Mr Skinner, Observations on the Minute Structure of Ice. 33 
Observations on the Minute Structure of the Surface Ice of 
Glaciers. By S. Skinner, M.A., Christ’s College. [With Plate II.] 
[. Received 20 December 1900.] 
The structure of glacier ice has been the subject of much 
discussion, and it seems to be generally admitted that at some 
distance below the white surface of a glacier the ice is compact, 
transparent and free from fissures through which any flow of liquid 
can occur. Experiments in support of this are those of Huxley 1 
who showed that there was no infiltration of coloured liquids 
poured into cups cut in the solid ice. Helmholtz 2 has shown 
that closed fissures can be formed in solid ice under pressure, and 
Tyndall 3 has shown that closed cavities can be formed by the 
action of radiant heat. 
If a block of the solid compact ice be exposed to the light and 
heat of the solar radiation it becomes porous and with sufficient 
exposure to intense sunlight will break up into prismatic granules 
of various sizes. Hence above the compact ice the layer which is 
thus exposed during summer is permeable to coloured fluids 
which flow in the spaces between the granules. This porous layer 
may be as much as a foot in thickness depending on the exposure 
of the ice. The top layer of this granular portion is modified in 
a further manner, and the experiments described in the following 
paper had as their primary object the examination of the minute 
structure of this first layer which forms the brilliant white surface 
of a clean glacier. 
A convenient method of examining the superficial structure of 
ice is that of Lohmann 4 who pours a mixture of ice-cold water 
and plaster of Paris on the surface. In this way a cast is formed 
which shows, in reverse, details which are difficult to make out by 
direct examination. He has applied the method in the caverns 
of the Hartz mountains in which ice is found during the whole 
year, and the casts show a remarkable regularity of structure. 
Similar casts have been obtained by the present author in the 
Schafloch 5 , a limestone cavern north of Interlaken, and as these are 
1 Huxley, Phil. Mag., 1857, vol. xiv. p. 241. 
2 Helmholtz, Popular Lectures on Scientific Subjects, Ice and Glaciers. 
3 Tyndall, Glaciers of the Alps, p. 853. 
4 H. Lohmann, Das Hohleneis unter besonderer Berucksichtigung einiger Eis- 
hohlen des Erzgebirges. Jena, 1895. 
5 Two and a half hours above Merligen on Lake Thun ; 5840 feet above sea level. 
3 
VOL. XI. PT. I. 
