Several years ago, when the subway was being built, a dynamite magazine accidentally exploded in front of the Murray Hill Hotel. The magazine probably contained at least a ton of dynamite. A lot of windows were broken in the vicinity, some persons were injured, and a multitude badly scared, but the damage done even to the Murray Hill Hotel was comparatively small. It has been predicted that Germany would send across the Channel a large fleet of airships and blow up British towns with the bombs that her great gas-bags might drop out of the heavens. Now, at last, the much-vaunted and long-anticipated Zeppelin invasion has come, and what is the result? Four peaceful citizens killed, and about ten thousand dollars' worth of property damage. Let us suppose that the Germans should send a fleet of a hundred airships to drop bombs upon the city of London, returning to Germany each day for a new supply; and let us suppose that each airship should carry explosives enough to destroy two houses every day, which would be far more than they could actually average. Yet, if this aërial fleet should be able to destroy two hundred houses a day, or say, roughly, sixty thousand houses a year, it would succeed in destroying just about the annual growth of London, for that city has, during the past ten years, built sixty thousand new houses every year. The dirigible balloon has one signal advantage over the aëroplane in the matter of bomb-dropping. It can both carry bigger bombs and remain stationary and hover while it drops them. With the aëroplane, however, there is necessarily great difficulty in hitting underlying objects, on account of the high speed at which it must travel to sustain flight. In order to float, an aëroplane must travel about thirty miles an hour. Even at this speed, it is moving forward at the rate of forty-four feet a second, and as a bomb travels at the same speed as the aëroplane, except for the retardation of the air, it moves forward forty-four feet the first second, while dropping sixteen feet. The next second the bomb falls sixty-four feet and moves forward forty-four feet, and so on. Sixty miles an hour is a moderate speed for an aëroplane, however, and at that speed the bomb travels forward eighty-eight feet per second when it is dropped, so that, during the first second, while it descends but sixteen feet, it moves forward eighty-eight feet. It falls sixty-four feet the next second, and moves forward eighty-eight feet, and so on, descending in a parabolic curve, so that, by the time it strikes the earth, it may be several hundred feet from the place at which it is aimed.