16 ROYAL SOCIETY OF CANADA 



found that the viscosity coefficient decreases with the load. Over the 

 range of his experiments he found the viscosity to be of the order lO^ 

 in C. G. S. units, the exact values depending on the load and on the 

 duration of the experiment. 



B. "Weinberg, in 1905, determined the viscosit)' of ice by a torsional 

 method. Tee was cut into cylinders and prismatic rods with their lengths 

 parallel to the optic axis. One end was fixed and the other subjected to 

 a twist. Attention was paid to the effect of temperature and the follow- 

 ing expression was given 



u = (1.244 — 0.502T + 0.0355T2) x 1013 gm./cm. sec. 



He gives Young's modulus also as 



5 X 109 at a temperature of — 1°C. 



In a further study of the viscosity of ice, Weinberg, in 1907, dis- 

 cusses the relation with the shearing rate and shows that this has a con- 

 nection with the relaxation theory as' developed by Maxwell and Schwe- 

 doff. Judging from the value of the coefficient of viscosity, the author 

 concludes that the critical velocity of the ice current in a glacier must 

 be of the order of the velocity of light. 



Small values of the rigidity, of the limit of elasticity and the visco- 

 sity, and the greater influence of the temperature, is regarded by the 

 author as an indication of the weakness of the limiting regions between 

 the individual grains, and of a " wet " friction produced by regelation 

 in addition to the " dry " friction. He shows that the latter form of 

 friction is possible in ice on account of the gradual shearing in direc- 

 tions normal to the optic axis, when local excess of pressure is quite 

 excluded. 



R. M. Deeley, in 1908, has given some calculations of the viscosity 

 of the ice of the Swiss glaciers. A viscosity of 125 x 10^2 is as near an 

 estimate of what he calls the average effective viscosity of such a form of 

 ice as can be given. In winter he concludes that it is probably doubled 

 owing to low temperature. 



From actual experiments carried out with pitch, which he compares 

 with McConnell's experiments, he considers that the nature of the shear 

 produced in an ice crystal at right angles to the optic axis very closely 

 obeys the law of viscous flow. If this view is further verified he points 

 out that it means, in the case of crystalline ice, that a solid may be liquid 

 along one plane only, resembling the case pointed out by H. A. Miers, 

 that a liquid of low viscosity may have a crystalline structure. 



Deeley gives, as a result of a study of McConnell's work, the visco- 

 sity of an ice crystal in a direction at right angles to the optic axis as 



2 X 1010 at the freezing point. 



