350

Proceedings of the Royal Institution.

THE weekly meetings of the members of the Royal Institution were resumed for the season, on Friday, the 23d of January. Upon the table in the Library was a bust of the late Daniel Moore, Esq., executed in marble by Sievier, for the Royal Institution, to which Mr. Moore was a most liberal benefactor. Various Hindu mythological paintings and drawings were exhibited, relating to the history of Crishna, the Apollo of the Hindus. A variety of bows and arrows, illustrative of the history of the weapons of various nations, were upon the table; as also some remarkably fine castings in bronze, and various novelties in literature and the fine arts.

In the Theatre, Mr. Brande gave an account of the present state of the supply of water to the metropolis. In bringing this subject before the members of the Royal Institution, he said he was actuated by two motives: the one, that of calling and keeping up attention: to a subject of the utmost importance to the comforts and health of the inhabitants of London; and the other, that of divesting it of certain prejudices which have too often attended the discussion, and of shewing the possibility and plausibility of effecting such improvements in respect to it, as should tend to meet all solid objections. He observed that there were numerous points of interest involved in the general consideration of this question, and that the quality of the water, as affecting health, was a principal one-it must be in itself salubrious, or it may produce direct mischief, and there must be abundance of it to wash away those accumulations of filth, which would otherwise generate Malaria, and various diseases. In respect to salubrity, some waters are so evidently contaminated, as to be unfit for general purposes, and which, though used from necessity in certain localities, could not be tolerated for the supply of a town; of these it was unnecessary to speak. Others, although not obviously unpalatable, might be injurious, from certain contamination of organic substances in peculiar states of decay-this seems formrely to have been the case with the water of the Neva-perhaps also with that of the Seine-the subject is of importance, because such contaminated waters, although containing very minute and almost undetectable quantities of noxious matter, may slowly impair the constitution, and render it susceptible of peculiar disorders. The principal points referable to abundance of water as a source of health, were then touched upon, the influence of extensive drainage, and

properly constructed sewers, of street-watering, and of allowing large quantities of water to run to waste: these several points were enlarged upon, and their general influence upon the cleanliness and sweetness of London shewn, notwithstanding the great evil the town has to cope with in the torrents of smoke with which it is infested, and which evil promises to be aggravated by the utter neglect of all attempt at its consumption, and by the recent invention of circular polished flues, which throw all the soot into the air, instead of allowing, as in common constructed chimnies, much to be deposited in the flues. To make persons more content with the present supply of water, Mr. Brande contrasted the quantity and quality of that supplied to London with the supplies of other large towns on the continent, where it is carried in driblets from house to house, where there are no sewers, and where all kinds of discomforts arising from these causes are severely felt. How far the decoration and ornament of a town might be connected with its supply of water, were next considered. The unostentatious abundance in London was contrasted with the ostentatious penury of Paris: a very little water easily made a great show in a well-constructed fountain, and in these respects we are apt to be much misled by appearance. At the same time, ornament is not to be depreciated where it may be so admirably associated with utility; the grand fountains of Rome were cited as instances, and regret expressed at the utter inattention to decorative water-works in our new buildings. It was well understood that the excellent opportunity now offered of effecting something good in this line, by the reconstruction of the Chelsea Company's reservoir in the Green Park, was to be neglected.

From these general considerations Mr. Brande proceeded to such details as affected London in particular, noticing especially the extent of the metropolis, and the peculiar mode of supply-many hundred miles of pipes of different dimensions were required, capable of sustaining the pressure of one hundred feet of water; for this purpose iron was a necessary requisite, great capital was necessarily expended in machinery and utensils fitted for this supply, and for throwing into the town a daily supply of thirty millions of gallons, which is the average consumption.

The sources whence the water for the supply of London was obtained, were next particularized, and the relative quantities drawn from the New River and the river Thames were estimated. In further illustration of this subject, the following Table was shewn, specifying the name of the Company, the quantity of supply, the number of tenants supplied, and the number of engines employed.

atrored vratnemeileg ødt ni badeildug bus eranoiasimmon adt bas COMPANIES. edonizebiagos nigra 25 diedt hay19204ggregate Gallons supplied Cubic Feet todat ons ni brot Daily 291fsupplied Daily, supplied to Engines Power

Mr. Brande said, that this Table furnished abundant matter for discussion and reflection; but the point to which he should now principally call the attention of his audience was, that the greater part of the Thames' supply was taken from the most objectionable parts of the river; that is, from those parts which immediately receive the drainage of London: and although there is certainly a constant and considerable admixture of fresh water supplied by the descending river, and partly, perhaps, by the influence of the tides, there could, he said, be no doubt as to the mass of water being materially affected by the impurities thrown into it; and as these have greatly increased within the last twenty or thirty years, so there has been a proportionately increasing deterioration during that period. Mr. Brande then went into the proofs of this deteriorati, and detailed its various causes, principally from the evidence laid before

the Commissioners, and published in the Parliamentary Reports. He observed that it was surprising, considering the abundant and prolific sources of all kinds of impurities to be found in the district alluded to, that the water was not more polluted; and that at times the supply was tolerably unobjectionable, especially when it had been subjected to filtration: whence we should infer that the chief evils arise from matters mechanically suspended in, and not chemically combined with, the water. He observed, however, that this remark was not made to justify the present sources of supply: for, even if the water were quite unobjectionable, the very circumstance of its being drawn from a part of the stream polluted by the contaminations of a million of human beings, to say nothing of the thousands of other animals and other sources of mischief, should awaken suspicion, induce us to suspect its cleanliness, and most undoubtedly to discontinue the supply from such sources, unless impelled to retain it by the sternest necessity, by the utter impossibility of getting water elsewhere, which fortunately is not the case. The question as to the purity of the water with which London is supplied, involves two important points-its salubrity-its composition. In reference to the first, even a professed chemist must allow, that water may be insalubrious, though chemical analysis cannot detect the cause of the evil; air may be eminently so, and why therefore not water? It was by no means meant to imply that the water is unwholesome, because all general facts were against such a conclusion, but merely to insinuate that we should not be thrown off our guard. In respect to the actual analysis of the Thames water, the following is a comparison of the purest and impurest specimens 10,000 parts leave, by evaporation,

Carbonate of lime

Sulphate of lime ...

Purest. Impurest. 1,53

0.15

11 Common salt and muriate of magnesia 0.20

3001,55 0.12

19.23

1.90

2.02

8.92

3190By reference to the above, and other data, laid before the commissioners by Dr. Bostock, it appears that the extreme impurity of much of the water with which London is supplied, is referable to matters mechanically suspended in it, and that it consequently may much improved by keeping it for a due time in tanks or reservoirs properly constructed to admit of the subsidence of the

impurities, and the drawing off of the clear portion. Mr. Brande then described the efficacy of this operation as conducted on the works of the Grand Junction Company at Paddington, and adverted to the signal improvement which had thus been effected in their supplies. He next described the process of filtration as applicable to very large quantities of water, and gave an account of the works lately carried into effect for this purpose by the Chelsea Company, and shewed a model of their arrangements for the purpose, for which, as well as for the following particulars, he was indebted to Mr. Simpson, the engineer to that Company:--

"The pond which contains the filter bed is forty-four feet square at top, and made with sloped banks, the bottom being twenty-six feet square; it is six feet deep; the mode of forming the bed was as follows:-After the pond was made water tight, with a drain through the bank to the well, the bottom was covered with coarse gravel, in which drains were built without any cement between the joints of the bricks; they were covered with coarse gravel, and then with finer gravel, with coarse sand and finer sand, until the strata of gravel and sand were each two feet thick, both gravel and sand. having been selected with care, and well washed. The reservoirs were each thirty-two feet square at top, twenty feet at bottom, and four feet deep; the low water line of them being level with the high water line of the filter bed; the reservoirs were worked alternately on to the filter bed, and it was regulated to filter 12,000 cubic feet of water every twenty-four hours; and the water was remarkably pure and limpid after it had passed the bed. The silt which was stopped on the bed was regularly cleaned off with a small portion of the sand every fourteen days; the principle of the action depends upon the strata of filtering material being finest at the top, the interstices being more minute in the fine sand than the strata below, and the silt, as its progress is arrested, (while the water passes from it) renders the interstices between the particles of sand still more minute, and the bed generally produces better water when it is pretty well covered with silt than at any other time. The silt has never been found to penetrate into the sand more than three inches, the greatest portion always being stopped within the top half inch of the sand, and in cleaning the silt off, it has never been found necessary to scrape any more of the sand off with the silt than the first half inch depth, and sometimes only half that depth was removed. The small air pipes from the drains are to prevent injury to them or the filtering materials by condensation or otherwise.