It is here that reference must be made to some of the special work undertaken by Mr. Eric S. Bruce, which dealt with the management of captive balloons under different conditions, and with a system of signalling thus rendered feasible. Mr. Bruce, who, since Major Baden-Powell's retirement from the office, has devoted his best energies as secretary to the advancement of the British Aeronautical Society, was the inventor of the system of electric balloon signalling which he supplied to the British Government, as well as to the Belgian and Italian Governments. This system requires but a very small balloon, made of three or four thicknesses of goldbeaters' skin, measuring from 7 to 10 feet in diameter, and needing only two or three gas cylinders for inflation. Within the balloon, which is sufficiently translucent, are placed several incandescent lamps in metallic circuit, with a source of electricity on the ground. This source of electricity may consist of batteries of moderate size or a portable hand dynamo. In the circuit is placed an apparatus for making and breaking contact rapidly, and by varying the duration of the flashes in the balloon telegraphic messages may be easily transmitted. To overcome the difficulty of unsteadiness, under circumstances of rough weather, in the captive balloon which carried the glow lamps, Mr. Bruce experimented with guy ropes, and gave a most successful exhibition of their efficiency before military experts at Stamford Bridge grounds, though a stiff wind was blowing at the time.