NUMBERS. 
not be crowded together, nor feveral words of the fame ter- 
mination, efpecially if the accent falls on the fame fyllable in 
each of them ; ould a fentence end with a monofyl- 
lable: to which may be added, that very long words are not 
fuited to the beginning orconclufion of a pericd. Ward's 
Orat. vol. i. p..380, 
the period affumed for the revolution of the firft is to the pe- 
; 43 a olanet framed a. 
To afcertain numbers f{uitable 
for planetary wheelwork, both as to accuracy and practical 
convenience, is to fele& out of' all the infinite variety of nu- 
merical figures, that permutation would produce, thofe par- 
ticular relative numbers that fulfil the conditions beft, and 
the 10 
{elf or friends, which are as yet unknown to the public, but 
which it is our intention to defcribe under their proper titles 
of Orrery and Pranretarium, when we afrive at thofe ar. 
ticles. In the mean time, the reader will be enabled to judge 
of the comparative merits of fuch machines, by a careful 
perufal of our prefent article, which naturally divides itfelf 
into three heads; viz. 
ft. That which relates to the exa€ periods of the plane- ” 
tary revolutions ; 
adly. That which regards the periods as produced by 
wheelwork already conftruéted ; and, 
. That which regards the calculation of planetary 
numbers intended to produce an exact reprefentation of thofe 
periods. 
For the fake of perfpicuity, we propofe to confine 
ourfelves to this order; but each of the two laft heads 
will be fubdivided into diftin@ cafes, for the putpofe of af- 
fording pra¢tical examples in each cafe, fuch as may ferve 
at once to illuftrate the theory, and to promote the praCtical 
application of planetary numbers, in the examination and 
pines conftruction of machines for illuftrating the folar 
em. 
The firft head that prefents itfelf to our confideration is 
that which relates to the exact periods of the planetary re- 
volutions themfelves, fo far as the prefent flate of our know- 
ledge goes ; 
calculations dependin 
acy. le are tnerefore unwilling to copy the accounts 
of our predeceffors, which have been handed down without 
due attention to correétnefs, and which our contemporaries 
have not taken the trouble to corre&, fince the moft perfe& 
m 
Nautical Almanac and White’s Ephemeris, which regifter 
the apparent places of the heavenly bodies, and phenomena 
arifing out of their relative motions. 
The tables of the planetary motions are fo arranged in 
months, d hours, minutes, and 
we {hall have the 
4 " 
Mercury. 1126 212 = 87 days. 
© 3.55 19 = 23 hours. 
© © 2 23 = 14 minutes. 
0 0 O 6 = 35.2 feconds. 
The amount 12 0 0 o = 874 23h 14" 35".2 for 
: ’ the whole tropical period. 
VENUS. 11 28 53 9 = 224 days 
o 1 4 § = 16 hours 
© 0 244 = 41 minutes. — 
© 0 oO 2 = _ 30 feconds. 
The amount 2249 16" 41™ 30° for 
the tropical period. 
EARTH: 
