I append here the results of some additional experiments made with the Plane-Dropper to determine the law of falling of a horizontal plane having a horizontal velocity of translation. It will be recalled that the preceding data given in the chapter on the Plane-Dropper show only the total time of falling a distance of four feet, and that we cannot determine from it the law of fall, unless we know, in addition, the relative diminution in the acceleration during the descent, and whether at the end of the fall the plane has attained an approximately constant velocity. For high horizontal velocities and for the most advantageous planes, it is not impossible that an approximately constant velocity is reached within the four-foot fall of the Plane-Dropper. In order to obtain these additional data, I placed electric contacts upon the Plane-Dropper at intervals of every foot, and introduced other modifications into the method of experiment. The accuracy with which it was necessary to measure the relative times of fall through successive feet precluded the further use of the stationary chronograph for the registration, and I adapted a K nig chronoscope to this purpose.

This chronoscope consists of a tuning-fork of low pitch, which is made to vibrate by the action of an electro-magnet. The vibrations are registered by a pen-point on a strip of paper covered with lamp-black, which is passed over a roller during the time of fall. A second pen-point worked by an electro-magnet records the passage...