The Dominion of the Air [94]
another nature was being courageously attempted at this time. Otto Lilienthal, of Berlin, in imitation of the motion of birds, constructed a flying apparatus which he operated himself, and with which he could float down from considerable elevations. "The feat," he warns tyros, "requires practice. In the beginning the height should be moderate, and the wings not too large, or the wind will soon show that it is not to be trifled with." The inventor commenced with all due caution, making his first attempt over a grass plot from a spring board one metre high, and subsequently increasing this height to two and a half metres, from which elevation he could safely cross the entire grass plot. Later he launched himself from the lower ridges of a hill 250 feet high, when he sailed to a distance of over 250 yards, and this time he writes enthusiastically of his self-taught accomplishment:--
"To those who, from a modest beginning and with gradually increased extent and elevation of flight have gained full control over the apparatus, it is not in the least dangerous to cross deep and broad ravines. It is a difficult task to convey to one who has never enjoyed aerial flight a clear perception of the exhilarating pleasure of this elastic motion. The elevation above the ground loses its terrors, because we have learned by experience what sure dependence may be placed upon the buoyancy of the air."
As a commentary to the above we extract the following:--"We have to record the death of Otto Lilienthal, whose soaring machine, during a gliding flight, suddenly tilted over at a height of about 60 feet, by which mishap he met an untimely death on August 9th, 1896." Mr. O. Chanute, C.E. of Chicago, took up the study of gliding flight at the point where Lilienthal left it, and, later, Professor Fitzgerald and others. Besides that invented by Penaud, other aero-plane models demanding mention had been produced by Tatin, Moy, Stringfellow, and Lawrence Hargrave, of Australia, the subsequent inventor of the well-known cellular kite. These models, for the most part, aim at the mechanical solution of the problem connected with the soaring flight of a bird.
The theoretical solution of the same problem had been attacked by Professor Langley in a masterly monograph, entitled "The Internal Work of the Wind." By painstaking experiment with delicate instruments, specially constructed, the Professor shows that wind in general, so far from being, as was commonly assumed, mere air put in motion with an approximately uniform velocity in the same strata, is, in reality, variable and irregular in its movements beyond anything which had been anticipated, being made up, in fact, of a succession of brief pulsations in different directions, and of great complexity. These pulsations, he argues, if of sufficient amplitude and frequency, would be capable, by reason of their own "internal work," of sustaining or even raising a suitably curved surface which was being carried along by the main mean air stream. This would account for the phenomenon of "soaring." Lord Rayleigh, discussing the same problem, premises that when a bird is soaring the air cannot be moving uniformly and horizontally. Then comes the natural question, Is it moving in ascending currents? Lord Rayleigh has frequently noticed such currents, particularly above a cliff facing the wind. Again, to quote another eminent authority, Major Baden-Powell, on an occasion when flying one of his own kites, found it getting to so high an angle that it presently rose absolutely overhead, with the string perpendicular. He then took up a heavy piece of wood, which, when tied to the string, began to rise in the air. He satisfied himself that this curious result was solely due to a strong uptake of the air.
But, again, Lord Rayleigh, lending support to Professor Langley's argument, points out that the apparent cause of soaring may be the non-uniformity of the wind. The upper currents are generally stronger than the lower, and it is mechanically possible for a bird, taking advantage of two
"To those who, from a modest beginning and with gradually increased extent and elevation of flight have gained full control over the apparatus, it is not in the least dangerous to cross deep and broad ravines. It is a difficult task to convey to one who has never enjoyed aerial flight a clear perception of the exhilarating pleasure of this elastic motion. The elevation above the ground loses its terrors, because we have learned by experience what sure dependence may be placed upon the buoyancy of the air."
As a commentary to the above we extract the following:--"We have to record the death of Otto Lilienthal, whose soaring machine, during a gliding flight, suddenly tilted over at a height of about 60 feet, by which mishap he met an untimely death on August 9th, 1896." Mr. O. Chanute, C.E. of Chicago, took up the study of gliding flight at the point where Lilienthal left it, and, later, Professor Fitzgerald and others. Besides that invented by Penaud, other aero-plane models demanding mention had been produced by Tatin, Moy, Stringfellow, and Lawrence Hargrave, of Australia, the subsequent inventor of the well-known cellular kite. These models, for the most part, aim at the mechanical solution of the problem connected with the soaring flight of a bird.
The theoretical solution of the same problem had been attacked by Professor Langley in a masterly monograph, entitled "The Internal Work of the Wind." By painstaking experiment with delicate instruments, specially constructed, the Professor shows that wind in general, so far from being, as was commonly assumed, mere air put in motion with an approximately uniform velocity in the same strata, is, in reality, variable and irregular in its movements beyond anything which had been anticipated, being made up, in fact, of a succession of brief pulsations in different directions, and of great complexity. These pulsations, he argues, if of sufficient amplitude and frequency, would be capable, by reason of their own "internal work," of sustaining or even raising a suitably curved surface which was being carried along by the main mean air stream. This would account for the phenomenon of "soaring." Lord Rayleigh, discussing the same problem, premises that when a bird is soaring the air cannot be moving uniformly and horizontally. Then comes the natural question, Is it moving in ascending currents? Lord Rayleigh has frequently noticed such currents, particularly above a cliff facing the wind. Again, to quote another eminent authority, Major Baden-Powell, on an occasion when flying one of his own kites, found it getting to so high an angle that it presently rose absolutely overhead, with the string perpendicular. He then took up a heavy piece of wood, which, when tied to the string, began to rise in the air. He satisfied himself that this curious result was solely due to a strong uptake of the air.
But, again, Lord Rayleigh, lending support to Professor Langley's argument, points out that the apparent cause of soaring may be the non-uniformity of the wind. The upper currents are generally stronger than the lower, and it is mechanically possible for a bird, taking advantage of two