ASTRONOMY.
1
Quantity of matter, If being 1, (M. tieLa Grange)
Quantity of matter, If being 1, (M.Bailly)
Quantity of matter, 2X being I, (M.La Place)
Diameter, If being 1, as deduced fromM. Bailly and M. de La Lande’s de-termination of the satellites’ appar.diam. as seen from IIMagnitude, If being 1Diameter, the © being 1Magnitude, the © being 1 L
Diameter, expressed in whole mini-!
bers and fractions, the © being 1 IMagnitude, expressed in whole numbersI and fractions, the © being 1 i
I.
II.
0,00006869
0,00002417
0,0000638
0,0000211
0,0000672011
0,0000237103
0,09930350,000985141,08080701,2619618
0,0777411
0,00046926
0,8444364
0,6015917
Ws
0*4
244933
38S7S2
III. IV.
0,0000687
0,0000638
0,00005 .
0,0000872128
0.00005446S1
0,0938811
0,00082743
1,0197365
1,05993803
0,0709347
0,00035675
0,77049271
0,45699361
‘T&V
1 A
1002909
621187
(200.) TABLE III. Satellites of Saturn.
Satellite, j
Periodic
revolution.
Synodic revolution.
Dist. from fj insemid. of the ring(Bradley.)
Dist. from insemid. of!j (Bradley.)
Dist. from Ij inminutes and se-conds.
Dist. from
d.
h.
m.
s.
•d.
h.
in.
s.
'
f
1/
I. or VII.
0
22
37
23
0
22
37
30
*
0
28-|
112,000
II. or VI.
1
8
53
9
1
8
53
24
0
37
140,000
III. or I.
1
21
18
26,222
1
21
18
54,778
2,097
4,893
0
431
172,000
IV. or II.
2
17
44
51,177 -
2
17
45
51,013
2,686
6,268
0
56
217,000
V. or III.
4
12
25
11,100
4
12
27
55,239
3,752
8,754
1
18
315,000
VI. or IV.
15
22
41
13,052
15
23
15
20,175
8,698
20,295
3
0
709,000
VII. or V.
79
7
53
42,778
79
22
3
12,883
25,348
59,154
8
42 J-
2,126,000
(201.) TABLE IV. Satellites of IIerschel.
Satellite.
i
Sidereal Revolu-tion.
Synodic Revolu-tion.
Mean Dist. from $m minutes and se-conds.
Dist. from i§ insemidiameters of
Dist. from IjJ inmiles.
When discovered.
d.
h.
m.
s.
cl.
h.
HI.
s.
'
«
I.
5
21
23
22
5
21
25
0
0
25,5
13,1443
226450
1798
II.
8
16
57
43
8
17
1
19
0
33,0
17,0103
293053
1787
III.
10
22
5S
20
10
23
4
0
0
38,6
19,8969
342784
1798
IV.
13
10
56
29
13
11
5
1
0
44,2 '
22,7835
392514
1787
V.
38
0
39
4
38
1
49
0
1
28,4
45,5670
785'028
1798
VI.
107
7
35
10
107
16
40
0
2
56.8
91,1340
1570057
1798
Sect. XVI. Of the Fixed Stars .
(202.) The fixed stars are particularly distinguished from theplanets, in their not sensibly changing tHeir situation with regainto one another. They are also, in our climates, known by theirtwinkling, which seems to depend on the atmosphere ; for we areassured, that where the air is exceedingly pure and dry, the starsappear with a light absolutely fixed. The distance of the fixedstare is so great, that the diameter of the Earth ’s orbit, which is191 millions of miles, is but as a point in comparison; for there isno sensible difference in the aspect of a star from whatever pointof the Earth ’s orbit it is viewed, that is, it has no sensible annual pa-rallax. Some astronomers, however, assert that they have dis-covered, in certain stars, an annual parallax of a few seconds. Cas-sini says, he found the parallax of Arcturus 7", and ofCapella 8";this would make the distance of Arcturus about 20250 times thedistance of the Sun from the Earth , or about 2 millions of mil-lions of miles. Ollier astronomers, who have made careful obser-vations, have not been able to discover even the small parallaxabove mentioned, neither have we any certain method for deter-
mining the true distance of the fixed stars; the most probable con-jecture makes the nearest of them about 200 thousand times.fur-ther distant than the Sun, or 19 millions of millions of English miles, for Dr. IIerschel says, if the parallax amounted even'to asecond, he is certain lie could have observed it. Besides the wantof a sensible annual parallax, what renders the above account oftheir distances exceedingly probable, is that the apparent diameterof a fixed star is not sensibly magnified by the best telescopes, butappears only as a luminous point. The stars, on account of their im-mense distance, seem to be fixed in a vast concave Sphere, ofwhich the orbit of the Earth is the centre, and because ol their ap-parently various magnitudes, have been distributed into severalclasses, or orders. Those which appear largest, are called stars ofthe first magnitude ; the next to them in lustre, stars of the secondmagnitude ; and so on to the sixth, which are the smallest that arevisible to the bare eye. This distribution having been made longbefore the invention of telescopes, the stars which cannot he seenwithout the assistance of these instruments, arc distinguished by thename of telescopic stars.
9
(2 03.) The