ORRERY. 
a ae to the proper ftems which om the wheel- 
work w ox, are adapted a {mall terreftrial globe, 
a a Aes motions pes moon : the globe has the annual 
me is m made 
Pr a gs inclined 5 aoe ving the etter motion of me 
and a motion on its axis to fhew the ee Fgren 
u 
lengths of the fucceffive ek and nights, dees ae eee 
with the motions of the planets. 
e wheelwork is fo one: that one turn of the 
handle anfwers to 24 hours of mean folar time; when a 
quicker motion is required a ey can be inftantly cnade, 
fo that one turn is equivalent to ten days: this latter motion 
will be found more convenient when the relative velocities of 
the planets round the fun, the inequality of the motion of a 
planet in the different parts of - tes and the apparent 
motions as feen from the earth, er a in the fyftem, 
nti bands 
0 the e fun. 
This pola was conftructed with the See of its being 
placed on a ftand, which would admit of its being grain 
paneer or tur cel back from the audience, and at the fam 
time of being moveable on an axis round its es fo as to 
ring any part of the ecliptic in front. When the face of 
th orrery is ere towards the com pany; the pofition, 
excentricity, &c. of the orbits, and the motions and mag- 
nitudes of the plone. are more confpicuous; and the motion 
: 9. 13... rotations per annum, or one, 
mon 83 % ig 10078 { as it refpe€ts the Earth, in 
8 40 320 20 
- —x == — of 365.4 - 
Mercury 3 7328" or = 0 365.924 
Venus - i x oe ad or 27 of ditto . 
83 24 1992 83 
Mars - — % oe 1S or oe of ditto 7 
83 12 996’ 83 
: 8 16 8 8 ; 
Jupiter - = x 4 = = or a of ditto - 
88 222 19536 2442 : 
Saturn - 33 x= ore or = of ditto - 
Diurnal Motion - x : x 7 = 365.24, or - 
Parallelifm - a2 x 47 x 3° = 26790 = I year, or - 
235 «19 6 26790 
‘ 1 
Lunation - aa of 365.24 - 
turned out of a s horizontal padaag the handle may be in- 
ferted into a made ath the box, in which fitua- 
tion the lecture a Teaareaieile turn the handle, 
the 
ty) r’s 6 affiftant 
whilft the leurer is pe iagiaer ng the effects produced by the 
particular portions of the m 
To demonttrate in the or aad manner the phenomena 
round the fa ns onthein fide 
ars thereof that 
paratus for fhewin 
of the ory exa 
a ipe 
the furface of ou 
ing ie 
of this rim 
n each fide of it 
e planets, as feen 
m is drawn, or intended 
to be drawn, the ecliptic with - conftellations, or principal 
lie within 10° 
the appa aut motions of the planets, 
above deferibed, is to be ufed along with ee rim ; when the 
wire paffing through the centres of the e 
will fhew, by means of a {mall bead affixed a its extremity, 
the apparent place, ae motion of the ria among the ftars 
f as they would appea 
the eyeo cator, viewing the fame in the heavens from 
lobe. 
he ap- 
rth and planets 
at the time to 
The wheelwork confifts of the following trains; viz. 
From the handle 
55 ¥ 72 
9 * 10 
Io 
3 
Io 
z= 365.2, that is, one 
turn per day very ees ; or by moving a flide the portion 
55; 
2. is difcharged, and the train becomes 
x 
hebel —_— = 
36 10 
36.52 turns ina year, or one turn in ten days hal eae, 
The large wheel of 83 teeth revolves once in a year, a 
gives motion to the 
everal whe 
and 
els and pinions placed round 
it, which aad phe periodical revolutions of the planets, 
as under ; 
* Ca a 
Moon’s Nodes 56 (cftimated thus 3) == 18} years 
59 3 
D. 
rt a8 
88 
20 
