CLOCK, 
dead beat in clocks, wliich the celebrated 
Tonipion and Graham were unable to ef- 
fect. These circumstances render his tes- 
timony of considerable weight. 
Huygens must, how'ever, .still be con- 
sidered as the chief introducer of the in- 
vention, which no one disputes having been 
made by him, even though otliers may be 
supposed to have made it likewise un- 
known to him. He also invented a clock 
with a centrifugal regulator, which is con- 
trived to perform its movement in a curve 
that be has demonstrated, will render its 
gyrations isochronal, and which, at least, 
is worthy of a farther Investigation before 
it be condemned to an oblivion that it 
probably does not merit. But his disco- 
very of the isochronism of all vibrations 
made by a pendulum formed to move in 
a cycloidal curve, is that which is the most 
noted, although it has never yet been 
really applied to use. Mr. Huygens’ raeUiod 
of doing so has been shewn clearly to be 
erroneous, by Mr. Alexander Cummings, in 
his “Treatise on Clock and Watch Making,” 
published an 1766, who has also asserted 
that the cycloidal principle would not be 
of the benefit imagined, “ as the inequa- 
lity of the vibrations of the pendulum mov- 
ing in a circular arc, correct those caused by 
tire altei'ation of its weight from the varia- 
tions of atmospherical gravity, so as mu- 
tually to balance each other, while in those 
moving in cycloidal curves, there is no 
principle to counteract the variations of 
gravity.” It must, however, be noticed, 
that Mr. Cummings is evidently not cor- 
I’ect in his statement, that the loss of spe- 
cific gravity in the pendulum, caused by 
an increase in the weight of the atmosphere, 
W'ould equally tend to prolong its vibra- 
tions, as the increased resistance caused to 
its motion by the same means, would tend 
to diminish them ; as he has by no means 
proved the equality of those opposite ef- 
fects. Mr. Cummings also mistakes the 
loss of relative gravity, for the loss of real 
gravity ; the momentum of a body in mo- 
tion is generally considered to be the same 
in different mediums, except so far as the 
additional resistance from a denser medium 
retards it, and so far from Mr. Cumming’s 
opinion in opposition to this being as evi- 
dent as he supposes, it is well known that 
no proof has ever been advanced to sup- 
port it. 
Many very carious and useful theorems 
Lave been discovered relative to tlie pen- 
dulum, most of wliich originated with Huy- 
gens, among these one of the most noted 
is that, “ Tlie times wherein pendulums of 
different lengths perform their vibrations, 
are to one another in the same proportioir 
with the square roots of the lengths of the 
pendulums. 
The length of a pendulum vibrating 
Inches. 
in a second is 539-125 Halley. 
lisf^-1 
<39.207 Newton. 
9.781 Halley. 
ini a second is ^ 
^ <9.801 Newton. 
And from these data, and the above 
theorem, the lengths of pendulums to vi- 
brate any other required time may be de- 
termined. 
The next improvement of consequence 
on clocks after the pendulum, was the es- 
capement performed with anchor pallets, 
whicli Berthoud states to have been the 
invention of Clement, a London clock 
maker, in the year 1680. The escapement 
used by Huygens, and still continued in 
many chamber clocks and all the wooden 
clocks, Ls tliat made by two flat pallets 
attached to an horizontal arbor, acting at 
opposite sides of the upper part of a hori- 
zontal crown wheel ; the anchor pallets on 
the contrary, act on a vertical swing wheel, 
and move in the plane of the wheel. The 
cliief advantage of the anchor pallets is, 
that they will permit the escape to take 
place with a small angle of vibration, so as 
to prevent the maintaining power from 
acting on the pallets a long time by a di- 
rect push, as was the case with the crown 
wheel escapement. 
Dr. Hooke also claimed the invention 
of the anchor escapement, which he as- 
serted that he exhibited to the Royal So- 
ciety in a clock of his construction in 1666, 
At the same time with the anchor es- 
capement, the mode of suspending the pen- 
dulum from a cock by a piece of watch, 
spring was introduced. 
The anclior escapement causes a recoil 
in the swing wheel, from the same face of 
the pallet striking the tooth of the wheel 
in its descent, which is afterwards impelled 
by the same tooth in its ascent ; tliis occa- 
sions tlie clock, in which it is used, to go 
faster when the maintaining power is in- 
creased, or when the weight of the pendu- 
lum ball is diminished. 
The advantage gained by the anchor esr 
capemeut shewn above may be considered 
in reality an approximation to a detached 
escapement ; a farther step was made tOr 
