THE 
GHOLOGICAL MAGAZINE. 
NEW. SERIES), DECADE),V...j,.VOLEe. IV. 
No. XII.— DECEMBER, 1907. 
ORL GEN ALL, AR iiGingsS-_ 
I.—Tue Srrucrure or Gracrer Icz. 
By R. M. Deenzy, M.I.C.E., F.G.S. 
(PLATES XXIII AND XXIV.) 
N the Geoxocican Macazrne for April, 1895, p. 152, the results 
of some observations made by Mr. George Fletcher, F.G.S., and 
myself on the structure of glacier ice were given. 
Thin plates of ice were made by cutting and melting, and then 
examined in polarized light. In all cases it was found that the 
individual crystals were in close contact, there being no evidence of 
the presence of a eutectic separating them. The crystals in the same 
piece varied very greatly in size, and had very irregular outlines. 
As the sections which we figured were in all cases drawn by 
hand, I thought it advisable to construct a special form of instrument 
with which to obtain actual photographs of thin sections of glacier 
ice. The instrument eventually used consisted of two bundles of thin 
glass plates, one being used as a polarizer and the other as an analyser. 
They were fixed vertically above each other, and between them was 
the glass stage upon which the thin ice sections rested. Below the 
analyser was a small lens throwing the image of the ice section upon 
a photographic plate. 
Last Summer, accompanied by Mr. H. Arnold-Bemrose, M.A., F.G.S., 
who kindly assisted me in the matter, I visited the Furka Pass, and 
we obtained photographs of the ice of the Rhéne Glacier. 
Figs. 1 and 2 are full-sized photographs of thin slices of ice. 
Samples with small crystals were selected, so as to bring many crystals 
within the limits of the field. The ice section was about -03 inch 
thick, and where the surface between two crystals is at an angle with 
the glass plate upon which the ice section rested, interference fringes 
are consequently to be seen. 
In the ice caves we noticed the beautifully lined surfaces of the 
erystals of which the glacier is formed, and were successful, by 
adopting very simple means, in obtaiming correct reproductions of the 
structure. The lines consist of alternate ridges and furrows, and we 
found that by placing a piece of paper upon the ice surface and 
rubbing with a pencil, very beautiful copies could be obtained. 
Figs. 3 to 7 are reproductions of these. 
DECADE V.—VOL. IV.—NO. XII. 34 
