LETTER COPYING BY PHOTOGRAPHY.
A TIME AND LABOUR-SAVING
Once again America is first in the field with an invention which promises to revolution- ise office work. In fact, its value is such that all the United States Government De-
partments have been equipped with it. This is known as the photo-copying machine a machine that makes photograph copies "of manuscript. "Years ago there was a good deal of talk about such a machine, but its use was not practicable,because of certain defects. It could not, for instance, make a photographic copy of any kind of type except of a dark colour on white paper.
Six Hundred Words a Minute.
These defects have been overcome by us- ing a peculiar kind of photographic paper, and also a colour screen, which strains out the white rays, so that indistinct words on tissue manuscript, for example, are made even clearer in the photographic copy than '31 the original itself.
The documents to be copied are placed upon a table, which is illuminated by strong -mercury-vapour electric lamps at each side of glass tubes about three feet long. At ordinary temperatures the mercury is in the metallic form, but when the electric current passes through it, it is vaporised, and the vapour becomes brilliantly incandescent, with a peculiar greenish-blue light that has a photographic value.
The time of the exposure of the manu- script to the lens of the camera depends upon the kind of material to be copied, and from four to thirty seconds is necessary. The entire operation, from the beginning of the exposure, through the developing, to the completion, of the fixing in the hypo solution of the print, is about a minute.
The photo-copying machine copies two typewritten pages at once. This is at the rate of 600 words a minute, which is four times faster than a good stenographer writes shorthand, and about ten times quicker than a fast typewriting operator. Allowing for delays and rests, the photo machine will copy in a day 400 typewritten pages of 300 words each.
Does Work of Sixteen Typists.
A good typist is necessary to copy stea- dily every day as many as twenty-five pages of typewriting, 300 words to a page, and at the same time make comparisons and corrections. The photo-machine will, there- fore, do the work of, say, sixteen good typists, such as would command iudividual salaries of at least £250 a year. It is not unlikely, therefore, that the photo-machine will save the Government thousands of pounds yearly.
On the point of accuracy, everything, of
course, is in favour of the photo-machine. In this there is as much difference between the photo-copy as there is between a hand
sketch and a photographic print of some- thing. The photo-machine gets everything,
such as initials of a letter, facsimile signa-.
tures, and even a fly that happens to be
passing at the time.