234 Right Hun. Lord Rayleigh on Flight. [Jan. 19, 



showed one or two experiments illustrating the curious effects that 

 might be obtained from a plaue exposed obliquely to wind. In one 

 of these it was seen that a light piece of sheet brass, evenly pivoted 

 in, and nearly filling up, an aperture through which air was issuing 

 under pressure, tended to set itself square to the aperture so as to 

 block it as much as possible, but, if started, it continued to rotate in 

 either direction, emitting a roaring sound. This phenomenon had 

 never been properly explained, nor had the somewhat analogous 

 action of a piece of card, which, when dropped, reached the ground 

 with a rotatory motion. As to the pressure of the wind on a hori- 

 zontal plane surface, if the latter was falling vertically at the rate, 

 say, of four miles an hour, and also moving horizontally at, say, 

 20 miles an hour, did the horizontal motion make a difference to the 

 pressure that existed at its under surface? It might be argued that 

 it did not ; but the argument was fallacious, and the truth was that 

 the horizontal motion much increased the pressure under a vertically 

 falling plane, a fact on which depended the possibility of flight, 

 natural and artificial. Lord Eayleigh showed how this point might 

 be illustrated, and even investigated, by means of a simple variation 

 of the ordinary windmill. This was a light wheel having six vanes, 

 each of which could be set at any desired angle, and it was used by 

 setting four at a particular angle, and finding at what angle the 

 other two must be placed so as to compensate the rotation of the 

 wheel produced by the former when it was moved quickly through 

 the air.* He next observed that not only was there pressure under- 

 neath a bird's wing or an aeroplane, but that the suction above was 

 not an unimportant matter ; and he performed an experiment to show 

 the reality of this suction, about which he said there had been some 

 scepticism. Turning to flight on a large scale, he remarked that it 

 was a natural question to ask, Was it possible for a man to raise 

 himself from the ground by working a 6crew with his own muscular 

 power only ? The investigation was not difficult, and the answer 

 was that it was quite impracticable for him to do so. Artificial 

 flight was a question of the speed of the horizontal motion. A bird 

 did not use a revolving mechanism like a screw to propel itself, but 

 he had no doubt that a revolving mechanism was the most suitable 

 for artificial flying-machines. Whether the difficulties of these 

 would be surmounted he did not know, but he was disposed to agree 

 with Mr. Maxim that it was mainly a question of time and much 

 money. Still, he did not think flight would ever be a safe mode of 

 conveyance for those who were desirous of going out for a day's 

 shopping, for it was hard to see how alighting on the ground could 

 ever be rendered quite free from danger. But, as Mr. Maxim once 

 remarked, the first use of flying-machines would be for military 

 purposes, and they had not yet succeeded in making war quite safe. 



* This apparatus was more fully described in the Wilde Lecture (Manchester 

 Memoirs, vol. xliv., Part 4, pp. 1-26"), where also some other matters here referred 

 to are treated in greater detail. 



