ORRERY. 
fyftem, and thofe in the moft natural way. It would lead us 
beyond our original intention to arrange and exemplify a fy{- 
tematic feries of problems, that may be folved by the moft 
improved orrery, which we hope foon to fee publifhed in a 
feparate pamphlet ; but we conceive our article will not be 
confidered as complete without the addition of fome general 
precepts for its rectification, that may enable its pofleffor to 
moving, 
In general it will be found 
mofl convenient to adjuit the planetary bodies to their places 
or the beginning of the year, if the motions reprefented are 
mean, becaufe they are given in the tables without calcula- 
tion, and then turning the handle till the annual index arrives 
at the given day, will put all the bodies that have motion to 
their re{pective mean places for the day fo indicated; bu 
oe 
may be made from the almanac with equal convenience on any 
o- 
from it, as though the mean and equated places were the time for which an orrery, for either mean or equated mo- 
fame ; whereas they never coincide, except in the perihelion tions, 13 required to be retified, and the requifite places will 
and aphelion points of their refpeCtive orbits: when, there- be found, as they appear in the fubjoined table ; viz. 
Planets. Mean Longitude. Aphelion. Mean Anomaly. Equation of the Cen.re. Posen hie 
Ss o 4 8 Oo i $ 0 i Tl ar) j ul tn a) ] FY) 
Mercury - - 3 8 48 36 8 14 33 2 6 24 15 34 + 0 12 28 50 3 21 17 26 
Venus - ~ 6 12 15 29 10 68 46 43 8 3 28 46 + © ©O 42 30 6 12 57 59 
Earth - ° 3 10 44 39 9 9 42 28 6 1 21 + 0 02 rf 3 I0 46 40 
Mars : - 6 20 5I 44 5 2 37 48 1 18 13 56 —- © 722 3 6 13 29 41 
Vetta : - I 15 52 45 2 Q 50 32 Io 6 2 13 + © 726 0 1 23 18 45 
Juno = . Il 13 52 25 72317 +I 3 20 35 24 — 0 29 34 0 Io 14 18 25 
ere - - 9 25 51 37 10 26 37 59 10 29 13 38 + O 414 0 10: O39 37 
Pallas - - 91341 4 [10 1 12 21 | 11 12 28 43 + © 634 oO 9 2015 4 
Jupiter = - 3 26 30 38 6 11 20 39 9 15 9 59 + 0 5 14 15 4 1 44 53 
Saturn - - gi12 811 8 29 18 29 © 12 49 42 Oo I 20 19 9 10 47 51 
Georgian - - 7 19 21 54 I 17 32 16 8 1 49 38 — 0 4 50 36 7 24 12 30 
pogee. — 
Moon - - 9 9° 25 40 I 427 12 7 25 58 28 + 11 22 58 18 8 23 23 58 
Moon’s node - ; 4 28 47 O 
In this table the firft column contains the names of the 
planets ; the fecond gives the mean longitudes from the tables 
of the epochs; the third fhews the place of the aphelion or 
apogee refpectively ; the fourth gives the difference between 
the fecond and third columns, when the latter is fubtracted ; 
the fifth contains the correfponding equation of the centre, 
taken from the table of mean anomalies, and the fixth fhews 
the funr or difference of columns 2 and 5, which is the equated 
longitude as feen from the fun. This laft column would 
be the fame as the column of heliocentric longitudes in 
the almanac, if the minor equations had been attended to, 
as contained in th tables; but the amount of thefe is fo 
{mall, that they may be negle&ted without fenfible error in 
the adjuftments of the-planetary bodies, when the places are 
not taken from the almanac. In this manner a table may be 
ealily conftruéted for the beginning of any particular year, 
but let it be remembered that the epoch for the planets begin 
the year on December 31, 1812, but the fun (or earth) and 
oon on Januar i 
3 
tables. Whenever an orrery for mean motions is rectified it 
mult be from column 2, and the equation in column 5 thews, 
by reverfing the figns + and —, how much the place is 
before or behind the apparent or true place at the beginning 
of the year; as for any other time the longitude of the 
aphelion muft be taken from the place of mean motion, for 
the mean anomaly, as the argument for the correfponding 
equation to be added or fubtracted, accordingly as the 
quantity is more or lefs than fix figns: but when an 7 
that 
