292 TT. M. Reade—Denudation of the two Americas. 
dence can we have of the importance of chemical action in geo- 
logical investigation; an importance that has hitherto been 
strangely overlooked. igs 
Not less surprising considering the apparent insolubility of 
silica by ordinary agencies* is the fact that in round numbers 
from 23,000,000 to 24,000,000 tons of silica are poured into the 
sea annually by this river, while there are 70,000,000 tons of 
carbonate of lime and magnesia. There is also an exceptional 
quantity of alumina and a low percentage of sulphates in this 
water. 
Tae River Puate or Rio pe ta Prata. 
The next river I shall deal with is the Rio de la Plata—the 
second greatest river of the South American continent. I am 
indebted to the very exhaustive series of observations and 
analyses of the waters of the river contained in the report to the 
ommission of running waters of the City of Buenos Ayres 
by Juan J. J. Kyle in 1872 and 1874,+ for most of the informa- 
tion relating to this river. is 
I find that the mean of 14 analyses of water taken at differ-, 
ent times (April, May and June) in the neighborhood of and 
above the City of Buenos Ayres gives a proportion of gzrz of 
solids in solution, which, taking the dry weather flow of the La 
Plata at 670,000 cubic feet per secondt (Bateman), will equal 
‘8886 tons per second or 91,000,000 tons per annum in roun 
figures. 
The dry weather flow of the La Plata equals the mean annual 
flow of the Mississippi. The mean annual flow of the La Plata 
1s not known but it must be greatly in excess of the dry weather 
flow and sufficient to bring up the total amount of dissolved 
analysis to havea less percentage of mineral matters in its waters 
gaze Of solids in solution.” Mr. Juan Kyle states that there 1s 
very little difference between the waters of the La Plata taken 
at 850 m. from the shore and the waters of the Parand de los 
Palmas. As the Parana supplied, according to careful measure- 
* Mr. M. E. Wadsworth has shown that ordinary atmospheric agencies produce 
a greater effect upon rocks of a siliceous character than is generally believed. See 
this Journal, Dec. 1884, p. 466, ; 
must here express my thanks to Mr. J. E. Hawkes for his valuable assist- 
ance in translating the pamphlet for me. 
See Chemical Denudation. p. 55. 
See Chemical Denudation, P. 23. 10-08 parts per 100,000. 
