DARWIN. 89 



American ostrich and many other animals here afforded 

 material for important observations. 



On the way to Buenos Ayres, the rugged Sierra de la 

 Ventana, a white quartz mountain, was ascended. 

 Buenos Ayres was reached on September 20, 1833, and 

 no time was lost in arranging for an expedition to Santa 

 Pe", nearly 300 miles up the Parana. On October 3, 

 Santa Fe was entered, and near it many more remains 

 of large extinct mammals were found. The remains of a 

 horse, in a similar fossil condition, greatly astonished 

 our explorer, for it seemed indeed surprising that in 

 South America a native horse should have co-existed 

 with giant extinct forms, and should itself have become 

 extinct, to be succeeded in modern times by the count- 

 less herds descended from the few horses introduced by 

 the Spanish colonists. These and other strange facts in 

 the distribution of mammalian animals in America led 

 Darwin to make some pregnant comments. The enor- 

 mous number of large bones embedded in the estuary 

 deposits became continually more evident, until he came 

 to the conclusion that the whole area of the Pampas was 

 one wide sepulchre. 



Unfortunately ill-health compelled the explorer to 

 return, and on October 1 2th he started for Buenos Ayres 

 in a small vessel. During this journey he had an 

 opportunity of examining the shifting and variable 

 islands of the muddy Parana, on which the jaguar 

 thrives. Arrived at Las Conchas, a revolution had 

 broken out, and Darwin was detained to a certain 

 extent under surveillance ; but by the influence of 

 General Rosas' name, he was allowed to pass the 



