482 Mr. J. Ball on the Structure of Glaciers. 
Although circumstances did not permit me to undertake any 
continuous series of observations, accompanied by accurate 
measurements, it has seemed to me that some notes made at 
the time, and of the accuracy of which, as far as they go, I 
feel confident, may deserve the notice of thosewho are interested 
in the subject. If I have ventured to draw some conclusions 
from facts, or to point out what appear to be objections to the 
deductions of other more competent physical observers, I am 
well aware that it becomes me to do so with great hesitation. 
That. hesitation is somewhat lessened by the expectation that 
the subject is about to receive further illustration from the con- 
tinued labours of Professor Tyndall, and to no more able and 
candid judge could any facts or arguments seeming to tell 
against his own conclusions be proposed. 
The chief, but not the only peculiarities of glacier struc- 
ture that have attracted the attention of observers, are the fol- 
lowing :— : 
1. Stratification of the Névé. 
. Veined structure of the middle and lower region. 
. Dirt-bands of Professor Forbes. 
. Dirt-bands of M. Agassiz*. 
. Crevasses. 
. Capillary fissures in the compact ice. 
. Air-bubbles included in the ice. 
These are all so familiar to those who have either observed for 
. themselves, or who have studied with care the writings of Forbes, 
Agassiz, and other glacier authorities, that it would be super- 
fluous to describe them, and I shall merely offer such remarks 
in regard to each of them as have some bearing on the theory 
of glacier structure. 
1. The stratification of the névé, its arrangement in parallel 
layers of more and less crystalline snow, the diminished thickness 
of the layers in the lower part of exposed sections, accompanied 
by a consolidation of the substance of the névé into ice, more 
or less filled with air-bubbles, are facts familiar to those who 
have dwelt much in the upper regions of the ice-world, where 
in concave hollows, or still more often, on slightly convex 
plateaux, the vast accumulations are formed which give birth to 
the greater glaciers. 
On one point, many of those who have described the forma- 
tion of these beds seem to be certainly in error. 
Each of the horizontal beds seen m an exposed vertical sec- 
tion of the névé is supposed to correspond with the whole annual 
fall of snow at the spot where the bed was formed. But this 
inference rests either on a great exaggeration of the effects of 
* Recently named Dirt-Streaks by Professor Huxley. 
STO Ot OO 09 
