ORRERY. 
uch way, 
, y view it bifecting both the planetary ball 
and the fun, left there fhould be too great a parallax in 
manual allowance will be neceffary. We will now fuppofe the 
arms adjufted to the heliocentric longitudes, mean cr equated, 
as the cafe may be; and that the earth and moon want 
adjufting : let the moon be firft put to her longitude, after 
index, together with the lunar plate for the moon’s age, 
m 
fame height as t the earth, when t 
latitude, the circles of the globe muft be put fuitable to the 
hich 
fixed acrofs one another at right angles, muft not be altered 
till fome problem is to be folved for a new latitude or longi- 
tude, or both, as the cafe may be; but muft be fuffered to 
revolve with the earth, care being taken that the eaftern and 
weftern points of the horizon circle bife& the globe when 
the adjuftment is finifhed, and alfo that the points of the 
meridian circle, in contact with the horizon circle, be 
at the latitude and co-latutide of the place re{petively. 
tween the two hands muft be put equal to the fun’s mean 
ginning of the year 1813, is on the gift of December 1812, 
at 9 38™, and the next fubfequent one on January 2, 1813, 
at 4" 6™ nearly ; the fecond has its immerfion into the fhadow 
of Jupiter on December 31, 1812, at 5" 26™, and again on 
January 3, at 18" 44™ nearly ; the third on January 1, at 
168 46™, and its emerfion, or departure out of the fhadow, 
at 20" 17™ nearly ; and laftly, the fourth has its immer- 
fion on January 11, at 16° 9", and its emerfion at 20" 32", 
negleGting the feconds, which cannot be eftimated in the 
1 Sat 2 Sat | 3 Sat 4 Sat. 
D. He M. | D-H. M.| D. H. M |[D. H. M. 
1813,Epoch} o 8 43 | 0 3 25/1 12 15 [tr 3 6 
Equat. A I §1 3 8 5 43 Iz 35 
1813, u 4 9 18 4l 
Conjun@ion | o 10 38 | 0 6 42 | 1 18 16 jr 16 22 
Thefe times of mean conjuntion may be turned into ap- 
parent times by applying the equation of time as given in 
the Almanac, and a comparifon of the refults with the 
{creen, at the extremity of Jupiter’s arm, receives the 
fhadows of the fatellites, as well as of Jupiter himfelf, and 
the perpetual change taking place in the apparently vi. 
bratory motions to the tight and left of Jupiter before 
and after they pafs before his body, or through his fhadow, 
affords a pleafing obje& of contemplation, while the exa& 
time af each configuration is marked by the fame hour in« 
dex that points out the time of any other contemporar 
? phenomenon, 
