192 
S. CRUZ , PATAGONIA 
CHAP. 
supposition would have been quite inadmissible ; because, the 
same step-like plains with existing sea-shells lying on their 
surface, which front the long line of the Patagonian coast, sweep 
up on each side of the valley of Santa Cruz. No possible 
action of any flood could thus have modelled 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 been 
hollowed out. Although we know that there are tides which 
run within the Narrows 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 surf, must 
have required to have corroded so vast an area and thickness 
of solid basaltic lava. Nevertheless, we must believe that the 
strata undermined by the waters of this ancient strait were 
broken up into huge fragments, and these lying scattered on the 
beach were reduced first to smaller 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 ram¬ 
bling up some of the narrow and rocky defiles, I could almost 
have fancied myself 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 reservoir for the scanty rain-water ; and 
consequently on the line where the igneous and sedimentary 
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 green 
herbage. 
April 2'jth .—The bed of the river became rather narrower, 
and hence the stream more rapid. It here ran at the rate of 
six knots an hour. From this cause, and from the many great 
angular fragments, tracking the boats became both dangerous 
and laborious. 
This day I shot a condor. It measured from tip to tip of 
the wings eight and a half feet, and from beak to tail four 
