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时间: 2019年12月13日 08:01

These comments are taken from a lecture delivered by Wilbur Wright before the Western Society of Engineers in September of 1901, under the presidency of Octave Chanute. In that lecture Wilbur detailed the way in which he and his brother came to interest themselves in aeronautical problems and constructed their first glider. He speaks of his own notice of the death of Lilienthal in 1896, and of the way in which150 this fatality roused him to an active interest in aeronautical problems, which was stimulated by reading Professor Marey鈥檚 Animal Mechanism, not for the first time. 鈥楩rom this I was led to read more modern works, and as my brother soon became equally interested with myself, we soon passed from the reading to the thinking, and finally to the working stage. It seemed to us that the main reason why the problem had remained so long unsolved was that no one had been able to obtain any adequate practice. We figured that Lilienthal in five years of time had spent only about five hours in actual gliding through the air. The wonder was not that he had done so little, but that he had accomplished so much. It would not be considered at all safe for a bicycle rider to attempt to ride through a crowded city street after only five hours鈥?practice, spread out in bits of ten seconds each over a period of five years; yet Lilienthal with this brief practice was remarkably successful in meeting the fluctuations and eddies of wind-gusts. We thought that if some method could be found by which it would be possible to practise by the hour instead of by the second there would be hope of advancing the solution of a very difficult problem. It seemed feasible to do this by building a machine which would be sustained at a speed of eighteen miles per hour, and then finding a locality where winds of this velocity were common. With these conditions a rope attached to the machine to keep it from floating backward would answer very nearly the same purpose as a propeller driven by a motor, and it would be possible to practise by the hour, and without any serious danger, as it would not be necessary to rise far from the ground, and the machine would not have any forward motion151 at all. We found, according to the accepted tables of air pressure on curved surfaces, that a machine spreading 200 square feet of wing surface would be sufficient for our purpose, and that places would easily be found along the Atlantic coast where winds of sixteen to twenty-five miles were not at all uncommon. When the winds were low it was our plan to glide from the tops of sandhills, and when they were sufficiently strong to use a rope for our motor and fly over one spot. Our next work was to draw up the plans for a suitable machine. After much study we finally concluded that tails were a source of trouble rather than of assistance, and therefore we decided to dispense with them altogether. It seemed reasonable that if the body of the operator could be placed in a horizontal position instead of the upright, as in the machines of Lilienthal, Pilcher, and Chanute, the wind resistance could be very materially reduced, since only one square foot instead of five would be exposed. As a full half horse-power would be saved by this change, we arranged to try at least the horizontal position. Then the method of control used by Lilienthal, which consisted in shifting the body, did not seem quite as quick or effective as the case required; so, after long study, we contrived a system consisting of two large surfaces on the Chanute double-deck plan, and a smaller surface placed a short distance in front of the main surfaces in such a position that the action of the wind upon it would counterbalance the effect of the travel of the centre of pressure on the main surfaces. Thus changes in the direction and velocity of the wind would have little disturbing effect, and the operator would be required to attend only to the steering of the machine, which was to be effected152 by curving the forward surface up or down. The lateral equilibrium and the steering to right or left was to be attained by a peculiar torsion of the main surfaces, which was equivalent to presenting one end of the wings at a greater angle than the other. In the main frame a few changes were also made in the details of construction and trussing employed by Mr Chanute. The most important of these were: (1) The moving of the forward main crosspiece of the frame to the extreme front edge; (2) the encasing in the cloth of all crosspieces and ribs of the surfaces; (3) a rearrangement of the wires used in trussing the two surfaces together, which rendered it possible to tighten all the wires by simply shortening two of them.鈥? He is at home, replied Castalia, slowly. "I asked him to come into the drawing-room, and he said he would by-and-by." I'll have the note traced! exclaimed Algernon, looking up for the first time. Weasel. [Lowering his voice.] When it was night, your honour, what sees I through the chink of the kitchen door in the passage but the three young Ladies lugging along a great bundle, and stopping and panting and puffing? So says I, I鈥檒l see to the bottom of this, so I pops out suddenly and says, 鈥楥an I help you, Misses?鈥?quite civil like. But O Sir, how Miss Sophy trembled and turned as white as a lily, and Miss Ratty stamped and sent me to the village鈥攁t that[50] hour, your honour, company in the house鈥攖he ground covered with frost鈥擨 subject to the rheumatics鈥攁nd what for, d鈥檡e think? to get her twopenceworth of shoe-ribbon, your honour; and when I brought it, would you believe it?鈥攕he roared out that it was too narrow and sent me back again. Whom nought but the lov'd Object can content. Some such thoughts were vaguely flitting through Diamond's mind when Rhoda raised her head, and, emboldened by the gathering dusk, looked up into his face and said, "You know it cannot be unless father consents." 亚洲免费无码中文在线_日韩 欧美~中文字幕 In giving the story of Charlotte Tucker, and of the growth of the Church at Batala, with which she was so intimately associated, it is of very real importance to show frankly both sides of the picture,鈥攖he dark side, as well as the bright; the cloudy as well as the sunshiny. There were of course disappointments as well as encouragements. There were goings backward as well as pressings forward. Missionary life is no more one of unbroken success, even at its best, than any other kind of hard-working life, with a high aim before it; and to present it as such, by omitting to describe failure side by side with success, would鈥攁nd often does鈥攑roduce only a sense of unreality. The story of the Church throughout the ages has always been a chequered tale. Left alone, Algernon drew his chair up to the fire and lit a cigar. He did not hasten himself to examine the letters. Bills, of course! What else could they be? He began to smoke and ruminate. He would have liked to see Castalia before going to the office. He would have liked to make his own representation to her of the story he had told Lord Seely. She must be got to corroborate it unknowingly if possible. He reflected with some bitterness that she had lately shown so much power of opposing him, that it might be she would insist on taking a course of conduct which would upset all the combination he鈥攚ith the help of chance circumstances鈥攈ad so neatly pieced together. And then he reflected further, knitting his brows a little, that at any cost she must be prevented from spoiling his plans; and that her conduct lately had been so strange that it wouldn't be very difficult to convince the world of her insanity. "'Gad, I'm almost convinced of it myself," said Algernon, half aloud. But it was not true. FROM THE REV. ROBERT CLARK. Charles. No anger, fair Miss Ratty, we had enough of this indignation at the brink of the vault, when you were near falling out with me because I would not fall in with your ideas, and fall into the vault. The student of dirigible construction is recommended to Santos-Dumont鈥檚 own book not only as a full record of his work, but also as one of the best stories of aerial navigation that has ever been written. Throughout all his experiments, he adhered to the non-rigid type; his first dirigible made its first flight on September 18th, 1898, starting from the Jardin d鈥橝cclimatation to the west of Paris; he calculated that his 3 horse-power engine would yield sufficient power to enable him to steer clear of the trees with which the starting-point was surrounded, but, yielding to the advice of professional aeronauts who were present, with regard to the placing of the dirigible for his start, he tore the envelope against the trees. Two days later, having repaired the balloon,343 he made an ascent of 1,300 feet. In descending, the hydrogen left in the balloon contracted, and Santos-Dumont narrowly escaped a serious accident in coming to the ground.