But although Italy may have done more than the other nations, history tells us that it was two Frenchmen, Stephen and Joseph Montgolfier, who were the first to bring the lighter-than-air craft prominently before the world.
The story goes that while rowing, Stephen’s silk coat fell overboard into the water. It was placed over a hot oven to dry, and watching it, Joseph noticed that the hot air tended to make it rise. The upshot of the affair was the Montgolfier balloon.
Throughout history the lighter-than-air craft has figured prominently in warfare. In the Franco-Prussian War, during the siege of Paris alone, as many as 66 balloons left the stricken city, carrying 60 pilots, 102 passengers, 409 carrier pigeons, 9 tons of letters and telegrams, and 6 dogs.
Gaston Tissandier went over the German lines and dropped 10,000 copies of a proclamation addressed to the soldiers, asking for peace, yet declaring that France would fight to the bitter end.
In the American Civil War an aeronaut named La Fontaine went up in a balloon over an enemy camp, made his observation, rose higher into the air, and succeeded in getting into a cross-current, which carried him back to his place of departure.
The first cross-channel flight was made by balloon in 1785, by Blanchard, who had with him an American doctor named Jefferies, together with a large supply of provisions, ballast and oars. This weighed the balloon down to such an extent that she almost sank into the sea a few moments after starting. Ballast was thrown overboard, and she rose, only to sink again. More ballast was dropped. Then they rose into the air and eventually landed in safety on the hills behind Calais.
Having thus shortly outlined the development of the one, we will endeavor to discover the fundamental difference between aeroplane and airship. It is simply the matter of “lift” obtained in the case of the latter from the property of being lighter than air, whereas the other craft being heavier than air must obtain its “lift” by mechanical propulsion.
The airship is merely an improvement on the old-fashioned balloon: a balloon to which mechanical propulsion has been applied. Different in shape, indeed, and fitted out with many modern improvements, its flight is still governed by the same laws of “aerostatics.”
For practical purposes we will divide the airship into two portions: the envelope or balloon, and the car. Atmospheric conditions influence the envelope to no small degree. The effect of heat upon gas—with which the envelope is filled—is to make it expand, and consequently cause the craft to rise. Cold, on the other hand, causes the gas to contract, and the craft to descend. Air pressure is another factor which must be taken into account, and this is greatest at sea-level. The greater the altitude, the less the pressure becomes, and the less pressure on the outside surface of the envelope the easier it is for the gas to expand; but this is compensated for by the fact that the atmosphere is considerably cooler at a high altitude.