ON THE AMAZON AND RIO NEGllO. 35 



an Indian village at the foot of the first falls, which I made my princi- 

 pal station, to be 0^ 13' N. My watch has proved almost useless in 

 determining longitudes, and I much regret I did not bring with me a 



■ 



telescope. I purchased indeed a telescope in the Barra of a rrauclscan 

 friar, who had bought it at Eio Janeiro; and it has proved of the 

 greatest service to me in my herborizations, enabling me to distinguish 

 green flowers on a tree at the distance of a mile, and, when sailing near 

 the bank of a river, to ascertain the form of the leaves of the adjacent 

 trees ; but it barely shows the satellites of Jupiter, and is not sufficiently 

 powerful to take an observation of them with accuracy. 



I intended at this time to have transmitted to Sir F, Beaufort my ba- 

 rometrical register, and a few scattered geographical observations ; but 

 have not time to copy them out. He did not state, along with the aneroid 

 he kindly sent me, whether or not it corresponded exactly with the mer- 

 curial barometer when it was put up. When I opened it out at the 

 Barra do Eio Negro, in September 1851, the zero point was consider- 

 ably higher than it ought to be (as much as four-tenths of an inch), and 

 it seems to have gone on gradually rising ever since. The instrument 

 however may be depended on for horary differences, and for low alti- 

 tudes. I mark every day the maximum and minimum ; and it is inte- 

 resting to observe with what regularity the atmospheric tides recur on 

 the equator, being apparently totally uninfluenced by changes in the 

 weather. During the space of nearly two years, it has only twice oc- 

 curred that the minimum has been considerably retarded beyond its 

 usual hour, which is from three to four o'clock, while the maximum is 



attained between nine and ten. 



Ever since I have been on the Eio Xegro, I have made inquiries re- 

 specting the position and possible means of reaching the sources of the 

 Orinoco, without any expectation however, on my part, of being able to 

 solve this interesting geographical problem. Quite unexpectedly the 

 means of doing it seem about to be placed within my reach. We were 

 lately visited at San Carlos by the Commisario Geral of the Canton of 

 the Eio Negro, Don Gregorio Diaz, who resides at San Fernando de 

 Atabapo ; and on my mentioning to him how much I should like to 

 reach the head-waters of the Orinoco, he at once entered ardently into 

 the project, saying that it was what he had all his life been longing to 

 do, and that if I would promise to accompany him, he would arrange 

 as many men well-armed as he could, to start on the expedition early in 



