2GC NAVIGATION OF THI EAPIDS. 





placed under them to serve as rollers, they are drawn as far 

 as the place where the river again becomes navigable. This 

 operation is seldom necessary when the water is high. "We 

 cannot speak of the cataracts of the Orinoco without recal- 

 ling to mind the manner heretofore employed for descending 

 the cataracts of the Nile, of which Seneca has left us a 

 description probably more poetical than accurate. I shall 

 cite the passage, which traces with fidelity what may be seen 

 every day at Atures, Maypures, and in some pongos of the 

 Amazon. " Two men embark in a small boat ; one steers, 

 and the other empties it as it fills with water. Long buffeted 

 by the rapids, the whirlpools, and the contrary currents, 

 they pass through the narrowest channels, avoid the shoals, 

 and rush down the whole river, guiding the course of the 

 boat in its accelerated faj.." * 



In hydrographic descriptions of countries, the vague 

 names of cataracts, cascades, falls, and rapids,f denoting 

 those tumultuous movements of water which arise from 

 very different circumstances, are generally confounded witL 

 one another. Sometimes a whole river precipitating 

 itself from a great height, and by one single fall, renders 

 navigation impossible. Such is the majestic fall of the 

 Rio Tequendama, which I have represented in my " Views 

 of the Cordilleras;' such are the falls of Niagara and 

 of the Rhine, much less remarkable for their elevation, 

 than for the mass of water they contain. Sometimes stony 

 dikes of small height succeed each other at great distances, 

 and form distinct falls ; such are the cachoeiras of the Rio 

 Negro and the Rio Madeira, the saltos of the Rio Cauca, 

 and the greater part of the pongos that are found in the 

 Upper Marafion, from the confluence of the Chinchipe to 

 the village of San Borja. The highest and most formidable 

 of these pongos, which are descended on rafts, that of 

 Mayasi, is however only three feet in height. Sometimes 

 small rocky dikes are so near each other that they form 

 for several miles an uninterrupted succession of cascades 

 and whirlpools (chorros and remolinos) ; these are properly 



* Nat. Qusest., lib. iv, cap. 2. (edit. Elzev., torn, ii, p. 609.) 

 f The corresponding terms in use among the people of Soutb America, 

 re saltos, chorros, pongos, cachoeiras, and raudalea. 



