PRISM

In use the small end is placed against the quoin, and the other struck by the mallet. Signature. A letter of the alphabet placed at the bottom of the first page of a sheet, and so on to each sheet consecutively through the alphabet, with the exception of the letters J, V, and W; their use is to facilitate collating a book, as a guide to the bookbinder in folding the sheets, and as a ready means of referring to any part of a work before it is bound. Sink. A corner of the pre room, generally inclosed and lined with lead, with loose boards upon the lead; in this sink are placed the lye trough and a wetting trough; it is here where the forms are washed, rinsed, and laid up. There is always a pipe to carry off the waste water. Sorts. It is generally used in the plural; it means any letter, point, mark, sjiace, or quadrat, that is either deficient or redundant in quantity. A work runs upon sorts; that is, a greater number of some particular letters are required than the regular proportion, an index for instance. Space. A piece of metal cast lower than a type, so as not to print, used to separate words; they are of different thickne es, so as to enable the compositor to arrange the words at equal distances from each other in the same line. Tt/mpan. A wooden frame attached to the carriage of the pre by joints, and covered with parchment, on which the sheet of paper to be printed is laid; there is another frame called the inner tympan, which fits into this, also covered with parchment; between these are placed pieces of woollen cloth, termed blankets, which form a soft medium between the types and the platen that tends to produce an equal impre ion. Tympan Sheet. A sheet of paper, the same that a work is printed on, laid upon the tympan, and fastened to it at the corners with paste; it is the guide on which the sheets to be printed are laid, by which means the margin is kept regular and uniform. Welting Trough. Two troughs joined together and lined with lead; one deep, containing the water; the other shallow, of sufficient size to contain a paper board. The paper is wetted for printing by drawing it througii the water, and opening it out on the board. [s. 993]