I833-] GEOLOGY OF THE PAMPAS. 33 



has suffered more from bloody and desperate revolutions. They boast 

 here of representatives, ministers, a standing army, and governors: 

 so it is no wonder that they have their revolutions. At some future 

 day this must be one of the richest countries of La Plata. The soil is 

 varied and productive; and its almost insular form gives it two grand 

 lines of communication by the rivers Parana and Uruguay. 



I was delayed here five days, and employed myself in examining the 

 geology of the surrounding country, which was very interesting. We 

 here see at the bottom of the cliffs, beds containing sharks' teeth and 

 sea-shells of extinct species, passing above into an indurated marl, and 

 from that into the red clayey earth of the Pampas, with its calcareous 

 concretions and the bones of terrestrial quadrupeds. This vertical 

 section clearly tells us of a large bay of pure salt-water, gradually 

 encroached on, and at last converted into the bed of a muddy estuary, 

 into which floating carcasses were swept. At Punta Gorda, in Banda 

 Oriental, I found an alteration of the Pampaean estuary deposit, with 

 a limestone containing some of the same extinct sea-shells ; and this 

 shows either a change in the former currents, or more probably an 

 oscillation of level in the bottom of the ancient estuary. Until lately, 

 my reasons for considering the Pampaean formation to be an estuary 

 deposit were, its general appearance, its position at the mouth of the 

 existing great river the Plata, and the presence of so many bones of 

 terrestrial quadrupeds ; but now Professor Ehrenberg has had the 

 kindness to examine for me a little of the red earth taken from low 

 down in the deposit, close to the skeletons of the mastodon, and he 

 finds it in many infusoria, partly salt-water and partly fresh-water 

 forms, with the latter rather preponderating ; and therefore, as he 

 remarks, the water must have been brackish. M. A. d'Orbigny found 

 on the banks of the Parana, at the height of a hundred feet, great beds 

 of an estuary shell, now living a hundred miles lower down nearer the 

 sea ; and I found similar shells at a less height on the banks of the 

 Uruguay : this shows that just before the Pampas was slowly elevated 

 into dry land, the water covering it was brackish. Below Buenos 

 Ayres there are upraised beds of sea-shells of existing species, which 

 also proves that the period of elevation of the Pampas was within the 

 recent period. 



In the Pampaean deposit at the Bajada I found the osseous armour 

 of a gigantic armadillo-like animal, the inside of which, when the earth 

 was removed, was like a great cauldron ; I found also teeth of the 

 Toxodon and Mastodon, and one tooth of a Horse, in the same stained 

 and decayed state. This latter tooth greatly interested me,* and I took 

 scrupulous care in ascertaining that it had been embedded contempora- 

 neously with the other remains ; for I was not then aware that amongst 

 the fossils from Bahia Blanca there was a horse's tooth hidden in the 

 matrix ; nor was it then known with certainty that the remains of 

 horses are common in North America. Mr. Lyell has lately brought 



* I need hardly state here that there is good evidence against any horse 

 living in America at the time of Columbus. 



