But the ambition of mankind is to control the air at a reasonable distance from the earth's surface and to navigate an element that is entirely free from all obstructions. The aim is to so control an ærial machine that it will not drift before every wind, but cleave the air and move along its course in defiance of the storm. To this must be added a guarantee of safety that the public is certain to exact before embarking upon an ærial voyage. Ærial navigation, no doubt, offers vast attractions but while sailing through the air, with the ease and grace of a bird, it might prove very inconvenient for passengers to fall out at a height of a mile or two and land through the roof of some peaceful, happy home or find themselves while unceremoniously falling securely hooked in the fork of a tree. Such little mishaps in ærial navigation had to be guarded against. Ærial navigation was perfected about the [The First Airships.] year 1925. After repeated failures of the Langley system from 1896 to 1920, the learned Washington professor changed his plans. Instead of endeavoring to lift flat-irons with wings from the ground, and watching turkey buzzards at anchor in the air over the Potomac river, Langley finally created an ærial machine that was operated by electricity and moved by a large, swiftly revolving propeller, somewhat resembling those employed in steam navigation, but with blades at a more abrupt angle. The flying machines which were constructed from 1920 to 1999 on the Langley plan, were built of Nickalum, an alloy of aluminum, crystalized, within a magnetic field. The specific gravity of Nickalum, as employed in the manufacture of ærodromes, or flying machines, was .512. It was lighter than a thin strip of pine wood, malleable as gold and impenetrable as steel. Ærodromes could not have been successfully manufactured in 1920 if Nickalum had not been employed in their construction. This new property was one of the marvelous products of the twentieth century. It was employed in nearly everything which required strength and elasticity. It was so malleable that waterproof garments, overcoats and shoes were manufactured of Nickalum as early as the year 1912. With this wonderful and cheaply manufactured metal, ærial navigation became a [Ærodromes of Nickalum.] possibility. The old fashion days of silk balloons drifting helplessly on air currents, had long passed away. These pre-Adamite curiosities belonged to the period of the nineteenth century, when man was yet living under primitive conditions, though by no means in a state of innocence. Ærodromes constructed of Nickalum were largely employed for traveling and commercial purposes between 1920 and 1925, while in 1999 they had reached a high stage of perfection. Ærodromes weighing four hundred pounds only, in 1925, could easily carry ten persons and cleave their way like an arrow through a high wind. Small ærodromes carrying four persons, weighed only one hundred pounds.