and to make available, as far as may be, the present mains. and pipes, as they are now laid down, so as to avoid the necessity of obstructing the pavements by being compelled to lay down others. It being stated in the reports, that the supplies of all the water companies in the metropolis and its suburbs are taken from the river Thames, except the New River Company and the East London, which latter company is supplied from the river Lea, and that a partial supply of the New River Company during the summer season, is also taken from the Thames, at an establishment formed at Broken Wharf, Upper Thames Street, I feel less difficulty in coming to the conclusion, that a filter may be. formed under the bed of the Thames itself for each. company, competent to furnish a quantity of water equal. to the consumption of the metropolis and its suburbs, and. in every respect more pure than filtration can make it generally, in consequence of the great depth at which the filtering bed may be made, as will be shown hereafter. The following is an extract from the Report of the commissioners appointed by his late Majesty, as before stated, on this important subject: 66 To obtain an effectual supply of clear water, free "from insects and all suspended matters, we have taken "into consideration various plans for filtering the river "water, through beds of sand and other materials; and 66 66 66 considering this on many accounts as a very important object, we are glad to find that it is perfectly possible. "to filter the whole supply, and this within such limits in point of expense, as that no serious objection can be urged against the plan on that score, and with such rapidity as not to interfere with the regularity of "service." 66 And in a subsequent part of such report, the com missioners quote Dr. Bostock's opinion in the following words: 66 66 66 "It appears that the water of the Thames, when free "from extraneous substances, is in a state of considerable purity, containing only a moderate quantity of saline " contents, and those of a kind which cannot be supposed "to render it unfit for domestic purposes, or to be injurious to the health; but as it approaches the metropolis, it becomes loaded with a quantity of filth, which "renders it disgusting to the senses, and improper to be employed in the preparation of food. The greatest "part of this additional matter appears to be only mechanically suspended in it, and separated by mere rest; it requires, however, a considerable length of time to allow of the complete separation; while, on "account of its peculiar texture and comminuted state, "it is disposed to be again diffused through the water, by a slight degree of agitation, while the gradual accumu"lation of this matter in the reservoirs, must obviously "increase the unpleasant odour and flavour of the water, "and promote its tendency to the putrid state. 66 66 66 Regarding the greatest part of the extraneous matter "in the Thames, as mechanically mixed with it, we may "conceive that a variety of incidental circumstances will "affect its quantity in the same situation, and under the 66 same circumstances of the tide; but the observations "are sufficiently uniform to warrant us in concluding that "the water is in the purest state at low tide, and the most "loaded with extraneous matter at half ebb. It would 66 appear, however, that a considerable part, if not the "whole of this extraneous matter, may be removed by "filtration through sand, and still more effectually by a "mixture of sand and charcoal." A consideration of these facts, and of the most simple method of obtaining a supply of pure water, has led to the following mode of carrying such an object into effect, which it is hoped will appear clear and easy, certain of success, not interfering with the navigation of the Thames, not throwing into disuse the expensive engines, pumping machinery, and supply pipes already in place for use, not too expensive, or otherwise objectionable for existing companies to avail themselves of, and perfectly within the reach (at a moderate outlay) of any new companies, for the supply of pure water, which may be formed hereafter. The following observations will, it is hoped, lead progressively to a development of the natural mode of filtering water, and shew how and at what probable expense, this mode may be adapted to general use, without any of the disadvantages noticed above. The wells on both sides of the river Thames, within a certain distance, it is well known, are affected by the rise and fall of the tide, which fact proves that such wells derive a supply by filtration from the river. I believe it is generally admitted that these wells give a supply of water wholly untainted with animal or vegetable matter, and evidence was given before the committee, that the water of the Thames, when filtered, is particularly wholesome, and the wells of water in its neighbourhood being pure, proves the efficacy of the filtration; and it being found that this water does filter through the surrounding soil, at a rate which, although unknown, must be very considerable (because it affects wells at a distance of many hundred yards) it must follow, that there can be no great difficulty in obtaining a similar supply, by means of a filter constructed on the same natural principles, under the bed of the river itself. The deposit of mud on the sides of the river Thames, does not reach beyond the low water mark, and the bed of the river throughout is generally a clean and strong, though porous gravel. The deposit of mud, therefore, will puddle in, and close the pores of the gravelly bed on which it lies, above the low water mark, so that the filtration into the neighbouring wells must take place below low water mark. It is therefore proposed to construct a filtering chamber below the bed of the river, from which a main pipe or tunnel will conduct the filtered water into a well on the river side, which may be taken from thence by the present steam power on shore, and delivered out by the mains and branches now laid down by the existing water companies. The drawing accompanying this paper (see Plate I.) exhibits this mode of operation, in a state of completion, and the means by which it is to be accomplished, are now to be more fully detailed. Fig. 1, is a vertical section of a portion of the river, shewing the proposed filtering bed, the supply pipe, the well, and the engine house. Fig. 2, is a plan or horizontal representation of the floor of the filtering bed, the conducting pipe and the section of the well. The line a, a, is the level of the river at high water; the line b, b, its level at low water; c, is the filtering bed, composed of materials as described below; d, is the filtering chamber, or receptacle for the water, when it has perculated through the bed; e, the pipe which conducts the pure water; f, the well in which the water rises to the level of the river; g, the suction pipe; h, the engine house. A coffer dam must be erected, of a sufficient capacity to enclose the area, estimated as requsite to filter any given quantity of water, and the bed of the river must be dug out, to allow the bed of brick work, set in cement, (or of stone) being laid, and the floor must be constructed as an inverted segment of an arch each way, and the walls stayed apart in the middle of their height, to prevent their being forced inwards. On the top of this wall are to be laid plates, and in the enclosed area, the granite blocks are to be set; upon these are to be laid the girders, and over these the joists, placed in such a way that they shall support a first layer of large flints, upon which smaller flints are to be laid, so as to be secure from falling through. Upon this second layer, another layer of smaller flints is to be placed, and upon that still smaller flints in succession, decreasing the size in each layer as it approaches the surface of the bed of the river, until the bed is prepared; upon which a stratum of fine clean shingle can be securely deposited. Upon this bed of clean shingle a bed of fine and very clean gravel should be strewed, and on that a bed of filtering sand, until arrived within one foot of the level of the bed of the river, which last space should be then filled up with clean gravel, thereby making a filtering bed in depth of To which add, for the brick work below And the top of the filtering bed will be 8 feet 7 do. 18 do. 4 thereby requiring piles of about 45 feet in length, to make the coffer dam. The water will percolate through these different strata, and the sides of the opening being puddled with clay, it will be found that no water can pass (by filtration or otherwise) into the chamber, without passing through the prepared strata, which will thoroughly clear it of all impurities, while the action of the alternate ebb and flood tide upon the surface of gravel, will prevent the possibility |