CLOCK. 
rod of iron, and two tubes of brass. The 
iron rod is about a quarter of an inch in 
diameter, and is suspended by a spring in 
the common manner : it is inclosed by the 
first brass tube, to which it is connected at 
bottom : an iron tube, supported by the 
top of the brass tube, then descends a little 
below it, and supports by its lower extre- 
mity the second brass tube, which rises 
a little above the former tubes, and from 
the top of it the second iron tube descends 
below all about two inches into the sub- 
stance of the pendulum bob, which is very 
large and heavy: the bottom of tliis last 
tube contains a nut, into which a screw 
(having a milled heqd beneath that sustains 
the bob), passes frelm below, and raises or 
lowers the bob, as required for the adjust- 
ment of the rate of going of the clock. We 
may date the invention of the tubular pen- 
dulum, from the foregoing information, about 
the year 1775, though it may yet be found 
to be of a still earlier period. The foreman 
of Mr. Villaumy, clock-maker to the Prince 
of Wales, Pall Mall, declares, that he re- 
members a tubular pendulum to have been 
made by Mr. Finney, a well-known clock - 
maker of Liverpool, upwards of forty years 
ago, and that it is now in the possession of 
Mr. De Membry, of Richmond; but time 
will not permit the farther investigation of 
this point at present. 
The last modification of the longitudinal 
compensation made public is that of Mr. 
Troughton, mathematical instrument maker; 
it differs from Chandler’s, tubular pendulum, 
in having but two tubes of brass, which af- 
ford the ascending compensations, while the 
descending ones are performed by five 
wires of steel. The order of brass and steel 
is the same as in Chandler's pendulum; but 
all the steel wires pass downwards through 
the internal brass tube. The last pair of 
wires connect the whole with the bob by a 
short cylindrical piece of brass, to which the 
bob is suspended by its centre. 
Mr. Troughton made this pendulum in 
July, 1804, and published the first account 
of it in December same year, in Nicholson’s 
Philosophical Journal : we believe he knew 
nothing of the priority of Chandler’s tubular 
pendulum to his, and that in thinking and 
declaring himself the, first inventor of tubu- 
lar pendulums, he only fell into an error 
common to many other ingenious men on 
similar, occasions ; and this error is the more 
excuseable, as at tlie time Chandler made 
his pendidum, there were no periodical w'orks 
in existence which professedly recorded the 
improvements ot arts and manufactures, and 
artists were in general more careful to con- 
ceal their discoveries than to acquire repu- 
tation by making them public. 
Before concluding the enumeration of 
various sorts of pendulums, one suggested 
by Mr. Troughton should be noticed, which 
seems worthy of trial. He proposes that 
its rod should be made of baked potter’s 
earth, of the same composition of Wedge- 
wood’s thermometer, and furnished with a 
metallic cap, by which it should be sustained 
by the knife-edge suspension, which the ce- 
lebrated Berthoud affirms has less friction 
than the spring suspension. 
The chief advantages which tubular pen- 
dulums have over those of the gridiron con- 
struction are, that they admit of being much 
lighter above the bob with equal strength; 
that they experience less resistance from 
the air in their vibrations ; and that they are 
less liable to those shakes and irregular mo- 
tions in their expansions which the others 
experience : on the other hand, as the out- 
side tube alone in them comes in contact 
with the air through which it passes in its 
vibrations, the inner tubes can receive much 
less of its influence as to temperature, which 
arises from this motion, and which Cum- 
mings has shewn to be of considerable con- 
sequence. In Troughton’s pendulum the 
great difference of the masses of matter be- 
tween the ascending and descending parts 
must be another source of error, as the small 
wires of which the latter consist indubitably 
will much sooner experience the influence 
of a change of temperature in the air than 
the more bulky substance of the tubes. In 
this latter respect Chandler’s tubular pen- 
dulum seems superior to Troughton’s, all its 
parts being much more nearly of the same 
magnitude. 
More accurate comparative trials be- 
tween these gridiron and tubular compen- 
sating pendulums than any which have yet 
been made seem, however, necessary to 
determine the superiority of either ; and the 
preference which many are now inclined to 
give the tubular construction seems more 
to arise from the greater neatness of its ap- 
pearance than from any sufficient experi- 
ence of its higher merit. 
That it may be superior is very possible ; 
we only aver that this has not been yet prov- 
ed. But if equal apertures were made at 
both sides of tubular pendulums, through all 
tlie tubes, it would obviate the chief objec- 
tion to tiiem, by admitting tlie air to act on 
all flieir parts at once. 
