' 51 



The common error into which they have fallen is, as appears to 

 me, pointed out in a paper of mine in the 8th volume of the trans- 

 actions of this academy. 



Although the above investigation is only exact to the first power 

 of the excentricity of the lunar orbit, yet it appears that the ex- 

 centricity does not enter the above expression for the motion of 

 the perigee, and therefore it follows that the excentricity of the 

 lunar orbit has but little effect in the motion of the perigee. 

 In fact only the second powers of the excentricities of the solar 

 and Imiar orbits and the second power of the tangent of the in- 

 clination of the lunar orbit to the plane of the ecliptic enter 

 into the more exact expression of the mean motion of the lunar 

 perigee. 



I 2 



