PRINTING AND MAKING OF BOOKS 



and setting machine an intricate piece of mechanism 

 about four feet high and slightly less in width, weighing 

 about twelve hundred pounds. On being placed in the 

 casting machine the ribbon is unwound in reverse order, 

 the operation of casting and setting proceeding in like 

 manner. The control of the casting machine by the 

 perforations in the ribbon is effected by the pressure of 

 air passing through the holes as the ribbon moves over a 

 rounded plate. Within this plate are thirty-two air- 

 tubes, and, as different perforations appear, different 

 connections are made through these tubes with the 

 working parts of the casting machine, a pressure of 

 eight pounds being maintained. The two hundred and 

 twenty-five matrices are contained in a die case measur- 

 ing about three inches square. The matrix case shifts 

 its position according to the kind or combination of 

 perforations passing over the air-tubes. The perfora- 

 tions for justification regulate the casting of space- 

 types between words, causing the mold to be opened 

 in a degree indicated by the justifying holes, in order that 

 the space-types may be cast of the proper size. Thus 

 from the record ribbon made at the keyboard, the cast- 

 ing machines cast type and insert mathematically correct 

 spaces at constant speed which may be kept up to the 

 limit of cooling metal. It is the work of only a few mo- 

 ments to remove one matrix case and substitute another. 

 Moreover, the molds in which the bodies of the types are 

 cast, also may be exchanged at short notice. 



"At one side of the casting machine is a melting-pot, 

 in which an automatic plunger forces the hot metal into 

 a nozzle leading directly to the mold upon which the 



