GLACIER SURFACE. 153 



the rock from which it had been originally 

 measured ; and, in 1839, twelve years from its 

 construction, it was found by M. Agassiz to have 

 travelled upwards of four thousand feet, or the 

 whole mass to have moved, on an average, up- 

 wards of three hundred feet a-year. 



We have no means of determining whether 

 there exists a similar movement on the Spitz- 

 bergen glacier ; but the extensive fissures, {cre- 

 vasses,) in the Waggon- way in particular, seem 

 to indicate a forward propulsion of the outer part 

 of the body. On the other hand, it is hardly pos- 

 sible to imagine a power capable of moving 

 so large a body, firmly united at its base, as it 

 must be, by perpetual frost to the ground. 



In the Arctic regions, the upper surface of 

 the glacier presents a smooth and slightly con- 

 vex plain, free from those ridges and pinnacles 

 which characterize the southern glacier. It 

 often extends two or three miles inland, in an 

 inclined direction until it attains the mountain 

 ridge, ^nd is surmounted only by the dreary 

 rocky peaks from which the glacier in part re- 

 ceives its supply. 



The surface of this plane is occasionally ren- 

 dered hard and crisp by frost, and is then capable 

 of being traversed on foot, but in so doing it is 

 necessary to guard against the danger of falling 



