This problem of information is then divided into two parts: the getting, and the transmitting. In getting information we must at once settle just how far the aeroplane will be available. There is a certain class of information, i. e., that concerning the road beds over which an army must move, the fords it must cross, the bridges it must travel over, the hills and valleys that might afford shelter for an offensive force or may be used defensively, the location, extent, thickness and amount of underbrush in woods, and much other, intimate, local knowledge that is of great and indispensable value to a commanding officer in the field. Such information can be gathered only from the ground. An aeroplane could be of use in such gathering only as a means for transporting the topographical sketchers quickly from point to point, allowing them sufficient time to do their work before again taking the air. Also an aeroplane would be of but little use in locating small bodies of the enemy. Where the aeroplane would begin to be of use, however, is in the locating of the main body of the enemy, his defences, his artillery positions, in determining the outline of his position, the natural or artificial boundaries which cover and protect his flanks, his main arteries of supply, the strong and weak points of his line of defence, etc. To accomplish these results the aeroplane must fly at a sufficient elevation to render difficult the hitting of a vital part of the machine or the aviator by hostile rifle or artillery fire. While the modern rifle in use in our army will fire a ball about three thousand five hundred yards straight in the air, it is generally accepted among aviators that an aeroplane would be practically safe, save from a chance shot, at three thousand five hundred feet. Of course there is a large chance that if enough rifles are directed at an aeroplane for a long enough time the machine or operator would be hit, at this altitude, but war is not a game of croquet, and the men who would man these machines in war would stand ready to take the risks demanded by the exigencies of the service. The proper machine to act as a gatherer of information is one that can carry a pilot, passenger, and wireless outfit. It is proposed to equip all information-gathering machines with wireless and to this end a special set has been devised and is being tested out at the U. S. Army Signal Corps Aviation School. That the wireless will be a success there is no doubt, for certain simple experiments with crude apparatus have been already tried out with remarkable success.