4o DRAWING-OFFICE ORGANIZATION
had two or even three stationary lamps instead of one moving arc lamp.
The current consumed is less, and less expense is entailed in replacing chim-
neys and carbons; moreover, the glasses can be placed nearer the lamp as
a less amount of heat is generated, thus avoiding to some extent the danger
to the glass by overheating. Prints can therefore be taken as rapidly with
one lamp as with several, and a more even exposure is obtained.
Fig. 13.—Halden's Duplex Radial Electric Photo Copying Frame. In position for photographing.
A recently improved form of machine (fig. 15), also supplied by Messrs.
Halden, has been put on the market, called the Rowsley Super-continuous
Electric Photo Copying Machine. It is claimed for the machine that it is
more economical than previous patterns in the use of electric current and
that it enables the operator immediately to increase the output.
The tracing and photographic paper are fed from a table, and are taken
close up against the glass by slow-moving rollers. When the end of the
tracing comes out, the photographer draws his knife sharply along the photo
paper at the top of the table, which is a glass slab, and lets it work its way