252 THE NARROW OF RKNTEMA. 



locks by whicli all these Narrows were formed underwent 

 many changes in the course of centuries. Thus a part 

 of the rocks forming the Narrow of Rentema, had been 

 broken up by a high flood a year before Humboldt's 

 journey ; and there had been preserved among the inha- 

 bitants, by tradition, a lively recollection of the precipitous 

 fall of the then towering masses of rock along the whole 

 of the Narrow — an event which took place in the early 

 part of the eighteenth century. This fall, and the con- 

 sequent blocking-up of the channel, arrested the flow of 

 the stream ; and the inhabitants of the village of Puaya, 

 situated below the Narrow of Rentema, saw with 'alarm 

 the wide river-bed entirely dry : but after a few hours 

 the waters again forced their way. Earthquake move- 

 ments were not supposed to have occasioned this remark- 

 able occurrence. The powerful stream appeared to be 

 incessantly engaged in improving its bed, and some idea 

 of the force which it exerted may be formed from the 

 circumstance, that notwithstanding its breadth it was 

 sometimes so swollen as to rise more than twenty -six feet 

 in the course of twenty or thirty hours. 



The travellers remained for seventeen days in the hot 

 valley of the Upper Amazons. Here Humboldt cor- 

 rected and revised the chart of the Amazon made by 

 Condamine, by sketching an accurate chart of this un- 

 known portion of the great river, partly from his own 

 observations, and partly from careful inquiries. This 

 done they ascended the easte^^n declivity of the Cordil- 

 leras, and arrived at the argentiferous mountain of Gual- 

 gayoc, the principal site of the silver mines of Chota. 

 Gualgayoc was an isolated mass of siliceous rock, tra- 

 versed by a multitude of veins of silver which often in- , 



