Concerning the Cause of the General Trade-Winds: By Geo. Hadley, Esq; F. R. S.
Author(s): Geo. Hadley
Source: Philosophical Transactions (1683-1775), Vol. 39 (1735 - 1736), pp. 58-62
Published by: The Royal Society
Stable URL: http://www.jstor.org/stable/103976 .
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( )8 )
left entirelydiJengaged,
andLil)ertyby thismeans
be givento ReEpiration
to makeboththeAlralone,
andtheAirmix'dwith the Tears,to pafscontinu
ally throughit.
In fille,theAdtionof theSeFluidsmaybe affiiRed
by the Appicationof Collrigms) andby making
frequentInjeAionsinto the PgnSa JacremaZia;
which,befidesthe cornanon
ESecLs
rhattuaybe t1aturallyexpedledfromtnem,xvillcontribute
to preb
ventthe Juice, thatre-unitesthe Woundmadeill
the Skin,fromover-fireight>ning
the Canal.
v.
coslcer?ZiRlF
theclre
ofrJ^-GeneralTrade
NSinds: §RyGeo. HsidtCy)
Fffiff;
F. (R.
S.
T ThinktheCauSesof tile GeneralTrade-Winds
1 haverlot been fuliy explained
by anyof tlzofe
whohavewroteon ehatSubjed,for xvalltof more
particularly
allddillirldbtiy
collfildering
the Sharethe
diurnallAiiotion
of the Eartlllas itl the Produd:ion
of them: Foralthough
-thishasl)cenmetltion
d by
fomeamongRthe CauSes
of thoSeWinds,yet they
halrenorproceededto Illewhowit contribures
to
theirProdudtxon
; orelfehaveappliedit to theEx_
plxcationof thelePhznomena,UpOll fitlchPrinciples as will appearupon Examination
not tO be
fufficient.
That theAd;tion
of the-Sunis the originalCauSe
of thefeTsnds, 1 thinkall areagreed, andthatit
does
( 59 )
of tlle Air
does it by caurlaga greaterRarefadtion
in thofePartsuponxs-llichits Raysfalllngperpendicularly,or rCarlyfo, producea greaterl)egreeof
Heat tlzere than in otherPlaces; by uthlchmeans
lighterthanthe
fpeciScally
tlle Airtherebeconzillg
reftroulldal)out,thecoolerAir\vill by rs greater
it outof its Placeto
andGravity,relnove
IJe£afty
fucceedinto it itS felf,alldmakeit rifeupssrards
Seems,this Rarefadl-ion haveno other
thanto cauSethe Airto rulllill fromallParts
EfFedc
into the PartwllerctiS S00 rarefied,eEpecially
theAir is coole>
fronztheNotthandSoutll?nvllere
and nor morefromtlle EaR thantheWeIt, as is
fuppoSed:tSothat,fetringafidcthe dicommoulyurnalMotionof the Eartll,the Tendencyof the
Air wouldbe fromescry Side toxvardsthatPart
Fttne Tinze,
theSun'sAdrionis mol}inte£afe
zZhere
and{o a N. T. Windbe producedin the Morning,
and a Nt.E.in the Afrernoou,by Turns-,on this
But it
utill
SIdeof the Parallelof tbe SUI1'S Declination;arlda
S.\Rf. and S.E. on theoehcr.
That the perpetualMotionof the Air towards
theWeR,cannotbederivedmeerlyfromtheAdtion
of the Sun uponit, appearsmoreevidentlyfrom
at ReR,thatMotion
this: 1f theEarthbe fiuppofed
tO the fuperficial
of the Airwill be communicated
Parts,andby littie andflittleproducea Revolution
of the Wholethe fameWay, excepttherebe the
fameQuantityof-Motiongiven the Air in a contraryDiredtionin otherPartsat the fameTimet
whicllis hardtO fuppoWe. Butif the Globeof thev
Earthhadbeforea Revolutiontowardsthe Ea0,
retardthisby the famemeansmuRbecontinually
H 2
ed:
( 60 )
ed : Andif thisMoeiollof the Airbe fupporedto
ariNefromany Adion of the Partsof it QU one
anotherX
the ConSequence
xvillbe thAfanze. For
this reafonit SeemsneceSaryto {hewhow thefe
Phzasmenaof the Trade-Winds
may be cauSed,
svithoutthe Produdrion
of anyrealgeneralA4OtiGA
of the Air>eftwards. This will readilybe done
by takingill the C:on&deration
of the diurnal
Mo-
tion of the lBarth: For, Ict us SuppoSe
the Air in
every Partto keepan equalPacexvithehe Earthin
its diurnalhIotion, in nvhichCaKe
therexxtillbe no
relativeNIoeioIlof the Sllrfaceof the EarthandAiry
and conSeaiuently
no Wind; then by the Adion of!
the Sun on the Parts about the Equator,and the
Rarefadrionof the Air proceedingtherefrot:n,let
the Air be drauZn
doxvnthitherfrom the N and S.
Parts. The Parallelsare each of thembiggerthatl
rheother, as theyapproachto the Equator,andthe
Equaeoris biggerthantheTropicks,nearlyitl the
Proportion
of tooo tO 9I7, andcouSequently
their
Diffierence
itl Circuitabout to83 Miles, andthe
Surfaceof the Earthat theI:quator
movesfo mucll
faIlerthan the Surficeof the Earthwithits Airat
the Tropicks. Fromwllichit folloxvs,thattheAir}
as it movesfromtheTropickstowardstheEquator,
havinga leSsVelocitythanthe Partsof tlle iDarth
it arrives ata will havea relativeMotioncontrary
to thatof the diurnal
Motionof theEarthin thoSe
Parts,which being combinedwith the Motion tov
wardstheEqllator,a N.E. Windwillbeproduc'd
on
this Sideof the E:quator,
anda S.E. on theSother.
TheSe,as theAircomesnearerto theEquator,wiIl
beso-mefirenger,and moreandmoreEafierls,and
be
( 61 )
to Exbe dueEaRat the EquatoritSelf,according
Curof lDoth
of the ConcourKe
perience,by reaSon
rentsfromtheN. andS. whereits Velocitywill be
at therate of to83 Milesin the Spaceof one Reor 297atural Day, and above
volutionof the E:arth
is greater
XMileand3 in a Minuteof Tiale; uthich,
thanthe Velocityof the Windis Suppofed to lzein
Storm, wllicll accordillgto Dr. SZ)erEvam'3
the greate{E
Oblervations,is nor above I lSlite in a Minute
thatbeforethe Airfrom
be confidered,
the Tropickscan arriveat the Equator,it muR
fromtheSurEace
havegainedfomeMotionEa(tutard
its relativeMotion
of the Earthor Sea,mJhereby
will be diminiihed,and in Severalfuccell:veCirc-ulatiotls,maybe fllppofedto-be reducedto the
it is foundto be of.
Strength
- ThusI thinkthe N.E. Willdson this Sideof rhe
andthe S.E. on the otherSideXarefully
Equator.>
accountedfor. The famePrincipleas neceSarily
BUt it iS tO
extendsto the Produdiorsof the WeRTrade-Winds
by eheHeat
withouttheTropicks; the Airrarefied
Parts?beingreof the Sun aboutthe Equatorial
fromtne cooler
Air
the
for
room
movedto make
arldas it
Parts,mullrifeupwardsfromthe E;arthX
is a Fluid,will then breaditEelfabroadover the
otherAit, andfo its Motiotlin the upperRegions
muAbe eo theN. arsdS fromtheEquator Being
goc up at a DiltancefromtheSurfaceof thel:arth,
it willfoonloSegreatPartof its Heat,andthereby
to makeit
acquireDenfityand Gravityfufficietle
SuppoIid
be
may
xvhich
agairl,
its Surface
approach
to be by thatTime'tis arrivedat ehofePartsbe_
yond the Tropickswherethe weRerlyWindsare
found.
rf 6
)
found. Being-Iilppos'd
at firRto have the Velocity
of the Surfaceof the Earthat the Equator,it will
llavea greaterVelocitytharlthe Pratts it now arrives
at; and tl;zerebyl)ecomea weRerly Windpnvith
Stren-gthp-roportionable
to the Di{krence of lTeloctty, svhichin SeveralRevolutionswill be reduced tO a certainDegree, as is faid before,cxf the
EafRerly Winds,
at the Equator : And thus the Alr
and gairs and lewSe-VeCoci.
ty by Turus from the Surfice of the Earth or Sea,
as it approaches
to or recedes from the Equator,
I do not think ic neceSary to apply theSe Principles
to folve the Phznomena
of the Variations
of thefe
Winds at diflRerent Times of the Year} and difFerent
Parts of the Earth-; and to do it vxould draw thesPaperinto greaterLengththanI propofe. From
xvhat has been Eaid it follows .
Wir/?, That- without the ASIlance
of the dturnal
Motion of theEarth, Navigation, efpecially EaReriy
and WeIlerlyX vvould be very tedioust ard to make
the xarhole Circuit of the Earth perhaps imprad;tiZ
cabie.
SerordD3t, That the N. E. and SZ E. Winds xvithin
thc Tropicks mulE be compenfated by as much N.W.
and S. W. in orner Parts, atld generally all 5>linds
from any on-e- Qarter
muR be compeaSated by a
contrary Wind lome where or other;
otherwiKe
N-ill
continue
tO circulate,
ChangemuRbe produced
in theMotionof
theEarthrz3und
itsAxis.
10me
VIT An