486 Mr. J. Ball on the Structure of Glaciers. 
ice is well consolidated, has hitherto been the point as to which 
science seemed most at fault in endeavouring to explain the 
phenomena of the ice-world. 
As one of those who had never been able to accept the con- 
jectural explanation given by Professor Forbes, who was the 
first to make known the true character of this phenomenon, 
and to perceive its importance, I could not fail to be much in- 
terested in the new hypothesis, which supplies a simple, and 
apparently an adequate explanation of the known facts. But 
the result of some consideration and recent observation has not 
removed all the difficulties which seem to me to stand in the 
way of an unqualified acceptance of this new theory, and with 
very sincere diffidence I venture to state them. 
In the first place, then, I would observe that while Professor 
Tyndall has abundantly proved the extensive influence of great 
pressure in modifying the internal arrangement of various bodies, 
he has not shown any instance in which the resulting structure 
at all resembles that which we find in glacier ice. In every case 
of lamination and consequent cleavage, attributable to pressure, 
the result seems to be due, either to a rearrangement of the rigid 
particles contained in the mass by which their flatter surfaces 
are disposed in planes perpendicular to the direction of pressure, 
or else to the compression of minute and comparatively soft 
nodules or accretions*, which alter their form under the force 
to which they are exposed, and each particle, from a rounded or 
irregular form, assumes that of a lamina or plate with its faces 
perpendicular to the direction of pressure. In either case the phe- 
nomenon of cleavage is the direct result of the arrangement of 
the particles of the mass in layers with flattened faces approxi- 
mately disposed in the same plane. Now, whether we examine 
the bands of compact blue ice, or the intermediate layers of 
white opake ice, we find no trace of lamination, or anything 
approaching to it, in the internal structure of the mass. 
At times, indeed, I have found, as Professor Forbes first 
noticed, a distinct tendency to cleavage along the surface of 
junction between the veins of blue and white ice, but on either 
side, both the one vein and the other have always appeared to 
me absolutely devoid of any tendency to split in the direction of 
the veined structure, nor does close examination show traces of 
molecular arrangement which could produce such a tendency. 
The cleavage planes above described seem to be by no means 
invariably present, and the phenomenon has to me the air of 
being superinduced by pressure upon the already existing veined 
structure, rather than its essential concomitant. 
* I apprehend that this is true of wax as well as the other substances 
cited by Professor Tyndall. 
