48 
Geology. 
cation to the elucidation of the drift phenomena of the ice age of 
America and Europe. Unless I misinterpret, I was fortunate 
enough to observe the process of introduction in progress. On 
the north side of a short lobe of the great ice-cap, which has 
been called from the peculiarity of its terminal face, the Gable 
Glacier, there was found a large embossment of rock over which 
the ice was forced to pass, and in so doing to rise in a dome-like 
fashion. One side of the ice dome was melted away, revealing 
the operations at its base. Here it was observed that trains of 
rock rubbish, apparently scraped from the surface of the emboss- 
ment, were being carried out into the ice in its lee. Some of 
these trains were short, while others extended several rods into 
the ice. They were somewhat inclined downward, but the slope 
of the glacier being greater they passed obliquely into its base, 
instead of following closely its bottom. On close observation it 
might be seen that the tongues of debris thus thrust in were really 
layers, or perhaps rather laminae, of ice doubled back upon them- 
selves. The doubling of such layers upon themselves was ob- 
served in several instances in connection with different glaciers. 
Combining a considerable number of observations, whose import 
was more or less distinct, the following interpretation of the pro- 
cess was derived. The bottom layer of the ice in passing over 
the crest of the embossment would be pressed with exceptional 
force upon it, and would, as a result, be specially liable to detach 
fragments from it and imbed them within itself. If debris was 
being pushed or dragged along between the ice and the rock sur- 
face beneath, it would be pressed into the ice and the ice com- 
pacted about it with exceptional force. As any given portion of 
the basal layer passed beyond the crest of the embossment, the 
vertical pressure would tend to cause it to follow down the lee 
slope, while the horizontal thrust of the moving ice would tend 
to force it straight forward. If any given portion yielded to the 
first and passed down the slope, it would produce a curve in the 
hardened basal layer of ice. As a result of this, the horizontal 
thrust, instead of continuing to act along the disadvantageous 
curved line, and against the superior friction of the bottom, 
would be disposed to cause the layer to buckle at the bend. The 
