GEOLOGY. 599 



sent very varied aspects. This is the case. Some moun- 

 tain chains, like those of Calabria, have crests toothed like 

 saws ; others resemble pointed crystals, as is seen in Savoy, 

 where, on this account, they are called aiguilles. Often 

 the tops are rounded and form a succession of paps ; finally, 

 at other times, as, for instance, is seen in the peaks of 

 Tierra del Fuego, these asperities of the globe are perfectly 

 conical, slender and pointed, exactly like gigantic sugar- 

 loaves. 



The exploration of lofty mountains is not always free 

 from danger. But the deplorable accidents of which they 

 become the theatre are often due to the imprudence of 

 travellers, who attend little to the advice of their guides. 

 A good guide holds in his hands the lives of those who 

 accompany him ; it is therefore necessary to make a care- 

 ful choice and to treat him kindly. I have always done so, 

 and have met with devoted men, who years after have pre- 

 served the memory of my ascents. 



When we have arrived at a moderate height the ascent 

 of any mountain becomes a heavy toil. Movement and 

 respiration become extremely difficult in proportion as we 

 rise. There even comes a time when, as De Saussure re- 

 marks, one is obliged to stop every fifty yards overwhelmed 

 by an inexplicable fatigue. Then the rarefaction of the 

 air renders the oppression greater and greater, and the 

 heart beats as if it would burst from the chest, and the 

 traveller feels every instant as if he would faint. Twice 

 Baron Mtiller, abandoned by his guides and companions, 

 fainted quite away on the borders of the crater of Orizaba, 

 whilst torrents of blood gushed from his chest. 



