198 NOTES OF A NATURALIST. 



as in many parts of the Rocky Mountains, it would 

 appear that the valleys are exclusively due to erosive 

 action, and, their direction being determined by merely 

 local conditions, they are extremely sinuous, and rarely 

 follow the same direction for any considerable dis- 

 tance. 



The road up the Aconcagua valley seemed to me 

 at the time to be about the worst over which I ever 

 travelled in a carriage, but I had not then made 

 acquaintance with the mountain tracks, which they 

 are pleased to call roads, in the United States. Look- 

 ing back in the light of subsequent experience, I 

 suppose that the Chilian roads should rank among 

 the best in the American continent, although this one 

 was so uneven that in awkward places, where it over- 

 hung the river, the carriage was often tilted so much 

 to one side that I was thankful not to have with me a 

 nervous companion. 



About half-way to the Resguardo the road crosses 

 the river by a stone bridge, where it rushes in a 

 narrow channel between high rocky banks. Seeing 

 botanical inducements, I descended to examine the 

 banks on either side, and in crossing the bridge 

 noticed, what I might otherwise have overlooked, 

 that the crown of the arch was rapidly giving way. 

 There was a large hole in the centre, and the structure 

 was sustained only by the still solid masonry on each 

 side, where the wear and tear had been less constant. 

 I have often admired the calm good sense displayed 

 by the horses in all parts of America, and was 

 interested in observing the prudent way in which our 

 steeds selected the safest spots on either side of the 



