PRINTING.

555

preferably driven from the cylinder, A, by means of toothed wheels attachedto their ends, so that the revolution of c may be more rapid than that of A.Since A is pressed upwards against B, the bearers of the trough and of itsroller are attached to the bearings of A, to preserve its contact with c ; b is asharp-edged ruler of gun-metal, steel, or German-silver, called the colour-doctor, screwed between two stiffening bars of gun-metal; the edge of thedoctor being slightly pressed at a tangent against the cylinder, A. The dodtorvibrates with a slow motion from right to left, so as to exert a delicate shavingadtion upon the engraved surface as this revolves in the direction shown bythe arrow; c is another sharp-edged ruler, the lint-doctor, serving to scrapeoff any filaments of cotton which may have come off the calico, and, which ifallowed to remain on the pattern-cylinder, might either smear the work, orprevent the colour from filling up some of the lines of the engraving. Thislint doctor presses very slightly against the cylinder, A, and has no transversemotion. The calico, shown by d, is carried in along with the blanket, a a, inthe diredtion of the arrow, and is passed on by the revolution of A, receivingthe pattern engraved upon that cylinder. The objedt of the colour-dodtor is

Fig. 26.

to remove any excess of the colour mixture. Where a pattern contains morethan one colour it requires a compound machine, with a corresponding numberof cylinders mounted in one frame. In arranging these machines severaladjustments become necessary. It is most important to ensure a corre-spondence between the parts of the design in the successive printing-cylinders,for unless those of the second and following are accurately inserted in theirplaces and register with the first, the pattern produced on the cloth will becomeconfused. Fig. 27 is the end elevation of a 4-colour machine, and Fig 28 asedtion. The same letters refer to both, a is the cast-iron frame, bolted to acorresponding frame by the bolts, B, with an interval of 3 to 4 feet between ;c is the hollow iron pressure cylinder, about 2 feet in diameter, and between3 and 4 feet long, according to the width of the cloth to be printed. D arethe copper rollers, the width of a piece of cloth ; E are wrought-iron mandrels,on which the copper rollers are forced. The mandrel is about 4 inches diameterwhere the roller fits on, but its journals are of less diameter. The pattern-roller is made with a projecting piece inside, about i inch broad and i inchdeep, extending all the width of the roller. This so-called “ tab ” fits in aslot cut in the mandrel, which thus causes it to turn without slipping on the