234 
INTERNAL STRUCTURE AND 
treat one series of facts without some reference 
to the other ; but such explanations as I have 
given of the mechanism of the glacier, in con- 
nection with its structure, are presented in the 
language of the unprofessional observer, without 
any attempt at the technicalities of the physicist. 
I do not wonder, therefore, that those who have 
looked upon the glacier chiefly with reference 
to the physical and mechanical principles in- 
volved in its structure and movement should 
have found my Natural Philosophy defective. I 
am satisfied with their agreement as to my cor- 
rect observation of the facts, and am the less 
inclined to quarrel with the doubts thrown on 
my theory since I see that the most eminent 
physicists of the day do not differ from me more 
sharply than they do from each other. The facts 
will eventually test all our theories, and they 
form, after all, the only impartial jury to which 
we can appeal. In the mean while, I am not 
sorry that just at this moment, when recent in- 
vestigations and publications have aroused new 
interest in the glaciers, the course of these arti- 
cles brings me naturally to a discussion of the 
subject in its bearing upon geological questions. 
I shall, however, address myself especially, as 
I have done throughout these papers, to my 
unprofessional readers, who, while they admire 
the glaciers, may also wish to form a general 
