EXPLORING THE SANTA CRUZ. 233 



up on each side of the valley of Santa Cruz. No 

 possible action of any flood could thus have mod- 

 elled the land, either within the valley or along 

 the open coast; and by the formation of such step- 

 like plains or terraces the valley itself has beca 

 hollowed out. Although we know that there are 

 tides, which run within the NaiTows of the Strait 

 of Magellan at the rate of eight knots an hour, yet 

 we must confess that it makes the head almost 

 giddy to reflect on the number of years, century 

 after century, which the tides, unaided by a heavy 

 suif, must have required to have corroded so vast 

 an area and thickness of solid basaltic lava. Nev- 

 ertheless, we must believe that the sti'ata under- 

 mined by the waters of this ancient strait were 

 broken up into huge fragments, and these lying 

 scattered on the beach were reduced first to small- 

 er blocks, then to pebbles, and lastly to the most 

 impalpable mud, which the tides drifted far into 

 the Eastern or Western Ocean. 



With the change in the geological structure of 

 the plains the character of the landscape likewise 

 altered. While rambling up some of the narrow 

 and rocky defiles, I could almost have fancied my- 

 self transported back again to the barren valleys 

 of the island of St. Jago. Among the basaltic cliffs 

 I found some plants which I had seen nowhere 

 else, but others I recognised as being wanderers 

 from Tierra del Fuego. These porous rocks serve 

 as a resei-voir for the scanty rain water; and con- 

 sequently, on the line where the igneous and sedi- 

 mentary formations unite, some small springs (most 

 rare occurrences in Patagonia) burst forth ; and 

 they could be distinguished at a distance by the 

 circumscribed patches of bright gi'een herbage. 



April 21 til. — The bed of the river became rather 

 narrower, and hence the stream more rapid. It 

 V 2 



