558 Salts in Sohition in Rivers. 



daily, or 290,905 tons annually. Adding the other 

 ingredients not included in Professor Prestwich's 

 calculation, such as chlorides of sodium and potassium, 

 sulphates of soda and potash, carbonate of magnesia, 

 silica, alumina, &c., the sum total of substances annually 

 carried to the sea in solution, will closely approximate 

 to my earlier calculation. 



If we consider that this is only one of many rivers 

 that flow over rocks which contain lime and other 

 substances easily soluble, we then begin to comprehend 

 what an enormous quantity of matter by this to the 

 eye perfectly imperceptible process is being constantly 

 carried into the sea. If we take all the other rivers 

 of the east, and those of the south of England (exclusive 

 of those of Devon and Cornwall), we find that they drain 

 more than 18,000 square miles, to a great extent con- 

 sisting of limestone and other calcareous rocks ; and if 

 we assume the amount of outflow from the sum of these 

 rivers to be only three times that of the Thames (and I 

 believe it must be more), we may have about 872,715 

 tons of bicarbonate of lime and other substances passing 

 with these rivers annually to the sea in solution. 



The rivers of the west coast of England and of the 

 whole of Wales drain about 30,000 square miles ; and 

 the waters, as a rule, are much softer than those of the 

 east of England. But it does not necessarily follow, in 

 the course of a year, that these rivers, in proportion 

 to rainfall and the areas which they drain, do not each 

 carry off as much matter in solution as those of the 

 east of England. Their softness is due to the circum- 

 stance, that the rock-formations of the west are much 

 less calcareous than those of the eastern division of 

 the kingdom. I have already shown that the greatest 

 amount of rainfall for given areas is in the west of 



