Shells or bombs of these varying types were dropped from airplanes as well as from the larger and steadier Zeppelins. The difference was entirely in the size. It was said that a Zeppelin might drop a bomb of a ton's weight. But so far as attainable records are concerned it is impossible to cite any instance of this being done. The effect on the great gas bag of the sudden release of a load so great would certainly cause a sudden upward flight which might be so quick and so powerful as to affect the very structure of the ship. So far as known 250 pounds was the topmost limit of Zeppelin bombs, while most of them were of much smaller dimensions. The airplane bombs were seldom more than sixty pounds in weight, although in the larger British machines a record of ninety-five pounds has been attained. The most common form of bomb used in the heavier-than-air machines was pear-shaped, with a whirling tail to keep the missile upright as it falls. Steel balls within, a little larger than ordinary shrapnel, are held in place by a device which releases them during the fall. On striking the ground they fall on the explosive charge within and the shell bursts, scattering the two or three hundred steel bullets which it carries over a wide radius. Bombs of this character weigh in the neighbourhood of six pounds and an ordinary airplane can carry a very considerable number. Their exploding device is very delicate so that it will operate upon impact with water, very soft earth, or even the covering of an airship. Other bombs commonly used in airplanes were shaped like darts, winged like an arrow so that they would fall perpendicularly and explode by a pusher at the point which was driven into the body of the bomb upon its impact with any hard substance.
It seems curious to read of the devices sometimes quite complicated and at all times the result of the greatest care and thought, used for dropping these bombs. In the trenches men pitched explosive missiles about with little more care than if they had been so many baseballs, but only seldom was a bomb from aloft actually delivered by hand. In the case of the heavier bombs used by the dirigibles this is understandable. They could not be handled by a single man without the aid of mechanical devices. Some are dropped from a cradle which is tilted into a vertical position after the shell has been inserted. Others are fired from a tube not unlike the torpedo tube of a submarine, but which imparts only slight initial velocity to the missile. Its chief force is derived from gravity, and to be assured of its explosion the aviator must discharge it from a height proportionate to its size.
In the airplane the aviator's methods are more simple. Sometimes the bombs are carried in a rack beneath the body of the machine, and released by means of a lever at the side. A more primitive method often in use is merely to attach the bomb to a string and lower it to a point at which the aviator is certain that in falling it will not touch any part of the craft, and then cut the string. Half a dozen devices by which the aviator can hold the bomb at arm's length and drop it with the certainty of a perpendicular fall are in use in the different air navies. It will be evident to the most casual consideration that with any one of these devices employed by an aviator in a machine going at a speed of sixty miles an hour or more the matter of hitting the target is one in which luck has a very great share.
There is good reason for the pains taken by the aviators to see that their bombs fall swift and true, and clear of all the outlying parts of their machines. The grenadier in the trenches has a clear field for his explosive missile and he may toss it about with what appears to be desperate carelessness--though instances have been known in which a bomb thrower, throwing back his arm preparatory to launching his canned volcano, has struck the back of his own trench with disastrous results. But the aviator must be even more careful. His bombs must not hit any of the wires below his machine in falling--else there will be a dire fall for him. And above all they must not get entangled in stays or braces. In such case landing will bring a most unpleasant surprise.
