136 SOME AEKONAUTICAL EXPERIMENTS. 



side it will also move over as if to meet it. Now, since neither the 

 wind nor the machine for even an instant maintains exactly the same 

 direction and velocit}', it is evident that the man who would trace the 

 course of the center of pressure nmst l)e very quick of mind; and he 

 who would attempt to move his bod}' to that spot at every change 

 must ))e very active indeed. Yet this is what Herr Lilienthal attempted 

 to do, and did do with most remarkable skill, as his two thousand 

 glides sufficiently attest. However, he did not escape l)cing over- 

 turned l)y wind gusts several times, and finally lost his life as the 

 result of an accidental fall. The Pilcher machine was similar to that 

 of Lilienthal. On one occasion, while exhi})iting the flight of his 

 machine to several members of the Aeronautical Society of (Jreat 

 Britain, it suddenly collapsed and fell to the ground, causing injuries 

 to the operator which proved sadly fatal. The method of managment 

 of this machine differed in no imyjortant respect from that of Lilien- 

 thal, the operator shifting his Ijody to make the centers of pressure 

 and gravity coincide. Although the fatalities which befell the design- 

 ers of these machines may have been due to the lack of structural 

 strength rather than to lack of control, nevertheless it had l)ecome 

 clear to the students of the problem that a more perfect method of 

 control must be evolved. The Chanute machines marked a great 

 advance in both respects. In the nudtiple wing machine the tips 

 folded slightly backward under the pressure of wind gusts, so that 

 the travel of the center of pressure was thus largely counterbalanced. 

 The guiding of the machine was done by a slight movement of the 

 operator's 1)ody toward the direction in which it was desired that 

 the machine should go. The double-deck machine, built and tried 

 at the same time, marked a very great structural advance, as it was 

 the first in which the principles of the modern truss bridges were 

 fully applied to Hying-machine construction. This machine, in addi- 

 tion to its greatly improved construction and general design of i)arfs, 

 also differed from the machine of Lilienthal in the operation of its 

 tail. In the Lilienthal machine the tail, instead of being fixed in one 

 position, was prevented b}' a stop from folding downward beyond a 

 certain point, but was free to fold upward without any hindrance. In 

 the Chanute machine the tail was at first rigid, but afterwards, at the 

 suggestion of Mr. Herring, it was held in place by a si)i'ing that 

 allowed it to move slightly either upward or downward with reference 

 to its normal position, thus modifying the action of the Avind gusts 

 upon it, very much to its advantage. The guiding of the niachint^ 

 was effected by slight movements of th(> operator's body, as in fh(» 

 multiple-wing machines. Both these machines were nuich more man- 

 ageable than the Lilienthal type, and their structural strength, not- 

 withstanding their extreme lightness, was such that no fatalities or 

 ev<Mi accidiMits mai-ked the slides in;ide with them, although Avinds 



