BASAL WATERS OF ICE-SHEETS. 307 



and ice before reaching- a depth of many hundred feet. But there are 

 abyssal animals in the sea far below those depths, and they have eyes, prov- 

 ing that even at such great depths ether waves of low refrangibility are not 

 absorbed by the water. The passage of radiant energy from the sun and 

 stars into the ice will be affected in considerable degree by the condition of 

 the ice surface. The rougher and more broken the surface ice, the larger 

 the proportion that will be refracted and reflected and radiated outward and 

 lost or absorbed in the surface ice. A residue remains of rays not absorb- 

 able by the ice or absorbed only after traveling a long distance in it, which 

 may be transmitted through it till they come to englacial debris or to the 

 ground. Here, being absorbed in part, they become changed to molecular 

 heat and melt the adjacent ice. "While the passage of stellar and solar 

 radiations to considerable depths in the ice is probable, the quantity is 

 unknown and has not been proved by observation. If we could prove that 

 any considerable amount of heat was thus transmitted through the ice, it 

 would greatly help to account for the accumulation of drumlins and the 

 glacial gravels and the dropping of englacial matter to become part of the 

 subglacial till, it would account for a part of the glacial waters and for 

 the maintenance of the internal temperature, and it would perhaps help to 

 answer the question. What effect did the pressure of surface waters,. streams, 

 pools, and shallow lakes have on the development of the subglacial till 

 beneath them! For surface waters would somewhat help to make the ice 

 more transparent, like a piece of ground glass flowed with water, and we 

 know that the larger superglacial streams remove the granular ice and reveal 

 only the clear solid ice in their beds. Such an hypothesis, if proved, would 

 be a welcome addition to our knowledge of glacial conditions, if for no 

 other reason than to account for the fact that the ice, after having taken 

 the englacial debris into its grasp where it is thicker, lets go of it again 

 subglacially where the ice is thinner. 



5. Subterranean waters issuing as springs beneath the ice. The rocks 

 beneath glaciers become charged with water, just as they do elsewhere, and 

 probably discharge it under the ice in many cases. Such waters would dis- 

 turb the distribution of the internal heat of the earth. In their subterra- 

 nean courses they would absorb some of the internal heat and transfer it to 

 their place of issuance. If this was beneath the ice, the heat would be 

 available for melting or maintaining 'temperature. 



