8o The American Geologist. February, wm 
observed imbedded in clear, compact, anthracite from the Lehigh 
region, Pa. X 70. 
Fig. 13. Part of a patch or cluster of seed-like bodies (apparently 
in situ), and associated with more or less solid black lamina; in an- 
thracite. X 5- 
THE ICE-CONTACT IN THE CLASSIFICATION 
OF GLACIAL DEPOSITS. 
By J. B. WOODWORTH, Cambridse, Mass. 
Several modes of classifying the glacial deposits have been 
put forward within recent years, all tending to closer discrimin- 
ation in regard to the form, structure, and names of these 
deposits and all embodying the theoretical principle of genesis. 
The most notable of these classifications are the comprehen- 
sive categories of drift made out by professor Chamberlin''^' 
and the tabulation of glacial effects from a geographical point 
of view by Mr. McGee.t 
In devising a genetic classification of glacial deposits, 
everything depends upon determining the geographic and 
physical relations of the products of change to the agencies 
which produced them. Of these agencies, there are two, the, 
ice and the water produced by the melting of the ice or com- 
ing into the field of glacial action in the form of rain. From 
observation of existing glaciers we learn to attribute the mass- 
ive, unstratified deposits to the direct action of the ice, the 
stratified and assorted drift to the action of water coming 
from the ice. From the structure and form of deposits of till 
and stratified drift we arrive at conclusions with regard to the 
position of the materials held in relation to a vanished glacier : 
as to whether the deposition took place inside or outside of the 
field of ice action, hence intraglacial and extraglacial deposits : 
whether, in the former case, the deposits had their character- 
istics determined on the ice, in it, or under it upon the ground 
*T. C. Chamberlin: La classification des depots pleistocenes, 5me 
Session, Congres Geologique Internationale, Washington, 1891, pp. 
176-192. 
tW J McGee: The classification of geographic forms by genesis, 
Nat. Geog. Mag., i. 1889, p. 36. Pleistocene History of Northeast- 
ern Iowa, nth Annual Report, U. S. Geol. Surv., pt. i. 1891, p. 256. 
