86 
TRANSACTIONS OF THE TEXAS ACADEMY OF SCIENCE- 
you a detailed description of the observations thus far. made upon the 
properties of various substances as influenced by recession of temperature; 
but proof is abundant that chemical action not only grows less, but en- 
tirely ceases., at very lqw temperatures. 
The influence of pressure (which means that the masses are brought 
nearer each other) upon the properties of matter is equally well marked. 
Combined influence of pressure and temperature would give us the de- 
sired conditions at higher temperatures than when either were used alone. 
In conclusion, then, let me suggest the possible existence of a “critical 
temperature,” at which one elementary substance will be transmuted into 
another elementary substance, that this “critical” point will be constant 
for each substance, growing lower and lower as transmutation proceeds 
nearer and nearer to the ultimate variety, and that when the real absolute 
zero is reached the atomic masses will lose their motion and be at rest. 
The University of Texas, Austin, Texas, December 30, 1896. 
Recent Publications Relating to the Geology of Texas. By Frederic W. 
Simonds, Ph. D. Read before the Texas Academy of Science, Febru- 
ary 3, 1899. 
I. 
The Lower Cretaceous Gryphocas of the Texas Region. By Robert 
Thomas Hill and Thomas Wayland Yaughan. Bulletin of the United 
States Geological Survey, Ho. 151, Washington, Government Printing 
Office, 1898. Pp. 66. PI. xxxv. 
The chief object of this paper is to set aright the confusion that has 
long existed regarding the stratigraphical position of a series of fossil 
oysters commonly assigned to a single species — Gryphcea pitcheri, Mor- 
ton. They occur in especial abundance in the Lower Cretaceous strata of 
Texas, and when properly classified are of great value in determining 
the position of strata. 
From forms heretofore known as G. pitcheri at least eight species are 
here recognized (table, pp. 45-46), viz.: G. vesicularis , Lam., 1806; G. 
newberryi, Stanton, 1893; G. mucronata, Gabb, 1869; G. washitaensis, 
Hill 1889; G. navia, Hall, 1856; G. corrugata, Say, 1823; G. marcoui , 
Hill and Yaughan, 1898; G. wardi , Hill and Yaughan, 1898. It is 
found that even Morton’s species (so long considered the type) must be 
abandoned in favor of Say’s G. corrugata, 
