The acquisition and preservation of pamphlet and periodical literature should be sedulously cultivated by National Libraries. No fact is more familiar to students than the rapid disappearance of these ephemeral but often valuable publications. The chances of procuring any desired pamphlet a few months after its publication are incalculably smaller than those of securing copies of any book. Hence the importance of adding them to the one representative library of the Nation while they are yet fresh and procurable. As this species of literature is seldom protected by copyright, the greater portion of the pamphlets of any period must remain unrepresented in the Government Library unless their authors will take the trouble, by wise forethought, to send copies of their productions to Washington. Of the great value of pamphlets, as exponents of the thought of the time, and the questions which agitate the public mind, expressed frequently in condensed and forcible style, there can be no question. Of the periodical literature, in its vast extent and variety, now including, in the United States alone, more than twenty thousand different publications, a National Library should acquire and preserve the more important portions. These, in the absence of any possibility of providing room for all, may be held to embrace (1) All American reviews and magazines, with a selection of the leading English and European ones. (2) The daily newspapers of the larger cities of the country, and a few, at least, of the principal journals of England and the Continent, not forgetting the American republics, and Canada. (3) Two, at least, of the most widely circulated journals of each State and Territory in the Union, representing each political party. This has been the established policy of the Library for thirty years past, and the bound files of these periodicals constitute one of the most largely used portions of the Library. Only by keeping up full sets of the notable serials, whether literary, political, religious, historical, scientific, legal, medical, technical, agricultural, economic, etc., can the Library answer the just demands of the national legislature and of the public. In whatever direction American libraries may be inferior to those of other and older nations, they are (at least in the larger collections) well equipped with the literature of periodicals. The materials thus furnished to the politician, the historical writer, or the student of literature, are of great and incalculable value. A National Library is not for one generation alone, but for all time. So much the more important is its function of handing down to the readers and students of the future a full and authentic mirror of each age in its progressive growth, to be found most vividly in the pages of the daily and weekly journals, and the magazines and reviews of every class. These periodicals furnish the best impress of the times which can be derived from any single source.