HOROLOGY-. 
ing equal vibrations, fee the communications of Mr, Wil¬ 
liam Hardy to the Society of Arts, as contained in their 
• Tran factions, vol. xxv. p. 113-116. 
Of the Pivots and Pivot-holes. —It has been noted before, 
that jewelled holes leifen friction, and preferve the oil 
better. It has therefore become very common to let the 
pivots of the balance at leaft run in holes cut out of well- 
poliflied rubies. To render the friftion of the balance 
very fmall, but without weakening the pivots, the pivots 
are fometimes filed into a conical form, and of courfe the 
ruby-holes mult be fcooped out accordingly. 
The only objeftion, till lately, againft jewelled holes 
for all the pivots of longitude-watches, &c. has been the 
great expence. But Mr.P. P. Barraud, an excellent prac¬ 
tical watch-maker now living, is of opinion that this ex¬ 
igence may very well be fpared. The following is an ex¬ 
tract of a letter from him to Mr. Ezekiel Walker upon 
this fubjeft, dated January 28, 1804. “The ftate of my 
regulator I have already defcribed in a former letter ; from 
which I infer, that, lo far from jewelled holes being ad¬ 
vantageous in clock-work, they are abfolutely injurious. 
That they are equally fo in chronometers, I ha/e had 
abundant experience, having found, almoil without ex¬ 
ception, in chronometers coming oft' a long voyage, the 
oil in a much worfe condition in the jewelled holes (par¬ 
ticularly in thofe where the friftion was confiderable) 
than in the brafs ones. I have therefore been induced, in 
every inftance, to rejeft jewelled holes, and introduce 
thofe of brafs; and the alteration has been conftantly fa¬ 
vourable to the performance of the time-keeper. I ihould 
be happy in having a communication with you viva voce 
on this theme, See. See." 
That Mr. Barraud had not made this alteration in his 
chronometers in a halty manner, will appear from the fol¬ 
lowing extraft taken from another of his letters to the 
fame gentleman, of an earlier date, namely, July 17, 1800. 
“ Dear Sir, Since we parted, I have found additional rea- 
fons to believe that jewelled holes (where friftion is great) 
are injurious. A box time-keeper which I have recently 
taken to pieces, on its return from a long voyage, had 
the oil in the brafs holes in a much purer ftate than in 
the jewelled ones. In the former it ftill remained in a 
ftate favourable for aftion; but in the latter, the pivots 
were fo fixed by the. tenacity of the oil, as to require 
force to extricate them; the Iteel was alfo deeply ftained, 
and had parted with all its luftre, See. Sec. 
From thefe and many other obfervations made by Mr. 
Barraud upon the effects of oil on time-keepers, it ap¬ 
pears that fmall particles of fteel are worn off by friftion 
in the jewelled holes, and, mixing with the oil, form a 
glutinous fubltance that caufes the time-keeper to go ir¬ 
regularly. 
It is a known property of fome oils, that they freeze 
much fooner than water. The oil of olives freezes at 
42^° on Fahrenheit’s fcale, confequently the pureft oil of 
this kind will lofe its fluidity fooner than that which con¬ 
tains fome aqueous particles. Hence we may conclude, 
that watch-makers ought to make choice of that oil which 
freezes with the leaft degree of cold; and, as cold has 
no power to decompofe olive-oil, it need not be rejected 
on account of its having afl'umed the concrete form. 
II. Of the MOVING POWER. 
To repair the lofs of motion in the regulator (whether 
pendulum or balance) of time-pieces, caufed by friction, 
the refiftance of the air, &c. we communicate to the regu¬ 
lator, through a train of wheels and pinions of increafing 
velocity, and by the fcapement, the reilorative effeft of 
an exterior agent, or moving power. It is not till after re¬ 
peated experiments that we can determine the required 
force of the moving power, fmee it is difficult to al’cer- 
tain the amount of the quantity of friftion in the wheel- 
work, the fcapement, and the regulator, added to the vis 
inertias ; which muft be known before we can afeertain 
by calculation the power neceifary to overcome them. 
The moving power is produced either by weights or 
319 
by fprings. In fixed pieces, as clocks, a weight is the 
moving power; in watches, or other pieces expofed to 
agitation from being moved about, a fpring, called the 
main fpring, is the moving power. Weights aft upon the 
firft mover of a clock by means of a cord wound round a 
cylinder combined with the firft mover. The eft'eft of 
weights is ever uniform; the moving power produced by 
them is the inoft equal polfible ; weights are therefore 
preferable to fprings wherever they can be applied. But 
in watches and in machines to go at fea, we are obliged 
to ufe fprings, which either aft immediately upon the 
wheel-work, or through the medium of a fufee,* or trun¬ 
cated cone. The fubltitution of a fpring inftead of a weight, 
as a moving power, was an ingenious thought; for by- 
this means the fize of time-pieces could be reduced, and 
hence came at length the invention of pocket-watches. 
Figures of thefe parts will be given further on, when- 
we come to deferibe the complete watch. The main fpring 
works in a box, or barrel ; it is coiled up in the manner we 
have defcribed the flat balance-lpring; and has a fquare 
hole at each end, one of which holes clings on to a hook 
in the inner circumference of the barrel, and the other 
to a hook on the barrel-arbor , the pivots of which turn 
freely in holes in the barrel. Under the barrel is a ratchet- 
wheel, or a wheel with Hoping teeth ; and in this works a 
click, which prefles again one or other of the teeth, fo as 
to allow the wheel to go one way, but not to recede ; and. 
is continually prefled againft the ratchet by a fpring. 
The main fpring, being coiled round the barrel-arbor, 
tends by its elafticity to refume its liberty, and afts with 
all its force upon the barrel-arbor and upon the barrel it- 
felf; but the arbor, being held by the ratchet and click, 
remains immoveable. 
The fpring, thus wound up, will continue to aft till it 
has loft all its tenfion. It is not neceifary to make all the 
coils of the fpring aft, nor to wind up to the extent; be- 
caufe, being fo (trained, it might be in danger of break¬ 
ing, or of lofing lome of its ftrength or of its elafticity. 
Neither Ihould the firft turns of the fpring be made to 
aft upon the wheel-work, or train, becaufe, as thefe would 
aft with but a fmall force comparatively with the lalf 
turns, the aftion of the fpring would be thereby made 
very unequal. Suppofing the thicknefs of the fpring and 
the diameter of the barrel and its arbor to be fuch as to 
admit the fpring to be wound feven turns, it will be pro¬ 
per, to avoid the danger of ftraining or breaking, to give 
it only five turns, in order that two may be at reft ; and, 
of thefe five, not more than two and a half or three Ihould 
aft upon the wheel-work. The longer the fpring,- and 
the more turns it makes within the barrel, (within cer¬ 
tain limitations,) the lefs fear is there of its lofing its 
elafticity, fince more turns are.left at reft, even though it 
be fully coiled up. A large barrel is therefore accounted 
delirable. If the barrel were fo large as to allow 9 turns 
of the fpring round the arbor, while two revolutions of 
the barrel were found fufficient for the going of the watch, 
the fpring might be wound four turns only; and then, 
allowing two more turns for winding up the watch, there 
will always be the quantity of three turns remaining at 
reft. And thus the fpring will aft with equality and eaie. 
Since many turns of the fpring is a definable object, it 
may be imagined that this might be attained by making 
the barrel-arbor of a fmall diameter. This,is however a 
dangerous error, though by no means uncommon. The 
diameter of the arbor ihould be about one-third of the 
diameter of fpace within the barrel; never fo little as one 
fourth; for, when the arbor is too fmall, the inner turns 
of the fpring refund it are too much contracted, while the 
outer turns are comparatively inaftive; producing an in¬ 
equality very unfavourable to the aftion of the ipring. 
The barrel-arbor ihould be perfectly cylindrical, and the 
barrel very ftraight and upright; or the,fpring cannot 
aft with freedom. 
The main-fpring ihould be made of good fteel, and as 
equally tempered throughout as poflible ; the whole ihould 
be. weil-polifhed, in order to foften the friction that muft: 
neceijarily 
