H O R O L O G Y. 
35<t 
equilibrio, by the weight P, at the end of the lever PM. 
The circular area C F is one end of the fpring-barrel in 
the middle of the movement, in which is included a fpring 
•as in a common watch. To this end of the barrel the 
arm or lever P M is fixed upon the centre M ; and thus, 
when the clock is wound up, the fpring moves the barrel, 
and coniequentiy the lever and weight P, in the fituation 
PM. In doing this, the centre of gravity is conllantly 
removed farther from the centre of the machine, and 
therefore it mull determine the clock to move upwards, 
which it will continue to do as long as the fpring is un¬ 
bending itfelfand thus the weight and its lever PM 
will preferve the fituation they firft have, and do the of¬ 
fice of a chain and ful'ee. See Phil. Tranf. Abr. vol. i. 
p. 467. 
C. Janvier prefented, in the year 1800, a beautiful 
clock,to the national inftitute at Paris, in which are re- 
prefented the nodes of the moon, the precelfion of the 
equinoxes, and the two parts of the equation of time. 
Alfo a machine which contains new inventions for eclip- 
fes, tides, latellites, the annual parallaxes, the true move¬ 
ments, See. in which machine the motions are not in- 
creafed fo as to affeft the moving power of the regulating 
wheel.. 
The Rev. Burgifs Allifon has given, in the American 
Philofophical Tranfaftions, 1803, a delcription of a newly- 
invented globe time-piece, by which the following pro¬ 
blems may be readily worked: 1. To find the hour and 
minute of the day. 2. To find, with great accuracy, the 
time of fun-riling and fun-letting in every part of the 
world. 3. To find the different l'eafons, and the length 
of day and night. 4. The fun’s place in the ecliptic, and 
the day of the month. 5. The phafes of the moon, her 
age, place of the nodes, eclipfes, &c. Sec. 
' it is to be lamented that we have not in the Englilh 
language any regular inftruftions for the fucceffive por¬ 
tions of work to be performed in the conftruftion of a 
good clock ; for, until the clock-maker by profeffion can 
proceed in his work on fcienttfic principles, he mult be 
content.to be a mere Have of imitation in an art, which 
is capable of affording him genuine pleafure, from the op¬ 
portunities it gives, of calling in fcience to his aid in 
every ftep that he takes, through an infinite variety of 
praftical cbnitruftions. We do not pretend, within the 
compafs of this fingle article, to fupply the defideratum ; 
but lome information will be expefted from us ; and 
which, if it may not afford the expert and informed work- 
man much inftruftion, will, we prefume, gratify the curi- 
ofity of the inquifitive mind, as far as the detail goes. _ 
We will fuppofe that a portable eight-day clock, with 
a half-feconds pendulum, and a fpring for a maintaining 
power, is fixed upon as the inftrument to be made. The 
firll thing to be done, and that in which the clock-maker is 
generally deficient, is, to calculate the movement, orproper 
number of teeth in the wheels, and of leaves in the pi¬ 
nions, of the going part of the mechanifm. Dr. Derham, 
in his Artificial Clock-maker, has treated this fubjeft at 
confiderable length, and has laid down rules which have 
tended more to puzzle than affift the workman in the 
choice of his numbers : he propofes to take at random a 
certain number of vibrations per hour for a pendulum of 
an affumed length, to reprefent his train, and then to 
find the faftors or numbers, which, uled as multipliers, 
fhall give the requifite product, or nearly fo ; after which 
each faftor is reprelented by a ratio of two optional num¬ 
bers, to conftitute a wheel and its pinion. We will not 
follow the doftor through his proceffes here, but merely 
obferve, that, by calculating his whole movement at one 
operation from an affumed number of vibrations, he has 
introduced a variety of fuch trains into portable clocks 
and watches, as make a vibration of the fhort pendulum, 
.and an ofcillation of the balance, no exaft fraftion of a 
fecond; in Ihort, he has begun at the wrong end; has 
fir It fixed on the length of his pendulum in inches, with¬ 
out confidering exaftly the number of vibrations it would 
make, and then calculated a train that would fo nearly 
fuit it, that the adjuftment for time by the bob would 
compenfate the defeft of the numbers; the confequence 
has been, that the exaft value of a vibration in a portable 
clock, and of an ofcillation in an ordinary watch, has hi¬ 
therto been difregarded in the conftruftion. On the con¬ 
trary, we recommend to the clock-maker, firff to fix upon 
his number of vibrations per fecond, and then to calcu¬ 
late the true length of his pendulum, and exaft value of 
his train, agreeably to the number of vibrations per fecond 
that he previoufly determined. 
The moll fimple way of calculating the numbers pro¬ 
per for the movement-of any dock, intended to (how fe- 
conds, is, by dividing it into three portions, and then by cal¬ 
culating the wheels and pinions for each/feparate portion, 
by a leparate calculation, beginning at the bottom of the 
train. Thus, 1. we firll fix upon the pinion of the hour- 
arbor to be, fuppofe 8, which is a good praftical num¬ 
ber ; and, as our piece is to go eight days, we will make 
the fufee to revolve in 12 hours, which conllruftion will 
require the great wheel on its arbor to be S x 12, or 96, 
becaul'e the pinion of 8 revolves, with the minute-hand on 
its projefting pivot, in one hour; hence if we divide 192, 
the number of hours in eight days, by 12, the time of one 
revolution of the great wheel, the quotient 16 will be the 
number of effeftive fpiral grooves necelfary to be cut on 
the circumference of the .fufee, in order that the piece 
may go juft eight days. This portion of the movement 
is not, however, called a part of the train, but only de¬ 
termines, as has been faid, the time that the clock Ihall 
continue to go after each winding up of the maintaining 
power ; and it is eafy to conceive, that, if a fufee or a 
barrel, with 24 turns of the catgut or chain, were placed 
on the hour-arbor, the clock would go a natural day 
without the large wheel; and alfo, that, if an interme¬ 
diate wheel and pinion where placed on the arbor between 
the hour-arbor and the great wheel, the time of going, 
might be prolonged to 10, 12, or even 20, times eight 
days ; but then the maintaining power muft be propor¬ 
tionally increafed ; which circumftance renders fuch a 
conftruftion by no means defirable in a regulator, parti¬ 
cularly as the auxiliary fpring now in ufe will keep the 
piece in motion during the aft of winding up. 
2. The remaining portion of the movement is properly- 
called the train, including thofe wheels and pinions only 
which are uled for counting the vibrations made in an. 
hour; the train is moll eafily afeertained by two calcula¬ 
tions, one for the two wheels and two pinions which mul¬ 
tiply the minutes into feconds, and the other for that 
wheel and pinion, or thofe w'heds and pinions, which 
fubdivide the feconds into vibrations ; the former of thefe 
two portions of the train, like the firft portion of the 
movement, or portion for the period of continuance, is 
the fame for all clocks, let the time of vibration be what 
it may, a circumftance not ufually conlidered: the ratio 
of velocity to be gained by the pinion on the arbor of 
the feconds-hand, compared with the wheel on the arbor 
of the m-inutes-hand, is required to be as 60 to 1 ; which 
effeft might be produced by one wheel of 300 teeth, and 
a pinion of 5 leaves, as is done in fome of the ornamental 
French pieces; but the fize of the wheel is cumberfome, 
therefore a pair of wheels, with a pair of pinions, one confti- 
tuting a ratio or vulgar fraction equal in value to 8, and the 
other equal to 7-J, making 8 X 7} = 60, or any other two 
numbers making'a fimilar produft, will produce the fame 
effeft with fewer teeth; for if the pinions be each 8, the 
wheels, in this cafe, will be refpeftively 64 and 60, the 
8 8 1 
compound ratio — X — being equal to the fimple— 
and, by the fame procefs, if pinions of 10 had been 
chofen/ the wheels would have been 8 X 10=280, and 
10 X 7 j = 75> which numbers would indeed have lefs fric¬ 
tion than the pr ceding ones, by reafon of their teeth aft- 
ing at Id's depth, the diameters of the wheels remaining 
