7 EA 
“ss, Examination of Kirkwood’s Analogy. = 
“e a : oe _ Conclusions from the above table. 
- From. this comparison of authorities, it appears that with a 
constant value of «= 15.300,t and with assumed masses of Mer- 
_-eury, Mars, and Uranus, equally plausible with those heretofore 
_ employed, the a, m, and 9, of the fifth or hypothetical planet 
a,’ may be thus interpolated : 
tages . *a=2.908.611 
1 
a  * 
| gel Sia Vn dee: 240 
Meg ret 6= 2.239.035 
) _ And then the system of nine values of a, m, and 0, will be 
‘Normal with reference to Kirkwood’s analogy, and each of the 
_ four fandamental conditions (I.) (II.) (III.) and (IV.) will be rig- 
- orously fulfilled for every middle planet of five. 
Mr. Kirkwood had remarked in his letter,t that his analogy 
required the assumption of a fifth planet between Mars and Jupi- 
ter. If the Geological Section was allowed the privilege of re- 
storing fishes, lizards, and elephants, there was no reason why the 
Physical Section should not be permitted to restore a planet. 
Remarks on the Degree of Constancy of «. 
‘The limits within which it is possible to vary the value of ~, 
without making some of the interpolated elements inadmissible, 
are about one-twentieth of the adopted mean value of 15.300. 
We may therefore conclude that, wHeTHER Kirkwoop’s ANALOGY 
THAT OF A PHYSICAL FACT IN THE MECHANISM OF THE UNIVERSE. 
The quantity D, on which the analogy is based, has such imme- 
diate dependence upon the nebular hypothesis, that it lends 
Strength to the latter, and gives new plausibility to the presump- 
tion that this, also, is a fact in the past history of the solar system. 
uch, then, is the present state of the question. Thirty-six 
elements of nine planets, (four being hypothetical, ) appear to har- 
Mouize with Kirkwood’s analogy in all the four fundamental 
equations of condition for each planet. 
‘lo suppose that so many independent variable quantities should 
harmonize together by accident, is a more strained construction 
of the premises than the frank admission that they follow a law 
of nature. , 
light on the internal organization of the planets, in their present, 
in any more primitive state, through which they may have 
* The mean di i that of the asteroids, except Hygeia, whi 
i a=8.18, anes is greater than of the asteroids, except Hygeia, which 
t This Journal [2], ix, 395. - 
