ANNOTATIONS AND ADDITIONS. 191 



plished traveller who, in pursuit of an object deriving all its interest 

 from the mind namely, in the self-imposed task of penetrating from 

 east to west, from the Valley of the Essequibo to Esmeralda suc- 

 ceeded, after five years of efforts and of sufferings (which I can in 

 part appreciate from my own experience), in reaching the goal which 

 he had proposed to himself. Courage for the momentary execution 

 of a hazardous action is more easily met with, and implies less of 

 inward strength, than does the resolution to endure patiently long- 

 continued physical sufferings, incurred in the pursuit of some deeply- 

 felt mental interest, and still to determine to go forward, undismayed 

 by the certainty of having to retrace the same painful route, and to 

 support the same privations in returning with enfeebled powers. 

 Serenity of mind, almost the first requisite for an undertaking in in- 

 hospitable regions, passionate love for some class of scientific labor 

 (be it in natural history, astronomy, hypsometrics, magnetism, or 

 aught else), and a pure feeling for the enjoyment which nature in 

 her freedom is ready to impart, are elements which, when they meet 

 together in an individual, ensure the attainment of valuable results 

 from a great and important journey." 



In discussing the question respecting the sources of the Orinoco, 

 I will begin with the conjectures which I had myself formed on the 

 subject. The dangerous route travelled in 1739 by the surgeon 

 Nicolas Hortsmann, of Hildesheim; in 1775 by the Spaniard Don 

 Antonio Santos,, and his friend Nicolas Rodriguez ; in 1793 by the 

 Lieutenant-Colonel of the 1st regiment of the Line of Para, Don 

 Francisco Jose Rodriguez Barata; and (according to manuscript 

 papers, for which I am indebted to the former Portuguese Ambas- 

 sador in Paris, Chevalier de Brito) by several English and Dutch 

 settlers, who in 1811 went from Surinam to Para by the Portage of 

 the Rupunuri and by the Rio Branco j divides the terra incognita 

 of the Parime into two unequal portions, and serves to limit the situa- 

 tion of a very important point in the geography of those, regions 

 viz. the sources of the Orinoco, which it is no longer possible to 

 remove to an uncertain distance to the East, without interfering 

 thereby with what we know of the course of the Rio Branco, which 

 flows from north to south through the basin of the Upper Orinoco : 

 while that river itself, in this part of its course, pursues for the most 



