Correspondence. 25T 
canic, is ^,000 feet, indicating considerable subsidence during tlieir for- 
mation. 
The author then discusses the evidence for the age of the beds that 
he has described, and says that the arguments drawn from the fossil ver- 
tebrates are not conclusive in either direction, because the age of the 
beds in which the types were found has not itself been decided. Hence, 
to employ them as a test of the age of other strata elsewhere, is in fact 
reasoning in a circle. 
Mr. C. S. Prosser contributes to the Proceedings of the Rochester Acad- 
emy of Science a paper on the thickness of the Devonian and Silurian 
strata of Western New York, along the line of the Genessee river, which 
is of present interest as relating to the ground of the meeting of the- 
American Association. He briefly sums up the various attempts in the 
early days of American geology to correlate the strata and to determine 
their thickness, and then from a careful comparison of four well kept 
borehole records, deduces the mean and actual thickness of the rocks. 
"Taking", he says, "the sum of these maximum estimates, we have a 
series of rocks 6,810 feet in thickness between the base of the Olean con- 
glomerate and the top of the Archfean(?). The same section compiled 
from a series of well-records gives a thickness of 7,100 feet. At Roch- 
ester the thickness from the top of the Medina to the top of the Trenton 
is 1,756 feet, and at Wolcott 1,720 feet. Leaving out of consideration all 
well-records, a conservative estimate of the thickness of this series of 
rocks at Rochester, based on published data, would be from 1,350 feet ta 
1,500 feet. 
COEKESPOE^DEE'CE. 
Some Remarks on professok Henry S. Williams' Address Be- 
fore Section E., A. A. A. S., at Rociip:ster, N. Y., August, 1892; on 
"The Scope of Paleontology and its Value to Geologists," in the 
American Geologist for September, p. 148. — In a letter printed in 
the American Geologist for January, 1889, p. 61, I have given facts at 
variance with professor Williams' expressed opinions on nomenclature 
and classification of the American Devonian; which have been accepted 
and made use of, by him, in his paper, entitled "Correlation Papers — 
Devonian and Carboniferous" {Bull. U. S. Qeol. Sure, No. 80, 1891); and 
now I hope he will receive, as fairly, some important facts touching the 
real history of the discovery and use of paleontology in geological sci- 
ence, which are in a measure overlooked in his paper before the Ameri- 
can Association for the Advancement of Science. 
After the first paper of Cuvier, read before the Institut National, of 
France, the 1st pluviose an iv of the Republic, and published in 1800, ra 
which he spoke for the first time of the existence of an entire fauna, 
anterior to the existing one, stratigraphy was begun in earnest round 
