This section devoted to bibliographies of individual authors exhibits some faults typical of Petzholdt's plan. A subdivision (pp. 156-166) without any heading begins the section and is terminated by three asterisks in the middle of the page. Although it is set off typographically, the lack of a heading makes it difficult to perceive that we have in it a list of the very important biobibliographical dictionaries of religious orders and learned academies. There is no indication of this category in the table of contents and the names of the religious orders and the academies do not appear in the index. I do not see how one can readily find a biobibliographical dictionary of the Dominicans or the Jesuits in this arrangement. Not all of us can bring to mind immediately the names Quétif and De Backer that are needed to find the references. In his list of individual bibliographies Petzholdt goes so far as to include books (not bibliographies, be it noticed) dealing with such artists as Jost Ammann, Rembrandt, and Velasquez. He could have found another place for books about famous publishers named Aldus and should probably have made a special place for dictionaries of homonyms.[152] He follows this section of individual bibliographies with a list of books containing portraits ("Ikonographische Literatur," pp. 273-279). Its pertinence to a bibliography of bibliographies seems debatable to me.
Petzholdt's execution of his plan leaves something to be desired. He provides the obviously necessary table of contents, but fails to include in it many subdivisions that he expresses by means of headings or typographical devices or only implies by the arrangement of titles. Experience teaches a reader that Petzholdt begins a section with general works, often a modern annual bibliography, proceeds through a chronological list, and concludes with specialized antiquarian catalogues. This is an altogether logical order. Subdivisions of a large category follow the general section. After the general bibliography of medicine, for example, Petzholdt continues with bibliographies of pathology and therapeutics (pp. 597-600). This arrangement makes necessary a full record of the subdivisions in an index, but Petzholdt's index is only an author index. There are occasional failures to include authors' names in the index. We must judge these flaws kindly, for all men are fallible, and bibliographers are no exception to the rule.
Writers of bibliographies of bibliographies have usually preferred a classification according to subjects to an alphabetical arrangement of titles with subject indexes. Joris Vorstius defends their preference eloquently and with good arguments.[153] There is, however, something to be said against it. Convenient as a classified bibliography is as first issued, it cannot be easily revised or enlarged.[154] When library cataloguers adopt new methods, when new categories are set up in science, theology, law, and literary history, a classified bibliography of bibliographies becomes difficult to use.
In the history of bibliographies of bibliographies we can look back to at least three occasions when men discarded the classified bibliographies made by their predecessors. Men of the seventeenth century seem to have made little use of Gesner's Pandectae, men of the eighteenth century found as little use for the difficult classification employed in Labbé's and Teissier's books, and few of us can use Petzholdt's categories easily. The lesson is that each age must create its own bibliography of bibliographies.
Petzholdt's Bibliotheca bibliographica is a classified bibliography that shows signs of obsolescence. The organization of knowledge and the categories that seemed suitable to Julius Petzholdt in 1866 are often confusing rather than helpful today. Keenly interested as he was in the theory of classification, no one was more competent than he to select the right headings. But a modern scholar who consults the Bibliotheca bibliographica must put himself in the place of a man who lived almost a century ago. For example, he must remember that Hungary was associated politically with Austria and Austrian cataloguers and dealers listed and sold Hungarian books. Consequently, Petzholdt cites (pp. 320-321) bibliographies of Hungarian books along with bibliographies of German books and makes no entry in the table of contents for Hungarian bibliographies. I do not say that he was wrong, but I do say that a modern reader must remember the political situation of 1866 to use Petzholdt's book.
Petzholdt's adoption of a classified arrangement required him to be very careful in assigning books to categories and to provide abundant cross-references. As we have seen, his subdivisions of categories are not clearly marked and may escape the notice of an experienced user of bibliographies. For example, a bibliography of "Programme" (learned essays issued with the annual reports of German secondary schools) appears (p. 293) properly enough among the bibliographies of German and Swiss publications but few will find it. A few pages later (pp. 298-299) Petzholdt lists bibliographies of German and Swiss journals. Since these two categories are not named in the table of contents or the index, the information is almost completely buried. "Prognostica" or prophecies of future events—a genre of writings that was very popular in the late Middle Ages and the Renaissance—gave Petzholdt trouble. Some of these are listed as pseudo-philosophy (see p. 467: Heuschling), and others are perhaps more appropriately found with almanacs ("Calenderliteratur," pp. 539-540). A bibliography of Swedish almanacs (p. 399) appears in the section for Swedish literature without a cross-reference to or from the bibliography of almanacs. "Loosbücher" or books telling how to interpret omens are in the section for psychology (p. 467), and this is a heading under "Philosophische Litteratur." Examples are wearisome, and I shall give no more.
A classified bibliography must have an exhaustive table of contents, a full index of authors, and an adequate alphabetical subject index. Petzholdt's Bibliotheca bibliographica is probably as carefully made as any such book can be made, but its table of contents is a scanty recapitulation of the very largest headings, its index of authors is incomplete, and a subject index is lacking. I have already expressed sincere admiration for the book and feel all the more keenly the presence of these defects.
Petzholdt's frequent disparaging remarks show that he did not esteem highly the bibliographical achievements of the sixteenth and seventeenth centuries. We need not defend them here, but we must recognize that his low opinion of them explains many omissions of early bibliographies in his own work. His admirable survey of books that a scholar would find useful in 1866 gives no adequate account of the historical development of bibliography or of the wealth of bibliographical work before 1750. His very convenient chronological arrangement of titles in the various categories does often suggest the historical development and at times his choice of older books is generous.
Petzholdt has not compared his accounts of some fields with easily available bibliographies and therefore fails to include obviously important books. In the field of national bibliographies, Petzholdt chose to pass over many older bibliographies that seemed to him to be no longer useful. Both the Latin and the German editions of Heinrich Pantaleon's rare sixteenth-century German biobibliography could perhaps be dispensed with, and I shall not object to his omission of them.[155] I think he should not have passed over without mention Henning Witte's biobibliographical dictionaries, which are still useful sources of information about obscure seventeenth century writers. To be sure, Witte's Repertorium biblicum is cited (p. 286), but this is the least useful of Witte's books. Petzholdt's account of German regional biobibliographies (pp. 299-322) can only be called superficial. In Robert F. Arnold, Allgemeine Bücherkunde zur neueren deutschen Literaturgeschichte,[156] which I have compared only for the first page (the entries extending from Aargau through Bayern), I find twelve books published before 1866 that Petzholdt does not name. If we turn to works of larger scope, one cannot easily find a reason for omitting D'Herbelot, Bibliothèque orientale. First published in 1697, improved and enlarged in later editions, and brought up to date by J. T. Zenker's continuation of 1846-1861, it remains the only general account of Oriental studies for its period. Petzholdt neglects to mention the seventeenth-century biobibliographies of Italian and French Orientalists compiled by Paul Colomies and deemed worthy of revision by no less a scholar than J. C. Wolf. With all its faults Namur's Bibliographie could have helped Petzholdt to fill such gaps.