The Editor,
The Journal of Glaciology
Sir, Bismuth and Ice
At the Joint meeting of the Society with the British Rheologists and the Institute of Metals, Dr. C. H. Desch suggested the investigation of bismuth for its analogies with ice. The enclosed leaflet, a reprint of the Bulletin de la Société Vaudoises des Sciences Naturelles dated 17 April 1907, shows that this problem did not escape my attention many years ago.
But the experiment was not easy owing to the difficulty of maintaining the metal exactly at the right temperature −267° C., which is a few degrees below its melting point. Another difficulty was its brittleness and the fact that only very small quantities of the metal were available. As you will see I used small rods of bismuth 1 cm. in diameter and placed on them an iron wire 0.3 mm. in diameter, weighted with a weight of nearly 3 kg., giving a pressure of 100 atmospheres. The rods were completely cut through but no regelation of the incision took place. The iron wire was, in places, covered with melting bismuth and traces of local melting were visible during the experiment.
It would be interesting to repeat this experiment with larger quantities of the metal and under temperatures better controlled than was possible for me at the time.
The Growth of the Glacier Grain
Since Hugi over a century ago demonstrated the grain structure of the glacier no definite answer has been given to one fundamental question: has the growth of the crystal in its course from the peaks to the valley been assisted or retarded by the movement of the glacier?
Emden showed in 1880 that the crystals in ice could grow even in the complete absence of movement provided only that the temperature fluctuated around the zero point, which, of course, is the case, too, in the moving glacier.
I should like to take this opportunity of saving from oblivion certain observations I made as early as 1897 at the Montanvers section of the Mer de Glace and which I communicated to the Société Vaudoise des Sciences Naturelles. I had hoped to supplement these before they were published—an aim which remained unachieved.
I made 14 records of crystal sizes across the glacier by a method suggested by Forel—using a glass plate as a tracing medium with copying ink and taking off “pulls.”
The results were as follows:—
The answer is clear: on average the crystals at the two margins of the stream were about four times larger in area (on the exposed face) than those in the centre and about eight times as large in volume. This seems to agree with the recent researches of Mr. G. Seligman (Journal of Glaciology, Vol. 1, No. 5, p. 254–66).
It seemed to me that crystals at the margins owed their greater size to their being more exposed to daily fluctuations of temperature caused by radiation from the banks, and also because they had travelled for a longer time and were therefore older. If on the other hand the flow of the glacier had been the predominant factor of growth the grains ought to have been larger in the centre of the stream where the movement was more rapid.
14 September 1949
