412 



the preponderance of the families of the gutti- 

 ferae, the sapotae, and the laurinese, in the equa- 

 torial regions. The serenity of the sky promis- 

 ing us a fine night, we resolved at five in the 

 evening to rest near the Piedra di Culimacari, 

 a solitary granitic rock, like all those which I 

 have described between the Atabapo and the 

 Cassiquiare. We found by the bearings of the 

 sinuosities of the river, that this rock is nearly 

 in the latitude of the mission of San Francisco 

 Solano. In those desert countries, where man 

 has hitherto left only fugitive traces of his exist- 

 ence, I constantly endeavoured to make my ob- 

 servations near the mouth of a river, or at the 

 foot of a rock distinguishable by it's figure. It 

 is such points only, immutable by their nature, 

 that can serve for the basis of geographical 

 maps. I obtained in the night of the 10th of 

 May a good observation * of latitude by & of 

 the Southern Cross ; the longitude was deter- 

 mined, but with less precision, by the time- 

 keeper, taking the altitudes of the two beautiful 

 stars which shine in the feet of the Centaur. 



* All the partial altitudes differ but from six to ten se- 

 conds from the mean latitude. See my Obs. Astr., vol. i, p. 

 239. A defect in the figures in my journal would have 

 rendered the longitude uncertain to forty-four seconds of 

 time, or nearly one sixth of a degree j but the horary angles 

 taken at San Carlos being exact to three or four seconds 

 nearly, we have reduced the longitude of Culimacari from 

 that of the little fort of S. Carlos. 



