AERONAUTICS. 59 



and vibratory surfaces are not conducive to steady soaring; their 

 practical effect is to increase the head resistance. No curved 

 surfaces made of muslin have yet soared; the nest for the vortex 

 must be hard and smooth. 



The tubular rod and two end cells form really a cellular kite, 

 and their head resistances are reduced to the utmost. In Fig. 1 

 the total area exposed is 1*27 square inches without making any 

 deduction for rounded edges. In addition to this there is the drift 

 of the two strings which in practice will be dispensed with. The 

 horizontal projected area of the cylindrical cells is 46 # 8 square 

 inches, that of the propeller 165 square inches, total 211-8 square 

 inches ; the total weight 1-53 lbs. gives a weight of 1*04 lbs. per 

 square foot. 



The force of the wind required to make any show at all with 

 the model depicted must be at least fourteen miles per hour ; light 

 north-east and west winds have been a sore trial to the writer's 

 patience, south-east and east being the only winds from which 

 any results can be expected in the locality where the experiments 

 are being carried on. 



The centre of gravity in Fig. 1 is 2*6 inches abaft the leading 

 edge of the propeller and 3*725 inches forward of the middle of 

 the tubular rod. The string is attached to the centre of gravity. 

 The vulcanite propeller is fastened in such a manner that the 

 angle it makes with the rod and cells can be varied from + 1° to 

 - 14J°; the best results in light winds have been obtained with 

 about 3J° negative angle. There is no way of finding accurately 

 at what angle the wind strikes the cells ; the rod appears to be 

 horizontal. 



A light string is tied to the after end to prevent the kite rush- 

 ing over the horizontal cord; this string is slackened out till the 

 kite is near the level of the top of the poles and in a horizontal 

 position facing the wind; it then soars to windward, sometimes 

 over but more frequently under the cord. Sometimes the kite 

 can be steadied near the zenith by means of the tail string. 



