ATMOSPHERIC CUBBLHTTB. 147 



the zeiiith can have so powerful an influence on the meteo- 

 rological variations ? 1 am of opinion that no local cause 

 determines the commencement of the rains within the tro- 

 pics ; and that a more intimate knowledge of the higher 

 currents of air will elucidate these problems, so complicated 

 in appearance. We can observe only what passes in the 

 lower strata of the atmosphere. The Andes are scarcely 

 inhabited beyond the height of two thousand toises ; and at 

 that height the proximity of the soil, and the masses of moun 

 tains, which form the shoals of the aerial ocean, have a sen- 

 sible influence on the ambient air. What we observe on 

 the table-land of Antisana is not what we should find at the 

 same height in a balloon, hovering over the Llanos or the 

 surface of the ocean. 



We have just seen that the season of rains and storms in 

 the northern equinoctial zone coincides with the passage of 

 the sun through the zenith of the place,* with the ces- 

 sation of the north-east breezes, and with the frequency 

 of calms and bendavales, which are stormy winds from 

 south-east and south-west, accompanied by a cloudy sky. 

 I believe that, in reflecting on the general laws of the 

 equilibrium of the gaseous masses constituting our atmo- 

 sphere, we may find, in the interruption of the current that 

 blows from an homonymous pole, in the want of the renewal 

 of air in the torrid zone, and in the continued action of 

 an ascending humid current, a very simple cause of the 

 coincidence of these phenomena, While the north-easterly 

 breeze blows with all its violence north of the equator, it 

 prevents the atmosphere which covers the equinoctial lands 

 and seas from saturating itself with moisture. The hot and 

 moist air of the torrid zone rises aloft, and flows off" again 

 towards the poles; while inferior polar currents, bringing 

 drier and colder strata, are every instant taking the place of 

 the columns of ascending air. By this constant action of 

 two opposite currents, the humidity, far from being accumu- 

 lated in the equatorial region, is carried towards the cold 

 and temperate regions. During this season of breezes, 

 which is that when the sun is m the southern signs, the 



These passages take place, in the fifth and tenth degrees of north lat. 

 between the 3rd and the 16th of April, and between the 27th of August 

 And the 8th of September. 



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