994 TZ. M. Reade—Denudation of the two Americas. 
The annual amounts of solids in suspension in the La Plata 
waters has never to my knowledge been determined or even 
approximately estimated. 
Tue Str. Lawrence. 
The next river on the American Continent of which we have 
any knowledge worth speaking of is the St. Lawrence. The 
elements for a calculation such as I wish to make are however 
unfortunately rather vague. Even the area of its basin is stated 
differently by different authors. According to Guyot* its basin, 
including, I presume, the area of its immense lakes, is two-fifths 
that of the Mississippi, while it is said to pour into the sea more 
than twice its volume. This must, however, be an error, for it 
would give 40 inches of rain run off the area per annum, 
whereas, according to the Rainfall Map of the World, prepared 
by Loomis (this Journal, vol. xxv, p. 88, January, 1883) 
ground per annum, or half the stated delivery, after deducting 
the area of the great lakes, the chemical denudation would still 
be enormously great. The only analysis I have met with gives 
the proportion of solids in solution at ¢yg,t so that the denuda- 
tion would amount to, at that rate, over 200 tons, per square 
mile per annum. The one thing probable, however, is, that 
the matter removed in solution is more per square mile than 10 
the Mississippi basin. The matter removed to the sea in sus 
pension must be comparatively small from the clearness of the 
water due to its passing through the great lakes. 
Tue AMAZONS. 
tially filled with the remarkable deposits of red sandstones and 
clays covering an immense area which the river is now engaged 
* Physical Geography. _ + 16-05 per | 00,000 parts, Jahresbericht der Chemie. 
t Geological sketches—Physical History of the Valley of the Amazons, p. 171. 
