Artificial and Natural Flight

by Hiram S. Maxim

Fig. 3.—While in the Pyrenees I often observed eagles balancing themselves on an ascending current of air produced by the wind blowing over large masses of rock.

Many unscientific observers of the flight of birds have imagined that a wind or a horizontal movement of the air is all that is necessary to sustain the weight of a bird in the air after the manner of a kite. If, however, the wind, which is only air in motion, should be blowing everywhere at exactly the same velocity, and in the same direction—horizontally—it would offer no more sustaining power to a bird than a dead calm, because there is nothing to prevent the body of the bird from being blown along with the air, and whenever it attained the same velocity as the air, no possible arrangement of the wings could prevent it from falling to the earth.

It is well known that only a short distance above the earth’s surface, say 30 or 40 miles, we find an extremely low temperature sometimes referred to as interstellar temperature or absolute zero. In order to illustrate the extremely low temperature of space, I would cite the following instance:—

One evening, in the State of Ohio, a farmer saw a very brilliant meteor; it struck in one of his fields not more than 100 feet from his house. He at once rushed to the spot, and, pushing his arm down the hole, succeeded in touching it; but he very quickly withdrew his hand, as he found it extremely hot. Some of the neighbours rushed to the spot, and he told them what had occurred, whereupon one of them put his hand in the hole, expecting to be burnt, but, much to his surprise, the tips of his wet fingers were instantly frozen to the meteor. The meteor had been travelling at such an exceedingly high velocity that the resistance of the intensely cold and highly attenuated outer atmosphere was sufficient to bring its temperature up to the melting point of iron; but the heat did not have time to pass into the interior, it only extended inwards perhaps ¹⁄₈ inch, so that when the meteor came to a state of rest, the heat of the exterior was soon absorbed by the intensely cold interior, thus reducing the surface to a temperature much below any natural temperature that we find at the surface of the earth.

Nothing can be more certain than that the temperature is extremely low a slight distance above the earth’s surface. As the air near the earth never falls in temperature to anything like the absolute zero, it follows that there is a constant change going on, the relatively warm air near the surface of the earth always ascending, and, in some cases, doing sufficient work in expanding to render a portion of the water it contains visible, forming clouds, rain, or snow, while the very cold air is constantly descending to take the place of the rising column of warm air. I have noticed a considerable degree of regularity in the movement of the air, especially at a long distance from land, where the regularity of the up and down currents is, at times, very marked.

On one occasion while crossing the Atlantic in fine weather I noticed, some miles directly ahead of the ship, a long line of glassy water. Small waves indicated that the wind was blowing in the exact direction in which the ship was moving, and as we approached the glassy line, the waves became smaller and smaller until they completely disappeared in a mirror-like surface, which was about 300 or 400 feet wide, and extended both to the port and starboard in approximately a straight line as far as the eye could reach. After passing the centre of this zone, I noticed that small waves began to show themselves, but in the exact opposite direction to those through which we had already passed, and these waves became larger and larger for nearly half an hour. Then they began to get gradually smaller, when I observed another glassy line directly ahead of the ship. As we approached it, the waves again completely disappeared, but after passing through it, the wind was blowing in the opposite direction, and the waves increased in size exactly in the same manner that they had diminished on the opposite side of the glassy streak ([Fig. 4]).

Fig. 4.—Air currents observed in mid Atlantic, warm air ascending at a, a, a, and cold air descending at b, b, b. c, c, c represent the lines where the waves were the largest.

This, of course, shows that directly over the centre of the first glassy streak, the air was meeting from both sides and ascending in practically a straight line from the surface of the water, and then spreading out high above the sea, setting up a light wind in both directions.