502 Mr. J. Ball on the Structure of Glaciers. 
the condition of the greater part of the materials of this glacier 
is such as to make the formation of regularly stratified beds 
quite possible, and it may even be admitted that the interval 
between the dirt-lines would probably correspond with the annual 
deposit, but as each bed so formed would have the shape of a 
hollow cone with its apex turned upwards, it seems all but im- 
possible that its upper surface can correspond with that traced 
by a dirt-line in the middle of the glacier, whose form must be 
that of an inverted cone or deeply concave curyed surface. 
It is not for me to pronounce whether the facts and laws of 
physical science yet known are adequate to solve these difficulties, 
but I may be allowed to express the conviction, that in a complete 
theory of glacier structure, some further account than has yet 
been taken will be made of the process by which the materials of 
the glacier are originally deposited and consolidated. I am not 
less sure that the potent influence of pressure in modifying in- 
ternal structure, which has been so fully developed by Professor 
Tyndall, will be recognized hereafter as one of the physical 
principles that will help to explain the intricate phenomena of 
glacier structure. 
_P.S. Nearly the whole of the foregoing pages were written 
before I had an opportunity of reading the interesting paper by 
Professor Huxley, contained in the October Number of this 
Journal. I will venture to make a few remarks on the con- 
clusions which Mr. Huxley has drawn from his recent obser- 
vations. 
_ Absence of capillary fissures in the deep ice—Mr. Huxley has 
fully proved the incorrectness of the common opinion, founded 
mainly on the statements and observations of Agassiz, which 
supposed the whole mass of the ice to be penetrated by capillary 
fissures through which water could percolate; but I do not 
think that his experiments enable us to conclude that there are 
no such fissures in the interior of the glacier. If we are to adopt 
that conclusion, we must then cease to believe with Professor 
Tyndall, that glacier ice is enabled to advance in conformity 
with the law of viscous motion, by fracture and regelation. For 
in the midst of new observations we must not lose sight of the 
main facts already well established, and we owe to Professor 
Forbes the certainty that the glacier advances by the gradual dif- 
ferential motion of contiguous portions of the mass, and not by 
the separate advance of large masses which are divided by cre- 
vasses or open cracks. I may observe, that all the conclusions 
of Professor Forbes on this head were confirmed by observations 
made by me in 1845 on the Gorner and Findelen glaciers near 
Zermatt, which have remained unpublished, because I conceived 
