Encyclopaedia Britannica, or, a Dictionary of arts, sciences, and miscellaneous literature : enlarged and improved. Illustrated with nearly six hundred engravings > Volume 18, RHI-SCR

AMUSEMENTS OF SCIENCE.
I'feceanifi
.Ke^rca-
Many more inftances might be pointed out, in which
the beats of a good watch would be extremely fervice-
tlon5’ ,, able in the practical branches of philofophy j but the
occurrence of fuch inftances will always point out the
propriety of the application, when it is once known and
practifed.
We Ihall therefore mention only one further advan¬
tage which feems peculiar to this mode of counting a
limited number of feconds by a watch, namely, that it
is free from any error which might arife from the gra¬
duations of a dial-plate, or unequal divifions in the teeth
■of wheels and pinions, where the feconds are counted
by a hand.
In order to introduce this method of meafuring fmall
portions of time accurately, it is defirable that a watch
be conftrufted fo as to make an exadl number of beats
per fecond rvithout a fraction, for then the reduflion of
beats into feconds would be more readily made. With
the view of promoting this objeft, Mr William Pearfon
has calculated mimbers for a watch, which will produce
the defired effeft, and which, as they are equally prac¬
ticable with thofe in ufe, we (hall here infert. By the
method of arrangement already given, the numbers pro¬
per for fuch a watch, as will indicate hours, minutes,
and feconds, by three hands, and alfo make juft four
beats per fecond, will ftand thus, viz.
50 great wheel
10—60 centre wheel
8—64 third wheel
8—48 contrate wheel
6—15 crown wheel
2 palats.
Dial work as ufual.
Six fpirals on the fufee—to go 30 hours.
By the preceding general rule for afeertaining the
beats per fecond in any watch, the calculation of thefe
numbers will be thus: 60 X 64 X 48 X 15 X 2=5529600,
and 8 X 8 X 6=384 *, then —-^^=14400 the beats
x 3°4
in an hour, and "^^—4 exactly, for the beats per fe¬
cond ; which agreement with the rule is a proof of the
accuracy of the numbers.
Before we conclude this fubje<3:, we may caution me¬
dical gentlemen againft an impofition which is pra61ifed
by fome watchmakers in the faleof watches with fecond
hands. It is no uncommon thing with fome of thefe
workmen to put a fecond hand with a flop and an ap¬
propriate face to a watch, the wheel work of which is
not calculated for indicating feconds. The fecond
watch, the numbers of which are fet down a little
above, was of this kind. In this watch that part of the
train which lay between the axle of the centre wheel
and that of the contrate wheel on which the hands are
placed, viz. x to only 56.25, inftead of 60, fo
that 3^ feconds are deficient in every minute, a defi¬
ciency which in 16 minutes is equal to a whole revolu-
i Nr- tion of the fecond hand *.
your. Jor the pUrp0fe Qf bringing to our afliftancte the fenfe
5'U1’ °f feeling, in teaching the ufe of the mechanic powers,
Mr Edgeworth has cortftrudted the following apparatus,
Ts p?.. to which he gives the name of panorganon.
•aon. It is compofed of two principal parts, a frame for
containing the moving machinery, and a capftan or
windlafs erefted on a Ji// or plank that is funk a few
inches into the ground. By thefe means, and by braces
or props, the frame is rendered fteady. The crofs rail
or trarfom is ftrengthened by braces, and a king-pojl to
make it lighter and cheaper. The capftan confifts of
an upright fhaft, on which are fixed two drums (about
either of which a rope may be wound), and two arms
or levers, by which the capftan may be turned round*
There is alfo an iron ferew fixed round the lower part
of the fhaft, to fhew the properties of the ferew as a me¬
chanic power. The rope which goes round the drum,
pafles over one of the pulleys near the top of the frame,
and below another pulley near the bottom. As two
drums of different fizes are employed, it is necefiary to
have an upright roller, for conducing the rope to the
pulleys in a proper direftion, when either of the drums
is ufed. Near the frame, and in the direction in which
the rope runs, is made a platform or road of deal boards,
one board in breadth and 20 or 30 feet long, on which
a fmall fledge loaded with different weights may be
drawn.
Fig. 53. reprefents the principal parts of this a; * a- Fi^. 53.
ratus. FF, the frame ; b, b, braces to keep the frame -
fteady; o, or, a, angular braces, and a king-poft to
ftrengthen the tranfom ; S, a round taper fhaft, ftrength-
ened above and below the mortices, through which
the levers pafs, with iron hoops 5 L </, two arms or levers
by which the fhaft, &c. are to be moved round ; DD,
the drums, which are of different circumferences $ R,
the roller to conduct the rope; P, the pulley, round
which the rope paffes to the larger drum ; P 2, another
pulley to anfwer to the fmaller drum ; P 3, a pulley
through which the rope paffes w hen experiments are
made with levers, &c* $ P 4, another pulley through
which the rope paffes when the fledge is ufed j Ro, the
road of deal boards for the fledge to move on 5 S /, the
fledge with pieces of hard wood attached to it to guide
it on the road. ^
As this machine is to be moved by the force of men Ufesof the
or children, and as this force varies, not only with the PanorSa-
ftrength and weights of each individual, but alfo accord-ntm'
ing to the different manner in which that ftrength or
weight is applied, we muft in the firft place eftablith
one determinate mode of applying human force to the
machine, as well as a method of determining the rela¬
tive force of each individual, whole ftrength is-employ~
ed in fetting it in motion.
I.
To ejlimate the force with which a perfon can draw
horizontally by a rope over his (boulder.
Hang a common long feale-beam (without feales or
chains) from the top or tranfom of the frame, fo that
one end of it may come within an inch of one fide or
port of the machine. Tie a rope to the hook of the
feale-beam, where the chains of the fcale are ufually
hung, and pafs it through the pulley P 3, which is
about four feet from the ground *, let the perfon pull
this rope from I towards 2, turning his back to the
machine, and pulling the rope over his (houlder (fig.
58.). As the pulley may be either too high or too Fig. c!,
low to permit the rope, to be horizontal, the perfon w'bo
pulls it ftiould be placed 10 or 15 feet from the ma¬
chine, which will leffen the angular dire&ion of the
cord, and thus diminifti the inaccuracy W the experi-
4^2 meat.