204 Valley of Santa Cruz. paet h. 



we ascended, it was sixteen miles wide in a north and 

 south line ; and forty-five miles in length in an east 

 and west line. It is bordered by the escarpments, one 

 above the other, of two plains, which diverge as they 

 approach the Cordillera, and consequently resemble, at 

 two levels, the shores of great bays facing the moun- 

 tains ; and these mountains are breached in front of the 

 lower plain by a remarkable gap. The valley, therefore, 

 of the Santa Cruz consists of a straight broad cut, 

 about ninety miles in length, bordered by gravel-capped 

 terraces and plains, the escarpments of which at both 

 ends diverge or r expand, one over the other, after the 

 manner of the shores of great bays. Bearing in mind 

 this peculiar form of the land — the sand-dunes on the 

 plain at the head of the valley — the gap in the Cordil- 

 lera, in front of it — the presence in two places of very 

 ancient shells of existing species — and lastly, the cir- 

 cumstance of the 355 to 453 feet plain, with the 

 numerous marine remains on its surface, sweeping from 

 the Atlantic coast, far up the valley, I think we must 

 admit, that within the recent period, the course of the 

 Santa Cruz formed a sea-strait intersecting the con- 

 tinent. At this period, the southern part of South 

 America consisted of an archipelago of islands 360 

 miles in a X. and S. line. We shall presently see, that 

 two other straits also, since closed, then cut through 

 Tierra del Fuego ; I may add, that one of them must 

 at that time have expanded at the foot of the Cordillera 

 into a great bay (now Otway Water) like that which 

 formerly covered the 4-40 feet plain at the head of the 

 Santa Cruz. 



I have said that the valley in its whole course is 

 bordered by gravel-capped plains. The following sec- 

 tion, supposed to be drawn in a N. and S. line across 

 the valley, can scarcely be considered as more than 



