32] REMARKS ON SIR GEORGE AIRY'S NUMERICAL LUNAR THEORY. 267 



value of M to be 1 '0027259, which agrees very closely with the value found 

 by Sir George Airy by comparing the constant terms on the two sides of his 

 equation (10). 



The other two ways of finding M proposed by Sir George in p. 76 

 of his Theory, viz. by comparing the quantities on the two sides of the 

 equations (10) and (12), corresponding to the arguments 2 and 301 respec- 

 tively, are not satisfactory, as the results will be affected by errors in the 

 theoretical determinations of the mean motions of the Moon's perigee and 

 node respectively. 



The multiplier M, representing the sum of the masses of the Earth 

 and Moon, must be employed wherever the mutual attraction of these two 

 bodies comes in question. In Sir George Airy's note at p. 254 of the 

 March number of the Monthly Notices, he calls M the coefficient of the 

 solar term, but this is plainly a mistake. I should mention that I have 

 already communicated the substance of this paper to Sir George Airy himself. 



342 



