352 POPULAR LECTURES AND ADDRESSES. 



in precipices of 170 to 200' feet in height. Mr. 

 Croll's calculation is invalid beyond a certain 

 limit, because it has been made on the supposition 

 that the slope is uniform from the shore line in- 

 wards. He estimates that 'at the South Pole the 

 thickness of the ice-sheet would be 12 miles. I 

 say the slope cannot be uniform, and any reason- 

 ing, dependent on the assumption of uniform 

 slope, must be fallacious. 



Let us look at the realities of this Antarctic 

 Continent in the light of what we know regarding 

 the viscosity of ice. Through the kindness of 

 Mr. Murray of the Challenger, I am enabled to 

 place before you this splendid map (from which an 

 outline sketch is given in Fig. 7). You see here 

 Victoria Land, explored by Sir James Ross. We 

 have here high mountains running up to a height 

 of 8,000 feet, and a volcano, Mount Erebus, 12,000 

 feet high also discovered by Ross. There is an 

 ice-barrier running 200 miles towards the west, 

 which is everywhere about 170 or 200 feet high 

 above the sea. Here it is in our model Antarctic 

 Continent already referred to. We break a piece 



