50 
Geology. 
tion of the two, and it appeared possible that this, by catching 
the sunlight and melting back faster than the pure ice above, 
might explain some part or all of the phenomena, and suspicion 
arose that the inference of overthrust might be illusive. In fol- 
lowing a given projection laterally it was seen sometimes to 
terminate where the earthy material ceased. To be sure, it might 
be supposed, with good reason, that the shearing of the ice and 
the inthrusting of material were companion phenomena, and 
should naturally begin and end together. But none the less there 
was ground for hesitancy in trusting this class of evidence. In 
casting about for means of avoiding this possible source of 
error, the suggestion arose that pieces of rock lying at the junc- 
tion of the layers would produce grooves or flutings if the upper 
layer were thrust forward faster than the lower one, and search 
was made for such groovings. It was found that the under sur- 
faces of many of the projecting layers were fluted, and this, at 
first sight, seemed abundant confirmation of the hypothesis of 
overthrust. But here again, a more careful study made it quite 
certain that some of this fluting, indeed, much of it, as it was 
actually observed, was due to water trickling down the face 
of the overlying layer, which, instead of dropping freely away 
when it reached the edge of the projection, turned under and fol- 
lowed the lower surface backward, and in so doing fluted it. It 
may be that the fluting had been initiated by shearing, and was 
merely further developed by this backward running of the water, 
but in most cases I could not tell whether this was certainly so 
or not. Most of the projections were too high to be reached 
and critically examined. In searching for flutings that could 
not be attributed to water action, I found instances where the 
junction plane between the layers was marked by a layer of 
debris which was itself fluted. The earthy material was like a 
corrugated sheet passing backward from the edge between the 
layers of ice, the upper one of v hich projected over the lower. 
Another class of evidence was derived from blocks of the 
stratified ice which had fallen from {he face of the glaciers and 
had entered upon the initial stages of disintegration sufficiently 
to disclose the intimate nature of their mass. Glaciers are for 
