7 



regularly every day under the tropics, we as- 

 certained the possibility of taking the level of 

 the country by means of the barometer, without 

 employing correspondent observations at Cu- 

 mana. The greatest changes in the pressure of 

 the air in these climates, on the coasts, arise 

 only to 1 — 1*3 of a line; and if at any given 

 hour, or place, the height of the mercury be 

 once marked, we may with some probability 

 determine the variations, which this height ex- 

 periences throughout the whole year, at every 

 hour of the day or night*. Hence it results, 

 that, under the torrid zone, the want of corres- 

 pondent observations can scarcely produce an 

 error exceeding 12 or 15 toises, which is of 

 small importance relative to geological levelling, 

 or the influence of height on the climate, and 

 the distribution of plants. 



The morning was deliciously cool. The road, 

 or rather path, that leads to Cumanacoa, fol- 

 lows the right bank of the Manzanares, pass- 

 ing by the hospital of the Capuchins, situate 

 in a small wood of lignum vitae and arbores- 

 cent capparis*f\ On leaving Cumana we en- 

 joyed during the short duration of the twilight 



* See my Astronomical Observations, vol. 1. p. 289. 



f These caper-trees are called in the country, pachaca, 

 olivoj ajito : they are the capparis tenuisiliqua, Jacq., c. ferru- 

 ginea, c. emarginata, c. elliptica, c. reticulata, c. racemosq. 



