It is not enough to dust the tops of the books periodically; a more full and radical remedy is required, to render library books presentable. At no long intervals, there should be a thorough library cleaning, as drastic and complete as the house-cleaning which neat housewives institute twice a year, with such wholesome results. The books are to be taken down from the shelves, and subjected to a shaking-up process, which will remove more of the dust they have absorbed than any brush can reach. To do this effectually, take them, if of moderate thickness, by the half-dozen at a time from the shelf, hold them loosely on a table, their fronts downward, backs uppermost, then with a hand at either side of the little pile, strike them smartly together a few times, until the dust, which will fly from them in a very palpable cloud, ceases to fall. Then lay them on their ends, with the tops uppermost on the table, and repeat the concussion in that posture, when you will eliminate a fresh crop of dust, though not so thick as the first. After this, let each volume of the lot be brushed over at the sides and back with a soft (never stiff) brush, or else with a piece of cotton or woolen cloth, and so restored clean to the shelves. While this thorough method of cleansing will take time and pains, it will pay in the long run. It will not eliminate all the dust (which in a large collection is a physical impossibility) but it will reduce it to a minimum. Faithfully carried out, as a periodical supplement to a daily dusting of the books as they stand on the shelves, it will immensely relieve the librarian or book-owner, who can then, (and then only) feel that he has done his whole duty by his books. Another dangerous enemy of the library book is damp, already briefly referred to. Books kept in any basement room, or near any wall, absorb moisture with avidity; both paper and bindings becoming mildewed, and often covered with blue mould. If long left in this perilous condition, sure destruction follows; the glue or paste which fastens the cover softens, the leather loses its tenacity, and the leaves slowly rot, until the worthless volumes smell to heaven. Books thus injured may be partially recovered, before the advanced stage of decomposition, by removal to a dry atmosphere, and by taking the volumes apart, drying the sheets, and rebinding--a very expensive, but necessary remedy, provided the books are deemed worth preserving. But a true remedy is the preventive one. No library should ever be kept, even in part, in a basement story, nor should any books ever be located near the wall of a building. All walls absorb, retain, and give out moisture, and are dangerous and oft-times fatal neighbors to books. Let the shelves be located at right angles to every wall--with the end nearest to it at least twelve to eighteen inches removed, and the danger will be obviated.