On Kirkwood’s law of the rotation of the Primary Planets. 219 
Kirkwood ; column fifth exhibits the sidereal times of revolution 
of each of the planets round the sun; column sixth, the probable 
times of rotation upon their axes ; and column seventh exhibits the 
computed value of dl which, according to Kirkwood, should 
be a constant quantity. Columns second and fifth are taken from 
the last edition of Sir J. Herschel’s Astronomy, with the exception 
of Neptune, which is taken from Mr. Walker’s computations, and 
the asteroids, which are taken from the latest orbits ; column third 
is taken from Encke’s Memoir in the Ast. Nach., No. 443, with 
the exception of Neptune, which is derived from Bond’s observa- 
tions of the satellite ; and the asteroids, which I have assumed as 
together equal to Mars; column sixth is taken from Madler’s 
Populaire Astronomie, 4te Auflage, with the exception of the 
Asteroids, whose period is assumed at 27 hours, being the time 
assigned for Juno in the Edinburgh Encyclopedia, vol. ii, page 
601, and Uranus, which is taken from Herschel’s Astronomy, 
page 648. 
Diameter of 
Meandistance. Mass, _ |the sphere of| Sidereal revolution. |Rotation onaxis, C. 
nen attraction. 
a AS me ee 
Mere’y, 03870981, 554751 87-969258024 528°3 
Venus, 0°7233316 7 5!s75 0°395664, 224-7007869 23 2121-93, 928 
Earth; 1-0000000 =; 0°525483) 365°25636122356 4-09) 961 
Mars, | 1:5236923,,¢3-537 0°651042| 686-9796458 24 37 20:4 |1275 
| | 0 
Astr’ds,2545 5.45 0562186, 1488 3138 
Jupiter, 52027760 y 574-71 9'409019, 43325848212, 955 26°56) 833 
Saturn, 95387861 z547- 8'546946 10759:2198174 1029 168 | 985 
Uranus, 1918239 | 22). fr-7igeedanees-sanszog 930 (3614) 
\ +o 
Nept’ne 30-0395 T9400 
The numbers in the last column of this table are not constant, 
Y one-twentieth of its whole value. The time of revolution of 
ranus about the sun is well known. The only remaining ele- 
Ment which enters into the computation, isthe rotation of Uranus 
Upon its axis. If we assume that this planet requires thirty-seven 
