In reference to airship raids over cities, it has been suggested in America that the air in their immediate neighbourhood should be mined. This could be done by having a number of captive balloons or kites, the mines on which could be discharged electrically from the ground. For future wars there will no doubt be devised some form of travelling aërial torpedoes for destroying the intruding airships. Such torpedoes would, however, have to be capable of guidance. As has been pointed out by Mr. W. F. Reid, in 1884, at the siege of Venice, the Austrians used free balloons for the purpose of dropping bombs upon the town. The bombs were attached to the balloons in such a way that after the burning of a certain length of safety fuse, the connection was severed, and the bomb fell. The length of fuse was calculated according to the speed of the wind; but, unfortunately, when the balloons rose, they entered an upper air-current travelling in a different direction from that below, and many of the bombs burst in the Austrian lines, whence they had started. Thus it would not be expedient to let loose ordinary unmanned balloons loaded with timed explosives, even if the direction of the wind seemed favourable, for their meeting an approaching airship fleet, as an upper current might bring them back over the city, where they might do mischief. It is, however, quite conceivable that in the future aërial torpedoes may be devised in the shape of unmanned balloons or aëroplanes controlled by wireless waves of electricity. Those who saw the striking experiment of steering a small navigable balloon in a large hall entirely by wireless electric waves must have realised the possibilities which may thus be opened out in the future. * * * * * While writing, the news has come that another Zeppelin has dropped three bombs on Ostend, the casualty list being one dog. Two unexploded projectiles were found on a field near Waeragheim. These were probably thrown from the same airship. They show how constantly missile throwing from a moving airship may fail to come near the mark. There is no doubt that to hit particular objects aimed at from airships is by no means an easy matter. Success would seem to require considerable training in this particular method of warfare. The late Colonel Moedebeck, in his well-known pocket-book of aëronautics, makes the following remarks on the throwing of balloon missiles:-- We may assume that, if handled skilfully, the object aimed at will be hit very exactly. We must distinguish between the throw when the airship is at rest and that when it is in motion. In throwing out while at rest, which is only possible when the airship can travel against the wind, the following points must be considered:--