This is no doubt one of the greatest dangers the airship has to face in war. The aëroplane is the airship’s deadliest enemy. So terrible to the airship is this hornet of the air that the former has no chance of making an attack. It must ever remain on the defensive. The speed and quickly rising power of modern aëroplanes settles this question. When the aëroplane is advancing the airship cannot escape. Nor can it now any longer rise to safe altitude, for the nimbler heavier-than-air machines can easily outdo it. The only salvation of the attacked airship is its mitrailleuse gun fixed on the platform at its topmost part, but the chance of hitting the swiftly advancing aëroplane is fairly remote. There are more ways than one in which the fatal attack of aëroplane v. airship can be made. The airman can, indeed, ram the gas-bags by hurling himself and machine against it. Then destruction would be swift and sure, with the probable loss of the airman’s own life. Better tactics would be to fly above, and drop suitable weapons on the fragile gas-bag; a few sharp and jagged stones would probably suffice. Sharp darts of steel would be all-effective. So easy, indeed, would it be for one aëroplane skilfully handled to end the existence of the largest airship that one cannot refrain from asking the question whether on this account alone it can survive as the instrument of war? 9. _Insufficient power of quickly rising._ This is a point which wants the attention of the aëronautical engineer. The old-fashioned spherical balloons were made to rise and fall by the alternate sacrifice of gas and ballast. Thus the very life-blood of the balloon became quickly exhausted. It was obvious that when airships supplanted balloons the former must be supplied with a less exhausting process of vertical movement. As has already been mentioned, when treating of the Zeppelin airship, for the purpose of rising horizontal planes are now fitted to airships. Some engineers have thought these should be supplemented by a mechanical device, so that the speed of rising might be augmented. The late Baron de Bradsky provided his airship with a horizontal screw placed beneath the car. But one horizontal screw beneath an airship tends to twist it round--to convert it into an aërial top. To avoid this effect it would be necessary to have two horizontal screws rotating in opposite directions. This precaution was absent in de Bradsky’s construction, and it kept on twisting round, with the disastrous effect that the steel wires which held the car to the balloon snapped, with tragic results. But the idea of the horizontal screw is worth reviving. It has been a cherished plan of M. Julliot to include the principle in his designs, but on account of extra weight he has, I believe, hitherto not tried the interesting experiment. The colour of most of the airships is a disadvantage, though this is a matter so easy of alteration that it has not been included in the list of disadvantages.