Turning now from the consideration of the subdivisions, a few words may be useful in regard to the cross-references from subject headings to related subjects. In general, it may be said that references are made from the more inclusive to the smaller subjects, and not ordinarily back from smaller to larger. We should refer from Grain to Maize and Rye, but not from Maize and Rye back again to Grain. Where practicable, references are made from the most inclusive to somewhat more limited subjects, and from these latter to subjects still more specific, rather than from the inclusive to the specific subjects. We refer from Art to Engraving, from Engraving to Stipple-engraving, not directly from Art to Stipple-engraving. These general principles have been departed from where it has seemed expedient, the desire being to render the list useful and practical, rather than to make it adhere too strictly to rigid rules of procedure. The seeming incompleteness of references from many subjects, references which obviously are needed to round out the various aspects of subjects is due to the fact that certain headings are not as yet introduced in the Library of Congress catalog. We have been very conservative about introducing new headings until called for by the books in hand, judging that the headings should be made to conform to the literature, rather than the literature to the headings. The printing of a subject in antique type indicates that, in the library catalog, the subject has country subdivision, as in Education, Labor and laboring classes, Insurance, etc. It may be helpful to add here that the country is subordinated to the subject in our catalog, when it seems desirable to keep the material on a topic together, rather than to distribute it under the country headings. This includes many subjects in technology, science, art, and the social sciences. The numbers which follow the subject headings indicate where the material dealing with those subjects is classified in the Library of Congress. The explanatory words following these numbers serve merely to guide those interested in the classification scheme. They are in different form from the subject headings, and should not be confused with them. In the matter of hyphens, the Century dictionary has been used as an authority. At the present time the list of headings has been completed through the letter P. Q and R are now ready for the press, and will probably be issued in the course of a few weeks. The editor of the list sometimes feels it to be a cause for gratitude that the English alphabet is composed of only 26 letters. Should it contain as many letters as some other alphabets, the Sanskrit for example, the day of completion of the list might indeed be far away.