GEOLOGY OF THE CORDILLERA. 71' 



Patagonia lived, there must have been there a sub- 

 sidence of several hundred feet, as well as an en- 

 suing elevation. Daily it is forced home on the 

 mind of the geologist, that nothing, not even the 

 w^ind that blows, is so unstable as the level of the 

 crust of this earth. 



I will make only one other geological remark : 

 although the Portillo chain is here higher than the 

 Peuquenes, the waters, draining the intermediate 

 valleys, have burst through it. The same fact, on 

 a grander scale, has been remarked in the easteni 

 and loftiest line of the Bolivian Cordillera, through 

 which the rivers pass : analogous facts have also 

 been observed in other quarters of the world. On 

 the supposition of the subsequent and gradual ele- 

 vation of the Portillo line, this can be understood ; 

 for a chain of islets would at first appeal', and, as 

 these wei'e lifted up, the tides would bo always 

 wearing deeper and broader channels between 

 them. At the present day, even in the most re- 

 tired sounds on the coast of TieiTa del Fuego, the 

 currents in the transverse breaks which connect 

 the longitudinal channels are very strong, so that 

 in one transverse channel even a small vessel un- 

 der sail was whirled round and round. 



About noon we began the tedious ascent of the 

 Peuquenes ridge, and then for the first time experi- 

 enced some little difficulty in our respiration. The 

 mules would halt every fifty yards, and after resting 

 for a few seconds the poor willing animals started 

 of their own accord again. The short breathing 

 from the rarefied atmosphere is called by the Chi- 

 lenos "puna;" and they have most ridiculous no- 

 tions concerning its origin. Some say, " all the 

 waters here have puna ;" others, that " where there 

 is snow there is puna;" and this, no doubt, is true.. 



