ELECTRIC BLUE-PRINT MAKING, a modern process of wholesale photographic printing by the aid of machinery, the electric light and the blue-print (q.v.). One of the best machines is continuous in its operation, and is fed by the operator with great lengths of tracings and blqe paper in much the same man ner as the washerwoman feeds the wet clothes into a wringing machine. The large wooden drum, around which the tracings and printing paper pass, is moved either by a connection with the shafting or by an electric motor mounted on the apparatus, the speed of the drum being regulated by a device shown on the top of the machine. A traveling apron of transparent material takes the place of the glass in the printing frame of the ordinary type, and as it is under tension at all times, it ensures an even and close contact at all points. This apron is wound on a small drum at the top and after passing along the large drum where the contact and exposure take place, it is wound up on the drum below; after the printing operation has been completed it is rewound by hand back on the upper drum. In the rear of the machine are
three arc lamps with reflectors, which concen trate the light on the tracings which, with the exposed prints, drop out into the box in front. The blue paper may be kept in a roll ready for use on the upper front part of the machine, or may be fed in small sheets with the traangs where the work being done is of ordinary size.
The machines are made in two widths, 30 and 42 inches; the apron supplied with them is 70 feet long, and prints of this size can be made as readily as smaller ones where it is desired. The ability to make prints of this size greatly enlarges the sphere of usefulness of the blue-print