114 FieELD CoLuMBIAN MusEUM—GEOLOGY, VOL. I. 
retreat of the ice would leave them in the position occupied by the 
crevasse. 
\ ZEN 
3% 

Fig. 2. GATHERING OF BOWLDERS BY A CREVASSE, PORFIRIO DIAZ GLACIER. 
Sketched by the Author. 
TERMINAL PORTION OF THEGLACIER. ‘This isshownin Pl, XV 
which looks up the glacier from a point about half a mile below. 
Nearly the whole course of the glacier is shown, Heilprin peak being 
in the middle background. The upper part of the mountain is hidden 
by clouds, which were fast descending when the photograph was. 
taken. Outlined against the surface of the ice in the middle fore- 
ground is the figure of a man, one of the zeveros or ice collectors who 
make a business of conveying the ice to the market at Ameca. His. 
form will give an idea of the size of the features shown. The ter- 
mination of the glacier shows a fanning out of the ice tongue and a 
convex surface such as is typical of a glacier terminus. From the 
border the ice ascended in a series of steps sufficiently well marked 
to be used by the zeveros as planes for cutting. These steps were cut 
through here and there by cross fractures or longitudinal crevasses. 
evidently caused by the bulging and spreading of the ice as it 
debouched into the broader part of the valley. At the top of the ice 
tongue a massing of the debris could be seen which indicated its col- 
lection in the central portion of the valley trough by the onward. 
movement of the glacier. 
