GYROPLANES AND HYDROPLANES. 643 



few experiments about to be mentioned throw a little light upon 

 the first question, and they, together with a few results with 

 hydroplanes, may possibly indicate an answer to the second. 



(1) Gyroplane Experiments. — Several gyroplanes of various 

 sizes, a few of which are exhibited, were caused to rotate with 

 their axes vertical, or nearly so, and while rotating they were 

 allowed to drop through 42 feet from a bridge to water in a river. 

 Discs, of the same diameters, were dropped at the same place, and 

 the times occupied in falling were compared. Also, for purposes 

 of comparison, two gyroplanes were thrown horizontally from a 

 height of about 46 feet. These, after first falling slightly and 

 then rising — boomerang fashion — fell in the water some 150 feet 

 from the bridge. The effect of spinning a helix was also com- 

 pared with that of spinning the gyroplanes. The arms of the helix 

 were shaped like those of the gyroplanes, and, like them, were 

 about 2^ inches wide, but they were tilted upwards slightly in 

 the direction of their rotation, their inclination being about 1 

 in 10. The times of falling were ascertained by means of a stop- 

 watch. The following are the results : — 



