POPOCATEPETL AND IXTACCIHUATL—F ARRINGTON. II5 
TERMINAL MORAINE. Immediately in front of the ice lay a 
small ridge of detritus, making a bank for the muddy torrent which 
ran out from beneath the ice, but there was no large mass of drift. 
From the foot of the glacier westward the valley was strewn for a 
distance of several hundred yards with an irregular accumulation of 
bowlders, and sand, resulting from the decomposition of the latter. A 
peculiarity of the drift was the extremely friable character of many of 
its constituent pebbles and bowlders. Though appearing hard and 
tough externally, they crumbled into powder at a stroke of the 
hammer. Apparently their passage in the glacier had caused them to 
suffer rapid decomposition, an action favored by the coarse, porphyritic 
structure of the rock. The material of the drift was uniform in 
character with that of the component rock of the mountain, a coarse, 
porphyritic amphibole-andesite. There was some variation in color 
from black to red or paler, according to the degree of oxidation of the 
iron, but the structure and constituents of the rock were everywhere 
similar. Very many of the bowlders, especially the larger ones, 
showed smoothed and scored surfaces and rounding of the solid 
angles. This it is important to note because Felix and Lenk in 
their observations on the glacier state that they did not find scored 
and scratched surfaces. It is not easy to understand how they could 
have overlooked these, for not only most of these bowlders but those 
of the old lateral moraines and many rock surfaces farther down the 
mountain side showed distinct smoothing and scoring from glacial 
action. 
The debris for the distance mentioned, lay about evenly distrib- 
uted, there being no ridges which indicated stages of retreat or. 
advance by the glacier. At a distance of about a quarter of a mile 
from the foot, however, the material rose to a somewhat ridge-like 
form and terminated, making a distinct barrier across the valley as 
seen from below.. This I consider to represent the terminal moraine 
of the stage of the glacier which formed the old lateral moraines to 
be described later. Jt has been cut through by the stream flowing 
out from the present glacier and its form and arrangement have 
thereby been much changed, but its general connection with the 
lateral moraines was apparent at a glance. Since between this 
moraine and the present foot of the glacier only a bare, stony tract 
" intervenes, having no well-marked ridges of debris, it may be assumed 
that the glacier is at present retreating. No opportunities for positive 
determination of this could, however, be gained in so short a time 
for observation. 
EVIDENCES OF FORMER EXTENT GOS EHE UGUAGCIER.- ¢-OLD 
LATERAL MORAINES. To the northand south and somewhat west of 

