Fig. 72.—A modern Balloon.
The airship is a development of the balloon; and the balloon we owe to Stephen and Joseph Montgolfier—two French brothers who, after watching clouds floating in the sky, had the notion that if they could fill a light envelope with “some substance of a cloud-like nature” it would raise itself into the air. Their father was a paper manufacturer, and so they had facilities for making a number of very large paper bags. Under these they lit fires of chopped straw, allowing the hot air and smoke to rush up into the bags, and, when they were released the bags ascended, carried up by the lifting influence of the heated air within them. Thus was invented the hot-air balloon; and we buy paper replicas of it to-day.
Delighted with their first success, the Montgolfiers built a paper balloon 30 ft. in diameter, and this was sent up at Annonay, in France, on 5th June 1783. It flew for ten minutes before the heated air inside it became cold, and reached a height estimated at more than a mile. After this came the ascent of a spherical balloon—one, that is to say, the shape of a modern-type balloon. It was made of linen, covered with paper, and had a small car attached. At Versailles, in France, on 19th September 1783, this balloon was sent up with passengers in the car; not human beings, though, for no man cared to ascend, fearing that the upper atmosphere might have some strange effect upon him. The actual occupants were a sheep, a cock, and a duck; and these three unwilling voyagers made a flight which lasted eight minutes. When they descended the sheep and the duck were found to be unharmed, although greatly perturbed; but the cock showed symptoms of not being well! At first, when learned men examined him, it was thought the rarefied atmosphere had in some way affected him, and this view was held until practical folk were able to show that the bird had been trampled upon by the sheep.
From this, of course, the next step was the ascent of a man, and on 15th October 1783 an adventurous youth named Pilatre de Rozier went up in a balloon built by the Montgolfiers. The balloon was attached to a rope and not allowed to ascend more than 100 feet; and at this altitude the aeronaut remained for about four minutes. A month later de Rozier and a passenger—the Marquis d’Arlandes—were bold enough to risk a flight in a Montgolfier balloon. This time the ascent was made from Paris, and the balloonists flew for five minutes before descending, reaching a height of 500 feet.
Fig. 72a.—The car of a modern Balloon.
A.A. Ballast bags filled with sand; B. Instruments (such as a statoscope, which shows at any moment whether the balloon is rising or falling; and an altitude meter); C. Ring by which car is attached to balloon.
Coal-gas superseded hot air in the filling of balloons, the latter being unsatisfactory, seeing that it cooled rapidly and allowed the balloon to descend; the only alternative being to do what some of the first aeronauts did, and burn a fire below the neck of their balloon even when in the air. But the dangers of this were great, seeing that the whole envelope might easily become ignited. With balloons filled with coal-gas—modern examples of which are seen in Figs. [72] and [72A]—long flights were possible, but they had always this disadvantage—the voyagers were at the mercy of the wind, and could not fly in any direction they might choose. If the wind blew from the north then they were driven south, the balloon being a bubble in the air, wafted by every gust. Aeronauts became disgusted with this inability to guide the flight of a balloon, and many quaint controls were tested; such, for example, as the use of a large pair of oars with which the balloonist, sitting in the car of his craft, rowed vigorously in the air. But this method found little favour; and it was followed in due course by the use of small steam engines and electric motors, which were made to turn propellers such as are used in aeroplanes. For such experimental craft, the rounded form of gas-container was abandoned and a cigar-shaped envelope adopted, pointed at both ends, which could be more easily driven through the air. An airship of a crude and early type is seen in [Fig. 73]. It was built by an experimenter named Gifford, and in 1852 it flew at the rate of seven miles an hour.