The keyboard has a formidable appearance. It contains 225 keys, providing as many characters; also thirty keys to regulate the spacing of the words. At the back of the machine a roll of paper runs over rollers and above a row of thirty little punches worked by the keys. A key being depressed, an opened valve admits air into two cylinders, each driving a punch. The punches fly up and cut two neat little holes in the paper. The roll then moves forward for the next letter. At the end of the word a special lever is used to register a space, and so on to the end of the line. The operator then consults an automatic indicator which tells him exactly how much space is left, and how much too long or too short the line would be if the spaces were of the normal size. Supposing, for instance, that there are ten spaces, and that there is one-tenth of an inch to spare. It is obvious that by extending each space one-hundredth of an inch the vacant room will be exactly filled. Similarly, if the ten normal spaces would make the line one-tenth of an inch too _long_, by _decreasing_ the spaces each one-hundredth inch the line will also be “justified.” [Illustration: _By kind permission of_] [_The Monotype Co._ _The Monotype Casting Machine. A punched paper roll fed through the top of the machine automatically casts and sets up type in separate letters._] But the operator need not trouble his head about calculations of this kind. His indicator, a vertical cylinder covered with tiny squares, in each of which are printed two figures, tell him exactly what he has to do. On pressing a certain key the cylinder revolves and comes to rest with the tip of a pointer over a square. The operator at once presses down the keys bearing the numbers printed on that square, confident that the line will be of the proper length.