726 LOUIS AGASSIZ. 



though under a general plan laid out by him. 

 M. de Pourtales and Dr. Steindaehner as- 

 cended the mountain to the left of the val- 

 ley, following its ridge, in the hope of reach- 

 ing a position from which they could discover 

 the source and the full length of the glacier. 

 In this they did not succeed, though M. de 

 Pourtales estimated its length, as far as he 

 could see from any one point, to be about 

 three miles, beyond which it was lost in the 

 higher range. It made part of a net-work of 

 glaciers running back into a large massif of 

 mountains, and fed by many a nev6 on their 

 upper slopes. The depth as well as the length 

 of this glacier remains somewhat problemat- 

 ical, and indeed all the estimates in so cursory 

 a survey must be considered as approximations 

 rather than positive results. The glazed sur- 

 face of the ice is an impediment to any exam- 

 ination from the upper side. It would be im- 

 possible to spring from brink to brink of a 

 crevasse, as is so constantly done by explor- 

 ers of Alpine glaciers where the edges of the 

 cracks are often snowy or granular. Here 

 the edges of the crevasses are sharp and hard, 

 and to spring across one of any size would be 

 almost certain death. There is no hold for 

 an Alpine stock, no grappling point for hands 



