval form. This would only render walking more difficult, without essentially ameliorating the conditions of the flow of water. The fact cannot be disguised : in the primary sewers there is a contradiction between the two functions. It is impossible that sewers of the Types 12 and 13, for instance, having, so far as current is con- cerned, to depend on their own supply, should not retain in their in- verts, whatever may be their inclination, all or much of the substances delivered to them by private drains. The difficulty is augmented if through the inlets these sewers receive sand and other heavy detritus from the public streets. The best plan is, when one is confronted with a system that is fundamentally defective, to change it completely rather than to attempt by ingenious devices to correct it. What has just been said of these primary sewers is applicable, with more force, to private drains. Hear what M. Ilumblot, Engineer-in-Chief, says in his exposition of the 15th of December, before the First Sub-Commission : — “ On leaving the house,’’ he says, “ we find the private branch drain leading to the public sewer the waters of the property. In these branch drains the outlet-pipe generally ends at the exte- rior line of the property, and terminates in an hydraulic trap which cuts off all communication between the air of the sewer and that of the house. “ Sometimes the pipe is extended to the junction of the private branch with the public sewer. “ Under the first arrangement the house waters soil the invert of the branch drain ; and when the quantity of water and the inclination are insufficient, they deposit ordure which gives out offensive odors. We may imagine,” says M. Humblot in passing, ^‘how great would be the infection if f cecal matters were thus arrested. ‘‘ Under the second arrangement the pipes are often obstructed, 4 THE SEWERAGE OF PARIS. especially when their inclinations are slight and their outlets subject to periodic or almost constant submersion by the waters of the sewer, which often deposit solid matter in the mouth of the pipe. The work- men employed by house-owners to remove these obstructions often succeed in doing so only by breaking the pipes. This difficulty, which ' is rare,’’ M. Humblot finally says, “ in sewers deep enough to allow the house-drain to reach them with a steep fall, is almost inevitable in those central districts where the inverts of the sewers of the old type are at little depth below the surface of the street ; in these central quarters the outlet pipes generally stop at the side of the house.” So far as private drains are concerned, we have nothing to add to tjiese suggestions. Let us remember only the circumstance that the hydraulic traps have to be broken to effect their cleaning. This is one of the objections to complicated apparatus, and this complication l is made imperative by the need for withholding from the house the vitiated air of the sewers. I W e might stop our citation here, but it will not be without use to j follow M. Humblot a little farther. He goes on, in the apprehen- > sion with which the delivery of faecal matter into the sewers inspires i him, to confirm, with regard to the primary sewers, what we have ] already expressed. “ Now we see,” he says, ‘‘ these matters delivered into the public ' sewer. If this is a direct sewer, that is to say, beginning in the street in which it is laid — and this is the case for more than one-half of the sewers — it generally receives only the water of the houses, for its inclination is almost always in the direction of the inclination of the street, and the water used for washing the gutters only readies the sewer at its lower end. Also, when there are no industrial estab- lishments on the street, such as laundries, baths, etc., the volume of water flowing into the sewer is but slight. We must ask, then, what becomes of faecal matter so delivered ? If there is formed at the out- let of each private drain a little cone of faecal dejections, as the Com mission may see at those points where the experiment of direct dis- charge has been made, it is necessary to remove this accumulation of ordure at least once a day. What would be the quantity of water necessary to facilitate the dilution of these matters, their removal, and the rinsing of the sewer? What would be the minimum interval between two successive washings ? These are questions which must be solved.” The demonstration seems complete. In the actual state of things, the sewers which receive, aside from the water of extended rains, only the water of the washing of the street under which they are placed, and the liquids derived from the houses which border the street, have a current which bears no proportion to the dimensions of the channel which they afford ; these sewers are thus placed in a most unfortunate condition, whether from the point of view of cleanliness or that of general salubrity, and to remedy this essential defect, the (][uantity of supplementary water necessary to use would be extremely great. M. Humblot tells us that more than one-half of the sewers are of this character. THE SEWERAGE OF PARIS. 5 If we pass from primary sewers to secondary ones, and then to ter- tiary ones, and so on to the collectors, the objections cited above de- crease more or less rapidly, according to circumstances. In the secondary sewers the flow increases and becomes more regu- lar without an increase in the size of the invert. Therefore the con- ditions of cleanliness and salubrity are 'better, and the improvement continues until we reach the collecting sewers, which carry constantly an abundant flow, and to which there is also applied apparatus for automatic cleansing, which could not without exorbitant cost be made to operate in sewers of less importance, which are thus far ill adapted for their use. It results from the present conditions that in the actual state of things, from a sanitary point of view, it is the sewers of the least im- portance which offer the greatest difficulty ; that it is in these that the difficulties are the hardest to correct ; and that it is in these, also, that the causes of infection to which they are already subjected would be the most increased by the discharge into them of domestic wastes. Everything, then, leads to the concdusion that for the evacuation of domestic wastes it is necessary to seek some arrangement which may be substituted for these sewers. AVaring’s system, as it has been set forth by M. Poutzen before the Second Sub-Commission, seems to furnish, under excellent conditions, the elements of this substitution. If the trials, which are to be made in pursuance of the determina- tion taken by the Second Sub-Commission, confirm the principal ad- vantages attributed to this system — if the trials demonstrate : - 7 - (a) That by means of simple arrangements, easily to be adapted to soil-pipes and house-di*ains, the house can be connected by a bell- mouthed branch (of earthenware), of which the diameter varies from 10 to 15 centimetres, with pipe-sewers established under the public street, having a diameter of from 15 to 20 centimetres for the pri- mary pipes, increasing successively as the needs of the current require ; (b) That in these pipe-sewers, of such size as to run only one-half full with the ordinary flow, with an average velocity of 70 to 80 centi- metres per second, the variations of flow from hour to hour are slight, so that deposits will not easily be produced, and that provision is made for the removal of such dejiosits as may accidentally be formed by means of automatic flushing, more or less frequent, suffi- cient to clean the walls of the sewer, alternately made wet and left dry by variations of the flow ; (c) That in these pipe-sewers the air above the level of the liquid is never stagnant, and that its circulation, artificially increased by fresh-air inlets established at the successive junctions of the sewers, is assured by the extension of soil-pipes above the tops of the houses; and, (d) That under these conditions, household wastes and water-closet matters — diluted ordinarily in the proportion of one part solid to eighty or ninety parts liquid — being rapidly carried forward, take on and give out no foul odor, not even requiring the use of traps under closets. If these fortunate conditions are practically established, it seems to us that Waring’s system offers an important means (ressource pre~ dense) of urban sanitation. 6 THE SEWERAGE OF PARIS. The flow, and this is essential, is produced in this system by thA simple force of gravitation ; there is no complicated mechanism at any point, not even in the automatic flush-tanks ; there is no clock-worki; there is no trapping of the pipes ; there is no indispensable water- . seal; all is simple, sure, and inexpensive. Let us add, from another point of view, that unless we wilfully disregard the most elementary rules of hydraulics, we cannot avoid securing, in the ordinary condi- tions of flow, constant movement at every point at a predetermined velocity. A single circumstance may suggest some difficulties : the absence of sufficient fall. Although the lack of fall may be supplemented in great measure by an augmentation of force or an increase in the num- ber of the flush-tanks, it is necessary from an economical point of view not to go beyond certain limits in the volume of water to be used. Under the conditions of this system this difficulty is not grave. We may always increase the fall by having recourse to pumj)ing, and were this condition necessary in certain parts of Paris, it would cost but an insignificant outlay. The daily discharge of the sewers of W aring’s system will rarely represent, including the flushing water, more than 20 litres for each of the population. That is to say, 45,- 000 cubic metres for all Paris.* Were it necessary to pump a tenth part of the whole flow one horse- power for each metre of lift would be sufficient. There is therefore in this nothing which need disturb us. From the foregoing summary it seems that a clear idea may be j obtained of the applicability of Waring’s system for the removal of ' household water and faecal matters. Paris may be divided into a certain number of local districts. These local districts would be i drained of their domestic wastes by the pipe-sewers of W aring's sys- j tern, and the product of each district could be delivered either by nat- J ural fall or by pumping — if that should be necessary for some districts I — into one of the collecting sewers conveniently selected and having | a sufficient minimum flow. If we suppose the daily discharge of the col- | lectors, to-day 300,000 cubic metres, should be increased within a short , time to 400,000 cubic metres, and that also the daily discharge of all ' the Waring drains would be for all Paris about 45,000 cubic metres, we see that these special affluents would carry, on the average, to the points of discharge only about eight or ten per cent of the present flow of the collectors which would receive them. Should an objection be raised thereupon, especially in view of the faSt that the affluents contained only matters which have not yet entered into fermentation, it is to be met by the fact that the total removal of household and fascal matters by means of sewers must, for other motives, be abso- lutely prescribed. flow shall the Waring sewers be established in each district? These are details which we need not now consider. Where there are now no large sewers they cannot be otherwise placed than in the ground under the public streets. Where large sewers already exist, must they necessarily be placed within these ? Some persons answer in the affirmative. But if private drains are not now connected, we THE SEWERAGE OF PARIS. 7 doubt that they are right, and hold the matter in abeyance. It is, after all, a question of detail which in no respect affects the system, and which will receive a practical solution. It is more interesting to consider the change that the proposed dis- position will produce in the sanitary condition of the existing sewers. Completely relieved of household waters and all faecal matters — for the public urinals and cliMets can be drained by the Waring sys- tem — the primary sewers will henceforth receive, aside from rain- water, only the water used for washing the public streets. Can they also be relieved of the waters of manufacturing establishments, includ- ing in the series the discharge of abbatoirs, markets, and public baths and laundries ? It seems to me that this cannot be doubted. The flow of water to be considered is nearly constant, and indeed they can be received into these pipes with advantage, the diameters being increased as may be necessary, because they would increase the cleansing effect of the current. In any case the percentage of nitrogenous matters in the whole sys- tem of primary and secondary sewers, and even in each collector above the junction with a Waring affluent, would be very greatly reduced. Furthermore, all the branches of the system corresponding almost to the total surface of the city would be entirely relieved of suspected germs. We should have a complete change of condition, not only in this ensemble of sewers, from the point of view of cleanliness, but also for those regions of the city which lie x.above them in all that relates to healthfulness. As to the cleansing of the sewers, there would remain but one serious question : that of sand. But, independently of many other considerations, it is clear that in eliminating the solid matters conveyed by household waters and excrernental liquids, which now soil these solid deposits, compacting them and impregnating them with foul odors — a difficulty which will be greatly increased after the delivery of all faecal matters into the sewers — we shall render the removal of the sand less disagreeable and therefore less costly. The inlets of the primary and secondary sewers, which more or less always, but especially in summer, send out such offensive odors when the inverts of the sewers become dry, will be relieved of this objection, which so seriously affects the public health ; and it will be useless to think of borrowing the trapped inlet-basins of Brussels, which even there are not irreproachable, and which would be inapplicable in Paris by reason of the greater abundance of street detritus. < The atmosphere in which the sewer gangs work, and to which they are acclimated, but which is nevertheless not without effect on their health, will become nearly as pure as the free air. The question of cleansing, already solved for the collectors, but so difficult in the case of the minor sewers, will be entirely transformed, and the work will become much more economical. Let us add — and this is not one of the least of the advantages of Waring’s system — that the drainage of Paris, so far as it is prac- tically necessary, can be applied much more rapidly and with a con- 8 THE SEWERAGE OF PARIS. siderable reduction of cost. There is now in fact a great extent of streets without sewers. Nearly all that are yet to be constructed are primary sewers, draining only the streets under which they lie. With the present idea of delivering all foul matters to the sewer {lout a Vegout) these sewers are indispensable. The use of Waring's system would allow them nearly all to be suppressed or their construction to be postponed to a distant day. Not that such sewers are absolutely without their use, especially in connection with the distribution of water ; but the final ramification of the water-pipes could perfectly well be placed in the ground. As to the water used in washing the streets, there are but few points where they now have to run far in open gutters. We could therefore avoid constructing immediately almost the whole of these sewers. This would result in a considerable economy, which may be estimated, supposing the Waring sewers to cost from fifteen to twenty francs per metre, at not less than eighty to eighty-five francs per metre ; and besides that, what an economy for householders in all that relates to branch connections ! In a recent paper, the Direction of the Works of Paris, estimating the length of sewers of only local interest still to be constructed at 343,429 metres, and the outlay required therefor at 35,000,000 francs, we estimate that at least 250,000 metres, and perhaps 300,000 metres of this length could be suppressed, at an economy of 80 francs per metre. This would be 20,000,000 or 24,000,000 francs, of which the necessity would be totally suppresseu, or at least postponed for a long time. These figures are not to be disregarded. They add an important consideration to the adoption of the Waring drainage within the limits above indicated. And to whoever would charge this combination with complication, it may be replied that the special- ization of functions that it secures is rather a progress. It is the specialization of organs and the localization of functions that charac- terizes the most perfected organisms. The objection seems to us without value. There remains, however, one question in connection with this sys- tem : that of determining whether or not the augmentation of the per- centage of nitrogenous matter in the waters of the sewer, as a result of the total yemoval of domestic wastes by this means, will not be in itself objectionable, either during the subterranean flow of the sewage or in connection with its purification. As to purification we have nothing to say. As to the current in the sewers, by causing this increase in the percentage of nitrogenous matter in the collecting sewers which have a large flow — where organic matters rapidly carried forward will have arrived without fti’- mentation — the objections will be much less than if the increase was produced within sewers of feeble current, where these matters have often ample time to enter into putrefaction. Will these objections nevertheless exist? This is a point which we cannot decide ; but we believe that they will at least be unimportant. It may be further remarked that the circumstance described is not the only one that may ultimately be urged for the extension of Wait- ing’s system, which may be made to withhold from the collecting sewers themselves all domestic wastes. THE SEWERAGE OF PARIS. 9 If the progress of industrial chemistry succeeds in finding means by which artificial manure can be made from domestic wastes without the emanation of dangerous gases, and without the production of a foul liquid residuum, and under conditions which can cause no preju- dice to the public health, it is quite possible that we shall be led to establish a system of complete and absolute separation between domes- tic wastes and the ordinary sewer water. The latter may continue to flow to the purification fields ; but the former will be sent directly to factories, where they will receive their chemical treatment. It is not at all necessary to insist on this rational point of view, which, however, it was necessary to indicate as a part of the complete question. The industrial progress referred to may never be attained, or we may have to wait long for it. Should it be attained, and should the absolute separation referred to become necessary, we should have to regret, because of the provisional discharge of the Waring drains into the collectors, only an insignificant wasted expenditure. We might almost everywhere in effect place within the present collecting sewers the collecting pipes of Waring^s system, the dimensions of which, even for all Paris, would not exceed narrow limits. We may, then, in all that relates to the expulsion from Paris of all its foul wastes, go on without fear in the way above proposed. It seems essential, so far as relates to the discharge of household wastes and faecal matters, to substitute the sewers of Waring’s system for our primary sewers, which carry an insufficient flow of water. It is the object of the present paper to call attention to this point, believing that the considerations that are here developed constitute a reason for hastening the practical trial of Waring’s system, as asked for by the Second Sub-Commission. This will be for the moment our only conclusion. After the full discussion of the whole subject, of which the paper of M. Vauthier was an important element, the Technical Sanitary Commission of Paris has passed the following resolutions — those requiring the discharge of water-closet matter into the sewers being carried by a vote of twenty-one to six. Water-Closets. Article 1. In every house there should he a water-closet for every apartment [suite]. In case of need this may be placed outside the apart- ment [suite], if on the same floor with it. Art. 2. Every water-closet shall be supplied from a reservoir, by a sup- ply-pipe, or by other means with a sufficient quantity of water to insure a minimum supply of ten litres per person per day. Art. 3. Each water-closet should be furnished with a water-seal trap below the bowl. Household Waters and Rain. Art. 4. The waste-pipes of sinks must be trapped near the upper end. Art. 5. All leaders should be intercepted so as to prevent direct com- munication with the sewer. Art. 6. Every soil-pipe or sink-waste should be carried above the roof to establish active and permanent ventilation. Art. 7. It is desirable that these soil-pipes carried above the roof, as before said, should be flushed by automatic intermittent flush-tanks, located on the highest story where there are closets. 10 THE SEWERAGE OF PARIS. Art. 8. In order to insure a hermetic and permanent interception be- tween the sewer and the house, the outlet pipes shall be supplied wdth traps at their lower ends before entering the public sewers. Art. 9. Waste-pipes shall be tight, of cast-iron or vitrified earthenware, and carried through the house branch2 to the public sewer. Vaults. Art. 10. It, is necessary to continue the suppression of the system of fixed vaults. To that end new vaults will not be established, except in cases to be determined by the administration, where the absence of a sewer, the arrangement of the existing sewer, the insufficient supply of water, etc., will not permit the direct discharge either into the existing sewer, or a special sewerage system. Art. 11. A basin with sloping sides should be sunk at the bottom of the vault, under the man-hole cover, to render the work of emptying easier and more rapid. Art. 12. In vaults now existing ventilation should be accomplished by inlet-pipes, and by pipes open at their upper ends, and carried above the roof of the house. Art. 13. It is necessary to insure, with the aid of a sufficient force, a more complete surveillance as to the tightness of vaults, and over the work of emptying them. Art. 14. The emptying of vaults should not be authorized, except by aid of the most perfect apparatus, especially such as, creating a vacuum in the chambers, have arrangements for the disinfection of the escaping gases. Movable Tubs. Art. 15. Movable tubs, of which the overflowing is inevitable, should be suppressed without delay wherever this is possible. Art. 1(). a temporary exception may be made in the favor of recepta- cles supplied with dry and absorbent substances, which are of great service in one-story buildings and for the ground floor, when the renewing of their absorbents is assured by a regular service. Apparatus for Separation or Dilution. Art. 17. Apparatus for separation or dilution constitutes only an im- perfect adjunct of a discharge to the sewer. Art. 18. Such apparatus should be so arranged as to render overflow into the cellar impossible, and to insure the direct flow of the surplus to the sewer. They are permissible only in houses abundantly supjflied with water. Discharge of Water-Closet Matter into the Sewer. Art. 20. The total discharge of excremental matters into the sewers may be authorized in the case of sewers having a large and constant flow of water, not subject to an accumulation of sand, and in which matters are car- ried without halting to the point of discharge in the collecting sewer. Art. 21. It may be permitted also in sewers less abundantly supplied than the above, but having fall and flow sufficient for the removal of all matters, on the condition that the improvements be carried out which are indicated in Articles 23 and following. Art. 22. In sewers Avhich do not satisfy the conditions specified in Ar- ticles 20 and 21, or in which the back water of the collecting sewers may check the flow, the discharge of excremental matters can be made only in tight pipes placed inside of the large sewers, and carried far enough to reach sewers which do meet the prescribed conditions. Maintenance and Cleansing of the Sewers. Art. 23. Flushing wagons carried on rails may be established in 7,600 metres of the old sewers which now receive much sand. Art. 24. The angles of all inverts should be rounded. A gallery running from the sewer to the line of property. THE SEWERAGE OF PARIS. 11 Art. 25. It will be necessary to increase the size, or to reconstruct old sewers to a length of about 10,000 metres. The inclination of their inverts will be increased for about 8,000 metres. Art. 26. To insure the cleansing of the sewers, independently of the water admitted at the inlets and such as comes from habitations, there will be established a system of flushing by means of reservoirs discharging ten cubic metres of water, placed at the head of each sewer, and at maximum intervals of 250 metres along its course. These reservoirs will be emptied instantaneously once or twice each twenty- four hours. Gangs of workmen will follow the movement of the water discharged to cause deposited matters which remain attached to the walls of the sewer to be carried on with the flow. The length of the sewers in which this mode of cleansing by flush-tanks may be employed is about 424,000 metres. Art. 27. There will be established in the collecting sewers a certain number of sand-boxes (fifteen at the outside) in such a way that the cleaning boats or wagons ma}^ secure the removal of these matters with a delay of not more than twent 3 "-four hours. Art. 28. Movable catch-basins will be established at the inlets of sewers under paved streets, or others which discharge sand, manure or heavy mat- ters into the sewers. The number of these catch-basins is estimated at two thousand. Art. 29. The central system of collectors will be so completed as to re- lieve the collectors of the Coteaux and of Clichy, and to provide a discharg- ing capacity of 400,000 cubic metres per day. Art. 30. The waters of the lower parts of Grenelle, of Bercy and of the Thirteenth Arrondissement of Paris will be discharged into the collectors. Art. 31. There will be established at the outlet of the collector at Clichy flood-gates and movable dams to prevent the reflux of the waters of the Seine in time of flood. The flow of the waters of the collector will then be assured by modifying the pumps at Clichy, so that they may raise and throw these waters into the Seine to the amount of 660,000 cubic metres per twenty-four hours. Purification of Sewage Water. Art. 32. The waters of the sewers of Paris, taken in their present con- dition, that is to sa}^, containing a large proportion of excremental matters, can be subjected to processes of purification by the soil without danger to the public health. Art. 33. It is proper to ask the Government to take the measures neces- sary to interdict the discharge of impure waters into the course of the Seine and of the Marne in their passage through the two departments of the Seine and Seine-et-Oise. Art. 34. A study will be immediately undertaken as to the purification of the waters of the departmental collectors of the Seine and of the sewers of Paris, which will be connected with them by the irrigation of the plains bordering the river above Paris. On the 31st of July the Municipal Council of Paris appropriated 50,000 francs for the construction of Waring’s system of sewerage in the Rue du Temple, and for the drainage, under his direction, of the public buildings adjoining. This improvement will be completed this season, the work being done by the Drainage Construction Company of Boston.