An admirable essay, _Some Aspects of Bibliography_ (1900), by John Ferguson (d. 1916) suggests the cooperative aspect that is characteristic of bibliographical studies in the last two generations. Although it is not a full-length bibliography of bibliographies, it reviews the kinds of bibliographies that have been made and appeals to scholars to compile the bibliographies necessary to satisfy the most obvious needs. Ferguson's modest list of some four hundred bibliographies is intended to serve two purposes. It is an effort to show the great variety of bibliographies that have been made and it offers a supplement to Petzholdt's _Bibliotheca bibliographica_. Ferguson's clear and very instructive classification of bibliographies is as follows: bibliographies according to (1) date; (2) place; (3) printer; (4) material;[185] (5) type;[186] (6) size;[187] (7) illustrations; (8) language; (9) subject; (10) groups of authors;[188] (11) individuals; (12) single books;[189] (13) anonymous books;[190] (14) suppressed books;[191] (15) rare books; (16) general bibliographies. Some categories of bibliographies might be added to this list. For example, he probably includes bibliographies of private presses in (3). He has no good place for bibliographies of translations, which do not fit easily in the ninth category of bibliographies according to subjects. Nor is there a convenient place for bibliographies of belles lettres according to genres like the novel, the essay, or the book review. The first bibliography of bibliographies published in the twentieth century is _A Register of National Bibliography with a selection of the chief bibliographical books and articles printed in other countries_ (3 v., 1905-1912) by W. P. Courtney (1845-1913). It is also the first effort of this sort to be made by an Englishman. Like the American Sabin, Courtney limits the bibliographies published in languages other than English to a selection. In the course of twenty years Courtney had accumulated a great many references and four years of work in preparation of the _Register_ greatly increased the number. He acknowledges the assistance of G. L. Apperson, who later published a useful collection of English proverbs, and Robert A. Peddie, who wrote a very large subject bibliography. He has taken references from Henri Stein's _Manuel_, especially references in the Slavic languages. He found that the vast number of bibliographies in print made necessary some limitations on the scope of his work. He excludes sale catalogues (although a few are cited), catalogues of manuscripts, and lists of maps and charts. Probably few will quarrel with his decision. He also omits many headings in the bibliography of geology, India, and other unspecified large fields. Here it would be helpful to know more accurately what these omissions were.