Thames Water. 557 



found that about twenty-two and a half grains of various 

 matters, chiefly bicarbonate of lime, occur in solution 

 in each gallon, thus giving 187,717 grains per second 

 passing seaward. This is equal to nearly 96,540 Ibs. 

 per hour, 2,316,960 Ibs. per day, or 377,540 tons a 

 year : and this amount is chiefly dissolved out of the 

 bulk of the solid rocks and surface soils of the country, 

 aided by sewage matter derived from the drainage of 

 towns, and mineral and animal manures used in agri- 

 culture, the whole passing out to sea in an invisible 

 form, known only to the analytical chemist. What 

 proportion of this is exclusively derived from substances 

 contained in the rocks I am unable to say, but Professor 

 Prestwich in his Presidential Address to the Geological 

 Society in 1872 mentions that, according to different 

 estimates, the average daily discharge of the Thames at 

 Kingston has been variously estimated by Mr. Beard - 

 more at 1,145 millions, and by Mr. Harrison at 1,353 

 millions of gallons. 



' Taking,' says Professor Prestwich, ' the mean daily 

 discharge at Kingston at 1,250 million gallons, and the 

 salts in solution at 19 grains per gallon, the mean 

 quantity of dissolved mineral matter there carried down 

 by the Thames every twenty-four hours is equal to 

 3,364,286 Ibs. or 1,502 tons, which is equal to 548,230 

 tons in a year. Of this daily quantity, about two-thirds, 

 or say 1,000 tons, consist of carbonate of lime, and 238 

 tons of sulphate of lime ; while limited proportions of 

 carbonate of magnesia, sulphates of soda and potash, 

 silica, and traces of iron, alumina, and phosphates con- 

 stitute the rest. . . . Therefore' (with some minor 

 eliminations) 'the quantity of carbonate of lime 

 carried away from the area of the Thames basin above 

 Kingston (2,072 square miles) is equal to 797 tons 



