In the months that followed before the next target practice, the Captain did some experimenting, and finally determined making the projectile itself displace a length of piano-wire fixed across the muzzle of the gun, and thus actuate the electrical system and operate the shutter. In this way he eliminated troublesome variables of recoil, elasticity of the carriage, etc., leaving to determine only the time element of the electrical system to function. This result was admirable, and, after taking several similar pictures, the captain found that he could now operate with great precision--that is, he could get the same phase of the discharge with almost identical shapes of gas-cone and smoke-cloud, and he could get these every time. In the fall of 1912 Captain Behr succeeded in obtaining a series of extremely rapid photographs showing a twelve-inch mortar battery in action. In taking these pictures the camera was placed on an elevation about ten feet above the concrete floor and about sixty feet back of the mortars. The electrical device for working the shutter was actuated by the mortar itself in its recoil. These pictures were taken in about one five-thousandth of a second--which is the more remarkable as the last two were taken in the shade after 4.30 A.M. The first three were taken about noon, in the sunshine, as the shadows show. So great was the precision of the electrical device as to render possible the photographic recording of these mortar projectiles, moving at great velocities, in almost any desired position after the discharge, say two feet away from the muzzle, or six feet away, or twenty feet away, or right at the muzzle, as shown in the first mortar picture, where the great projectile has been caught in its flight half way out of the mortar. Pictures Never Seen By the Human Eye. ~A CAMERA THAT IS FASTER THAN THE EYE~ It is interesting to note that of these five mortar pictures, representing five phases of the firing, only the last two are ever seen by the human eye. The far swifter camera, acting in about one five-thousandth of a second, has caught all these phases as reproduced here; but, to the ordinary observer standing by, the first visible impression after firing is that of the smoke-cone as developed in Number Four. The strange “powder-puff” effect shown in Number Three is never seen; nor the earlier effects in Numbers One and Two. Nor is any sound heard by an observer or by the gun crew until the third or fourth phase has been reached. This is a matter of simple calculation.