m 



Often, in a very strong wind, we enjoyed an 

 extraordinary coolness, although the thermo- 

 meter had only lowered 1.5° R., and the hygro- 

 meter of Deluc had moved but 3° towards the 

 point of extreme humidity. The stars do not 

 scintillate at Cumana, above 25° of elevation ; 

 yet on the 24th and 26th of October, the scintil- 

 lation became very sensible to the zenith, when 

 the thermometer had descended rapidly to 

 18.5° R. The scintillation seems to augment 

 at Cumana, less by the humidity, than by a 

 sudden cooling, and by ascending and descend- 

 ing currents that mix layers of air of very dif- 

 ferent densities. The hygrometer indicates so 

 little scintillation, that I have seen it pass from 

 50° to 59°, even to 62° (division of Deluc), and 

 yet the stars, far from scintillating, preserved, 

 below 25°, their tranquil and planetary light. 

 These phenomena confirm the ingenious expli- 

 cation given by M. Arago, of scintillation. 

 (Vol. iii, p. 313-315, 538; Vol. iv, 94, 467). 

 No hail ever falls at Cumana, although the 

 electric explosions are frequent two hours after 

 the maximum of heat. When the thermometer 

 was 24° R. in the air, the coolest water which 

 the inhabitants prepared by evaporation (by 

 exposing it to the currents of air, in pots that 

 transude a little), was 21° R. Mr. Chisholm 

 says " I never could refresh water within the 

 tropics, in vases, below 72° Fahr." (17.7° R.) 



VOL. VI. 3 F 



