viii PREFACE TO PART I. 



of each new set of papers was little more than a guess until all the 

 writings in any one subject were collected. When this was done it was 

 possible to decide upon their bearing and importance, and then the work 

 of transcription was generally straightforward, though here and there it 

 became anything but easy. For example, in his lectures on the Lunar 

 Theory there were in most cases many drafts of each lecture, differing 

 substantially, and these had to be united ; or again, it was often very 

 hard to find the source of some formula or number quoted without 

 reference. 



At first it seemed that there was a danger that some considerable 

 work might be overlooked altogether, but I am confident that such is not 

 the case ; and that no lacuna worth mention is to be found in the following 

 pages is the best proof that I can offer. One which I was obliged to 

 pass at first is mentioned on p. 127, but, as will be seen on p. 237, 

 I was able to fill it up after the earlier sheets were printed off. 



Very few, probably, have written their studies in a form so finished 

 as Adams ; " he never blotted a line ;" it is impossible to exaggerate the 

 impression left by a study of these unrevised papers of his absolute 

 mastery _of every detail of this most intricate and difficult subject, of 

 freedom and ease in handling it from any standpoint, and of certainty and 

 exactness in his operations, seeming indeed to symbolize as well as to 

 calculate the motions of the stars. But it will easily be understood that 

 from such material it was impossible in all cases to reproduce his own 

 words and order ; to do so would have done unnecessary violence to the 

 matter, burdening it with any crudity that chanced to accompany its 

 conception ; and such a course would have been most repugnant to Adams's 

 own fastidious care. It was in fact necessary that I should rewrite the 

 papers. In doing so I have tried not to disturb what was characteristic, 

 and have added nothing to the matter but an occasional explanatory 

 sentence, and this is enclosed in brackets. Where a paper proved incom- 

 plete, it either appears with its defects, or is suppressed altogether. 



R. A. SAMPSON. 



DURHAM, 



2 May, 1900. 



