334 Intelligence and Miscellaneous Articles, 



that is, at what pressure displacement of the ice-particles occurs. 

 He found that, in order to rend a cj^linder of ice, a weight of from 

 70 to 116 lbs., or from 5| to 9 atmospheres, per square inch of the 

 cross section was necessary, according to the temperature; to crush 

 it by pressure 101'8 lbs. on the square inch were requisite ; and to 

 produce shearing 97*89-118 lbs., or a pressure of 7*5-9 atmospheres, 

 must act upon the square inch. I have this winter (1875) made a 

 series of experiments in order to obtain somewhat nearer numerical 

 values on the requisite degrees of pressure which are capable of 

 altering still more demonstrably the form of ice, since for glacier- 

 motion the important point is just this — what is the minimum of 

 pressure under which ice is still plastic or yielding. 



The results which I have obtained are, to any one who keeps in 

 view the brittle nature of ice, quite as striking as the mobility of 

 such a mass of ice as a glacier appeared at first to every one striking 

 and wonderful. They show, namely, that even the slightest pressure 

 is sufficient to displace the particles, if it acts continuously and the 

 temperature of the ice and around it is near the melting-point. Even 

 Moseley recognized the influence of temperature on the mechanical 

 properties of ice, but clearly not to the full extent. 



It follows from my experiments that ice, near its melting-point, 

 behaves indeed like ivaoc, and with a pressure of only two atmo- 

 spheres shows itself so yielding, that e. g. a hollow cylinder of iron 

 of 11-5 millims. diameter and 1*7 thickness of the sides penetrated 

 in two hours, at a temperature between — 1° and o, 5, to a depth 

 of 3 millims. into the ice. Respecting the influence of the tempe- 

 rature I will cite only a few data from my experiments. 



The same cylinder, under the same pressure, with a temperature 

 between —4° and —1°, sank in 12 hours to a depth of 1| millim.; 

 w T hile with the temperature varying between — 6° and — 12° the 

 sinking in five days, under a pressure of 5 atmospheres, amounted 

 to only 1 millim., consequently only ^ millim. in 12 hours ! 



If the surrounding temperature rises above the melting-point, 

 the softness of the ice becomes so great that in one hour the same 

 iron cylinder, under an equally slight pressure, sank to a depth of 

 3 centims., although it was completely enwrapped in snow, in order 

 to avoid the raising of the temperature of the cylinder above zero. 

 That in fact melting of the ice (which of course, on account of the 

 lowering of the freezing-point below 0° by pressure, cannot be 

 entirely avoided) had scarcely a perceptible influence in this experi- 

 ment was shown by this — that the inner cylinder of ice filled out 

 the iron cylinder quite tightly, so that it would not fall out, but 

 required to be pressed out, and scarcely a trace of liquid water 

 appeared in the depression left when the iron cylinder was lifted. 



The pressure was applied, in all the experiments, by means of a 

 one-armed lever, consisting of a steel bar of rectangular cross 

 section and 8G centims. length, which was perforated at its hinder 

 end and fixed on a steel pin upon winch it turned easily. By this 

 simple arrangement any pressure could be maintained constant as 

 long as desired. 



