A Librarian's Work. 361 



in such matters. Nevertheless, the complexity of 

 the questions involved requires that appeal should 

 often be made to him, and that he should always 

 review the work, for the correctness of which he 

 is ultimately responsible. As for the designation 

 of the proper entry on the subject-catalogue, the 

 cases are rare in which this can be entrusted to 

 any assistant. To classify the subject-matter of 

 a book is not always in itself easy, even when the 

 reference is only to general principles of classifica- 

 tions ; but a subject-catalogue, when once in ex- 

 istence, affords a vast mass of precedents which, 

 while they may lighten the problem to one who 

 has mastered the theory on which the catalogue 

 is constructed, at the same time make it the more 

 unmanageable to any one who has not done so. 

 To assign to any title its proper position, you must 

 not merely know what the book is about, but you 

 must understand the reasons, philosophical and 

 practical, which have determined the place to 

 which such titles have already been assigned. It 

 is a case in which no mere mechanical following 

 of tradition is of any avail. No general rules can 

 be laid down which a corps of assistants can fol- 

 low ; for in' general each case presents new fea- 

 tures of its own, so that to follow any rule se- 

 curely would require a mental training almost as 



