THUNDER-STORM MYSTERIOUS SOUNDS. 203 



vegetables were differently distributed; 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 Cor- 

 dilleras, 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 climates, 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 thun- 

 der continued a part of the night, and the river in- 

 creased considerably. The granitic rock on which 

 they slept is one of those from which travellers on 

 the Orinoco have heard subterranean sounds, re- 

 sembling 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 intercept the crev- 

 ices may contribute to modify their expression.* 



* Many examples of mysterious sounds produced under similar cir- 

 cumstances are on record. In the autumn of 1828, a recent traveller 

 crossing the Pyrenees, when in a wild pass with the Maladetta moun- 

 tain opposite, heard "a dull, low, moaning, JEolian sound, which alone 

 broke upon the deathly silence, evidently proceeding from the body of 

 this mighty mass." The air was perfectly calm, and clear to an extra- 

 ordinary degree ; no waterfall could be seen even with the aid of a tele- 



