168 VIEWS OF NATURE. 



by the reflecting surface of decomposing talc, or mica 

 schist. 



During the five days that we passed in the neighbourhood 

 of the cataracts, we were much struck by the fact that the 

 roar of the rushing torrent was three times as great by 

 night as by day. The same phenomenon is observed in all 

 European waterfalls. To what can we ascribe this effect in a 

 solitude where the repose of nature is undisturbed? Pro- 

 bably to ascending currents of warm air, which producing an 

 unequal density of the elastic medium, obstruct the propa- 

 gation of sound by displacing its waves ; causes which cease 

 after the nocturnal cooling of the earth's surface. 



The Indians showed us traces of ruts caused by wheels. 

 They speak with wonder of the horned cattle, (oxen,) which 

 at the period of the Jesuit missions used to draw the 

 trucks, that conveyed the canoes, along the left shore of the 

 Orinoco, from the mouth of the Cameji to that of the Toparo. 

 The canoes at that time were transported without the dis- 

 charge of their cargoes, and were not as now injured by being 

 constantly dragged over sharp-pointed rocks, or stranded. 



The topographical plan which I have sketched of the locality, 

 shews that a canal might be opened between the Cameji 

 and the Toparo. The valley in which these two abundantly 

 watered rivers flow is a gentle level ; and the canal, of which I 

 suggested a plan to the Governor-General of Venezuela, would 

 become a navigable arm of the Orinoco, and supersede the 

 old and dangerous bed of the river. 



The Raudal of Atures is exactly similar to that of 

 May pur es, like which it consists of a cluster of islands between 

 which the river forces itself a passage extending from 18,000 

 to 24,000 feet. Here too a forest of palm trees rises from 

 the midst of the foaming surface of the waters. The most 

 celebrated ledges of the cataract are situated between the 

 islands of Avaguri and Javariveni, between Suripamana and 

 Uirapuri. 



