Page:Library Construction, Architecture, Fittings, and Furniture.djvu/151

purposes for which it is to be used, whether flat, like table tops or shelves, or irregular, as for the tops of books. The action of the cleaner is as follows: the air, as it is drawn through by the action of the bellows, is concentrated into a small compass, and so produces a very powerful current, which, being directed sufficiently close to the dust, instantly carries it away into the dust-bag. The latter is placed immediately under the lid A, and is made of porous calico, which arrests the dust, but allows the air to pass through and escape at the exit. The machine is in use at several of the larger libraries for dusting books without removing them from the room, and has received great praise from those who have used it. It cannot be too strongly impressed upon librarians that no system of dusting can be adequate that does not insure the absolute exportation of dust from the premises, instead of its mere removal from the books to be deposited upon surrounding objects.