THE THEORY OF THE AEROPLANE 135 



at right angles, allowing the thicker ends to project 2 cm. The 

 smaller ends of these two sticks are lashed to the ends of a 

 third stick, 1 cm. X .7 cm., tapered to 1 cm. X .4 cm. at each 

 end, 170 cm. long, for a distance of 20 cm. from each end. 

 This forms a triangle with all three sides bending in. Now 

 strongly lash the ends which project 2 cm. to a stick 1.5 

 cm. XI. 5 cm., tapered to 1.5 X. 7 cm., 170 cm. long 7 cm. 

 from the larger end. Tie a string, at its middle point, to the 

 smaller end of this last stick, having the two ends of the string 

 long enough to reach the outer ends of the cross sticks; pull 

 down the ends of the cross sticks equally until a line joining 

 their two extremities is 135 cm. distant from the bottom of 

 the kite. Paper the kite by fitting the paper over the string 

 first, covering the cross sticks last. Leave the paper quite 

 loose. Fasten the bridle as in the Malay kite. 



If this kite is made so that it balances and sheds the wind 

 equally from both sides, it may be so hung that it will fly at a 

 very slight angle from the vertical. If for any reason the 

 kite comes down, it lands like a bird, without damage to itself. 



99. THE THEORY OF THE AEROPLANE 



The aeroplane consists, essentially, of a plane, or planes. 

 It is forced through the air by means of powerful propellers, 

 differing but slightly from electric fans. The theory of the 

 aeroplane is very similar to that of the kite. In the case of 

 the kite the plane stays still and the wind goes by; with the 

 aeroplane the air may be stationary, but the plane moves. In 

 both cases there is a component of the total force which is 

 opposed to gravity, and the kite and the aeroplane rise, al- 

 though both are heavier than air. There must be motion 

 between the planes and the air in both cases. 



