Chap. VII. EIO NEGRO. 335 



ber of discoloured punctures that are crowded together. 

 The irritation they produce is more acutely felt by some 

 persons than others. I once travelled with a middle- 

 aged Portuguese, who was laid up for three weeks 

 from the attacks of Pium ; his legs being swelled to 

 an enormous size, and the punctures aggravated into 

 spreading sores.* 



A brisk wind from the east sprang up early in the 

 morning of the 22nd : we then hoisted all sail, and made 

 for the mouth of the Rio Negro. This noble stream at 

 its junction with the Amazons, seems, from its j^osition, 

 to be a direct continuation of the main river, whilst the 

 Solimoens which joins at an angle and is somewhat nar- 

 rower than its tributary, appears to be a branch instead 

 of the main trunk of the vast water-system. One sees 

 therefore at once, how the early explorers came to give a 

 separate name to this upper part of the Amazons. The 

 Brazilians have lately taken to applying the convenient 

 term Alto Amazonas (High or Upper Amazons), to the 

 Solimoens, and it is probable that this will gradually 

 prevail over the old name. The Rio Negi'o broadens 

 considerably from its mouth upwards, and presents the 

 appearance of a great lake ; its black -dyed waters hav- 

 ing no current, and seeming to be dammed up by the 

 impetuous flow of the yellow, turbid Solimoens, which 

 here belches forth a continuous line of uprooted trees 



* The Piiim belongs probably to tbe same species as tlie Mosquito of 

 the Orinoco, described by Humboldt, and which he referred to the 

 genus Simulium, several kinds of which inhabit Europe. Our insect 

 is nearly allied to Simulium, but differs from the genus in several points, 

 chiefly in the nervures of the wings. 



