266 Mr. J. Ball on the Veined Structure of Glaciers. 



structure is, in fact, a form of stratification, arising from the 

 gradual consolidation of tbe original beds of neve. I have said 

 that it is undistinguishable from the ordinary veined structure 

 which I now believe to be due to pressure ; but it is probable 

 that closer examination would show that the structure produced 

 by two different causes is similar only, and by no means iden- 

 tical. It seems probable, for instance, that the layers consti- 

 tuting the structure will be found to be more continuous in 

 glaciers of the second order — if there it be really a result of 

 stratification — than in the great glaciers, where it arises from 

 pressm-e. The peculiar molecular condition of the ice which 

 causes cleavage may also be a characteristic of the Pressure 

 Structure, as distinguished from the Stratification Structui'e. 



Turning from this (which, at the utmost, would merely esta- 

 blish an exception to the ordinary law regulating the origin of 

 the veined structure) to the fundamental experiment upon which 

 the physical theory of the subject is now based, it will certainly 

 not have escaped the acute mind of its author that experiments 

 upon solid ice, though they may furnish fair ground for infer- 

 ence, fall a good way short of demonstration as to the result of 

 pressure upon that curious mixture of ice, water, and air which 

 constitutes the mass of ordinary glacier ice. Close examination 

 shows it to be a sort of breccia, or conglomerate, made up of 

 angular fragments of ice closely adhering together, filled through- 

 out with air-bubbles, each separate fragment having the small 

 air-cells more or less flattened in the same direction, but no 

 general parallelism in the direction of flattening being traceable 

 amongst adjoining portions of the ice. The cells are sometimes 

 — ]Mr. Huxley thinks, always — partly occupied by water along 

 with the air which they contain. After seeing the experiments 

 by which Professor Tyudall shows that mere pressure applied to 

 a mass of pure ice, will, without change of temperature, cause 

 partial liquefaction extending in fissures transverse to the direc- 

 tion of pressure, a person, arguing a priori as to the effect of 

 intense pressure ujion such a mass as glacier ice, w^ould be apt 

 to conclude that liquefaction would proceed on the free surface 

 of the interior of each air-cell, and in such a direction as would 

 enlarge the cells into the form of lenses sensibly parallel to each 

 other. But, instead of this, we find the air-cells in the white 

 veins showing no signs of change, while, at moderately regulai' 

 intervals, we find veins from which nearly all the air-bubbles 

 have been driven out. I am far from putting this as an objec- 

 tion to the pressure theory; it seems to be an example, but 

 surely a very remarkable one, of an extensive and still obscm'e 

 class of physical phsenomena, wherein force, transmitted through 

 a resisting medium, manifests itself in apparent intermitteuce^ 



