286 



SCIENCE 



[N. S. Vol. XXIX. No. 738 



in which S is the power, V the velocity. 



Now W varies as the second power of 

 the velocity, as shown by the first equation, 

 and / varies as the power 1.85, as will be 

 shown later. Hence we conclude that the 

 total resistance -B of the air to the aero- 

 plane varies approximately as the square 

 of its speed, and the propulsive power prac- 

 tically as the cube of speed. 



Most Advantageous Speed and Angle of 

 Flight.— Again, regarding W and A as con- 

 stant, we may, by the first equation, com- 

 pute a for various values of V, and find f 

 for those velocities from the skin-friction 

 table to be given presently. Thus a, B and 

 n may be found for various velocities of 

 flight, and their magnitudes compared. 



The question of stability is a serious one 

 in aviation, especially as increased wind 

 velocities are encountered. In machines of 

 the aeroplane type there must be some 

 means provided to secure fore and aft 

 stability and also lateral stability. 



A large number of plans have been pro- 

 posed for the accomplishment of these ends, 

 some based upon the skill of the aviator, 

 others operated automatically, and still 

 others employing a combination of both. 

 At the present time no aeroplane has yet 

 been publicly exhibited which is provided 

 with automatic control. There is little dif- 

 ference of opinion as to the desirability of 

 some form of automatic control. 



The "Wright aeroplane does not attempt 

 to accomplish this, but depends entirely 

 upon the skill of the aviator to secure both 

 lateral and longitudinal equilibrium, but it 

 is understood that a device for this purpose 

 is one of the next to be brought forward by 

 them. Much of the success of the "Wright 

 brothers has been due to their logical pro- 

 cedure in the development of the aeroplane, 

 taking the essentials, step by step, rather 

 than attempting everything at once, as is 

 so often the practise with inexperienced 

 inventors. 



The aviator's task is much more difficult 

 than that of the chauffeur. "With the 

 chauffeur, while it is true that it requires 

 his constant attention to guide his machine, 

 yet he is traveling on a roadway where he 

 can have due warning, through sight, of 

 the turns and irregularities of the course. 



The fundamental difference between op- 

 erating the aeroplane and the automobile 

 is that the former is traveling along an 

 aerial highway which has manifold humps 

 and ridges, eddies and gusts, and since the 

 air is invisible he can not see these irregu- 

 larities and inequalities of his path, and 

 consequently can not provide for them until 

 he has actually encountered them. He 

 must feel the road since he can not see it. 



Some form of automatic control whereby 

 the machine itself promptly corrects for the 

 inequalities of its path is evidently very 

 desirable. As stated above, a large number 

 of plans for doing this have been proposed, 

 many of them based on gyrostatic action, 

 movable side planes, revolving surfaces, 

 warped surfaces, etc. A solution of this 

 problem may be considered as one of the 

 next important steps forward in the devel- 

 opment of the aeroplane. 



in. HTDROMECHANIC RELATION'S 



At the present moment so many minda 

 are engaged upon the general problem of 

 aerial navigation that any method by which 

 a broad forecast of the subject can be made 

 is particularly desirable. Each branch of 

 the subject has its advocates, each believing 

 implicitly in the superiority of his method. 

 On the one hand, the adherents of the dirig- 

 ible balloon have little confidence in the 

 future of the aeroplane, while another class 

 have no energy to devote to the dirigible 

 balloon, and still others prefer to work on 

 the pure helicopter principle. As a matter 

 of fact, each of these types is probably of 

 permanent importance, and each particu- 

 larly adapted to certain needs. 



