On Kirkwood’s law of the rotation of the Primary Planets. 221 
flection naturally suggests itself, that inasmuch as several new 
asterol ntly been discovered, we must be quite igno- 
rant of their total number; and hence if these planets were 
once united in a single body, there must be great uncertainty 
with regard to its mass and the dimensions of its orbit. It is, 
asteroids amounts to only about one twentieth of Mars. It seems 
then to be a very liberal allowance to admit that all the asteroids, 
discovered and undiscovered, are equal in volume to the planet 
Mars. Mr. Walker has computed (Am. Jour., vol. x, p. 22) thata 
planet with a mass double that of Mars would harmonize perfectly 
with Kirkwood’s law. 'The existence of so large a mass appears 
to me improbable. ; 
double mass, has obtaingd a period of 58 hours. Is thisanallow- ._ 
Shag 
: ae 
harmonize well with Kirkwood’s law. 
Mr. Walker bias | 
long ago computed the mass‘of Mars to be 32375) (Mee. Cel., 
Vol. iii, p. 334), Barekhardt in the Connaissance des Tems for 1816, 
| diminished this by one twentieth, making it equal to sss3a37 
| id this is the mass now generally adopted. ‘To increase it 
Without any authority by more than one fifth of its value, seems 
altogethe i se fii : : ; : 
r inadmissible. 
