1876.] Proceedings of Societies. 317 
exposed in moist air vegetable tissue rapidly oxidizes in decay; when 
buried under water or in earth the process is retarded, and the constitu- 
ents react on each other, forming carbonic acid, carbonic oxide, water, 
carburetted hydrogen, petroleum, etc., which escape, leaving peat, lignite, 
coal, anthracite, and graphite as residues in different stages of this pro- 
gressive change. Petroleum and marsh gas are constantly escaping from 
all considerable carbonaceous strata, and especially from bituminous shale, 
beds of which underlie all our productive oil regions, and are the sources 
of the oil and of the gas with which it is always associated. 
The carbonaceous shales of the Lower Silurian system supply the 
petroleum of Burkesville, Kentucky, and Collingwood and probably En- 
niskillen, Canada. The petroleum of Western Pennsylvania is derived 
from the Devonian black shales (“ Cadent” of Pennsylvania, “ Huron ” 
of Ohio), which have a thickness of several hundred feet, and underlie 
all the oil region. When escaping from them the oil and gas rise into a 
series of overlying sandstones and conglomerates, which serve as reser- 
voirs, and are confined there by sheets of nearly impervious clay shale 
The oil wells of West Virginia are bored in the coal measures, but in 
a much disturbed region, and the oil probably comes from the Huron 
shale. The oil of Mecca and Grafton, Ohio, is Lower Carboniferous. It 
is found in the Berea grit, but originates in a black shale (Cleveland 
shale) which underlies it. 
PHILOSOPHICAL SOCIETY or Wasuineton. — March 11th. Dr. 
Woodward continued his observations on Frustularia Saxonica, showing, 
by means of illustrations thrown upon a screen, the misapprehensions into 
which some continental microscopists had been led by mistaking for this 
Species another diatom, Navicula rhomboides. 
March 25th. Mr. Gilbert gave an aceount of lake formations, showing 
the various means by which lakes are produced, and, among others, one 
which had frequently been in his opinion mistaken for, glacial action. 
In cliffs of which the upper portion is subject to easy vertical cleavage, 
large masses are frequently detached, falling into adjacent valleys, dam- 
Ming up streams and forming lakes in this way with a mass of detritus 
Which had been, or was liable to be, mistaken for the material deposited 
by a terminal moraine. These views were corroborated by Major Pow- 
ell, who mentioned several instances of such lake formations. 
Professor Mason then addressed the society on an international sys- 
tem of archzological symbols. . 
Acapemy or NATURAL Scrences, Philadelphia. — March 14th. 
r. Meehan spoke of the mode of propagation of the Florida moss or 
Tillaudsia, Since he had before spoken on the subject he had had oppor- 
tunities of observing that where the seeds germinate they do so on the 
under side of the branches, and where the bark is smooth rather than 
rough, thus indicating the presence of some adhesive matter on the seed. 
Professor Cope called attention to a cetacean which he had observed 
