FLYING-MACHINE MOTORS AND CELLULAR KITES, 79 
These kites have a fine angle of incidence, so that they corres- 
pond with the flying-machines they are meant to represent, and 
differ from the kites of our youth, which we recollect floating at 
an angle of about 45°, in which position the lift and drift are 
about equal. The fine angle makes the lift largely exceed the 
drift and brings the kite so that the upper part of the string is 
nearly vertical. Theoretically, if the kite is perfect in construc- 
tion and the wind steady, the string could be attached infinitely 
near the centre of the stick, and the kite would fly very near the 
zenith. It is obvious that any number of kites may be strung 
together on the same line, and that there is no limit to the weight 
that may be buoyed up in a breeze by means of light and hand 
tackle. 
The next step is clear enough, namely, that a flying-machine 
with acres of surface can be safely got underway, or anchored and 
hauled to the ground by means of the string of kites. If the 
string of kites gets into contrary currents of air, kites and suspended 
weight may be disconnected from the earth and will remain sup- 
ported, drifting in a resultant direction determined by the force 
of each current and the number of kites exposed to it. 
Kites z. and F. are of equal weight and area. In kf. the hori- 
zontal surfaces are curved, with the convex sides up; F. has all 
the surfaces plain. Roughly, £. pulls twice as hard on the string 
as F. does. So that a flying-machine with curved surfaces would 
be better than one with a flat body plane, if the form could be 
made with the same weight of material. This is proved in another, 
the old windmill, shown in the paper last year; this was fitted with 
four flat sails which could be changed for four curved ones. When 
the flat sails are turned so that they and the axis are in two planes 
no rotation takes place. But when the curved sails are put on 
symmetrically with the chords of the curves and the axis in two 
planes, there is a slow and powerful rotation in the direction of 
the convex sides of the sails. Rotation ceases when the sails are 
twisted in their sockets, so that the wind is tangential to the curve of 
the sails about three-fourths of their width from the forward edge. 
