Artificial and Natural Flight

by Hiram S. Maxim

I spent the winter of 1890-91 on the Riviera, between Hyères les Palmiers and Monte Carlo. The weather for the most part was very fine, and I often had the opportunity of observing the peculiar phenomena which I had already noticed in the Atlantic, only on a much smaller scale. Whereas, in the Atlantic, the glassy zones were from 8 to 15 miles apart, I often found them not more than 500 feet apart in the bays of the Mediterranean. This was most noticeable at Antibes ([Fig. 5]), very good photographs of which I obtained. It will be observed that the whole surface of the water is streaked like a block of marble.

Fig. 5.—Glassy streaks showing the centres of ascending and descending columns of air in the Bay of Antibes, Alpes Maritimes.

At Nice and Monte Carlo this phenomena was also very marked. On one occasion, while making observations from the highest part of the promontory of Monaco on a perfectly calm day, I noticed that the whole of the sea presented this peculiar effect as far as the eye could reach, and that the lines which marked the descending air were never more than 1,000 feet from those which marked the centre of the ascending column. At about three o’clock one afternoon, a large black steamer passed along the coast in a perfectly straight line, and its wake was at once marked by a glassy line, which indicated the centre of an ascending column. This line remained almost straight for two hours, when finally it became crooked and broken. The heat of the steamer had been sufficient to determine this upward current of air.

Fig. 6.—Air currents observed in the Mediterranean, ascending currents at a, a, a, and descending currents at b, b, b.

In 1893 I spent two weeks in the Mediterranean, going and returning by a slow steamer from Marseilles to Constantinople, and I had many opportunities of observing the peculiar phenomena to which I have referred. The steamer passed over thousands of square miles of calm sea, the surface being only disturbed by large patches of small ripples ([Fig. 6]), separated from each other by glassy streaks, which, however, were not straight as on the Atlantic, and I found that in no case was the wind blowing in the same direction on both sides of these streaks, every one of which indicated the centre of an ascending or a descending column of air. If we should investigate these phenomena in what might be called a dead calm, we should find that the air was rising very nearly straight up over the centres of some of these streaks and descending in a vertical line over the centres of others. But, as a matter of fact, there is no such thing as a dead calm. The movement of the air is the resultant of more than one force. The air is not only rising in some places and descending in others, but at the same time, the whole mass is moving forward with more or less rapidity from one part of the earth to another, so we must consider that, instead of the air ascending directly from the relatively hot surface of the earth and descending vertically in other places, in reality the whole mass of rotating air is moving horizontally at the same time.

Suppose that the local influence which causes the up and down motion of the air should be sufficiently great to cause the air to rise at the rate of 2 miles an hour, and that the wind at the same time should be blowing at the rate of 10 miles an hour, the motion of the air would then be the resultant of these two velocities. In other words, it would be blowing up an incline of 1 in 5. Suppose, now, that a bird should be able to so adjust its wings that it advanced 5 miles in falling 1 mile through a perfectly calm atmosphere, it would then be able to sustain itself in an inclined wind, such as I have described, without any movement at all of its wings. If it were possible to adjust its wings in such a manner that it could advance 6 miles by falling through 1 mile of air, it would then be able to rise as relates to the earth while in reality falling as relates to the surrounding air.

In conducting a series of experiments with artillery and small guns on a large and level plain just out of Madrid, I often observed the same phenomena, as relates to the wind, that I have already spoken of as having observed at sea, except that the lines marking the centre of an ascending or a descending column of air were not so stationary as they were over the water. It was not an uncommon thing, when adjusting the sights of a gun to fire at a target at a very long range, making due allowances for the wind, to have the wind change and blow in the opposite direction before the word of command was given to fire. While conducting these experiments, I often noticed the flight of eagles. On one occasion a pair of eagles came into sight on one side of the plain, passed directly over our heads, and disappeared on the opposite side. They were apparently always at the same height from the earth, and in soaring completely across the plain they never once moved their wings. These phenomena, I think, can only be accounted for on the hypothesis that these birds were able to feel out with their wings an ascending column of air, that the centre of this column of air was approximately a straight line running completely across the plain, that they found upward movement more than sufficient to sustain their weight in the air, and that whereas, as relates to the earth, they were not falling at all, they were in reality falling some 4 or 5 miles an hour in the air which supported them.

Again, at Cadiz in Spain, when the wind was blowing in strongly from the sea, I observed that the sea-gulls always took advantage of an ascending column of air. As the wind rose to pass over the fortifications, the gulls selected a place where they would glide on the ascending current of air, keeping themselves always approximately in the same place without any apparent exertion. When, however, they left this ascending column, it was necessary for them to work their wings with great vigour until they again found the proper place to encounter a favourable current.