EXPERIMENTS IN [CE MOTION. 929 
It seems, therefore, that this phenomenon grades insensibly into 
the preceding. A study of the lamina not associated with 
embossments showed many signs of doubling upon themselves in 
a similar way. It appears, then, that there is a gradation from 
laminz that simply suffered doubling up to layers that obviously 
sheared upon each other and produced manifest unconformity 
and overthrust.” Compare the figures of this paper and Cham- 
ljerlinns, Jigs Ay lel IW, Jenga. i eel 12, Jel, WIUUL 
The above might well serve as a description of the results of 
the experiments on the passage of wax over escarpments and the 
effect of drag. It might also serve as well to describe the for- 
mation of laminz in wax, especially when supplemented by the 
following (p. 204): ‘The débris layers are not all uniform in 
their distribution. Often they have much regularity and per- 
sistence; often they thin out and disappear within a short dis- 
tance; more often still they persist for a few rods and are replaced 
by adjoining layers which come in as these thin out. Thus a 
belt of layers has much persistence, while the constituent layers 
are freely entering and vanishing. Lenses of débris occasionally 
appear among the layers, and a doubling back of the layers upon 
themselves, giving a lenticular section is not uncommon.” Com- 
pare this description with Figs. 7-10. 
The action of the loops caused by drag in passing obstruc- 
tions is not discussed by Professor Chamberlin, but Figs. 6, 
Pl. V, of his article is almost identical in its main features with 
the anterior part of Figs. 9-10 of the present experiments. 
In discussing the origin of the stratification Professor Cham- 
berlin brings forward the hypothesis of the shearing motion 
between superincumbent layers of ice, citing as proof, the obser- 
vation of fluting inthe interpolated lamine of débris and the 
breaking of fallen blocks of ice along definite planes. ‘‘ But,” he 
says, p. 207, ‘‘the best evidence of the verity of shearing between 
ice-plates lies in the intrusion of the earthy material itself. I 
was fortunate enough unless I misinterpret, to observe the actual 
process of intrusion. The best illustration was found on the 
north side of a short lobe of the great ice-cap designated the 
