One of the earliest airships which achieved any success was invented by a Frenchman, M. Giffard, about the year 1852. He made his balloon of an elongated or cigar shape, a form adopted by airship inventors as offering less resistance to the air than the ordinary globular or pear shape. To this balloon, which was 104 feet long and 39 feet in diameter, he attached a steam-engine of three-horse power, weighing 462 lbs. and working a screw-propeller, which, by its rapid revolutions, urged the balloon onwards through the air, even as the screw of a steamship urges the vessel through the water. With this apparatus he succeeded on one occasion, for a very short while, in obtaining a speed of six and a half miles an hour. Twenty years later another Frenchman, M. Dupuy de Lôme, constructed another airship; but fearing to place an engine so near the gas of his balloon, he used the strength of eight men to work his screw. This was a very wasteful mode of supplying energy, for the weight of the men was very great in proportion to their strength, and this machine, during its trial, did not attain as great a speed as Giffard’s. Twelve years after a third Frenchman, M. Tissandier, took up the same experiments. His elongated balloon was smaller than the two previous, and his engine was an electric motor of one and a half horse-power. On one occasion a speed of nearly eight miles an hour was attained. By this time the French Government had become interested in the work, and provided money to continue investigations. The result of this was that in 1885 two officers of the French army, Captains Renard and Krebs, brought out by far the most successful airship yet constructed. It was 165 feet long, 27 feet in diameter, and was driven by an electric motor of nine horse-power. That this machine proved itself perfectly capable of being guided in the air is amply shown by the fact that it returned to its shed five times out of the seven on which it was publicly taken out. It also attained a speed of fourteen miles an hour, and indeed it would seem that Renard and Krebs, although their names are now almost forgotten, accomplished nearly as great things twenty years ago as the popular airship inventors of the present day. One of the greatest difficulties with which early inventors had to contend was the enormous weight of their engines. The machinery they were obliged to use to drive their airships through the air weighed more than their balloons, unless made of unwieldy size, had power to lift. The same difficulty indeed exists at the present time, though to a much less degree. Of late years, and especially since the introduction of the motor-car, great progress has been made in the construction of light but powerful engines, or motors, and the employment of petrol vapour instead of coal or oil has very greatly lessened the weight of the fuel which has to be carried.