258 Prof. Huxley on the Structure of Glacier Ice. 
hope, of making the acquaintance of glacier structure on a new 
and gigantic scale. 
Viewed from the mule-path, or from the old moraine at the 
commencement of the pine wood celebrated by De Saussure, the 
lower part of the glacier of La Brenva exhibits numerous cre- 
vasses, which appear to run nearly parallel with its length, so that 
the icy mass is divided into a series of parallel crests or ridges. 
The lateral faces of these ridges form perpendicular cliffs of ice, 
and present dark stripes directed in a longitudinal and nearly 
horizontal direction; but where an end view of a ridge is ob- 
tained, the stripes run either horizontally and transversely (as 
in the more central parts of the glacier), or are curved up to- 
wards the sides (as in the more lateral parts). 
These markings are evidently those described and faithfully 
figured, as the “ structure” of the glacier, by Prof. Forbes ; but 
I cannot say I should have called them bluish-green. They 
looked to me simply dark and dirty. But I should state, that 
the weather, when I visited the glacier, was wet and cloudy. 
Nevertheless, on descending on to the glacier itself, I found 
its structure, though very beautifully developed, to be in no- 
wise remarkable for the size of its veins, which varied in length 
from an inch to eight or nine feet, and in breadth from a frac- 
tion of an inch to nine or ten inches. Veins of the latter dimen- 
sions, however, were rare; the majority having a thickness of 
less than an inch. The lenticular form was very well marked, 
and the veins were commonly separated by less than their thick- 
ness of white ice. I need hardly say that these veins became 
indistinguishable at a very short distance. 
The streaks so conspicuous a long way off, on the other hand, 
became less sharply defined as I approached, and at length 
showed themselves to be nothing more than accumulations of 
the fine dirt—spread more or less over the whole cliff-like wall 
of ice,—in streaks of four to ten inches in breadth, and of vari- 
able length. They ran parallel with one another and with the 
structure, at a distance varying from a few inches to six or seven 
feet ; and they were entirely superficial, the dirt never extend- 
ing deeper than the weathered superficial layer. 
It became clear, therefore, that the markings were neither 
structure nor stratification, but a peculiar kind of dirt-marks ; 
and the next point was to ascertain the conditions of their for- 
mation. 
On close examination, the face of the ice-cliff exhibiting these 
markings appeared to be worn into a sort of wavy or rippled 
surface, the length of the ripples having a general direction down- 
wards. The close-set veins, on the other hand, traverse the 
face of the ice, as has been said, nearly horizontally. The whole 
