Salts in Solution in Rivers. 559 



England and Wales, especially in the mountain regions, 

 and this extra amount of rainfall must have the effect- 

 of producing an extra amount of solution of the alkaline 

 and other constituents that so largely form the con- 

 stituents of those palaeozoic rocks that form the hilly 

 regions. If so, then, for given areas, the quantity of 

 matter carried to the sea by the western areas, may be 

 approximately equivalent in a year to that which is 

 found in the eastern-flowing rivers. This idea, new 

 to me, was first impressed on my mind by reading the 

 Presidental Address of Mr. T. Mellard Reade to the 

 Liverpool Geological Society, 1877, in which, among 

 other important matters, he states that ; a total of 

 68,450,936,960 tons of water run off the area of Eng- 

 land and Wales annually, equal to 18'3 inches in depth, 

 which leaves 13*7 inches for evaporation. The total 

 solids in solution amount to 8,370,630 tons, about 

 equal to 558,042 tons in a year, if reduced to a solid 

 state. This would cover four square miles of ground 

 with a stratum of limestone one foot thick, assuming 

 that 1 3^ cubic feet go to a ton, and also, for the sake of 

 argument, that all the matter in solution is in the 

 state of bicarbonate of lime. We know this not to be 

 the case, but this makes no difference in respect of the 

 amount of the various salts dissolved out of the rocks. 

 According to Mr. T. Mellard Eeade's estimate of 1 5 feet 

 to the ton, c the amount of denudation, if distributed 

 equally over England and Wales, reckoned at 58,300 

 square miles, would be *0077 of a foot per century, that 

 is, it would take 12,978 years to reduce it one foot.' 

 There is no doubt, however, that the quantity carried 

 away in solution varies much in different geological 

 areas, for of all the rocky formations, limestones are 

 most easily acted upon by carbonic acid in rain water. 



