327 



perature of the hottest month at Cairo is only 

 29'9°; it is at Madras 31 8°; and at Abushar, 

 in the Persian Gulf, where regular observations 

 have been made, it is 34° ; but the mean tem- 

 perature of the whole year is lower at Madras, 

 and at Abushar, than at Calabozo. Although 

 a part of the Llanos is traversed, like the 

 fertile steppes of Siberia, by little rivers, and 

 banks extremely arid are surrounded by land 

 that is inundated in the season of rains, the 

 air is in general very dry. The hygrometer of 

 Deluc* kept during the day at 34°, and by 

 night at 36°. 



In proportion as the Sun rose toward the 

 zenith, and the earth and the strata of superin- 

 cumbent air took different temperatures, the 

 phenomenon of mirage displayed itself with it's 

 numerous modifications. This phenomenon is 

 so common under every zone, that I mention it 

 only because we stopped to measure with some 

 precision the breadth of the aerial interstice 

 between the horizon and the suspended object. 

 There was constantly suspension, without inver- 

 sion. The little currents of air, that swept the 

 surface of the soil, had so variable a temperature, 

 that in a drove of wild oxen, one part appeared with 

 the legs raised above the surface of the ground, 

 while the other rested on it. The aerial inter- 



* See above, eh. xv, p. 80 of this vol. 



