Correspondence. 125 
CORRESPONDENCE. 
Tue Section or GeoLocy AND MINERALOGY oF THE New York AcAp- 
EMY OF SCIENCES; meeting December 16 
Mr. D. W. Johnson gave a paper on “Notes on the Geology of the 
Saline Basins of Central New Mexico.” This paper will be published 
in the next number of the American Geologist. 
Dr. D. S. Martin presented a paper entitled “Some Geological! 
Notes on the Neighborhood of Buffalo, N. Y., made in the summer 
of 1901.” Dr. Martin did not claim any special novelty for the data 
presented, but judged that they might be of interest to any members 
not acquainted with that region. Dr. Martin first outlined roughly the 
distribution of the series from the Medina to the Corniferous lime- 
stone, and then mentioned in detail certain special features. He par- 
ticularly noted certain joint seams in the Niagara limestone near Lock- 
port, N. Y., which have been much eroded and decomposed, and 
which are now filled with a dark-brown, clay-like material, contain- 
ing numbers of half decayed modern land shells, such as Helix albo- 
labris. He then described the series of rocks exposed in the quarries 
found on north Main street, Buffalo, which are now the source of 
the famous Eurypterus specimens. This series extends from the 
Corniferous limestone to the Sailna series, and is divisible into five 
members, known as the Corniferous limestoné, the Blue limestone, 
the Bullhead rock, the Water limestone and the Salina. Dr. Martin 
particularly emphasized the contact between the Bullhead rock and the 
overlying Blue limestone, and noted the occurrence of a sandstone 
dike extending to the top of the Bullhead series. 
Mr. A. J. Quereau, in a paper entitled “The Grain of Igneous 
Rocks,” said that a general observation might be made in regard to 
intrusive dykes. Near the margin the rock is dense, often glassy with- 
out any appreciable grain, whereas the grain begins to grow coarse ac- 
cording to some definite law, progressively as the distance from the 
wall increases. The present paper is based on the study of the laws 
governing such increase. It appears that the loss of heat is of para- 
mount importance.* ; 
The problem taken up is very analogous to the one presented by 
the cooling of a slab of finite thickness and of great length and depth 
with respect to the first dimension, viz. the thickness. The method 
followed rests on the Theorie de la Chaleur, of Fourrer, and on the 
general theory of cooling by professor R. S. Woodward.t The fol- 
lowing laws have been deducted: 1. The zone of varying grain will 
vary indirectly. as the initial temperature. From this follows that, 
a. Plutonic rocks, very deenly seated will not present a zone of 
varying grain to any extent. b. Rocks which come to rest at a tem- 
perature nearing their consolidation point will present a wide zone of 
*ALFRED C. LANE, Geol. Surv. of Michigan, vol. vii. 
tAnnals of Mathematics, vol. iii. 
