The wingless aeroplane is suspended from the balloon by cables of galvanized wire. There is a special arrangement by which the "pilot"—the man who steers and operates the airship—can at any time measure the pressure of hydrogen in the balloon, thus knowing what he has to count on in the way of carrying power.
The front part of the blimp's car is occupied by the engine and radiator, behind which is a bulkhead of sheet steel. In the rear of this bulkhead sits the pilot, and behind him the "observer," who makes sketches and takes notes of anything important that he sees. Behind the observer are the tanks for fuel oil and 300 gallons of water ballast. The body of the car is covered with aeroplane linen, save for the engine, which is sheathed with sheet aluminum.
In order to hold whatever position in the air may be desired, the blimp is equipped with two horizontal fins and three vertical fins. Not every blimp, that is to say, but the pattern approved and required of contractors by the Navy Department. These fins are made of wood and light steel tubing, reinforced with wire, covered with aeroplane linen rubber painted and finished with varnish.
THE "BLIMP" WELL EQUIPPED.
There are also two horizontal rudders and two vertical rudders, for steering up and down or sidewise. They work on ball bearings. A blimp, one should understand, is a fish in the ocean of air, a swimmer—just as the aeroplane is a flyer, like the bird.
The blimp's "car" carries an electric storage battery to furnish lights. The same battery energizes a searchlight for night scouting. A wireless apparatus, for transmitting information to the shore station, is part of the equipment.
The blimp, as already stated, is a sea scout. It is meant to be operated from a base on shore—which base is in constant communication by telegraph and wireless with the great radio stations that are strung all along our coasts at intervals of 200 miles. These stations, in turn, are in communication with the huge wireless outfit at Arlington (across the Potomac from Washington), whose "antennae," uplifted on tall steel towers, receive instantaneous war news from half the world.
Thus if (just for illustration) a blimp spies a hostile submarine, the news is instantly transmitted to the Navy Department. The department orders its "chasers" and warplanes nearest to the scene to go after the undersea boat. Within a few minutes the pursuit has started, and the U-boat finds itself in much the same situation as a fox hunted by hounds. In this case, however, the hounds are in the air, as well as "quartering" the aqueous terrain.
The United States' blimps are modeled on European patterns. But they are to have special improvements of their own. To make sure of their efficiency and structural correctness, each contractor, in offering bids to furnish them, was required to exhibit a model, exactly like the sausage balloons he proposed to make, but of toy size—one-thirtieth the length of the full-sized, completely equipped aerial sea scout.