441 



sitions from the water, and the water having 

 less velocity in proportion as it is more remote 

 from it's source, deposing necessarily more in 

 the lower than in the upper part of it's course, 

 many rivers of hot climates undergo a diminu- 

 tion in the quantity of their water, as they ap- 

 proach their mouth. Mr. Barrow has observed 

 these curious effects of sands in the southern 

 part of Africa, on the banks of Orange river. 

 They are even become the subject of a very im- 

 portant discussion, in the various hypotheses 

 that have been formed on the course of the 

 Niger. 



Near the Vuelta de Basilio, where we landed 

 to collect plants, we saw on the top of a tree 

 two beautiful little monkies, black as jet, of the 

 size of the sai, with prehensile tails. Their 

 physiognomy and their movements sufficiently 

 showed, that they were neither the quato [simia 

 beehebub, L.], nor the chamek, nor any of the 

 ateles. Our Indians themselves had never seen 

 any that resembled them. These forests abound 

 in sapajous unknown to the naturalists of Eu- 

 rope; and as monkeys, especially those that 

 live in troops, and for this reason are more enter- 

 prising, make long emigrations at certain pe- 

 riods, it happens, that at the beginning of the 

 rainy season the natives discover round their 

 huts different kinds, which they had never before 

 observed. On this same bank, our guides showed 



