Again, in 1742, the Marquis de Bacqueville, then sixty-two years old, made a contrivance with which he flew about nine hundred feet before he fell into a boat in the Seine River and broke his leg. The Marquis had announced in advance that he would fly from his great house in Paris, across the Seine River and land in the famous Garden of the Tuileries. A crowd assembled and marvelled when the nobleman sailed into the teeth of the wind supported by what apparently were great wings. Something went wrong after a flight that would be considered remarkable by a scientific glider to-day, and his fall resulted in a broken leg for the experimenter. According to the authorities, all these experiments were not very valuable to science, because while the flights were accurately described the construction of the fliers (except in the case of Leonardo da Vinci) was not given, or only indicated in the most uncertain and unscientific language. In 1781 a French scientist named Blanchard attempted to make a flying machine of which the man driving it was to be the power. He was still working with it when ballooning became known, and he took up that sport with avidity. At that point came the true division between heavier-than-air and lighter-than-air machines. Before 1783 many scientists had hinted at the practicability of a hot air or gas balloon, but all successful flying experiments had been made with what we suppose to have been some form of gliders. However, in 1783 Tiberius Cavallo, an Italian scientist living in London, made a small hydrogen balloon, and was followed by the manufacture of fairly successful balloons by the Montgolfier brothers, two French inventors. From that time ballooning, with which this chapter has no concern, made rapid strides, until to-day the balloon has reached the stage where great motor-driven balloons are used by the European armies, and also to carry passengers. The next step in the heavier-than-air machine, known these days as the aeroplane, was taken in 1810, by Sir George Cayley, an Englishman and a true scientist, who constructed a glider and tabulated much valuable information. It was this scientist who made the first conclusive demonstrations looking toward the proof that man can never fly like a bird, but must proceed upon the principle of sustained planes. Sir George set down many laws of equilibrium governing the control of flying machines, estimated the power necessary to carry a man, and even hinted at the possibility of a gas engine more powerful and lighter than the then crude steam engine. He declared that a plane driven through the air, and inclined upward at a slight angle, would tend to rise and support a weight, and also that a tail with horizontal and vertical vanes would tend to steady the machine and enable the pilot to steer it up or down. [Illustration: Courtesy of the Smithsonian Institution LANGLEY'S STEAM MODEL This tandem monoplane made several successful trial flights.]