990 7. UM. Reade—Denudation of the two Americas. 
Art. XL.—-Denudation of the two Americas ;* by T. MELLARD 
EADE, C.E., ¥.G.S. 
INTRODUCTION. 
WHEN in 1876 I had the honor to deliver a Presidential 
address to this Society I chose as its subject matter “ Geologi- 
eal Time,” I then had the pleasure to lay before you some cal- 
culations relating to ‘Chemical Denudation’’ which at the time 
ae some little novelty. Since the information was pud- 
ished, it has to a certain extent been incorporated with geolog- 
ical literature. The subject was, however, far from being 
exhausted, nor is it likely to be so for many years yet to 
me. 
In the meantime, having accumulated additional facts, it will 
be part of the object of this address to arrange and analyze 
them, so as to check the original generalizations and further to 
illustrate the value in geological speculation of an accurate 
knowledge of the relative magnitude of the various objects and 
things dealt with. 
My former calculations dealt almost exclusively with the 
amount of matter annually removed in river water from the 
surface of .England and Wales, and from some of the river 
basins of Europe. I now propose laying before you calcula- 
tions of a similar nature relating to some of the larger rivers of 
the two Americas. This done we shall be able to take a wider 
survey of the subject, and to ascertain how far the provisional 
generalizations to which previous investigations led are con 
firmed or otherwise by the greater experience since gained. 
Tue Mississiprt. 
First then we will see what the Father of Waters, the Miss!s- 
sippi, tells us. I may observe that for a long while I found 
great difficulty in obtaining answers to my various question- 
ings. Years elapsed and letters innumerable were written be- 
fore I could alight upon any analyses of the waters of the Mis- 
sissippi, reliable or otherwise. At last through the kindness of 
rof. J. W. Spencer, of the State University of Missouri, I was 
supplied with the following analysis: , 
Analysis of Mississippi water near Carrolton, a few miles 
above New Orleans:+ ~ 
* Substance of Presidential Address to the Liverpool Geological Society, Session 
1884-5. Communicated by the author. 
+ Avequin, Journ. Pharm. [3], xxxvii, p. 258, 1857. 
