676 THE JOURNAL OF GEOLOGY. 
sive one. It was very obvious from an inspection of the face of 
the glacier than wherever débris was embedded in it the radiant 
energy of the sun was caught and converted into sensible heat 
and melting was thereby promoted and so the darkened por- 
tions of the ice became sunken. From this obvious and very 
general fact, the suggestion arose that the overjutting layers 
were due to differential melting faciliated by the débris in the 
under layer. Observation showed that in most cases the under 
layer was darkened with débris and that it was therefore dis- 
posed to melt more rapidly than the overjutting layer which 
was usually white and free from débris. There was further evi- 
dence of like import in the fact that in some cases—indeed in 
many cases—the overjutting cornice when traced right and left 
was found to disappear simultaneously with the disappearance of 
the débris in the under layer. It cannot be supposed that there 
would be differential motion that would correspond accurately 
with the débris in the layers, although there might be a genetic 
connection between the formation of the layers and the intro- 
duction of the débris. Furthermore, in some instances the over- 
jutting portion was too restricted in length and too sharply lim- 
ited to accord with the hypothesis of differential motion. On 
the other hand, when it was found that the overjutting layers 
extended for long distances and that the projection reached two 
or three feet, and in some cases eight or ten or even fifteen feet, 
the hypothesis that the phenomenon was due simply to the 
superior melting of the underlayer seemed unsatisfactory if not 
untenable. 
It occurred to me that if the upper layer moved over the 
lower layer, rock fragments at the junction of the two layers 
would give rise to fluting of the under surface of the upper layer 
as it was forced over it, and that perhaps evidence might be 
found along this line which would demonstrate the supposed 
mode of motion. I found upon the south side of the South Point 
glacier a very pronounced case of overjutting reaching an extent 
of two to three feet in which the junction plane between the 
upper and lower layers was corrugated and was marked by a 
