RAPIDS AND THUNDER-STORM. 935 
nous plants. There was therefore a remote period, 
when the tribes of vegetables were differently dis- 
tributed ; when the animals were larger, the rivers 
wider and deeper. There stop the monuments of 
nature which we can consult. We are ignorant if 
the human race, which at the time of the discovery 
of America scarcely presented a few feeble tribes to 
the east of the Cordilleras, had yet descended into 
the plains, or if the ancient tradition of the Great 
Waters, which we find among all the races of the 
Orinoco, Erevato, and Caura, belong to other cli- 
mates, whence it had been transferred to this part 
of the new continent.” 
On the llth they left Carichana at two in the 
afternoon, and found the river more and more en- 
cumbered by blocks of granite. At the large rock 
‘known by the name of Piedra del Tigre, the depth 
is so great that no bottom can be found with a line 
of 140 feet. Towards evening they encountered 
a thunder-storm, which for a time drove away the 
mosquitoes that had tormented them during the 
day. At the cataract of Cariven the current was 
so rapid that they had great difficulty in landing ; 
but at length two Saliva Indians swam to the shore, 
and drew the canoe to the side with a rope. The 
thunder continued a part of the night, and the 
river increased considerably. The granitic rock on 
which they slept, is one of those from which tra- 
vellers on the Orinoco have heard subterranean 
sounds, resembling those of an organ, emitted about 
sunrise. Humboldt supposes that these must be 
produced by the passage of rarefied air through 
the fissures, and seems to think, that the impulse 
of the fluid against the elastic scales of mica which 
