March i6, 1876] 



NATURE 



393 



of surrounding land has not accompanied the withdrawal 

 of vast volumes of water from the deep wells at Deptford, 

 Thames Head, Caterham, Canterbury, Watford, Tring, or 

 Lichfield, and it is singular that Mr. Evans should have 

 overlooked the fact that moisture is supplied to growing 

 plants from above and not from below. However nume- 

 rous the wells of a given district may be, the rain must 

 still fall upon the surface of, and soak through, the land 

 before it can reach them. 



As the dry-weather flow of the Thames even above 

 Teddington lock is 600 millions of gallons daily, it would 

 be waste of time to discuss seriously the possibility of 

 canals and navigable rivers sinking into their beds in 

 consequence of the abstraction of about one-eighth of 

 that volume from springs and deep wells in that portion 

 of the river basin. With regard to the water-cress 

 interest, it is true that the Rivers Commissioners have not 

 been so deeply impressed as Mr. Evans with the stupen- 

 dous importance of this department of Thames agri- 

 culture, but it can scarcely be doubted that a wealthy 

 city, containing 4,000,000 of inhabitants, would be able 

 and willing to pay for any damage which it might inflict 

 upon this or any other branch of industrj'. 



The two most disgusting impurities revealed by the 

 microscope in Thames water, as delivered for dietetic 

 purposes in London, are the fibres of partially digested 

 flesh meat, and those of variously coloured rags. The 

 presence of these objects in our potable water clearly in- 

 dicates the two chief kinds of insoluble polluting matter 

 cast into the Thames, although chemical analysis cannot 

 always trace to its sources the dissolved animal and vege- 

 table impurities which it finds accompanying these in- 

 soluble materials. The question raised, therefore, is 

 simple enough : — Shall the inhabitants of this " over- 

 grown city," as Mr Evans contemptuously terms it, drink 

 the pure spring water which nature offers them in singular 

 abundance in the Thames valley, or shall they not be 

 permitted to taste this sparkling beverage until the paper 

 manufacturers, in the exercise of what they call their 

 rights, have washed their filthy rags in it, and half a 

 million of people have polluted it by their drainage ? 



It is remarkable that whilst Mr. Evans shows so much 

 consideration, in his presidential address, for the pockets 

 of the «atercress-growers, he has so little to bestow upon 

 the inhabitants of the overgrown city, for he does not 

 hesitate to propose that the latter should encounter the 

 expense of two separate water services — one (pure) for 

 dietetic, and a second (polluted) for other domestic pur- 

 poses. Now, leaving out of consideration altogether the 

 risk of the polluted water being often used for dietetic 

 purposes instead of the pure, and the enormous cost and 

 inconvenience of laying and maintaining a new set of 

 water-mains throughout the hundreds of miles of London 

 streets ; the supply of each house with a new water service, 

 together with the necessary alterations of the old pip)es, 

 could not cost, on the average, less than 4/. In February 

 last 523,801 houses were supplied with water by the eight 

 metropolitan companies, and we have consequently here 

 an expense of more than 2,000,000/. Surely a very small 

 fraction of this sum would suffice to buy up any injured 

 watercress-growers, even at " fabulous ' prices. 



In their sixth report, the Rivers Commissioners of 1868 

 state that the basin of the Thames, including that of its 

 tributary, the Lea, is upwards of 5,000 square miles in 

 .extent. Rather more than one half of this area, including 

 the oolitic and cretaceous formations, is covered by a 

 porous soil upon a permeable water-bearing stratum, the re- 

 mainder being occupied by the Oxford, Kimmeridge, gault, 

 and London clays. The annual rainfall of this district 

 averages about 28 inches, or 5,217 millions of gallons per 

 day. Two-thirds of this vast volume of water is lost by 

 evaporation, while, of the remaining one-third, one-half 

 passes away in floods, and the other half only is at pre- 

 sent available for springs and deep wells. But even this 



small fraction amounts to 870 millions of gallons daily, 

 and it is proposed to take for the supply of the metro- 

 polis only 120 millions of gallons after it has practically per- 

 formed all its fertilising functions ; whilst, of this volume, 

 there is even now supplied to London, in dry weather, 

 about twenty-two millions of gallons. It is highly prob- 

 able, however, that the volume of water available at present 

 for springs and deep wells could be augmented to an extent 

 commensurate, or nearly so, with the amount so abstracted 

 for the supply of London. The chalk, and to some extent 

 the oolite of the Thames basin, constitute an immense 

 sponge which sops up the water falling upon it and main- 

 tains it, partly by capiUary attraction and partly by its 

 resistance to flow, at considerable elevations above the 

 nearest rivers. This sponge has been aptly likened by 

 Mr. Thomhill Harrison to an inverted reservoir, and just 

 as the dry-weather flow of the Thames and its tribu- 

 taries could be augmented by the judicious use of artificial 

 storage reservoirs, so could the total yield of spring water 

 from this vast natural reservoir be increased, by artificially 

 bringing the water in it to a lower level before the occur- 

 rence of the autumn and winter floods. The spongy 

 reser\'oir would thus be rendered capable of receiving 

 those heavy rainfalls which, at present unable to find 

 storage room below, either run off the saturated surface 

 and constitute the winter floods, or immediately displace 

 a corresponding volume of spring water from the sf>onge 

 forcing it into the Thames and its affluents. 



In the concluding paragraphs of his address Mr. Evans 

 tries to show, from the results of chemical analysis, that 

 the polluted water of the Thames is purer than the spring 

 water from the chalk, and he thus seeks to make the in- 

 habitants of the metropolis content with their present 

 supply. His statements on this subject are founded upon 

 an entire misconception of the meaning of the analytical 

 results. A most exhaustive chemical examination of the 

 river waters of the Thames basin, on the one hand, and 

 of the spring and deep-well waters on the other, has 

 shown, in the most unmistakable manner, the immense 

 superiority of the latter for dietetic purposes. Indeed, it 

 is obvious that, even with the most efficient river conser- 

 vancy imaginable, aided by the best efforts of the Legis- 

 lature, the Thames must always receive so much pollution 

 as to render its use for the supply of the metropolis highly 

 objectionable. No preventive measures can hinder the 

 washings of highly-manured land, the excrements of 

 cattle, the imperfectly purified sewage of towns and vil- 

 lages, and the partially cleansed discharges from paper- 

 mills, skinneries, and tanyards, from mingling with the 

 stream in enormous volumes. Such matters, though not 

 ob\nously offensive to the senses (when this highest prac- 

 tical stage of purification has been reached), are still, from 

 a sanitary point of view, of a very dangerous character. 

 But even if this were not so, and if fatal results had never 

 been known to follow the domestic use of such water, the 

 refined feeling which separates the civilised man from the 

 savage, and which excites loathing at the bare idea of 

 organic matter, v/hich has recently formed part of a 

 human body, being supplied for human consumption, 

 ought here to assert itself, and secure the rejection of 

 such a beverage. E. Fraxkland 



SCIENTIFIC NOTES TAKEN IN THE 



HIM ALA YAS 



I. — Atmospheric Absorption. 



THE following notes refer chiefly to spectroscopic work. 

 and they are, I think, of interest, as they show 

 the importance of establishing a regular series of similar 

 observations at different points of the globe. 



Prof. Vogel has lately published in Poggendorff's 

 Antialen the results of his observations taken in the 

 Red Sea and in the Indian Ocean. He comes to the 



