390 POPULAR SCIENCE MONTHLY. 



system of combined aeroplanes and lifting screws for flying apparatus. 



A good deal of experimenting has been done with power-driven 

 flying models. The more recent types have been actuated by twisted 

 rubber threads, by compressed air and by steam, and the most notable 

 experiments in order of date are those of Penaud, Tatin, Hargrave, 

 Phillips, Langley and Tatin and Eichet. The data for these (except 

 the first) will be found by searchers in such matters in the London 

 Times edition of the 'Encyclopaedia Britannica,' in the article on 

 aeronautics. The most successful experiment was that of Professor 

 Langley, who obtained in 1896 three flights of about three fourths of 

 a mile each with steam-driven models, the apparatus alighting safely 

 each time and being in condition to be flown again. 



The one great fact which appears from all these various model 

 experiments is that it requires a relatively enormous power to obtain 

 support on the air. Omitting the cases in which the power was prob- 

 ably overestimated, the weights sustained were but 30 to 55 pounds to 

 the horse power expended, thus comparing most unfavorably with the 

 weights transported by land or by water; for a locomotive can haul 

 about 4,000 pounds to the horse power upon a level track, and a 

 steamer can propel a displacement of 4,000 pounds per horse power 

 on the water at a speed of 14 miles an hour. 



But models are, to a certain extent, misleading. They seldom fly 

 twice alike and they do not unfold the vicissitudes of their flight. 

 Moreover, the design for a small model is sometimes quite unsuited 

 for a large machine, just as the design for a bridge of ten feet opening 

 is unsuited for a span of one hundred feet. 



After experimenting with models three celebrated inventors have 

 passed on to full-sized machines, to carry a man. They are Maxim, 

 Ader and Langley, and all three have been unsuccessful, simply because 

 their apparatus did not possess the required stability. They might 

 have flown had the required equilibrium and strength been duly pro- 

 vided. 



At a cost of about $100,000, Sir Hiram Maxim built and tested in 

 1894 an enormous flying machine, to carry three men. It consisted 

 in a combination of superposed aeroplanes, portions of which bagged 

 under air pressure, and it was driven by two screws 17 feet 10 inches 

 in diameter, actuated by a steam engine of 363 horse power with steam 

 at 275 pounds pressure. The supporting surface was about 4,000 

 square feet, and the weight 8,000 pounds. The machine ran on a 

 track of 8-feet gauge, and was prevented from unduly rising by a 

 track above it of 30-feet gauge. At a speed of 36 miles per hour all 

 the weight was sustained by the air, and on the last test the lifting 

 effect became so great that the rear axle trees were doubled up and 

 finally one of the front wheels tore up about 100 feet of the upper 

 track ; when steam was shut off and the machine dropped to the ground 



