countries, and having proposed the term “homotaxis” to 
designate such phenomena. 
Pror. D. S. MARTIN read, in the absence of its author, a 
paper entitled, “Notes on the Coal-Measures of Beaver 
County, Penn.” By I C. WuHire; published in the Annals; 
Vol. XI, No. 1. 
Mr. White finds along the steep banks of the Beaver River, 
which flows southward into the Ohio, near the western line of 
Pennsylvania, a very complete and interesting section of the 
Lower Coal Measures, from the Tionesta to the Mahoning 
sandstones inclusive. He gives a concise description of the 
entire series as there developed. 
THE PRESIDENT remarked on the paper of Mr. White, with 
much interest, and drew sections of the adjacent and closely 
corresponding series, as developed by the Ohio survey, in 
Columbiana Co., Ohio, just across the Pennsylvania line. 
Pror. Wurtz presented some facts and illustrations con- 
cerning the use of the streak or trace left upon paper, asa 
means of distinguishing between various carbonaceous mate- 
rials, as cannels, asphalts, ete. The differences of color and 
aspect in these streaks are very remarkable, though little 
known; and the whole subject deserves attention, as a ready 
means of field determination. The blackest trace obtained 
is that of Albertite; it isintense and velvety. Grahamite, on 
the other hand, gives a deep reddish or maroon-colored 
streak. Other like substances differ in various ways. In 
one instance, he had already applied this test with much ad- 
vantage, to distinguish a valuable slaty cannel from a closely - 
associated carbonaceous shale. The two are indistinguisha- 
ble to the eye, even by the workmen in the mine, save after 
long familiarity; but the streak serves to indicate in a 
moment. This was at one of the mines of the so-called 
Darlington Cannel, in Ohio. 
