1858.] Drinking Waters of the Metropolis, 467 



into the blood by the agency of water. Fats were reduced to 

 soluble soaps, and proteinaceous matters were formed into, soluble 

 albumen before being taken into the system. 



The great source of water for these purposes was the ocean, 

 which spread over the surface of the earth, raised into the atmos- 

 phere by heat, and precipitated again by cold, formed snow and 

 rain. These collecting on the surface of the earth, formed rivers, 

 or penetrating the rocks, appeared again as springs. Both kinds 

 of water contained organic and inorganic substances. The latter 

 were dissolved, the former for the most part suspended. In 

 river waters the inorganic matters varied according to the rocks 

 over which they flowed. The Dee contained five grains in the 

 gallon ; the Exe, fifteen grains ; the Wandle, seventeen ; and the 

 Thames, twenty. The organic matters of rivers are derived from 

 the plants and animals which live in them, and from the vegetable 

 and animals refuse cast into them. 



Spring waters contained more and less inorganic matters than 

 rivers. When the quantity was large or peculiar, they were called 

 mineral waters. When the salts of lime abounded they were called 

 hard waters ; and when free from the salts of lime, and very large 

 quantities of other salts, soft water. Spring waters generally con- 

 tained less organic matters than river waters. 



The water used in London for drinking purposes was obtained 

 from both rivers and springs. The Thames and the New River, 

 and partially other rivers, supplied the river water. The spring 

 water was of two kinds. First, from surface wells, obtained by 

 digging through the gravel which covered the London clay in the 

 western parts of the metropolis, and into the clay itself. Secondly, 

 from deep wells, which generally passed through the London clay 

 and penetrated the chalk below. The surface wells received the 

 soakage of the water which fell over London, and the water was 

 contaminated by the contents of cesspools, drains, and sewers. The 

 deep wells received their supply of water from the chalk which 

 formed the sides of the great " London Basin." All these waters 

 contain more or less of the following mineral constituents : — 



1. Carbonate of Lime, of which 3 to 17 grains are contained 

 in the gallon. Although insoluble itself, it is held in solution by 

 carbonic acid. This gas is produced by the decompositio/i of 

 organic matters, and is one source of the carbonate of lime in the 

 surface well waters. The carbonate of lime is the most common 

 source of the hardness of the waters of London. It may be got 

 rid of by Clark's process, which consists in adding lime to the 

 water ; the lime combines with the carbonic acid, and throws down 

 a double quantity of carbonate of lime : that is, the carbonate 

 formed, and that held in solution. This process would greatly 

 improve the Thames water, [t throws down not only carbonate 

 of lime, but a considerable quantity of organic matter. This plan 

 is carried out most successfully on a large scale at Plumstead. It 



2 k2 



