HOROLOGY. 
spring, to give to the balance, by its elas- 
ticity, a power which renders tiie action of 
this sort of regulator similar to that of gra- 
vity in the pendulum, isL undoubtedly due 
to Dr. Hooke, though it is not so clear 
whether he ever applied it in the shape of 
a spiral, as has been so long practised since. 
F. Berthoud, in his “ Histoire de la Mesure 
du Temps,” (vol. i. pp. 134 to 141), gives a 
body of extracts from several works rela- 
tive to this subject; and concludes, that 
Dr. Hooke only applied a straight spring to 
the balance, and that M. Huygens improved 
upon that idea, and contrived the spiral 
spring, which is more favourable to the vi- 
brations of the balance. M. Huygens, in- 
deed, applied in France a balance spring, 
the account of which has been published iu 
the Philosophical Transactions for 1675, 
No. 112 ; but Dr. Hooke, in the Postscript 
to his Description of Helioscopes, asserts, 
that the hint was taken from the experi- 
ments he had made in 1664, in Gresham 
College, where he explained above twenty 
several ways by which springs might be ap- 
plied to do the same thing. 
In relating the progress of time-piece 
making, we must not omit mentioning the 
use of precious stones, particularly rubies, 
to form the holes in which the pivots of the 
wheels turn, and the pallets upon which the 
action of the teeth is exercised. These 
jewels, by the high polish given to them, 
reduce the quantity of friction ; and, not 
being liable to the wear which takes place 
in metal rubbing upon metal, the machine 
with that addition, not only becomes more 
durable, but acquires a degree of unifor- 
mity in the motion of the pieces, which is 
very favourable to the regularity of its 
going. 
That extraordinary man John Harrison 
having produced the first portable machines, 
which, upon repeated trials, met with suc- 
cess, to the extent required for the great 
reward offered by the British parliament, 
must be reckoned the father of modem 
chronometry ; and his long and active ca- 
reer has proved extremely useful, by stimu- 
lating with so bright an example other artists 
to similar endeavours. The principles of 
Mr. Harrison’s watches are well known ; 
and, as most parts of his construction have 
been superseded by more simple contri- 
vances, we shall only mention the principal 
inventions of which he appears to be the 
author, and which are still used by the 
watchmakers of the present day. 
The going fusee is one, among those in- 
ventions, which has proved the most gene- 
rally useful in practice. By this simple 
mechanism, the main spring, while the watch 
is going, acts on an intermediate short spring, 
which Harrison calls the secondary spring, 
and is constantly kept bent to a certain ten- 
sion by the former ; and, when the watch is 
winding up, and the principal spring ceases 
to act, the secondary spring being placed in 
a ratchet wheel, which is hindered from re- 
trograding by a click, continues the motion 
without alteration. Other contrivances 
have been proposed, and executed, to make 
time-pieces go while winding up ; but none 
which, like this, combines the advantage of 
simplicity, and the property of providing a 
supplementary power, which is equal to that 
of the main spring when its action ceases. 
And it is to be observed, that the utility of 
the going fusee, which has induced manu- 
facturers to introduce it into all good watch- 
es, is peculiarly important in those time- 
pieces which have not the power of setting 
themselves in motion, as is the case with 
the best modern escapements. 
Harrison invented also a compensation for 
the effects of heat and cold, which at the 
time was perfectly new, and has led to the 
improvements made afterwards in that es- 
sential requisite of time-keepers. 
The alterations to which the length of the 
pendulum is liable by the different degrees 
of heat and cold, affect the going of clocks 
witli that sort of regulator (see Pendulum) ; 
and watches, with a balance, are still more 
subject to irregularity from that source ; be- 
cause not only the balance expands or con- 
tracts, according to the rise or fall of the 
thermometer, but the regulating spring it- 
self, while it suffers similar changes, be- 
comes weaker or stronger ; so that, from 
these canses, a time-piece must go slower 
or faster in too great a proportion to be 
overlooked or neglected. Graham (Philo- 
sophical Transactions, 1726), is the first who 
thought of applying two metals of different 
expansibility, to correct the errors proceed- 
ing from the variation of temperature in a 
pendulum ; but as he seemed to have had 
in view to effect it immediately, without 
the aid of mechanism, He was obliged to fix 
on steel and mercury, these being the me- 
tals which offered to him the greatest dif- 
ference of dilatation and contraction. Har- 
rison, by multiplying the bars, increased 
the total length of the two metals acting on 
one another, without exceeding the limits 
of the pendulum ; and thereby produced 
a sufficient compensation vyith brass and 
