Now the aid which a well equipped library can furnish to all these higher institutions of learning, the academy, the seminary, the college, and the university, is quite incalculable. Their students are constantly engaged upon themes which not only demand the text-books they study, but collateral illustrations almost without number. The professors, too, who impart instruction, perpetually need to be instructed themselves, with fuller knowledge upon the themes they are daily called upon to elucidate. There is no text-book that can teach all, or anywhere near all there is upon the subject it professes to cover. So the library, which has many books upon that subject, comes in to supply its deficiencies. And the librarian is useful to the professors and students just in proportion as he knows, not the contents, but the range of books upon each subject sought to be investigated. Here is where the subject catalogue, or the dictionary catalogue, combining the subjects and the authors under a single alphabet, comes into play. But, as no catalogue of subjects was ever yet up to date in any considerable library, the librarian should be able to supplement the catalogue by his own knowledge of later works in any line of inquiry. The most profitable studies carried on in libraries are, beyond all question, what we may term topical researches. To pursue one subject though many authorities is the true way to arrive at comprehensive knowledge. And in this kind of research, the librarian ought to be better equipped than any who frequent his library. Why? Simply because his business is bibliography; which is not the business of learned professors, or other scholars who visit the library. The late Librarian Winsor said that he considered the librarian's instruction far more valuable than that of the specialist. And this may be owing largely to the point of view, as well as to the training, of each. The specialist, perhaps, is an enthusiast or a devotee to his science, and so apt to give undue importance to the details of it, or to magnify some one feature: the librarian, on the other hand, who is nothing if not comprehensive, takes the larger view of the wide field of literature on each subject, and his suggestions concerning sources of information are correspondingly valuable.