114 Mr. T. Andrews. [June 5, 



rapidly and considerably increased after reaching, and whilst it after- 

 wards remained at, a temperature of 32 F. 



General Remarks. 



1st. Referring to the results of Diagram I, and taking the relative 

 penetration of the steel rod at the respective temperatures as an in- 

 dication of the plasticity of the ice, it will be noticed that there was 

 a considerable reduction of plasticity as the temperature lowered. 

 Regarding as a guide the total depth penetrated by the steel rod, 

 during equal and comparative periods of time (as, for instance, the 

 results at 2, 3, 4, 5, 6, 7, &c., hours, Diagram I, curves 1, 2, 3), into 

 ice at different temperatures, these comparative experiments show, 

 in a majority of instances, that, if the plasticity of the ice at 35 F. 

 be called one, at F. it would be about twice as much, and at 28 F. 

 the plasticity would be about four times as great as at F., or eight 

 times as much as at 35 F. When the ice was maintained at a 

 temperature of 32 F., it will be seen that the plasticity very con- 

 siderably increased, this being probably owing to the reduced 

 cohesion at this temperature between the faces of the ice crystals 

 forming the mass. 



2nd. It will be further noticed that the plasticity was greater 

 during the gradual molecular changes occurring in course of the 

 slow rising of temperature from F. to 32 F., see results on Table 

 III, than when the ice was maintained at even temperatures, as in 

 the experiments on Diagram I. 



3rd. Reverting to the observations on Table IV, if the time required 

 for the steel rod to penetrate a certain depth, say, 6^ inches, into the 

 ice under conditions of experiments 1, 2, and 3, Table IV, be taken as 

 an indication of the relative plasticity of the ice under conditions of 

 , these experiments, it will be seen that the plasticity was roughly 

 about 579 per cent, greater in No. 2 than No. 1, and 1400 per cent, 

 greater in No. 3 than in No. 2, these results showing proportion- 

 ately the rapid manner in which the mass of ice was becoming 

 internally plastic, although retaining an outward apparent rigidity. 

 The Rev. Coutts Trotter, in his paper ('Roy. Soc. Proc.,' vol. 38, 

 1885, p. 92), states that " the 'viscosity ' of ice probably diminishes 

 very rapidly with the temperature," and it appears probable from the 

 experiments of M. Person (' Comptes Rendus,' vol. 30, 1850, pp. 

 526528) that 2 C. is the temperature at which ice begins to 

 soften. The Rev. C. Trotter, after summarising the experimental 

 evidence, also arrives at the conclusion that the general interior and 

 bottom portions of a glacier, near the surface of the earth, are of a 

 constant temperature of about C., and my experiments recorded on 

 Diagrams I and II and Tables III and IV demonstrate the greater 



