832 THE JOURNAL OF GEOLOGY. 
in contact with the débris-charged ice, would be retained, and 
thus add to the accumulation. The stagnant mass would be 
under pressure, and both by the addition of material and the 
removal or plucking away of material, would be given a shape 
which would present least resistance to the ice flowing past it, and 
its longer axis would be parallel with the direction of ice move- 
ment. That is, it would have the form characteristic of drumlins. 
As already stated, when the ice at the base of a glacier is 
generally charged with débris, it may forma stagnant layer over 
which the clearer ice above will flow. On final melting, the débris 
in such a layer would form a ground moraine. If inequalities 
existed in the bottom over which the glacier moves, or the supply 
of englacial débris is not uniform, stagnant débris-charged ice 
may be concentrated at one locality and erosion occur at the 
same time at an adjacent locality. The same thread of the ice 
current may deposit at one time and erode at another time and 
vice versa, according as it loses or gains in percentage of con- 
tained débris or its energy is varied by other causes. When 
the supply of débris carried by an individual portion of a gla- 
cier is long continued, elongated mounds and even lengthy 
ridges may be formed. All phases presented by drumlins from 
those accumulated about boss of rock, to oval mounds, elongated 
hills and long narrow ridges, may apparently be accounted for by 
the behavior of débris-charged ice and variations in the volume 
or constancy of the supply of englacial material. There seems 
no good reason why we might not have drumlins formed of 
gravel, sand or loess, as well as of till. 
While the explanations suggested in this paper may not all 
hold when more thoroughly considered, and when tested by 
observation and experiment, yet I feel confident that the princi- 
ple on which they are based is valid and will be found important 
both in discussing theories of glacial motion, and in explaining 
the mode of origin of many glacial deposits. 
IsRAEL C. RUSSELL. 
