210 A rea of Recent Elevation. past u. 



Most of the shells are broken ; I nowhere found two 

 valves united ; the fragments are not rounded, at least 

 in noue of the specimens which I brought home. 



"With respect to the breadth of the upraised area in 

 an east and west line, we know from the shells found at 

 the inner Narrows of the Strait of Magellan, that the 

 entire width of the plain, although there very narrow, 

 has been elevated. It is probable that in this southern- 

 most part of the continent, the movement has extended 

 under the sea far eastward ; for at the Falkland Islands, 

 though I could not find any shells, the bones of whales 

 have been noticed by several competent observers, lying 

 on the land at a considerable distance from the sea, and 

 at the height of some hundred feet above it. 1 More- 

 over, we know that in Tierra del Fuego the boulder for- 

 mation has been uplifted within the recent period, and a 

 similar formation occurs 2 on the north-western shores 

 (Byron Sound) of these islands. The distance from 

 this point to the Cordillera of Tierra del Fuego, is 360 

 miles, which we may take as the probable width of the 

 recently upraised area. In the latitude of the R. Santa 

 Cruz, we know from the shells found at the mouth and 

 head, and in the middle of the valley, that the entire 

 width (about 160 miles) of the surface eastward of the 

 Cordillera has been upraised. From the slope of the 

 plains, as shown by the course of the rivers, for several 

 degrees northward of the S. Cruz, it is probable that the 

 elevation attested by the shells on the coast has likewise 

 extended to the Cordillera. When, however, we look as 

 far northward as the provinces of La Plata, this conclusion 



1 'Voyages of the Adventure and Beagle,' vol. ii. p. 227. And 

 Bougainville's 'Voyage,' tome i. p. 112. 



2 I owe this fact to the kindness of Capt. Sulivan, B.N., a highly 

 competent observer. I mention it more especially, as in my Paper 

 (p. 427) on the Boulder Formation, I have, after having examined 

 the northern and middle parts of the eastern island, said that the 

 formation was here wholly absent. 



