[baknes] 



THE PHYSICAL CONSTANTS OF ICE 



15 



The values obtained by Hess ^re contained in the following table 

 taken from his work " Die Gletscher." (1904). 



As a mean for all his observations in the three directions he gives 

 E = (2.76 + 0.17) X 1010 cm.-i gr. Sec.-2 

 or expressed in the other units 



E = 27600 Kg/cm2 



Viscosity of Ice. 



It has been well established that ice behaves as a viscous solid quite 

 apart from any effect due to regelation on the movements of glaciers. 

 This matter has been the subject of some controversy. Tyndall claimed 

 that ice was not viscous, basing liis argument on the fact that glaciers 

 always cracked when subjected to tensile stress no matter how slow. 



McConnell was among the first to show that ice is capable of being 

 deformed without fracture by a stress. He showed that an ice crystal 

 can be sheared by very small stresses in a direction at right angles to the 

 optic axis. His main results show that the viscosity of the ice becomes 

 greater as the temperature falls and that the cube of the friction of the 

 sliding ice molecules varies as the square of the velocity. The coefficient 

 of viscosity, as determined by McConnell, has recently been recalculated 

 by E. M. Deeley, and is found to lie between 3 x lOio and 134 x lOiO in 

 C. G. S. units. 



Hess, in 1902, determined the viscosity and found that under the 

 loads he used the viscosity coefficient increased a little with the duration 

 of the experiment. With large loads, near to the breaking point, he 



