HOROLOGY. 
Ir? pradice it will be found very convenient to have a 
Table conftructed, fhowing the error of the chronometer 
at the noon of every day for leveral weeks, or during the 
efti mated time of the run to a place where its error 
and rate can be again fettled. To this Table a column 
fhould be added, containing its hourly rate continued up 
to 24. hours. 
Thus, fuppofmg the daily rate- of a chronometer, de¬ 
duced from a feries of obfervations, was — 4?'72, and its 
error for mean time. May 9, 1802, at noon was 3 m 58^6 
flow ; then we fliall have the fubjoined Table; viz. 
Error of Chronometer at Mean Noon. 
Hourly Rate. 
(J May 
9 
Error 
3 m 
58-6 
I 
hour — 
0 s *2 
9 - 
10 . 
— 
“ 
4 
3 '3 
2 
- = 
0 -4 
% ~ 
I I 
— 
— 
4 
8 -o 
3 
•— — 
0 °6 
9 - 
I 2 
— 
4 
12 '8 
. 4 
— =: 
0 -8 
L_b - 
13 
— 
= 
4 
17 ‘5 
5 
— = 
I *o 
O — 
14 
— 
— 
4 
22 *2 
6 
— “ 
I *2 
D — 
1 5 
— 
4 
26 - 9 
7 
— = 
1 ’4 
8 - 
l 6 
— 
4 
31 ‘6 
8 
— — 
i *6 
9 - 
17 
— 
4 
36 -4 
9 
— — 
1 -8 
% - 
18 
— 
4 
41 -i 
IO 
— 
2 ’O 
9 - 
!9 
— 
— 
4 
45 '8 
I I 
— — 
2 * 2 
b - 
20 
— 
Z 7 ~. 
4 
50 *5 
I 2 
— ~ 
2 ’4 
In all calculations, where the time is afcertained from 
an obfervation of the fun’s or of a ftar’s altitude taken at 
a diftance from the meridian, the accuracy of the refult 
w ill entirely depend on the accuracy of the obfervation 
which furnifhed the data ; it is, therefore, of the utmoft 
importance, that the heavenly body ihould be in a fitua¬ 
tion, or azimuth line, in which its change of altitude is 
the greateft pofiible in a given time; this precife fituation 
in the diurnal or nocturnal arc of any body, depends 
partly on the -latitude of the place of obfervation, and 
partly on the object’s declination; but, in all the heavenly 
objects, the fituation alluded to, is when they are in the 
prime vertical; i. e. when they are either due eaft or due 
welt of the oblerver; therefore, the nearer the obferved 
objedt is to the prime vertical, provided it be not too near 
the horizon, fo as to be too much affedled by refraction, 
the more likely will the determined time be to be accurate. 
Dr. Mackay, in Table XXV. of his Theory and Practice 
of finding the Longitude, p, 56, vol. ii. has given us “ the 
altitude to be obferved, in order to afcertain the apparent 
time with the greateft accuracy,” which Table is very 
convenient for determining very 'nearly when any hea¬ 
venly objedt is due eait or weft. And Jofeph de Mendoza 
.Rios, efq. has given not only the requilite altitudes, but 
alfo the correfponding diftances from noon in time in a 
parallel column, with the fame arguments and mode of 
arrangement, in Table XXVIII. of his valuable and very 
cheap volume. This volume contains a complete collec¬ 
tion of Tables for navigation and nautical aftronomy, that 
no navigator Ihould be without. Indeed the commiffion- 
ers of the board of longitude, and the court of directors 
of the Eaft-India company, with a liberality charafteriftic 
of the Englilh nation, have enabled the author (who as 
liberally gives up his right to the benefits of his labours) 
to give, for we can hardly fay fell, to the world the work 
in queltion for one-third of its real value, as an encou¬ 
ragement to nautical fcience. 
From what we have fhown of the prefent highly-im¬ 
proved ftate of machines for meafuring time, we are jufti- 
fied in concluding with the following quotation from M. 
de Lalande: “ Harrifon made marine watches which do 
notvary a minute-in five months’ navigation. Le Roy and 
Berthoud have made fimilar ones in France; and now it 
is aCtualiy polfible to make a tour of the terraqueous globe 
without entertaining the leaft doubt as to the longitude. 
To know what the hour is on-board a velfel, there is not 
even need of calculation ; the Horary Tables that Mad. 
de Lalande has publifhed, give the hour to a fecond in all 
countries of the globe. Clocks have bee.n brought to fuch 
a degree of. perfection, as not to vary a fecond per day in 
307 
the courfe of a year; I have even one which has been forty 
years at the fame fecond. Encouraged by the perfection 
of the inftruments, aftronomers have acquired fo conftant 
and familiar a ufe o t them, that they can divide a fecond 
of time into ten parts without erring one-tenth.” Con- 
fiderations on Aftronomy by Lalande, 1803. 
For the benefit of thofe who defire fuller information 
upon every point which relates to clock and watch¬ 
making, we fliall fubjoin an extenfive chronological cata¬ 
logue of the chief writings relating to it, both in theory 
and praftice. 
Carmen de Aftronomico Horologio Argentoratenfi, 
fcriptum a M. Nicodemo Frifchlino Balingenfi, Academia: 
Tubingenfis Profefiore. A. D. 1575. 
Defcriptio brevis et fucci-nCta Horologii rariftimi asque 
ac pretiofiflimi, ab ingeniofiflimo mechanico Jo. Divide 
Lieberkiihn conftruCti. 1576. 
Conradi Dafypodii Heron Mechanicus. Ejufdem Horor 
logii aftronomiei, &c. 1580. 
Brevis Defcriptio artificiofi novi et aftronomiei Auto- 
mati Horologii, cujus iimile ante hac non exftitit; Jacobi 
Cunonis. 1581. 
Traite de Geometric et d’Horologiographie pratique, 
par Jean Bullant. 1602. 
Horologium altronomicum Upfalienfe, cujus artificiofifli- 
maftruCtura, analyfis, et ufus,&c. Laurent. Fornelio. 1630. 
Jo. Sarazini Horographum Catholicum feu Univerlale, 
quo omnia Horologia Sciotherica del'cribuntur. 1G30. 
Le nouveau Sciatere pour fabriquer d’Horloges. 1633. 
Athanafi Kircheri Ars magnis Lucis et Umbrae. 1646.. 
Johannis Baptifta Trotta Novum Horologium NoCtur- 
nam e Stellis. 1651. 
Chriftiani Hugenii a Zulichem Conft. F. Horologium. 
1658. It was in this elegant little piece that Huygens firft 
treated of the regulation of time by the pendulum; and 
on this he entered more at large in his celebrated work. 
Horologium ofcillatorium. 
A Narrative concerning the Succefs of Pendulum- 
Watches at Sea for finding the Longitude, by Major 
Holmes. Phil. Tranf. No. 1. 1665. 
Antonio Tempera l’Horologio giufto utilifiimo a navi- 
ganti. 1668. 
Chr. Hugenii Zulechemii Conft. F. Horologium ofcilla¬ 
torium, five de Motu Pendulorum ad Horplogia aptato 
demonftrationes geometricae. Paris, 1673. 
I. S. Horological Dialogues, in three parts; fhowing the 
nature, ufe, and right managing, of clocks and watches: 
with an Appendix, containing Mr. Oughtred’s method 
for calculating of numbers. 1675. 
Very exaCl Portable Watches, by Mr. Huygens. Phil. 
Tranf. No. 112. A. D. 1675. 
M. Leibnitz on his Portable Watches. Phil. Tranf. 
No. 113. A. D. 1675. 
Compendium Horologico-fciotericum et Geometricum, 
Chr. Zuicker. 1675. 
Factum de M. l’Abbe de Hautefeuille touchant les Pen- 
dules de Poche, contre Mr. Huyghens. 1675. 
M. Campani de Alimenis Horologium folo naturse motu 
atque ingenio, &c. 1677. 
Traite d’Horologiographie du Pere de la Magdeleine. 
1680. 
D. 1 . 1 . Becheri, de nova Temporis Dimetiendi Ratione, 
et accurata Horologiorum ConftruCtione, Theoria et Ex- 
perientia. Lond. 1680. 
Horologia Seioterica Prselibata ad delineandum feiote- 
ricon Declinationis Solaris quantum indies eft perceptibi- 
lis, per N. Hanbury. Lond. 1683, 
Horologium Horologiorum deferiptum et explicatum, 
ab Joanne Bartholo. Fichelli. Venit. 1685. 
Henrici Coetiii Arnhemienfis Horologiographia plana, 
feu Methodus in Superficiebus Planis omnia Horologio¬ 
rum Genera deferibenda Methodus. Lugd. Batav. 1689. 
Horological Dilquilitions. A work very neceflary for 
all that would underftand the true way of rightly manag¬ 
ing docks and watches. By John Smidt, C.M. 1694. 
j idle 
