$<U H O R O 
which will Aide along it, and urge the pallet outwards 
during this Aiding action. When the tooth has fallen 
front the point of this pallet, an oppoAte tooth will be 
received on the circular furface of E, and will not affeift 
the variation, excepting when the Aope furface of E is 
carried out fo as to fuffer the tooth to Aide along it. This 
contrivance is known by the name of the dead-beat, or 
dead-fcapement ; becaufe the feconds index Hands Hill after 
each drop, whereas the index of a clock with a recoiling 
fcapement is always in motion, hobbling backward and 
forward. In this fcapement, an increafe of the maintain¬ 
ing power renders the vibrations larger and flower: be¬ 
caufe the greater preA'ure of the tooth on the edge of the 
pallet throws it round through a greater arch; and its in- 
creafed preA’ure on both furfaces of the pallet retards its 
motion. 
3. The effect of the fcapement which has been called 
horizontal, becaufe the laft wheel in watches of this con- 
II ruction has its plane parallel to the reft of the fyflem, is 
Jimilar to that of the dead-beat fcapement of Graham. In 
fig. 53, the horizontal fcapement-wheel is feen with twelve 
teeth, upon each of which is fixed a fmall wedge fup- 
ported above the plane of the wheel, as may be feen at 
the letters A and B. On the verge of the balance there 
is fixed part of a hollow cylinder of fteel or other hard 
material, the imaginary axis of which paifes through the 
pivots of the verge. C reprelents this cylindrical piece, 
into which the wegde D may be fuppofed to have fallen. 
While the vibration caufes the cylindrical piece to revolve 
in the direction which carries its anterior edge towards 
■the axis of the wheel, the point of the wedge will merely 
rub the internal furface, and no othenvife affect the vi¬ 
bration of the balance than by retarding its motion. But, 
when the return of the vibration clears the cylinder of 
the point of the wedge D, the wheel will advance, and 
the Aope furface of the wedge acting againft the edge of 
the cylinder will afiift the vibration of the balance. When 
the edge of the cylinder arrives at the outer point of the 
wedge D, its pofterior edge muff arrive at the pofition 
denoted by the dotted lines of continuation ; immediately 
after which the wedge or tooth E will arrive at the pofi¬ 
tion e, and reft on the outer furface of the cylinder, where 
it will produce no other effect than that of retardation 
from friftion, as was remarked with regard to the wedge 
D, until the courfe of the vibration Aiall bring the pofte¬ 
rior edge of the cylinder clear of the point of the wedge. 
III this laft fituation, the wedge will a£t on the edge of 
the cylinder, and afiift the vibration, as in the former cafe, 
until that edge Aiall arrive at the outer or pofterior point 
of the wedge; immediately after which the leading point 
will fall on the inner furface of the cylinder in the firft 
pofition, as was lliown in the wedge D. 
Horizontal watches were greatly efteemed during the 
laft thirty years, until lately, when they gave place to 
thofe conftructions which are known by the name of de¬ 
tached or free lcapements. In the common fcapement, 
fig. 51, an increafe of the maintaining power increafes the 
recoil and accelerates the vibrations: but with the hori¬ 
zontal fcapement there, is no recoil; and an increafe of 
the maintaining power, though it may enlarge the arc of 
vibration, will not necefiarily diminim or alter the time. 
It is accordingly found, that the experiment of altering 
the maintaining power by the application of the key, does 
not alter the rate in the fame perceptible manner as in 
commdn watches. 
4. Fig. 54, reprefents the free or detached fcapement of 
our belt portable time-pieces. Fig. 55, exhibits a part of 
the fcapement on a larger fcale;- but the fame letters refer 
to the fame parts in both figures. On the verge of the 
balance is fixed a circular piece of lapphire, or of hard 
fteel, EL, fig. 55, out of which a fectoral piece is cut. 
H G is a Itraight lpring fixed near its extremity H, and 
having at the other extremity a pin G, againft which one 
of the teeth of the wheel D refts when the train is at reft.. 
This fpring has a flight tendency towards the centre of 
LOGY. 
the wheel, but is prevented by the flop K, fig. 54, from 
throwing the pin further inwards tjian juft to receive 
the point of the tooth. I is a very fiender fpring fixed at 
the end I, and preffing very flightly againft the pin G, in 
a direction tending to throw it from the wheel D, but 
which, on account of the greater power of HG, it cannot 
effect. It may be obferved, that the fpring I proceeds a 
little beyond the pin G. F is a lever proceeding from the 
verge of the balance directly oppofite the* end of the fprino- 
I, and long enough to ftrike it in its vibration. 'The 
action is as follows: From the preffure of the main fpring, 
the'wheel, fig. 55, is urged from D towards F, but is pre¬ 
vented from moving by the pin G. Let the balance be 
made to vibrate, and the lever F wall move through the 
arc F f, ftrike. the inner extremity of the fpring I, and 
difplace the pin G. At this inftant the face E, which 
may be called the pallet, will have arrived at the pofition 
e, againft which the tooth of the wheel will fall, and com¬ 
municate its impulfe through about 13 0 or 16 0 of the vi¬ 
bration. But F quits the fpring I fooner than the wheel 
quits the pallet E, and consequently the pin G will have 
returned to its firft ftation before the wheel can have ad¬ 
vanced a whole tooth, and the fpring or detent HG will 
receive the wheel as before, immediately after its efcape 
from the pallet. The returning vibration of the balance 
will be made with the piece EL perfectly at liberty be¬ 
tween two teeth of the wheel, as in the Iketch, and the 
back ftroke of the lever F againft the tender fpring I will 
have no effe6t whatever on the pin G; this fpring being 
like the back fpring of the jacks of the harpficliord, ac¬ 
tive in one direction oniy. The third vibration of the ba¬ 
lance will unlock the detent as before ; the impulfe will 
again be given, and the whole procefs will be repeated : 
and in this manner, the balance, though it may vibrate 
through the greateft part of the entire circle, will be en¬ 
tirely free of the works, except during the very fmall time 
of the drop of the wheel. 
It is hardly neceflarjf to make any remark on this fcape¬ 
ment. It requires little or no oil; and when all the parts, 
particularly the balance-fpring, are duly adjufted, it is 
found that a-very great variation in the firft mover will 
remarkably alterthe arc of vibration without affefting the 
rate. The piece EL might have confifted of a fingle pal- 
letsor arm, inftead of a portion of a circle or cylinder; 
but fuch a piece w'ould have been rather I'efs convenient 
to make in fapphire, or ruby, as in the beft time-pieces, 
and would alio have been lefs ufeful. For, if by any ac¬ 
cident or fliock the pin G fliould be difplaced for an in¬ 
ftant, the wheel D will not run' down, becaufe it will be 
caught upon the circular furface of EL. It is indeed 
very ealy to obferve, that the piece E L would operate 
without the detent, though with much fridtion during 
the time of repole. The tooth of the wheel would in that 
onfe reft upon its circular face. 
Moft of the improved time-pieces lately produced are 
upon the principle of the detached fcapement combined 
with the dead-beat; for it is univerfally found that clocks 
and chronometers formed with detached lcapements re- 
gilter time with more accuracy than others. The dura¬ 
tion of the detachment does not exceed one fecond in any 
of thefe hitherto made; at the end of that period, the 
pendulum or balance comes again into contact with the 
train, receives a new impulle, and is again detached. 
Mr. Congreve (Patent, dated Aug. 1808) propofes to ex¬ 
tend the period of the detachment much beyond the com¬ 
mon time; fome of his methods ;how how to do this for 
the fpace of a minute ; and, though the principle of one 
of his inventions can extend it much longer, not having 
any limits but what conveniency may allign, yet this 
period is fully fufficient for every purpofe required, and 
will probably be that fixed on for ufe, on account of its 
being one of the chief divifions of time. 
Two primary methods of effecting the above purpofes 
are detailed in the fpecification annexed to his patent. 
The firft relates to a new mode of mealuring time ; the 
1 fecond 
