256 LIGHT SCIENCE FOR LEISURE HOURS. 



I should not be greatly concerned if the result of the 

 experiments I spoke of should not accord with my predic- 

 tion. But merely to put ice in water capable of melting 

 it, is not in any sense to represent the conditions of the 

 actual case. The addition of water from the ice as it 

 melts is not in accordance with these conditions. It 

 cannot surely be maintained that the oceanic circulation 

 depends on the addition of water from the melting of 

 ice ; and yet I apprehend that the melting of ice is no 

 unimportant feature of Dr. Carpenter's experiment. At 

 any rate, the ice does melt, and the movement comes to 

 an end when all the ice has melted away. Let the ice 

 be packed outside the arctic end of the canal, so as 

 merely to produce a refrigeration corresponding to what 

 actually takes place with water carried into arctic lati- 

 tudes, and I conceive that a very feeble circulation 

 would result. Under the actual circumstances, the 

 melting of the ice produces effects much more nearly 

 corresponding to those due to rainfall than to the mere 

 effects of arctic cold. The very activity of the circu- 

 lation shows that the water which moves towards the 

 ice does not undergo refrigeration. Water does not 

 cool quite so quickly. It is the melted ice-water which 

 descends ; and nothing takes place in the arctic regions 

 which corresponds to this continued addition of water 

 to that already circulating. Otherwise, the arctic ice 

 would be continually diminishing, which, of course, is 

 not the case. 



It will be gathered that I agree entirely with the 

 opinion which Sir W. Thomson expressed, as to the 



