HOROLOGY. 
not nffefted by the irregular tranfmiflion of the maintain- 
iag-power through the train of wheel-work; this con¬ 
trivance was ingenious, and obtained the name of runon- 
toir. The pendulum, howeve'r, was not only unfteady in 
its aftion during the tolling of a Ihip, but was fubjeft to 
a variation in its length by change of temperature, as 
well as to a change of weight depending on the parallel ot 
latitude. The balance, which had preceded the pendu¬ 
lum, was therefore again rei’orted to as a regulator; and, 
though it was found incompetent to its olfice in a de¬ 
tached ftate, yet, by the aid of a {lender fpring to quicken 
and regulate its vibrations, it hfs ultimately turned out 
to be of eminent utility. 
It has been contefted by Huygens and Dr. Hooke, 
which of thele two fkilful mechanicians firft introduced 
the fpring called ufually the pendulum-fpring, from the 
ilbchronal property which it poffefl’es, like the pendulum, 
when of a proper itrength, Ihape, and length ; but, 
whoever was the inventor, both balance and fpring Hill 
remained fubject to alterations in their dimenlions by the 
fuccefllve changes of heat and cold ; for, by the former ol 
thefe temperatures, the fpring became weaker, and the 
fize and confequent momentum of the balance greater, 
lo as to produce a very fenfible lofs in the daily rate of 
going of a watch with fuch a regulator; alfo an accelera¬ 
tion beyond a mean rate was foon oblerved to be the con¬ 
fluence of increafed cold, which, on the contrary, di- 
minifhed the dimenlions of the metallic parts, and thereby, 
at the lame time, gave additional Itrength to the. fpring, 
and likewife reduced the llze and momentum of the ba¬ 
lance. About the fame period Leibnitz attempted to con¬ 
iine the vibrations of the balance with a fpiral fpring, to 
be of equal extent, by means of an additional fpring to 
be applied to the balance-wheel, and to be, like Huygens’s 
remcntoir, wound up by the maintaining power; but his 
endeavours, whatever ideas they may have fuggefted to 
Harril’on, Mudge, or Haley, for their auxiliary Iprings, 
were not crowned with complete fuccefs. 
Hautefeuille alfp, in the year 1674., prefented to the 
Academy of Sciences at Paris, a balance with a ftraight 
fpring, acting fomehovv inilead of a fcapement; but 
how far it refembied the fpriVig-detent of Arnold we know 
not, nor do we find that it was adopted in praftice. 
This focsety, however, thought the fubjeft of fuch im¬ 
portance, that, in 1720, they propofed the following ques¬ 
tion to be determined for a public reward : viz. “What 
is the molt per fee! method of preferring .on the fea the 
equable motion of a pendulum, either by the coni!ruction 
of the machine,' or by the fufpenfion?” A memoir writ¬ 
ten by MaQy, a Dutch clock-maker, obtained the prize, 
but he had .not the farisfaftior, of feeing his plan executed. 
About a year afterwards, Henry Suliy, an Englifh clgck- 
inaker, who had fettled at Paris about eight years previ- 
oully, prefented the lame academy with a marine time¬ 
keeper, made in 1721, and publilhed- a defeription of it 
in French, by the title of “'Defeription abregee d’une 
Horloge de nouvelle invention pour la juile mefure du 
temps en mer.” Befides the above, Sully made a fecond 
marine time-keeper, which was tried at lea in 1726; but 
the inventor died two years afterwards, a martyr to his 
horological ftudies, before he had brought his machines to 
that Hate of perfection which their objeft demanded. Kis 
pieces had vertical balances carrying cycloidal metallic 
pieces, round which a thread, or (lender wire, was wound 
at the upper end, while the lower end was attached to a 
lever with an adjuHable weight to effeft the ifochronifm 
of the balance, imiead of a fpiral-fpring ; the horizontal 
pivots of the balance alfo moved on the angular point 
included between two large rollers, which method of lef- 
1’ening friftion, we believe, was the invention of this au¬ 
thor. He alfo made a marine watch with a fpiral fpring, 
into which friftion-rollers, like Mudge’s, were intro¬ 
duced ; and, had he lived longer, chronometry would no 
doubt have been greatly promoted by his labours. 
It was about this period, that jewelling, another effen- 
347 
tial improvement in time-pieces, was introduced, accord¬ 
ing to Berthoud, by Mr. Fatio, a native of Geneva, who, 
not meeting with encouragement in France, came over 
into England, and brought his invention into notice. • 
The Academy of Sciences at Paris again propofed a re¬ 
ward for the year 17+7 ; the fubjefl was “The bell me¬ 
thod of finding the hour at fea, whether by day, by twi¬ 
light, or at night, when the horizon cannot be diftin- 
guifhed.” The reward was obtained by Daniel Bernouilli’s 
memoir, intitled, “ Recherches mechaniques et aftrono- 
miques,” in which was difplayed much lcience; but the 
author’s want of Ikill in mechanical operations prevented 
his labours being attended with complete fuccefs. 
In the mean time, the changes in the length of the pen-, 
dulum began to be compenlated, firH by means of cjuick- 
iiiver contained in a tubular rod, by Graham, and foon 
after by the oppofite expanfions of different metals, by 
Harrifon, who, Simulated by the Britifh parliamentary re¬ 
ward that had been previoully offered to the public for 
marine time-keepers, applied the fame principle to a watch 
to effect a felf-regulating curb, for limiting the efteftive 
length of the fpiral pendulum-fpring to correlpond to the 
fuccefiive changes of heat and cold, which changes were 
now known to alter the force of this fpring, and the mo¬ 
mentum of the balance. See p. 309 of this article. From 
this origin we. may date the beginning of all the different 
kinds of compen/ation-mechanifn that’have proved perma¬ 
nently ufefui in time-keeping; and if we add to Flarri- 
fon’s invention of the metallic compenfation, his remon- 
toir, and his addition of a fecondary fpring as an equiva¬ 
lent.fubftitute for the maintaining-power during the time 
of winding up, which is an elfential requifite in producing 
permanent motion, he may be fairly confidered as the pa¬ 
rent of modem horometry. 
The Britifh parliament had, indeed, before the French 
academy, offered, fo early as the year 1714, in the reign 
of queen Anne, a reward of io,oool. for any method of 
determining the longitude within the accuracy of one de¬ 
gree of a great circle, of 13,000k within the limit of 40 
geographical miles, and of 20,000k within the limit of 30 
fuch miles, or half of a degree, provided fuch method 
fhould extend more than 80 miles from the coaft; and af¬ 
ter this aft, two others pafled in the reign of George II. 
flat. 14 and 26, to promote the fame purpofe. But an 
aft pafled in the prefent reign, in 1774, repealing all the 
former ones, and offering feparate rewards to-any perlon 
who fliould invent a praftical method of determining, 
within certain circumfcribed limits, the longitude of a (hip 
at fea; fora time-keeper, the reward held forth is, 5000I. for 
determining the longitude to or within one degree, 7500I. 
for determining the fame to 40 geographical miles, and 
io,oool. for a determination at or within half a degree. 
This aft, notwithftanding it3 abridged limits and dinii- 
nilhed rewards, has produced leveral candidates fince 
Harrifon (who received the whole reward of the firft aft) 
for parliamentary remuneration, of whom Mudge, the two 
Arnolds, and Earnihaw, have had their labours crowned 
with partial fuccefs. 
But, though Harrifon obtained the firft and moil am¬ 
ple reward for his inventions, we are not thence to con¬ 
clude that his pieces excelled all others; they were fpeci- 
mens of great ingenuity, and proofs of unwearied indul- 
try, which certainly were not overpaid ; but the inventor 
himfelf was candid enough to confefs that-the balance, 
balance-fpring, and compenfation-curb, were notcontem- 
poraneoufly affefted by heat and cold, but that fmali pieces 
of metal were iboner affebled than large ones, and alfo 
pieces in motion before pieces at reft; whence he was led 
to conclude, that if the provifion for heat and cold could 
properly be in the balance itfelf, as was the cafe with his 
gridiron-pendulum in clocks, the time-piece might be 
made much more perfeft. 
Hanilon’s fuggeition of a compcnfation-balance , in place 
of a compenfating-curb for the balance-fpriilg, found its 
way into France, and rouled the attention of the watch-, 
makers 
