.S5S H O R O 
touching it; the head of the adjufting-fcrew m is aifo fup- 
pofed to bear gently on the inner fide of the {aid fpring 
EF, or that neared to the wheel, and at the fame time 
the locking-pallet is fo placed, that one of the teeth, D, 
of the balance-wheel may juft take hold of it. This pal¬ 
let is not vifible in its proper place in the figure, being 
covered from fight by the {crew m, and part of the fpring 
EF; its pofition is therefore reprefented by the dot k, on 
the oppofite fide of the wheel, having the tooth A juft 
bearing up again ft: it. From the above defcription of the 
feveral parts of the fcapement, and their connection with 
each, other, it will be eafy to fee the mode of its adrion, 
which is as follows : 
“ A force being fuppofed to be applied to the balance- 
wheel, fo as to caufe it to move round in the dire&ion of 
the letters ABCD, one of the teeth, as D, will come 
againft the locking-pallet (as reprefented at A, and the 
locking-pallet by A). The wheel is then {laid to be locked, 
being prevented from moving forward by this pin. Let 
the balance be now fuppofed to reft in its quiefcent pofi¬ 
tion, and it will have the fituation reprefented in the 
figure; the lifting-point i of the pallet in will be juft clear 
of the projecting end of the {lender fpring, the face h l of 
the large pallet MSK will fall a little below the point of 
the tooth B, and the balance, having its fpiral -or helical 
(meaning cylindrical) fpring applied to it, remains per¬ 
fectly at reft in this pofition. Now, as the balance and 
the two pallets MSK and in, are fixed fall: to the verge, 
it is plain they muft all move together; let, therefore, the 
balance be carried a little way round in the direction of 
the letters MSK; by this motion the end i of the lifting- 
pallet in will be brought to prefs up againft the projefting 
end of the {lender fpring, and as this fpring is fixed on 
the fide of the fpring E F, neareft to the balance-wheel, 
the point i will prefs the two fprings together out from 
the balance-wheel; then, as only the point of the tooth 
D^jee its pofition at h) touches the locking-pallet, when 
the fpring E F was at reft againft the head of the fcrew in, 
it will, by the fpring being prefied out from the tooth, 
have dipt off (for the locking-pallet, which was before 
fuppofed at k, will now be at a, clear of the tooth A of 
the balance-wheel) ; the wheel being now at liberty will 
move round by the force fuppofed to be applied to it; but 
as the point i of the lifting-pallet moves on and prelfes 
out the fpring, the point l of the large pallet approaches 
towards the point of the tooth B of the balance-wheel, fo 
that, when the fpring E F is fufficiently puflied out to un¬ 
lock the wheel, the point l of the large pallet will be got 
to d, and in this pofition the point of the tooth B of the 
balance-wheel will fail upon it, at the dime time the point 
of the tooth D has juft dropped off from the locking-pallet 
m\ the force of the wheel being by this means applied to 
the top of the pallet hi, gives an increafed momentum to 
the balance, and adifts it in its motion in the lame direc r 
tipn, and by the continued motion of the large pallet in 
the direftion MSK; the point of the tooth B, which 
keeps prelling and urging it forward, moves up towards 
the bottom of the face of the pallet towards h, until the 
plain flat furfaces of the tooth and pallet come into con¬ 
tact; by this time the end, o, of the {lender fpring has 
dropt off from the point, i, of the lifting-pallet, and the 
two lprings have returned again into their quiefcent po¬ 
fition ; the fpring EF gently bearing againft the head.of 
the adjufting fcrew in, and the locking-pallet in a pofition 
to receive the next tooth C, of the balance-wheel. When 
the two furfaces of the tooth and pallet are thus in con¬ 
tact, the great eft force, of the wheel is exerted upon the 
pallet, and of courfe upon tire balance moving with it. 
The tooth {till prefling againft the face of the pallet, and 
the pallet moving in the direction MSK, it at laft drops 
off, leaving the balance at perfeCt liberty to move on m 
the fame' direction in which it was going. Jult as the 
point of the tooth B, which lias been prefling the large 
pallet round, is ready to leave it, the next tooth, C, of 
the wheel is almoft in contact with the locking-pallet m, 
L O G y. 
fo that the inltant the tooth B drops off - , the wheel is again 
locked, and the aCtion of that tooth upon the balance is 
finiflied. As thebalapce moves with the greateft freedom 
upon its pivots, the force of the tooth has given it a con- 
fiderable velocity, fo that the balance ftill keeps moving 
on in the fame direction, after the preffure of the tooth is 
removed by flipping off from the pallet, until the force 
of the pendulumripring (which is not reprelented in the 
figure), being continually increafed by being wound up, 
overcomes the momentum of the balance, which for an 
inftant of time is then ftationary, but immediately returns 
by the aCtion of the pendulum-fpring, which exerts a con- 
fiderable force upon it in unwinding itfelf. As the ba¬ 
lance returns, the point i of the lifting-pallet i n paffes by 
the ends of two fprings, E F, Y o, and, in paffing by, 
puflies. the projecting end, o, of the {lender fpring in to¬ 
wards the balance-wheel, until it has paffed it; after this, 
the projecting end o again returns, and applies itfelf dole 
to the hooked end of the fpring E F, as before. The fpring 
Ye is made fo fiender, that it gives but little refiftance to 
the balance, during the time the point i of the lifting- 
pallet is paffing it, and of courfe caulfes but little (if any) 
decreafe in its momentum. During the time the point i 
of the lifting-pallet is paffing in the fmall fpring Y o, the 
long fpring EF remains fteadily bearing againft the head 
of the adjufting-fcrew in, as the hooked end at o juft lets 
the end of the lifting-pallet pafs by without touching 
it. As the fpring has now been continually afting upon 
the balance, from the extremity of its vibration in the 
direflion MSK, it has given it the greateft velocity, when 
the point i of the lifting pallet is paffing the end o of the 
{lender fpring; for at this inftant the fpring, which was 
wound up by the contrary direction of the balance, is 
now unwound again, or in the fame ftate as it was in its 
quiefcent pofition at firft, and of courfe has no effeCt upon 
the balance at all in either direction ; but the balance, 
having now all the velocity it would acquire from the un¬ 
winding of the fpring, goes on in the direction SMK, 
until the force of this fpring again flops it and brings it 
back again, moving in the fame direction as at firft, with 
a confiderable velocity. By this return of the balance, 
the point i of the lifting-pallet comes up again to the 
projecting end o of the {lender fpring, puflies back the 
long fpring E F, and unlocks the wheel; and another 
tooth falling upon the face of the pallet h l gives frefh 
energy to the balance ; and thus the action is carried on 
as before.” 
In this quotation we have given the original letters of 
reference; but, as the balance and cocks are left out in 
our figure, the direction of the balance has been indicated 
by the letters referring to the large pallet, which, being 
placed on the fitme verge, has the fame motion. We have 
added two dotted lines in the large pallet, to fhow that the 
direction of the lines, bounding the notch in the circum¬ 
ference, is towards a point in the radius of it equally 
diftant from its centre and circumference ; alfo we have 
added two fimilar dotted lines from two ieparate teeth, to 
{how that the undercutting or doping of the interior fide 
of the tooth is likewife directed to a point equally diftant 
from the centre and circumference of the wheel. The 
locking-fpring points direCtly to the balance-arbor, but 
is laid in fuch a way as not to be an exact tangent to a 
radial line drawn from the centre of the wheel to the 
locking-pallet, the angle formed at the pallet being fome- 
what lefs than a.right angle, in order, as Mr. Earnlhaw 
lays, “ that the wheel may have a tendency to draw the 
fpring into it,” for fafe locking. 
On counting the teeth in Mr. Earnfhaw’s fcapement- 
wheel, which we have copied, we were furprifed to find 
only 12 teeth in it, particularly as we are informed, in 
his defcription, that his numbers are 13 and 15 refpeCi- 
ively; we can only account for this circumftance by fup- 
pofing that- the draftfman miftook the number ; which we 
here notice, left the reader ihould l'uppol'e the fault to lie 
in our figure exclufively. 
