-W I N 
thici. 1 black (as they generally are when fnow 
follows j ) and that, a little before noon, the Wind 
veered about to the north by weft, and lometimes to 
other points ; the clouds at the fame time flying 
fame north by weft, and fo me fou th -weft ; that about 
one o’clock it rained apace, the clouds fometimes 
flying north-eaft, then north and at laft both Winds 
and clouds have fettled north by weft ; and at that 
time the fleet fell very plentifully, and it grew 
very cold. 
From all which he obferves ; / 
Fir ft, that though the region bekw was warm, th< 
, region of t’ n e clouds was cold, as the black Inowy 
clouds fhev/ed. 
Secondly, That the ftruggle between the warmth o~ 
our region, and the cold of the cloudy region ftoppe.. 
the airy currents of both regions. 
Thirdly, That the falling of the fnow through our 
warmer air, did at firft melt into rain ; but after the 
fuperior cold had conquered the inferior warmth, it 
became fleet. 
Fourthly, That as the cold prevailed by degrees, it 
wheeled' about both the Winds and clouds, from the 
northward towards the fouth. 
; It is not at all improbable, that there is often affem- 
bled in the atmofphere, a iufflcient quantity of va- 
pours to maintain a lading condenfation •, and that it 
is alio quick enough at fome times to create a great 
Wind. 
For according to Dr. Halley’s experiment, it may t i 
computed, that there is 129,762,219 cubical miles j 
the atmofphere filled by vapours every day. This p: 
digious quantity, being divided and ranged in bou.cs 
at various fituations throughout the world, occanons, 
by the mutual condenfations, almoft confcant relults 
of the air, to fupply the empty places ; fo may be 
thought abundantly fufticient for producing and main- 
taining ail Winds univerfally. 
From thefe and other confiderations, it may be con- 
cluded, that the production' of Winds depends chiefly 
on the condenfadon of vapours ; and in order to con- 
firm this hypothefis, we (hall proceed to explain feve- 
ral properties and cafes foivable thereby. 
1. That the direction or courfe of any Wind is accord- 
ing to the fltuation of the body of vapours, whofe 
condenfation produces it ; fo if a concourfe of vapours 
be gathered over the kingdom of France, the conden- 
fation thereof would draw the air from England in a 
foutheriy direction, in Spain would be a ■ northerly 
Wind, in Germany would blow wefterly, at the Bay 
of Bifcay an eafterly Wind. 
2. That the force or intenfiry of a Wind is the exten- 
fion of the condenfing vapoun, and the quicknefs of 
their condenfations. 
3. This may account for there being more Winds 
about the equinoxes than at other feafons. 
4 We muff add that it is underftood, that the great- 
er quantities of rain that fall in the winter, muft 
occaiion more Winds than in fummer, there being a 
proportionable quantity of vapours condenfed ; and 
iikewife, 
5. That there are more Winds in diftant latitudes than 
toward the equator j becaufe the former are more 
fubject to rain. 
6. Why there is more rain and Wind in the winter 
than in the fummer, when the heat of the fun is in the 
former more weak and languid, by which it is inca- 
pable of raffing any great quantity of vapour to pro- 
duce that rain, and Wind. 
7. Why they have more rain and Wind toward the 
poles and about the equator, although, the latter is a 
part of the world where the fun makes the greateft 
evaporation. 
A 
The induftry of fome late writers have brought the 
theory and production, and motion of the Winds, to 
fomewhat of mathematical demonftration, we ftrall 
here give it to the reader in that form. 
Laws of the 'productions &c. of Winds . 
1. If the fpring of the air be weakened in any place., 
more than in the adjoining places, a Wind will blow 
through the place where the diminution is. 
For fince the air endeavours by its elaftic force to ex- 
pand itfelf every way, if that force be lefs in one 
place than another, the nifus of the more againft the 
Ids elaftic will be greater, than the nilus of the lat- 
ter againft the former. — The lefs elaftic air, there- 
fore, will- reflft with lefs force than it is urged by the 
more elaftic ; confequently, the lefs elaftic will be 
driven out of its place, and the more elaftic will 
fucceed. 
If now the excefs of the fpring of the more elaftic, 
to that of the lefs elaftic, be fuch as to occafion a little 
alteration in the barofeope, the motion both of the 
air expelled, and that which fucceeds it will become 
fenfible. 
2. Hence, fince the fpring of the air increafes, as the 
comprefling weight increales, and compreffed air is 
denfer than air lefs compreffed, all Winds blow into a 
rarer air out of a place filled with a denfer. 
3. Wherefore fince a denfer air is fpecificallv heavier 
than a rarer, an extraordinary lightnefs of the air in 
any place, muft be attended with extraordinary Winds 
or ftorms. 
Now an extraordinary fail of the mercury in the ba- 
rometer, fhews an extraordinary lightnefs of the at- 
mpfphere - s therefore it is no wonder if that foretels 
ftorms. . 
4 rr “he air be fuddehlv condenfed in any place, its 
-ng will be fuddenly dimimfhed •, hence, if this di- 
minution be great enough toaffed the barometer, there 
will be a Wind blow through the condenfed air. 
5. But fince it cannot be fuddenly condenfed, unlefs 
it has before been much rarefied, there will a Wind 
blow through the air as it cools, after it is violently 
heated. 
6. In like manner if air be fuddenly rarefied, its fpring 
is fuddenly increafed •, wherefore it will flow through 
the contiguous air, not afted on by the rarefying 
force. — A W ind therefore will blow out of a place in 
which the air is fuddenly rarefied ; and on this prin- 
ciple it is, in all probability, that 
7. Moft caves are found to emit Wind, either more 
or lefs. — Since the fun’s power in rarefying the air is 
notorious, it muft neceffarily have a great influence 
on the generation of Vvflnds. 
The rifing and changing of the Wind is determined 
experimentally, by means of weather-cocks placed 
on the tops of houfes, &c. — But thefe only indicate 
what paffes about their own height, or near the fur- 
face of the earth ; Wolfius affuring us, from obfer- 
vations of feveral years, that the higher Winds which 
drive the clouds, are different from the lower ones, 
which move the weather-cocks. 
Dr. Derham obferves, upon comparing feveral feries 
of oblervations made of the Winds in divers countries, 
viz. England, Ireland, Switzerland, Italy, France, 
New England, &c. that the Winds in thole feveral 
places leldom agree •, but when they do, it is com- 
monly when they are ftrong, and of long continuance 
in the fame quarter ; and more, he thinks, in the 
northerly and eafterly, than in any other points.* — Al- 
fo, that a ftrong Wind in one place is oftentimes a 
weak one in another ; or moderate, according as the 
places are nearer or more remote. 
The laws of the force and velocity of Wind. 
Wind being only air in motion, and air a fluid fub- 
je6t to the laws of other fluids, its force may be 
brought to a precife computation : thus •, 
The ratio of the fpecific gravity of any other fluid 
to that of the air, together with the fpace that fluid, 
impelled by the preffure of the air, moves in any 
given time, being given ; we can determine the fpace 
14 T which 
483 
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