1000000031

Jzws which he

h~s

impreíE.d upon ,htln

GrH. fo r

-if

fllould once lea\'e thl.'rn (o, their arder \VauJd in t Une

come [O an end; becl\urt: (he plancls

mun

nt:cdr.lrily dlf–

t urb one

another's motions

lhcir

mmual

au raCltons,

wheo fC!vera l of th: m are in lhe (anle qu,lrter of lhe

heavens; as. is

Ort~1l

lhe

Cc"\fC!:

.,nd lhel), 3S

{hey

aura..:-1:

t he fun more

lowarcls lh,H quutcr

than wllen

dltr

are

a manll:r

difpcrfed equ.lbly arround

!lim.

he!

\Vas nOl

al rhar time mflJe la defcribe a portian of a

hrgcr

cireJe

rouad (he cammon

ceOHe

of gravity.

lhe

bahnce

\Vollld

then be immediately deflro}'ed; and

ir cauld never re·

Hore

¡([dr

again. (be whole

fyficlll

wauld bcgin

(all

logecher, and

would

in time

uDite

in a mafs

rhe

fun .

-Of this diflurbance

\Ve

have a

very remarkable

¡nnance

io the

comct which :l.

ppe:l.red

lately; anu which.

going

Jall:

up before from Ihe (un, went (o aear

J upl ter,

"CInd

was fo affeéled by his auraél ion,· as tO have the figure of

jtS orbit mucA. changed; and not only

(o,

but to have its

period ahered. and its courra

dtffc=rent in tbe he;.!.\:ens

fro01 what il was Ja[t befo re.

11 .

T ake away

lhe

fork aod

from dle

whirling~

board, and place ,he trough AB ( g. 8 .) ,hereoo, fixiog

its centre tO

the

cemre of dWiU\'hirling-board by the

lo ,his troogh are ,wo balls D and E, of "oequal

weights, cooneéteJ by :l. wire

and made to Oide ealily

upon the wire

Hretched (rorll cnd to end of the trough.

and milde faíl: by out Ccre\Vs on (he oUllide of the ends.

Le, ,hefe ball. be fo plac:d upuo ,he wire C. ,ha' ,heir

common centre of gravity

may be dire(\:ly oyer (he

centre of the whirling board. Thc:n. turn the O1achloe

by ,he wioch ever fo

f\~iftly,

aod ,he trough aod ball,

wiB go round their cenlre of gravity fo

:l.S

ne:i ther of

them

will

fJy off; becaure, on account of the equihbri.

um,

each ball detaios

lhe

other

with <lO

equ:d for....e

aél–

ing againrl it. HU[ if the ball E be drawn a liule miJre

lowards the eod of the (rough at

it wil! remove tbe

centre of gravity towards that end from the e'!ntre of

motion; and then. upon turoing the md.chine. the litlle

ball E will

o/F,

aod IIrike wi th a coofiderable force a–

gainfi the end A, and draw the gre:at ball B ioto the

middle of the trough. Or, if ,he gre., bal l D be drawo

t .. wartls the end

of the trough. fo lhat the centre of

gmvity may be a linle towards thal

end

(ro01 lhe centre

of mmion, and the m....:hine be turned by che winch, the

grea, ball D will

off, and 11, ike violendy . gaioU ,he

eod Bol ,he trough . • od will briog ,he lill le b.1I

in,o

the m,ddle of

Ít.

rhe trough be not ffiade very firong ,

.he ball O will b,eak ,hrol1gh i,.

12 .

The rearon why lhe lides rife at the Carne abColute

time on oppof1te (jJes of rhe earth, and coofequently in

orpoCite dire(\:ions, is made ílbl10dantly plain by a ne\V

experiment

1he whirling t<tble. 'The cauCe of the-ir

ri(jog on the (jde next the moon cve:ry one under(f :l.nds

tObe owing tO the O1oon's attratlicn : but why tht!y fhould

rife

the

opro(jtc·fi¿~

at the: fame lime. where there is

n O

mooo to

;lUna

Ihem. is perhaps not (o generally uo–

der!tood . 1-"or it would feem tllat the

01000

Chould rathcr

draw the waters (as it were:) clofer to that GJc. than raife

,hem upon it. direCly

co~tr2ry

her aur;:¡élíve force.

L'!t the circlc

ahcd

(fig. 9')

re:pre(en t the earth , with

i(5

lid'!

turoCtl

lQwa;-d the moon, urhich will then attraét

e s.

l he: watcrs fo as to nif..: t!1em

Crom e

Z .

But t11.:

qudlion IS,

W'lY

fh :mld lhey ri le as high al that very·

tirHc on

the 0pP'Jfite lide

froJ\

orda'to ex...

pl. io ,hi" Je' ..here h. a plate AH (Iig

l O.)

fi-<eel

UpUD

one cnd of dH: fllt bar

O...:::;

wlth fu ch a circle dra\VQ

upon it as

abc:1

(i~

lig.

9 .)

reprefent

tbe

rouncll1gure

of (he c:trth a:ld Jea; anu fUi.:h an elJipfis as

~{gh

to re ..

pn.'(ent eh,: l"wcllrog of the tide

and

oce.lriooed by

t he:

iolll1~oce

of the: moon. O ver Ihis pllte

let lhe

t:lrce Ivory balls

e.f,g

b:: huog by the

lilk

lices

h,i,l,

f ...

(lt:llcd

tO lile tops of

¡he

crook.cd

",ires

H,I.K.

Cuch

a manner, lh:u the b,dl al

m,.y hang fredy O\'er

,h~

fide of [he circlc

which is fanhe:íl: froln the mocn

1\1

(a<

,he o,her eod of ,he bar;) ,he ball

may haog

fred y ovt:,· Ihe celltre, and tbe hall at

haog

O\'er

the

fide of the circle

which

neueH {he moon. The

bdl

nlAy reprerem lhe centre of the eanh, th e

b.JJ

fome water on the

lid:

ocx t the moon, and lhe ball

fome water

the orpol1tt:

Gde. On

lhe back of the

mouo

lVl

tht: fho:"t bar

para

lid

to the h.)fizon.

and there are lhree:

hol~s '

in it abovt: the little w.eigh ts

P.q.r'.

filk thread

tied tO lhe

Jioc

c1of~

aboye

• the ball

and,

paffin,;! by one,

Gde

tbe

moon

goes

through a hole in

Ih~

bar

N. and

has the wcigbt; hung

to it. Slleh anotber thread

is ticd to the Iloe

dore

abo\'c the ball

¡:

ando p,lfling through the centre of lhe

mooo M .ud m;rldle of ,he bar N, has ,he weigh,

huo¡:

it. wh,ch is lighter th:;¡n rhe weight

third dlread

tII

is ticd tO

Ule

line

dofe aboye the

b.dl

and pafling

by the other fide of the moon

~II.

through tbe bu

N .

h.n

the weight

hunC

it,

whi~b

ligln er

.tban the

weir,ht

The

ure of there three .unequal \\'cights is to repreCcnt

.t he moon's

\lncqua l .:.tttra~ioo

3t diftcrent d¡!br.nces (rom

he:r. Wilh wbat.cvcr force Che attr.é!:s lhe cen1re

(1,-

the

canh.

fue

att-aéts lhe fije oext her wilh a gre2ter degree

of .force, and the fide fartheH from her w¡lh a

lcfs.

So,

if ,he weights are lcft at Jibcrly, they will

nr<lw

all the

three balls towílrds the moon with diffcrent degrees of

force. and e,luCe them tO

m~ke

the appearanee (hewll in

(fir..

1' .)

by which meaos ,h y are evid<otly farlhe< from

( aeh other than they would be if they hUllg

liheny

the lines

h,i.k;

becaufl! rhe lioes wou lJ lhen hang per–

peodieularly. This fhews, '-that

ClS

rhe moon attr<léts

lhe fide of the earth which i9 neareU her with a grc<lter

degree of force than fh e does (he

e~ntre

of the e.tflh. Che

\ViII draw the water on that (jJe more :.han !he draws lhe

centre, and fo cí11.lfcs it to ri(<!

that fiJe: and

<lS

fhe

draws the centre more lhan fhe draws ,he oppofite Gde.

the centre \ViII recede (arther (rom the

rurfaecofth~

water

tltat oppofite fide, and fo leí1ve it as high

thcre

file

raifcd it on the ¡ide next tO her . For, as the centre wilI

be in the midole between the tOps of the oppofite elt=va–

,ioos, ,Ioey mun: of coorfe be equ.lly high on both fides

at the fame time.

Bur upon this ruppofition the c<lrth and mOOD \Vonld

fooo come logetlu'r; and

be fure tht:y would. if t!lCY

had DOt a m"olion ronnu thci r conllllon centre of gravity,

to create:

dcgree of centrifuga1 force fufficicnl to bol·

Itloce

th: ir nllHual attr;¡flion. This mOlion they have ;

fur as lhe mooll goc8 round her ol'uit e'lery mODth

the