Apparent Viscosity of Ice. 



121 



however, string is used instead of copper wire, this conduction 

 of heat does not readily occur. 



In repeating this experiment, water could be distinctly 

 seen moving quickly round the sides of the wire from its under 

 to its upper surface ; and in one particular case, when a brass 

 wire one tenth of an inch in diameter was used with two 

 weights of 56 lb, each, crystals of ice were seen actually 

 growing in the water on the upper surface of the wire, just 

 before it became completely buried in the ice. 



In order to determine the effect of conductivity an experi- 

 ment was made with five different wires. As a matter of 

 convenience, each wire was placed on a separate block of ice, 

 but the blocks were sawn to as nearly as possible the same 

 size. The times taken by the different wires in cutting through 

 the blocks were: — 



Wire. 



Time, in minutes. 



Conductivity. 



Silver 



192 

 184 

 267 

 300 

 314 



100 



736 



23-6 



11-9 



63 



Copper 



Brass 



Iron 



German-silver ... 



Each wire was *67 millim. diameter, and carried 2^ lb. 

 The numbers obtained show that the time taken increases as 

 the conductivity decreases; but there is an apparent exception 

 in the case of the silver and copper wires. To find whether 

 this was due to an} r difference in the blocks of ice, they were 

 interchanged, with the following result: — 



Wire. 



Time, in minutes. 



Conductivity. 



Silver 



103 

 110 



100 

 73-6 



Cooper 





In this case the silver has the advantage ; and the difference 

 in the times, in proportion to the total time taken, is greater 

 than before. 



Another experiment was made with the same two wires on 

 one block, each wire being weighted with 20 lb. Results : — 



