CHAPTER XIX. The Mongolfiers were undoubtedly first to send up balloons, but other experimenters were not far behind them, and before they could get to Paris in response to their invitation, Charles, a prominent physicist of those days, had constructed a balloon of silk, which he proofed against escape of gas with rubber鈥攖he Roberts had just succeeded in dissolving this320 substance to permit of making a suitable coating for the silk. With a quarter of a ton of sulphuric acid, and half a ton of iron filings and turnings, sufficient hydrogen was generated in four days to fill Charles鈥檚 balloon, which went up on August 29th, 1783. Although the day was wet, Paris turned out to the number of over 300,000 in the Champs de Mars, and cannon were fired to announce the ascent of the balloon. This, rising very rapidly, disappeared amid the rain clouds, but, probably bursting through no outlet being provided to compensate for the escape of gas, fell soon in the neighbourhood of Paris. Here peasants, ascribing evil supernatural influence to the fall of such a thing from nowhere, went at it with the implements of their craft鈥攆orks, hoes, and the like鈥攁nd maltreated it severely, finally attaching it to a horse鈥檚 tail and dragging it about until it was mere rag and scrap. The two-seater tractor biplane produced by Sopwith and piloted by H. G. Hawker, showed that it was possible to produce a biplane with at least equal speed to the best monoplanes, whilst having the advantage of greater strength and lower landing speeds. The Sopwith machine had a top speed of over 80 miles an hour while landing as slowly as little more than 30 miles298 an hour; and also proved that it was possible to carry 3 passengers with fuel for 4 hours鈥?flight with a motive power of only 80 horse-power. This increase in efficiency was due to careful attention to detail in every part, improved wing sections, clean fuselage-lines, and simplified undercarriages. At the same time, in the early part of 1913 a tendency manifested itself towards the four-wheeled undercarriage, a pair of smaller wheels being added in front of the main wheels to prevent overturning while running on the ground; and several designs of oleo-pneumatic and steel-spring undercarriages were produced in place of the rubber shock-absorber type which had up till then been almost universal. 鈥淚鈥檒l buy it if it breaks me鈥攁s a curiosity,鈥?cried Corinna, and she counted out two francs, seventy-five centimes. The principal engines of British, French, and American design used in the war period and since are briefly described under the four distinct types of aero engine; such notable examples as the Rolls-Royce, Sunbeam, and Napier engines have been given special mention, as they embodied鈥攁nd still embody鈥攁ll that is best in aero engine practice. So far, however, little has been said about the development of German aero engine design, apart from the early Daimler and other pioneer makes. 2018高清日本一道国产_2019最新国产不卡a_国内2018自拍视频在线 鈥淏ut,鈥?said Ernest, 鈥渉as not the Bible already told people what they ought and ought not to do, and is it not enough for us to insist on what can be found here, and let the rest alone?鈥? F茅lise flared up. She did not lack spirit. "The Major left this morning for Montreal," she replied, "but he has appointed Archie McKeracher to act in his place during his absence." Oh now, really, Mrs. Errington, I think you ought not to speak of Rhoda Maxfield in that way. She is a very good girl, and you hurt her terribly by your manner.