Before carrying out aerial practice with machine guns, embryo pilots and observers are required to attain a certain standard in camera gun work, both on the ground and in the air. The camera used is designed to resemble, both in operation and in appearance, the Lewis machine gun, the difference being that upon the trigger being released the camera gun registers a photograph upon a film. Reloading is by pulling back the cocking handle, which brings another film into place.

Practices being concluded, the cadet takes his own film to the nearest photographic sub-station, where it is developed in about ten minutes, and, still wet, is then submitted to the instructor, who forthwith criticizes the work of his pupil in the presence of the latter.

The camera gun is best suited for enabling the pupil (pilot or observer) to ascertain his proficiency in the use of deflection sights, and his ability to place the enemy machine in correct position in the ring, according to his line of flight. Errors in aiming are checked by the photograph being taken through a glass screen, this being marked with circles, each valued at seven and a half feet taken from 200 yards’ distance, which is the distance advised for commencing a combat. On examining the film, after development, the instructor can explain the error in deflection or elevation by the position of the machine in relation to the rings.

In the illustrations, these being from camera gun films, will be noted the enemy machine as seen by the gunner through the ring sight at the moment of firing. In the first case the aim is low and to the right. In the second print the pupil has fired low and in front. The encircled dot shows the point at which the gunner should have aimed when the pilot of the target machine was flying directly toward the inner ring at 100 miles per hour.

On taking to the air with the camera gun, the observer is piloted by an instructor, and is initiated not only in the photographing of other machines, but also in manoeuvres which have for their object the avoidance of being photographed by the opposing camera gun. Finally, the pupil engages in aerial combat with another machine piloted by a “hostile” instructor, and each machine attempts to “shoot down” the other. In this contest the pilot or observer who obtains the most accurate pictures is counted the victor. Every principle of aerial fighting as taught both in lectures and in the air, is practised, and upon its completion the results, as inflexibly registered by the camera gun, are subject to the keenest criticism.