5 . CRUZ , PATAGONIA 
CHAP. 
190 
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 24/A-—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. 
Amil 2 6th .—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 
