On Kirkwood’s Analogy. 9 
Art. I1.—On Kirkwood’s Analogy; by J. Braprorp Cuerri- 
man, M.A., Fellow of St. John’s Coll., Cambridge, Eng., and 
Dep. Prof. of Math. and Nat. Phil. in the University of 'To- 
ronto, U. C. 
In support of the remarks of Prof. Loomis in the American 
Journal, March, 1851, I beg to offer the following considerations. 
The statement of Kirkwood’s Analogy is that throughout the 
Planetary system, 
nts) D3 
where 7 is the ratio of the sidereal period of a planet to its time 
of rotation about its axis : 
D is the diameter of its sphere of attraction, 
k is a numerical constant. 
trary quantities, namely, the mass, mean distance, and time of 
Analogy in this case also to be indeterminate. 
Srconp Sens, Vol. XIV, No. 40.—July, 1852, 
