355 
HORO 
kept by Dr. Mafkelyne, Dr. Hornfby, count Briihl, Dr. 
(now Baron) Zach of Saxe Gotha, and Mr. Dutton, who 
had been partner with Mr. Mudge, yet the committee, at 
a lofs for an unerring rule by which to afcertain at all 
times an exadt rate to be depended upon in future trials, 
declared it as their opinion that fome of Mr. Arnold’s 
chronometers, particularly No. 36 and No. 68, “had gone 
with a degree of accuracy greater than could be Ihown 
on any correfponding trial of Mr. Mudge’s.” But in 
another part of the report of the leleft committee, which 
is too long to be copied at full length, it is faid, alluding 
to the foregoing report of the fub-committee that “ in 
virtue of this report, and of fuch other evidence as the 
inquiry has furnilhed, your committee have no difficulty 
in declaring, that they confider the improvement in ques¬ 
tion Sufficiently afcertained, and as likely to conduce to 
advantages Sufficiently important to attradl the notice of 
parliamentthen, after the attention of parliament had 
been directed to the circumftances of a life fpent in hope 
of benefiting the public more than of enriching the indi¬ 
vidual, the report concludes with thefe words : viz. 
“For thefe considerations, joined to thole above let forth, 
your committee think themfelv.es authorized to recom¬ 
mend the petitioner to the. attention of the lioufe, con¬ 
ceiving that the circumftances attending his cafe give him 
a Itrong plea to favour; and that the invention of which 
he is the author contains an important improvement in 
the art of conftrudting time-keepers, fuch as the houfe 
might well wilh to Secure to the public, as well as to re¬ 
ward the perfon by whom it was produced.” Accord¬ 
ingly, in the fame 3'ear 1793, the houfe of commons, af¬ 
ter the examination of various witnefles, notwithstanding 
the oppofition of the board of longitude, granted to Mr. 
Mudge, in addition to the 500I. juft mentioned, the fur¬ 
ther Sum of 2500I. under the aft of 1774. 
Mr. Mudge, jun. previoully to his father’s death, efta- 
bliffied a manufactory for thefe time-keepers, and em¬ 
ployed Meffrs. Howells, Pennington, Pendleton, and Col- 
man, to make them for him; fome few of which performed 
in a way that merited the approbation of certain naval of¬ 
ficers of great refpeftability, particularly lord Keith El- 
phinftone and lord Hugh Seymour ; but the difliculty of 
making the adjustments So accurately as Mr. Mudge fen. 
had done, and the high price put.upon them* about iso 
guineas each, induced the admiralty to decline giving any 
other than occasional orders for his majefty’s navy; the 
chronometers of. Arnold and Earnffiaw, which were deemed 
equally good by the board of longitude, being fold at an 
inferior price; though Kendal’s price for making a time¬ 
keeper after Harrifon’s model was 400I. 
We decline accompanying Mr. Mudge through his com¬ 
plaints againft his opponents, particularly againft Dr. Maf¬ 
kelyne, whom he has accufed of being too partial to his 
own darling child, the lunar method, to do juftice to any 
method purely mechanical for anfwering the fame impor¬ 
tant purpofe; a lerious complaint this, which is corrobo¬ 
rated by an aflertion, that Melfre. Harrifon and Arnold 
made fimilar complaints; but, in justification of the aftrono- 
mer royal, we will conclude our account of Mudge’s time¬ 
keeper with the concluding paffages of the doctor’s An- 
fwer to the Narrative: “The ufefulnefsof the board of lon¬ 
gitude is too well known to the public, and acknowledged 
by all but a difappointed artift, to require my pointing 
out instances in which they have materially ferved the 
public and done honour to the nation. Doubtlefs they 
deferve commendation in another refpeft, for having been 
careful concerning the distribution of the public money. 
They might indeed have been properly cenfured, if they 
had given it away to a perfon not legally entitled to it 
by the act of parliament, or by a partial preference of the 
lefs deServing perfon to the more deferving ones.” 
Arnold's Chronometer .—It would be fupertiuous to give an 
account of Such parts as are common in all modern time¬ 
keepers; we therefore propofe to omit the drawings of the 
movement and other portions of the mechanifm contained 
-within the frame of both Mr. Arnold’s and Mr. EarnShaw’s 
LOGY. 
chronometers, and beg leave to refer thofe readers who 
wish to fee all the individual portions of each of thefe two* 
to a pamphlet lately published by the commiffioners of 
longitude, in which are contained three plates of each 
author, with defcriptions, and the questions put by the 
board of longitude relative to each construction, with the 
anfwers. This pamphlet is entitled, “Explanations of 
Time-keepers constructed by Mr. Thomas Earnffiaw, and 
the late Mr. John Arnold,” 1806. The movements are 
made with pinions of 8 or 10, according as they are in¬ 
tended for pocket or box chronometers. It may be ne- 
ceffary to mention, that Mr. Arnold’s box chronometers 
have very Strong main-fprings, requiring a deeper barrel 
than is neceffary for the length of the frame-pillars ; on 
which account there is a cap fixed on the plane of the 
upper plate, to receive the lower pivot of the barrel- 
arbor, and to hold the click and click-fpring of the 
Itrong ratchet, as placed on the Square of this projecting 
arbor; but there is no occafion for Such addition in the 
pocket-chronometer. The lcapement-wheel A, Showm at 
fig. 91, is Mr. Arnold’s on an enlarged fcale, and 
is placed near the lower end of its arbor, within the 
frame, fo as to have only a fmall portion of it Seen by air 
eye placed over the cock, when the piece has its natural 
polition reverfed; this wheel is wffiat is called a funk one ; 
that is, it has its teeth, like thofe of a cylinder-fcapement- 
wheel in this refpeCt, projecting from the plane of the 
wheel. The Shape alfo of the teeth of the wheel before 
us differs from that of Mr. EarnShaw’s in another refpeCt; 
the triangular aCting part of each tooth, which is raifed 
from the plane of the wheel, is bounded by two Straight 
lines and a curve ; the curved portion, which aCts with' 
the jewelled face of the large pallet B, and which Mr. 
Arnold, jun. in his description calls a cycloidal curve, is 
defcribed as being generated by the revolution of a 
fmall circular piece of metal with a tracing-pin in its cir¬ 
cumference, while it rolls on the circumference of a larger 
metallic circle, as a bale; and is, therefore,properly Speak¬ 
ing, epicycloidal, a cycloid being generated by a circle 
rolling on a Straight line: the proportions of the generat¬ 
ing circle, and its baS’e are Stated to be as the diameter of 
the large pallet to that of the fcapement-wheel. 
“The Size of the pallet depends upon the number o£ 
teeth in the fcapement-wheel, (Says Mr. Arnold, in his 
Description of his father’s fcapement.) The radius of 
the pallet Should be equal to the distance between any 
two teeth of the wheel, and then their relative motions 
will be equal. If the wheel has twelve teeth, tile radius 
of the pallet will be thirty degrees, meafured on the cir¬ 
cumference of the wheel, and its diameter Sixty degrees 
(nearly) meafured in the fame manner, which will make it 
half the Size of the wheel. If it has thirteen teeth, the pal¬ 
let will, in diameter, meafure fifty-five degrees and a half; 
if fourteen teeth, fifty-one degrees and a half; and if fif¬ 
teen teeth, which is the number generally applied to 
pocket time-keepers, it will be forty-eight degrees. The 
marine (or box) time-keeper is made to beat half-Seconds^ 
the balance making 240 vibrations both ways in a mi¬ 
nute ; for if the balance-wheel has 15 teeth, the fourth 
wheel 80 teeth, and the balance-pinion 10 teeth, there 
will be 120 beats, or half-feconds, in one minute. It is. 
alS'o made with the fcapement-wheel of 12 teeth, the ba¬ 
lance-pinion having 7, and the fourth wheel 70, (count¬ 
ing from the great wheel;) confequently there will be 
120 beats or half-feconds in one minute, as before. It 
has been already remarked, that the pallet for 12 teeth' 
muft be half the diameter of the wheel, and for 15 teeth 
five-twelfths, or fifty degrees. The pocket time-keepers,, 
that they may not be difturbed by motion, have what is- 
called a quicker train, the Seconds-hand making 150 beats- 
upon the dial, or five beats in two Seconds. The fcape¬ 
ment-wheel has 15 teeth, the balance-pinion 8 teeth, and 
the fourth wheel 80; conlequently there will be 150 beats; 
in one-minute, the pallet being 50 degrees in diameter* 
meafured upon the circumference of the balance-wheel; 
No. mention has been.made of the numbers ol the teeth. 
in, 
