160 CHARLES DARWIN 



cow. When the pasture is tolerably long, the niata cattle 

 feed with the tongue and palate as well as common cattle; 

 but during the great droughts, when so many animals per- 

 ish, the niata breed is under a great disadvantage, and would 

 be exterminated if not attended to; for the common cattle, 

 like horses, are able just to keep alive, by browsing with 

 their lips on twigs of trees and reeds; this the niatas cannot 

 so well do, as their lips do not join, and hence they are found 

 to perish before the common cattle. This strikes me as a 

 good illustration of how little we are able to judge from the 

 ordinary habits of life, on what circumstances, occurring 

 only at long intervals, the rarity or extinction of a species 

 may be determined. 



November ipth. Passing the valley of Las Vacas, we 

 slept at a house of a North American, who worked a lime- 

 kiln on the Arroyo de las Vivoras. In the morning we rode 

 to a projecting headland on the banks of the river, called 

 Punta Gorda. On the way we tried to find a jaguar. There 

 were plenty of fresh tracks, and we visited the trees, on 

 which they are said to sharpen their claws; but we did not 

 succeed in disturbing one. From this point the Rio Uru- 

 guay presented to our view a noble volume of water. From 

 the clearness and rapidity of the stream, its appearance was 

 far superior to that of its neighbour the Parana. On the 

 opposite coast, several branches from the latter river entered 

 the Uruguay. As the sun was shining, the two colours of 

 the waters could be seen quite distinct. 



In the evening we proceeded on our road towards Mer- 

 cedes on the Rio Negro. At night we asked permission to 

 sleep at an estancia at which we happened to arrive. It was 

 a very large estate, being ten leagues square, and the owner 

 is one of the greatest landowners in the country. His neph- 

 ew had charge of it, and with him there was a captain in 

 the army, who the other day ran away from Buenos Ayres. 

 Considering their station, their conversation was rather 

 amusing. They expressed, as was usual, unbounded astonish- 

 ment at the globe being round, and could scarcely credit 

 that a hole would, if deep enough, come out on the other 

 side. They had, however, heard of a country where there 

 were six months of light and six of darkness, and where 



