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Of oppofite Concomitant Winds. 



It has often been obferved*, but of late, fince the invention of 

 baloons, evidently proved, that currents of air from different and 

 even oppofite points of the horizon, prevail at different heights in 

 the atmofphere, over the fame trads of land or water. This was 

 originally inferred from the different courfes of the higher and lower 

 clouds ; but as fuch obfervations were often liable to optical decep- 

 tions, better proofs were wanting. 



Mont Louis is within thirty miles of Perpignan, but about 

 5000 feet higher. Now in March 17S0 north and north-caft winds 

 prevailed at Perpignan and a wefterly wind at St. Louis. In 

 Auguft a north wind prevailed at Perpignan and an call: at Mont 

 Louis. Mem. De La Societe de Medecine de Paris, 1780. Der- 

 ham fufpededf , and Gentil has fince fhewn, that changes of fea- 

 fons conftantly begin in the upper atmofphere; while a flrong 

 wind blows from one point below, a wind from an oppofite point 

 reigns above, but more gentle, until at laft (in about three weeks) 

 it is propagated downwards. 2 Voy. p. 23 and 24., in 8vo. The 

 lower atmofphere, he fays, extends to the height of 2880 feet. 



4 vol. 



* 2 Ulloa's Voy. p. 62, Englifh. 



f 4 Phil, Tranf. Abridg. 2 Part. 125. 



