THE VOYAGE OF THE BEAGLE 201 



plane in the air (in which there is so little friction) cannot 

 be great, and this force is all that is wanted. The move- 

 ment of the neck and body of the condor, we must suppose, 

 is sufficient for this. However this may be, it is truly won- 

 derful and beautiful to see so great a bird, hour after hour, 

 without any apparent exertion, wheeling and gliding over 

 mountain and river. 



April zpth. From some high land we hailed with joy 

 the white summits of the Cordillera, as they were seen occa- 

 sionally peeping through their dusky envelope of clouds. 

 During the few succeeding days we continued to get on 

 slowly, for we found the river-course very tortuous, and 

 strewed with immense fragments of various ancient slaty 

 rocks, and of granite. The plain bordering the valley had 

 here attained an elevation of about noo feet above the river, 

 and its character was much altered. The well-rounded peb- 

 bles of porphyry were mingled with many immense angular 

 fragments of basalt and of primary rocks. The first of these 

 erratic boulders which I noticed, was sixty-seven miles dis- 

 tant from the nearest mountain; another which I measured 

 was five yards square, and projected five feet above the 

 gravel. Its edges were so angular, and its size so great, that 

 I at first mistook it for a rock in situ, and took out my com- 

 pass to observe the direction of its cleavage. The plain here 

 was not quite so level as that nearer the coast, but yet it 

 betrayed no signs of any great violence. Under these cir- 

 cumstances it is, I believe, quite impossible to explain the 

 transportal of these gigantic masses of rock so many miles 

 from their parent-source, on any theory except by that of 

 floating icebergs. 



During the two last days we met with signs of horses, and 

 with several small articles which had belonged to the Indians 

 such as parts of a mantle and a bunch of ostrich feathers 

 but they appeared to have been lying long on the ground. 

 Between the place where the Indians had so lately crossed 

 the river and this neighbourhood, though so many miles 

 apart, the country appears to be quite unfrequented. At first, 

 considering the abundance of the guanacos, I was surprised 

 at this ; but it is explained by the stony nature of the plains, 



