HOROLOGY. 
invention and application of compenfation-bars in the 
conftruftion of his balance, together with the invention 
and application of what he calls the helical, but which is 
properly the cylindrical, balance-Ip ring, the form of which 
is ill own on Piate VIII. fig. 48. The fecond patent was 
for three different ways of applying the compenfation- 
bars ; for an improvement in the balance-fpring, particu¬ 
larly in the bending of the laft coil at the end of it; for 
his invention anti application of the fpring-detent; and 
all'o for the cycloidal, or more properly epicycloidal, ihape 
of the teeth of the balance-wheel. It has been already 
Paid, that Peter le Roy was the firll who applied a metal¬ 
lic compenlation to the balance itfelf; but it does not ne- 
celfarily follow from thence, that Arnold did not all'o in¬ 
vent the one he adopted. We are perluaded that a man 
of Mr. Arnold’s known integrity and veracity would not 
make oath, in taking out a patent, of an invention which 
he did not at leait consider as his own. At all events, 
Mr. Arnold mull be allowed the merit of having intro¬ 
duced the compenfation-balance into general ul'e, when 
Peter le Roy preferred the thermometrical tube. 
The late Mr. Brockbank was the firft perlon who united 
the two metals by fufion, which le Roy had united by 
pins, that mult have interfered with the regularity of the 
flexure by different temperatures. Mr. Brockbank was 
alfo the firll who ufed the method of turning an expanfion- 
rim out of a folid compound plate, made by covering the 
Heel plate in a crucible of fufed brafs, and of cutting it 
into portions afterwards, thereby enfuring the uniformity 
both of figure and weight, which two properties are equally 
effential in any balance, as the name imports ; fo that, if 
it Ihoiild be contended that the conftrufilion of the com- 
penfation-balarice was not invented in this country, at 
lead the practical application of the principle is our own; 
to which confideration we may add, that Arnold lenior 
invented and introduced the ufe of the fpring-detent, 
which requires no oil. Mr. Arnold was likewife the firlt 
watch-maker in England who laid much Itrefs, not only 
on the Ihape, but alfo on the particular length, of the ba¬ 
lance-fpring in practice, which Dr. Hooke and Peter le Roy 
had both fiiown was neceflary to be to attended in order 
to render the fpring ifochronal under all arcs of vibration, 
which is an effential objeft of adjustment, and which no 
doubt influenced his choice of the Ihape of the fpring; 
and we are informed that he was fo far fuccefsful in his 
attempt to appertain the precife point for limiting the belt 
practical length of fome of his balance-fprings, that, af¬ 
ter the example of Peter le Roy, to whofe contrivances, 
it mull be confelfed, he leems to have paid great defer¬ 
ence, he fucceeded in making a movement go accurately 
without a fufee, by the mere regulation of an ifochronal 
fpring; which is an indubitable proof that the irregulari¬ 
ties of the maintaining-power can have but little influence 
on the rate of a chronometer with an ifochronal balance- 
fpring, efpecially when it has, moreover, a detached fcape- 
ment. Mr. Pennington, an excellent artill now living, af¬ 
firms, that there are many . ifochronal points in every fpring-, 
which dil’covery accounts for the different lengths of the 
various balance-fprings that are made of the fame clue. 
. Emery’s balance had weights Aiding on its erodes, and 
having their pofitions regulated under different degrees 
of heat by the variable flexure of compenfating-bars com- 
pofed of two different metals, in the Ihape of an'S : but 
this was one of the varieties invented by Arnold, whole 
workman afterwards went to Emery. The Brockbanks 
have their chronometers dillinguilhed by the pofition of 
their locking and unlocking fprings, and all'o by a pecu¬ 
liar method of banking by means of the protruiion of the 
coils of the balance-fpring. 
Earnfnavv’s chronometers differ from Arnold’s in the 
Ihape and poiition of the detent and fprings; in the Ihape 
of the balance-wheel, and ftrufture of the balance-fpring 
and balance; all which will prefently be explained. 
Recordon, fuccelfor to Emery, at Charing Crofs, has 
a compenfation-balance perforated at the circumference 
-VOL. X. No. 666. 
with various tapped holes, into which the ferews of ad- 
jultment for temperature and pofition may be l'ucceffively 
removed, according to circumltances : this mode of ad- 
jufiment is pradtifed by Pennington, a workman of extra¬ 
ordinary ingenuity and accuracy, and was, we underhand, 
originally his contrivance. 
Haley, a watch-maker at the corner of Wigmore-ftreei-, 
Cavendilh-fquare, took out a patent on the 17th of Au- 
gult, 1796, the particulars of which are given in the fixth 
volume of the Repertory of Arts, p. 145. The principle 
on which the patent was granted, confided chiefly of a (e- 
cond cylindrical fpring, and fpring-arbor with pallets, ScG. 
interpofed between the fcapement-wheel and the balance, 
to give an impulfe to the balance at each vibration, in- 
llead of the impulfe ufually given by the force tranfmitted 
through the train. 
Grimalde, in the Strand, who now makes a confiderable 
number of chronometers, fome of which, we learn, have 
the teftimony of naval officers in their favour, prefefles 
that he places the cock fo conveniently, and adjults for 
pofition fo readily, by a particular contrivance, which 
does not require the cock to be taken off, that it would, 
we think, contribute to the itock of improvements already 
known, if he would make his method public. 
Mr. Hardy has lately introduced a new mode of bank¬ 
ing, by a lever attached to the exterior coil of an helical 
fpring, which is thrown out to catch a pin in the balance; 
and has propofed a new mode of making the fpring ifo¬ 
chronal, by making the ftud moveable on a fecond fpring; 
but experience mult prove their utility. 
Wemight add a lift of other ingenious perfons who make 
chronometers, notin London only, but at Edinburgh and 
Liverpool, were we aware that there is any material dif¬ 
ference in the confirmation of their mechanifm or me¬ 
thods of adjuftment, from thofe, or fome of thofe, which 
we have notice'd. We therefore haften to a more particu¬ 
lar defeription of the machines themfelves. 
HarriJ'on's Time-keeper. —The following particulars, relat¬ 
ing to the dimenfions and other properties of this mecha- 
nifm, apply more particularly to the fourth piece made 
by the inventor, and are extracted chiefly from a pamph¬ 
let publilhed by order of 'the Comrniffioners of Longi¬ 
tude in 1767 ; for no accefs to the machine itfelf, for tiie 
purpofe of making correct drawings, can now be obtained, 
though it is depolited in the Royal Obl'ervatory at Green¬ 
wich, under the care of Dr. Malkelyne, afironomer-royal, 
and is of courfe, having been paid for by the public, pub¬ 
lic property.—The firlt obfervable diftinchon between 
Harrifon’s train of wheel-work and that of an ordinary 
watch, is, that the numbers of his wheels and pinions are 
higher than had been ufual, as will appear from the fob- 
joined arrangement, viz. 
Firlt or great wheel 96, 
Centre pinion act¬ 
ing with it - zi —no fecond wheel, which is concave. 
Its pinion iS—144 third wheel, 
Bal. wheel pinion 12 —15 bal. wheel, 
2 pallets. 
If thefe numbers be examined according to the ufual 
mode of notation, the value of the train will be 
120 x 14+ X 120 X 13 X 2- „ ., . 
-rr7-r—---— 1800 vibrations m an hour, 
18 X 16 X 
or jult five vibrations in each fecond. The firlt or great 
wheel will revolve in of an hour, or make one revolu¬ 
tion, along with the fulee, in 4y hours, fo that 5-J turns 
or Ipirals on the fulee will maintain a motion of 24 hours, 
61 will actuate the works 28^-, and 6 -fg jult 30 hours. 
The balance-wheel does not differ effentially from that 
in a common watch, but peculiar care is necellary in 
fiiaping the pallets. 
The bad efferi: produced in ordinary watches by an ir¬ 
regular tranfmifiion of the maintaining-power through the 
train, is here guarded againlt by the introduction of a lien- 
der fpring, or remontoir, which is wound up eight times 
4 U every 
