ANNOTATIONS AND ADDITIONS. 239 



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. Se- 

 renity of mind, almost the first requisite for an undertaking 

 in inhospitable regions, passionate love for some class of 

 scientific labour, (be it in natural history, astronomy, hypso- 

 metrics, magnetism, or aught else,) and a pure feeling for 

 the enjoyment which nature in her freedom is ready to im- 

 part, 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 j 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 Ambassador 

 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 Bio Branco ; divides the 

 terra incognita of the Parirne into two unequal portions, and 

 serves to limit the situation 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 dis- 

 ance to the East, without interfering thereby with what we 



