144 Mr. H. H. Howorth on 



experiments were made upon bars of ice from the harder 

 and firmer ice of the sand cones. When not too large these 

 showed similar signs of bending very quickly, and the 

 flexure in each case was permanent and not due to elasticity 

 {Nature^ vol. iv. 447). 



More remarkable were the experiments of Mr. John 

 Aitken, described in the 7th volume of the same periodical 

 (287 — 288), from which he deduced the conclusion that the 

 plasticity of ice depends largely on the amount of air it 

 contains. Having dissolved a large quantity of air in water, 

 he filled some tubes with it. When frozen he withdrew the 

 ice in the form of rods, which he then placed on supports 

 eight and a half inches apart, and hung a pound weight in 

 between. The beam, he says, at once began bending, and 

 ■continued bending so long as the weights were left on them, 

 thus proving the viscosity of the ice. In further experi- 

 ments with rods made from compressed snow, afterwards 

 frozen in a freezing mixture, and therefore more like glacier 

 ice, the results were even more marked, one of the beams 

 bending an inch in five minutes. Eventually Mr. Aitken 

 succeeded in twisting such ice rods round cylinders, and thus 

 forming solid ice rings from straight beams of ice. 



In 1877, Professor Pfaff published the results of some 

 <:areful experiments, which went to show that even the 

 slightest pressure when applied continuously, and when the 

 temperature of the ice is near the melting point, is sufficient 

 to displace the particles of ice. " It follows," he says, "that ice 

 near its melting point behaves indeed like wax." Again he 

 says, " It is still constantly assumed, on the ground of some 

 of Tyndall's experiments, that ice is destitute of extensibility 

 and flexibility^ although repeated observations recently 

 made compel us to ascribe to ice some flexibility. The 

 oldest observation of this kind known to us originated 

 with Kane, who remarked that a large lump of ice with 

 its edges resting on two others became curved in the 



