LECTURES ON THE LUNAR THEORY. 



[LECTURES on the Lunar Theory were given by Adams from 1860 with 

 few intermissions until 1889. Originally their aim was to illustrate geometri- 

 cally the analytical processes and thereby render them more comprehensible, 

 and they included some elegant theorems on the geometry of conies which 

 have since become common property ; but every year several lectures were 

 rewritten, and thus the whole fabric gradually changed into the form in 

 which it is here presented, the form, practically, in which he gave them 

 last. 



Perhaps it is superfluous to say that these Lectures stand upon a 

 different footing to treatises that are intended to form the basis of Tables. 

 With such, completeness is the first object and manner of presentation is 

 secondary. Immense as is the labour of forming a treatise of this de- 

 scription, there exist several that leave little to desire in respect to fulness 

 of detail. Indeed it may be suspected that their very perfection in the 

 quality they profess has stifled to some degree the proper development 

 of the subject, because at first sight it suggests that there is little left 

 to do in the Lunar Theory, unless one is prepared to track down the 

 inconsiderable errors that have eluded his Masters. This seems a mistake ; 

 the methods most suitable for the whole task adapt themselves comparatively 

 ill to each detail of it, and there seems much that remains to be done 

 in respect to inventing methods suitable for attacking separately, as far as 

 they permit of separate attack, the many difficulties into which the theory 

 divides at the outset, and thence perhaps approximating to a more adequate 

 knowledge than we now possess of the relative motion of Three Bodies. 

 So far, with the notable exception of Dr G. W. Hill and those that have 

 followed him, we have seen comparatively little effort in this direction. 



A. II. 1 



