An essential part of the drum is the double row of teeth cut on a metal edge attached to one of the outer rims of the drum. These are called indices and are of different pitch, say 648 and 432, corresponding to one or other of the scrolls. Each tooth is numbered consecutively, all round the rim; and the indices represent the total number of scrolls which can be printed, since the pitch of each tooth permits the drum to revolve just the width of the scroll pulley. A pawl or scotcher is arranged so as to engage in each tooth and stop the drum when required. Before printing, the drum is covered with strips of oilcloth, which are removable. [Illustration: FIG. 17 PRINTING DRUM, COVERED WITH YARN, PARTLY COLOURED] The actual printing or painting of the yarn is effected by means of the scroll pulley, which revolves in a box The arrows show where the repeats begin containing the colour, the whole being borne by a carriage running on rails across the width of the drum at the bottom of the frame. The colours are made up by an expert colourist to match the required shades, and by the admixture of flour and water are brought to the necessary consistency, which is about that of a thin paste, so that the colouring matter is dense enough to adhere, but liquid enough to penetrate the yarn fibres. In the carriage, the colour roller, which revolves in the colour, is supported by springs which tend to give it elasticity and keep it up against the face of the drum. The carriage is drawn across the drum by a rope which is mechanically actuated, and, of course, harmonises with the revolution of the drum. At the end of each traverse of the colour carriage there is a pause, which gives the printer time to change the pawl into the new tooth of the index at which it is required. The printer is guided in his selection of colours for each scroll that he prints by the “scale board” and the “design board.” Scale boards vary according to the pitch of the design paper, and according to the length of the design, and the number of times in which a design repeats in one revolution of the printing drum. Thus, for a design on squared paper running seven per inch in its length, the scale board is marked into divisions of seven to the inch throughout its length, so as to correspond with the horizontal divisions on the design paper. Supposing a design repeats four times in the whole revolution, a quarter board is employed; if it repeats twice a half board, the total number of scrolls being divided into four or two respectively. Thus, if the size of the drum is 648 scrolls and the number of wires in one repeat of the pattern is 162, the quarter board will have four vertical columns of figures, running respectively 1-162, 163-324, 325-486, and 487-648. The scale board has a bevel edge, and is preferably arranged so that it can be moved over the design board and aligned with the vertical line of the design which the printer is reproducing.