190 5. CRUZ, PATAGONIA chap. 



characterised by large thin ears and a very fine fur. These little 

 animals swarm amongst the thickets in the valleys, where they 

 cannot for months together taste a drop of water excepting the 

 dew. They all seem to be cannibals ; for no sooner was a mouse 

 caught in one of my traps than it was devoured by others. A 

 small and delicately-shaped fox, which is likewise very abund- 

 ant, probably derives its entire support from these small animals. 

 The guanaco is also in his proper district ; herds of fifty or a 

 hundred were common ; and, as I have stated, we saw one which 

 must have contained at least five hundred. The puma, with the 

 condor and other carrion-hawks in its train, follows and preys 

 upon these animals. The footsteps of the puma were to be seen 

 almost everywhere on the banks of the river ; and the remains 

 of several guanacos, with their necks dislocated and bones broken, 

 showed how they had met their death. 



April 2^tk. — Like the navigators of old when approaching 

 an unknown land, we examined and watched for the most trivial 

 sign of a change. The drifted trunk of a tree, or a boulder of 

 primitive rock, was hailed with joy, as if we had seen a forest 

 growing on the flanks of the Cordillera. The top, however, of a 

 heavy bank of clouds, which remained almost constantly in one 

 position, was the most promising sign, and eventually turned out 

 a true harbinger. At first the clouds were mistaken for the moun- 

 tains themselves, instead of the masses of vapour condensed by 

 their icy summits. 



April 26th. — We this day met with a marked change in the 

 geological structure of the plains. From the first starting I had 

 carefully examined the gravel in the river, and for the two last 

 days had noticed the presence of a few small pebbles of a very 

 cellular basalt These gradually increased in number and in size, 

 but none were as large as a man's head. This morning, however, 

 pebbles of the same rock, but more compact, suddenly became 

 abundant, and in the course of half an hour we saw, at the dis- 

 tance of five or six miles, the angular edge of a great basaltic 

 platform. When we arrived at its base we found the stream 

 bubbling among the fallen blocks. For the next twenty-eight 

 miles the river-course was encumbered with these basaltic masses. 

 Above that limit immense fragments of primitive rocks, derived 

 from the surrounding boulder-formation, were equally numerous. 

 None of the fragments of any considerable size had been washed 



