Of the various imitations of leather, or substitutes for it, we have leatherette, leather-cloth, duck, fibrette, feltine, and buckram. Buckram and duck are strong cotton or linen fabricks, made of different colors, and sometimes figured or embossed to give them somewhat the look of leather. Hitherto, they are made mostly in England, and I have learned of no American experience in their favor except the use of stout duck for covering blank books and binding newspapers. The use of buckram has been mostly abandoned by the libraries. Morocco cloth is American, but has no advantage over plain muslin or book cloth, that I am aware of. Leatherette, made principally of paper, colored and embossed to simulate morocco leather, appears to have dropped out of use almost as fast as it came in, having no quality of permanence, elegance, or even of great cheapness to commend it. Leatherette tears easily, and lacks both tenacity and smoothness. Both feltine and fibrette are made of paper--tear quickly, and are unfit for use on any book that is ever likely to be read. All these imitations of leather are made of paper as their basis, and hence can never be proper substitutes for leather. All torn leaves or plates in books should be at once mended by pasting a very thin onion-skin paper on both sides of the torn leaf, and pressing gently between leaves of sized paper until dry. Corners made of vellum or parchment are more durable than any leather. When dry, the parchment becomes as hard almost as iron and resists falls or abrasion. To use it on books where the backs are of leather is a departure from the uniformity or harmony of style insisted upon by many, but in binding books that are to be greatly worn, use should come before beauty. In rebinding, all maps or folded plates should be mounted on thin canvas, linen, or muslin, strong and fine, to protect them from inevitable tearing by long use. If a coarse or thick cloth is used, the maps will not fold or open easily and smoothly.