It has been suggested that in order to decrease the time of transmission a cylinder capable of
taking a print 7 inches by 5 inches be employed, the print being prepared from rather a coarse line screen—say 35 to the inch—and a traverse of about 1/50 inch given to the stylus, thus reducing the time of transmission to about twelve minutes. It is questionable, however, whether the increase in speed would compensate for the loss of detail, as only very bold subjects could be transmitted. As already pointed out, wireless transmission would only be employed for fairly long distances, and the extra time and expense required to receive a fairly good detailed picture is negligible when compared with the enormous time it would take to receive the original photograph by any ordinary means of transit.
The public much prefer to have passable pictorial illustrations of current events than wait several days for a more perfect picture—the original, and the advantage of any newspaper being able to publish photographs several days before its rivals is obvious. There can also be no doubt but that a system of radio-photography, if fairly reliable and capable of working over a distance of say thirty miles, would be of great military use for transmitting maps and written matter with a great saving of time and even life. Written matter could be transmitted with even greater safety than messages which are sent in the ordinary way in Morse Code, as the signals received in the receiver
of an hostile installation would be but a meaningless jumble of sounds, and even were they possessed of radio-photographic apparatus the received message would be unintelligible, unless they knew the exact speed at which the machines were running and could synchronise accurately.
CHAPTER III
RECEIVING APPARATUS
There are only two methods available at present for receiving the photographs, and both have been used in ordinary photo-telegraphic work with great success. They have disadvantages when applied to wireless work, however, but these will no doubt be overcome with future improvements. The two methods are (1) by means of an ordinary photographic process, and (2) by means of an electrolytic receiver.
In several photo-telegraphic systems the machine used for transmitting has the cylinder twice the size of the receiving cylinder, thus making the area of the received picture one-quarter the area of the picture transmitted. The extra quality of the received picture does not compensate for the disadvantage of having to provide two machines at each station, and in the writer's opinion results, quite good enough for all practical purposes, can be obtained by using a moderate size cylinder so that one machine answers for both transmitting