385 



only compared the temperatures indicated by 

 the degrees of the thermometer. A stagnant 

 air ingulfed in a hollow of the mountains, in 

 contact with a mass of barren rocks, acts dif- 

 ferently on our organs from air equally hot in 

 an open country. I am far from looking for 

 the physical cause of this difference only in 

 the modifications of the electrical charge of the 

 air ; I must however add, that a little to the 

 east of La Guayra, on the side of Macuto, far 

 from houses, and more than a hundred toises 

 distant from the rocks of gneiss, I could scarce- 

 ly obtain during several days a few feeble 

 signs of positive electricity ; while at the 

 same hours of the afternoon at Cumana, and 

 with the same electrometer of Volta, armed 

 with a smoking match, I observed a separation 

 of the balls of pith of elder from one to two 

 lines. I shall notice farther on the regular va- 

 riations which the electrical charge of the air 

 undergoes every day in the torrid zone, and 

 which indicate a striking relation between the 

 changes of the temperature and the height of 

 the Sun. The examination of the thermome- 

 trie observations, made during nine months 

 at La Guayra by a distinguished physician *, 



* Don Joseph Herrera, correspondent of the Medical 

 Society of Edinburgh. The observations (from the 2d of 

 May 1799 to the 17th of January 1800) were made in the 

 shade, far from the reflection of walls, with a thermometer 

 VOL. III. 2 c 



