GLEN ROY, IN SCOTLAND. 
51 
sion of which may be traced to water. It is 
true that in some localities, as, for instance, 
in the gravel-pit of Mount Auburn, near Cam¬ 
bridge, large masses of glacier-worn pebbles 
alternate with beach shingle; but it is easy to 
show that there was here a glacier advancing 
into the sea, crowding its front moraine and 
the materials carried under it over and into 
the shingle washed up by the waves upon the 
beach. Not infrequently also, river-pebbles 
may be found among glacial materials. This 
is especially the case where, after the disap¬ 
pearance of large glaciers, rivers have occupied 
their beds. Examples of this kind may be 
seen in all the valleys of the Alps. 
But, besides the special character of the 
individual fragments, the true origin of any 
accumulation of glacier -debris, commonly called 
drift, may be detected by the total absence 
of stratification, so essential a feature in all 
water deposits. This absence of stratification 
throughout its mass is, after all, the great 
and important characteristic of the drift; and 
though I have alluded to it before, I reiterate 
it here, as that which distinguishes it from 
all like accumulations under water. I may be 
