As the weight that a pigeon is able to carry in its flight is extremely small, microscopic photography was resorted to, so that, although each bird carried only a single quill in which were rolled thin collodion leaves, the whole weighing only fifteen grains, the amount of printed matter thus carried was sometimes more than is contained in an ordinary volume. By photographic methods, thirty-two thousand words, or about half an ordinary volume, were crowded upon a pellicule two inches long by one and one-quarter inches wide, and weighing about three-quarters of a grain! Twenty of these, representing six thousand words, or twice the amount of printed matter contained in such a book as Scott's _Ivanhoe_, or Prescott's _Conquest of Mexico_, were carried by each pigeon. One bird carried forty thousand complete messages on a single trip. When the bird arrived at its cote, the quill was secured and taken to the government office, where the little leaflets were carefully removed, placed in an enlarging optical apparatus, thrown upon a screen with a magic lantern, and copied. The messages were then distributed to their destination about the city. THE DIRIGIBLE BALLOON ACHIEVED By this war, France, the home of the balloon, was brought keenly to realize the advantages and the limitations of such flying-machines; and it was but natural, under the circumstances, that as soon as peace was restored, efforts should be made there to produce a dirigible balloon, or some other form of dirigible flying-machine. Giffard, as we have seen, had been fairly successful; and now M. Dupuy de Lome, chief naval constructor of France, took up the problem. He constructed a balloon with a cigar-shaped envelope one hundred and twenty feet long and fifty feet in diameter. Beneath this was a rudder placed in the same position as that of a ship; and suspended still further below was a large car fitted with a two-bladed screw-propeller, thirty feet in diameter. Manual labor was to be used for turning this screw, two relays of four men each relieving each other at the work. An ascent was made in February, 1872, with fourteen persons in the car, who, by working in relays, demonstrated that a speed of about seven miles an hour could be maintained in any direction in still air. As the wind was blowing about thirty miles an hour at the time, however, the course of the balloon could only be deflected, and the main object of the ascent--the return to Paris--could not be accomplished. In short, De Lome's balloon demonstrated little more than had been accomplished by Giffard with his steam-driven balloon. Both had shown that with sufficient power the balloon could be made to travel in any direction in still air, but neither had been able to make headway against a strong wind.