*j8 PORTILLO PASS. [CHAfr. xt 



the opposite shores of the ocean. In both cases, we must leave out of 

 the question those kinds which have been able to cross the barrier, 

 whether of solid rock or salt-water.* 



A great number of the plants and animals were absolutely the same 

 as, or most closely allied to, those of Patagonia. We here have the 

 agouti, bizcacha, three species of armadillo, the ostrich, certain kinds of 

 partridges and other birds, none of which are ever seen in Chile, but 

 are the characteristic animals of the desert plains of Patagonia. We 

 have likewise many of the same (to the eyes of a person who is not a 

 botanist) thorny stunted bushes, withered grass, and dwarf plants. 

 Even the black slowly-crawling beetles are closely similar, and some, I 

 believe, on rigorous examination, absolutely identical. It had always 

 been to me a subject of regret, that we were unavoidably compelled to 

 give up the ascent of the San Cruz river, before reaching the mountains : 

 I always had a latent hope of meeting with some great change in the 

 . features of the country ; but I now feel sure, that it would only have 

 been following the plains of Patagonia up a mountainous ascent. 



March 24/7*. Early in the morning I climbed up a mountain on one 

 side of the valley, and enjoyed a far extended view over the Pampas. 

 This was a spectacle to which I had always looked forward with 

 interest, but I was disappointed : at the first glance it much resembled 

 a distant view of the ocean, but in the northern parts many irregularities 

 were soon distinguishable. The most striking feature consisted in the 

 rivers, which, facing the rising sun, glittered like silver threads, till lost 

 in the immensity of the distance. At midday we descended the valley, 

 and reached a hovel, where an officer and three soldiers were posted 

 to examine passports. One of these men was a thoroughbred Pampas 

 Indian : he was kept much for the same purpose as a bloodhound, to 

 track out any person who might pass by secretly, either on foot or horse- 

 back. Some years ago, a passenger endeavoured to escape detection, 

 by making a long circuit over a neighbouring mountain ; but this Indian, 

 having by chance crossed his track, followed it for the whole day over 

 dry and very stony hills, till at last he came on his prey hidden in a 

 gully. We here heard that the silvery clouds, which we had admired 

 from the bright region above, had poured down torrents of rain. The 

 valley from this point gradually opened, and the hills became mere 

 water-worn hillocks compared to the giants behind : it then expanded 

 into a gently-sloping plain of shingle, covered with low trees and 

 bushes. This talus, although appearing narrow, must be nearly ten 

 miles wide before it blends into the apparently dead level Pampas. 

 We passed the only house in this neighbourhood, the Estancia of 

 Chaquaio; and at sunset we pulled up in the first snug corner, and 

 there bivouacked. 



* This is merely an illustration of the admirable laws, first laid down by 

 Mr. Lyell, on the geographical distribution of animals, as influenced by geo- 

 logical changes. The whole reasoning, of course, is founded on the assump- 

 tion of the immutability of species ; otherwise the difference in the species 

 in the two regions, might be considered as superinduced during a length of 

 time. 



