356 POPULAR LECTURES AND ADDRESSES. 



in, it might be found that there would not be 

 much difficulty in arriving at the South Pole. 



Among the first questions to be ascertained is, 

 Whether there is bare rock or ice at the Pole, and 

 what may be the effect of underground heat there ? 

 It is quite possible that the solid rock may slope 

 up to a mountain, and not be covered with snow 

 at all. I think it is covered with snow ; but there 

 may also be bare crags, as in regions where snow 

 cannot lie, and by boring into them something 

 may be learned of the underground temperature. 

 If we bore down a thousand metres and find 

 an increase of temperature at the rate of one 

 degree centigrade per 27 metres, we may infer th<it 

 it has been the same for many hundreds of years : 

 if we find that the increase is smaller, we may 

 be pretty sure that there has been a gain of ice ; 

 but if there is an increase of temperature of much 

 more than that, we may infer an opposite state of 

 things that there has been melting, and that we 

 are in a period subsequent to the melting. Put 

 take this case. Suppose the state of affairs to have 

 been steady for about 5,000 or 10,000 years, or 



