396 Kirkwood’s Analogy in the Periods of 
n’=the number performed by the latter; then it will be found 
3 
that n? 3 n/?::D* : D’?; or n=n’ (B® 
For,the sake of convenient reference, I subjoin the following 
tables. The masses of Venus, the Earth, Mars, Jupiter, and Sat- 
urn, are taken from your edition (1845) of Sir John Herschel’s 
Treatise on Astronomy. Those of Mercury and Uranus corres-. 
pond with my hypothesis, and are nearly identical with the most 
recent and reliable determinations of astronomers. In other 
words, the mass of Mercury is very nearly a medium between 
the two estimates of Encke,* while that of Uranus is more than 
4iths of Struve’s mass, ;;4;,; found by observations on the sat- 
ellites.+ The mean distances not being given in miles in Hers- 
chel’s Treatise, I have used the table of distances in the Astron- 
omy of Professor Norton. For Mars’s period of rotation (245 37™ 
20%. 6.) Ihave adopted the recent determination of Prof. O. M. 
Mitchel, (Sid. Mess., vol. i, p. 52) 
TABLE IL. 
, : No, rotations 
Frat? Pigs Diner fond ain” aryl ene | © Toe 
Mereury,| 36,814,000 277,000) 5263 87-63) 1-942653 
Venus, :787,000| 2,463,836) 1569-6, 230-9 |2°363424 
Earth, 95 10d. po0 2,817,409 1678°5 
144,908,000 392,735, 626-7, 669-6 |2825815 
upiter, | 494,797,000 953,570,222 30879:8 10471: |4-:019988 
Saturn, | 907,162,000 284,738,000 16874:124620- |4:391288 
Uranus, |1,824,290,000| 35,186,000, 5931-5 
The points of equal attraction between the planets severally 
(when in conjunction) are situated as follows:— » 
TABLE Y. 
Miles from the 1 tg the 
Between Mercnry and Venus, 8,029,600 23,943,400) 
«Venus and Earth, 12,716,600, 13,599,400 
« Barth and Mars, 36,264,600 13,540,400 
« Jupiter and Saturn, 266,655,000 145,710,000) 
ing to my empirical law, will be found to be as follows :— 
* See Prof. Encke’s letter to Mr. Airy, dated Dee, 20, 1841. 
¢ Edinburgh Phil. Journal, for July, i848. 
