The Theory of Glacier motion. 149 



is the great increase of velocity from the side to the centre 

 of a glacier. The most rapid increase mentioned by Heim 

 {Gletscherkunde^ 147) among the glaciers of the Alps is on 

 the Rhone glacier on a line 2,300 metres above the top of 

 the ice fall. At 100 metres from the Western bank, the 

 mean yearly motion, 1874 to 1880, was 12*9 metres ; at 160 

 metres from the bank it was 43*25 metres. This gives an 

 increase of velocity in each metre across the glacier of 

 0*00058 metres per hour." Having calculated out what 

 this means, our authors proceed : "Thus the maximum rate 

 of extension in the case we have taken on the Rhone 

 glacier is 0*0029 mm. per hour per length of 10 cm. This, 

 be it remembered, is the most rapid extension selected from 

 a large number of measurements on different glaciers and at 

 different times, and yet only one of the three specimens 

 of glacier ice showed a rate less than this, and that was 

 under one-third of the breaking tension. The larger the 

 specimen the greater average plasticity would it display." 



In some still more recent papers read before the Roya] 

 Society by Mr. Thomas Andrews, he shows experimentally 

 that the shearing force of ice is largely dependent on its 

 temperature. "In the majority of instances," he says, "it was 

 found that if the plasticity of the ice at —35 F, be called i 

 at o' F. it would be about twice as much, and at 28 F. the 

 plasticity would be about four times as great as at o' F, or 



eight times as much as at — 35 F This is in accord 



with the practical cessation of motion in glaciers during the 

 cold of winter. It was also noticed that the plasticity of the 

 naturally frozen pond ice was manifestly greater than that 

 of the prepared pure ice." 



These experiments have shewn conclusively that Mr. 

 Moseley's tests which misled so many scientific men were 

 based on a mistake, and with the disappearance of Moseley's 

 experiment, disappears the only evidence that has beea 

 forthcoming against the splendid induction of Forbes. 

 J 



