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时间: 2019年12月10日 01:35

In 1891 Mr Day invented a two-stroke cycle engine which used the crank case as a scavenging chamber, and a very large number of these engines have been built for industrial purposes. The charge of carburetted air is drawn through a non-return valve into the crank chamber during the upstroke of the piston, and452 compressed to about 4 lbs. pressure per square inch on the down stroke. When the piston approaches the bottom end of its stroke the upper edge first overruns an exhaust port, and almost immediately after uncovers an inlet port on the opposite side of the cylinder and in communication with the crank chamber; the entering charge, being under pressure, assists in expelling the exhaust gases from the cylinder. On the next upstroke the charge is compressed into the combustion space of the cylinder, a further charge simultaneously entering the crank case to be compressed after the ignition for the working stroke. To prevent the incoming charge escaping through the exhaust ports of the cylinder a deflector is formed on the top of the piston, causing the fresh gas to travel in an upward direction, thus avoiding as far as possible escape of the mixture to the atmosphere. From experiments conducted in 1910 by Professor Watson and Mr Fleming it was found that the proportion of fresh gases which escaped unburnt through the exhaust ports diminished with increase of speed; at 600 revolutions per minute about 36 per cent of the fresh charge was lost; at 1,200 revolutions per minute this was reduced to 20 per cent, and at 1,500 revolutions it was still farther reduced to 6 per cent. � 10 But while he was thinking like this in his heart, the Word of God came to him and said:鈥? 3 But when he transgressed My commandment, I deprived him of that bright nature, and he became dark. It would be a very good position. I am not certain of it yet, you know; but Dr. Bodkin has been very friendly, and has promised to canvass the governing committee for me. THE END. 青青青在线网站-青青青草国产线观-手机版青青青免费观看-依人青青青在线观看 A white boy, about fifteen years old, was placed on the stand. His hair was brown and straight, his skin exactly the same hue as other white persons and no discernible trace of negro features in his countenance. Do you? asked Rose McDougall tartly. "How odd! Now, as to me, nothing would surprise me more than to find Mrs. Errington ashamed of anything." � Both Cayley and Walker were theorists, though Cayley supported his theoretical work with enough of practice to show that he studied along right lines; a little after his time there came practical men who brought to being the first machine which actually flew by the application of power. Before their time, however, mention must be made of the work of George Pocock of Bristol, who, somewhere about 1840, invented what was described as a 鈥榢ite carriage,鈥?a vehicle which carried a number of persons, and obtained its motive power from a large kite. It is on record that, in the year 1846, one of these carriages conveyed sixteen people from Bristol to London. Another device of Pocock鈥檚 was what he called a 鈥榖uoyant sail,鈥?which was in effect a man-lifting kite, and by means of which a passenger was actually raised 100 yards from the ground, while the inventor鈥檚 son scaled a cliff 200 feet in height by means of one of these 鈥榖uoyant sails.鈥?This constitutes the first definitely recorded experiment in the use of man-lifting kites. A History of the Charvolant or Kite-Carriage, published in London in 1851, states that 鈥榓n experiment of a bold and very novel character was made upon an extensive down, where a large wagon with a considerable load was drawn along, whilst this huge machine at the same time carried an observer57 aloft in the air, realising almost the romance of flying.鈥? I had to make my choice without delay, Lord Seely. I regret to inflict this blow on you in your present suffering state of body; but, if I spared you, I could not have spared Castalia. I chose to spare my wife.