of the Atmofphere. ~ viz 
this equilibrium is deftroyed, the atmofphere -returns to its 
former ftate as. foon as the caufe of this derangement is re- 
moved. If this equilibrium is by any caufe deftroyed in any 
one place, a movement muft naturally follow from all fides, 
and continue until the equilibrium is again reftored; and in 
this we may difcover the principal caufe of the origin of 
wind. Every thing, therefore, which can derange the equi- 
librium of the atmofphere in any manner, muft be reckoned 
among thofe caufes which give rife to wind: fuch as the flux 
and reflux of the atmofphere, occafioned by attraGtion and 
heat; all other rarefaGtion of the air by heat; or the con- 
denfation of it by cold, &c.; the letting loofe of vapours by 
fermentation and evaporation into the atmofphere; the erup- 
tion from the bofom of the earth and afcent of elaftic vapours, 
volcanoes, earthquakes, and perhaps other caufes not fo evi- 
dent, and therefore lefs known. The exceedingly variable 
diregtions of the wind depend on the nature of the countries 
from which they blow; and, in particular, on mountains, 
forefts, rivérs, marfhes, lakes. In a word, every thing that 
‘ean oppofe or favour the free movement of the aérial fluid 
‘has an influence on the dire€tion of the wind. 
Among all thofe caufes which derange the equilibrium of 
the atmofphere, and contribute to the production of wind, 
. the principal and moft uniform is the rarefaction and con- 
denfation of the air, Both are the immediate effe&t of the 
different atmofpheric tides. The regular courfe of thefe tides 
from eaft to weft, in confequence of that of the fun and 
‘moon, muft produce a continual eaft wind; which is how- 
ever exceedingly weak, but continues without interruption, 
and prevails only in the immenfe feas of the Torrid zone, 
though with moft regularity in the Pacific ocean, on account 
of its va(t extent, The comprefied parts of the atmofphere 
in the neighbourhood ruth towards thofe moft rarefied by the 
atmofpheric tides, and follow them alfo.in their regular pro- 
grefs from eaft to weft. The parts of the atmofphere, how- 
ever, in the weft, will have a much lefs, or perhaps no move-~ 
ment towards thofe which proceed from the eaft, on account 
pf the atmofpheric flux moving towards them: at afy rate, 
the motion from eaft to weft will exceed that fmall motion 
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