SOME AERONAUTICAL EXPERIMENTS. 185 



Herr Otto Lilioiithal seems to have been the first man who loally 

 comprehended that balancing was the tirst instead of the last of the 

 great prol)lems in connection with human liiglit. He l)egan where 

 others left oil', and thus saved the many thousands of dollars that it 

 had theretofore l)een customary to spend in ])uilding and fitting 

 expensive engines to machines which were uncontrollable when tried. 

 He ])uilt a pair of wings of a size suitable to sustain his own weight, 

 and made use of gravity as his motor. This motor not only cost him 

 nothing to begin with, l)iit it i'e(|uired no expensive fuel while in 

 operation, and never had to be sent to the shop for repairs. It had 

 one serious drawback, however, in that it always insisted on fixing the 

 conditions under which it would work. These were, that the man 

 should first ])etake himself and machine to the top of a hill and fly 

 with a downward as well as a forward motion. Unless these condi- 

 tions were complied with, gravity served no better than a ])alky horse — 

 it would not work at all. Althougth Lilienthal nuist have thought tiie 

 conditions were rather hard, he nevertheless accepted them till some- 

 thing better shoidd turn u}); and in this manner he made some two 

 thousand flights, in a few cases landing at a point more than 1,000 feet 

 distant from his place of starting. Other men, no doubt, long before 

 had thought of trying such a plan. Lilienthal not only thought, Init 

 acted; and in so doing pro])a})ly made the greatest conti'ibution to the 

 solution of the flying pr()l)ltMn that has ever ])een made by any one man. 

 He demonstrated the feasibility of actual practice in the air, without 

 which success is impossible. Herr Lilienthal was followed by Mr. 

 Pilcher, a young English engineer, and by Mr. Chanute, a distin- 

 guished member of the society I now address. A few others have 

 built gliding machines, but nearly all that is of real value is due to the 

 exi)erimcnts conducted under the direction of the three men just 

 mentioned. 



The 1)alancing of a gliding or flying machine is vtny sim})le in 

 theory. It consists in causing the center of gravity to coincide with 

 the center of pressure. But in actual practice there seems to be an 

 almost ))oundless incompatibility of tempiu' which prevents their 

 remaining peaceably together for a single instant, so that tho oi^^rator, 

 who in this case acts as peacouakei', often suffers injury to himself 

 while attempting to Ijring theui together. If a wind strikes a vertical 

 plane, the j)ressure on that part to one side of th(>, center will exactly 

 balance that on the other side, and the part al»ove the center will 

 l)alance that below. But if the plane be slightly inclined, the pi'(>ssure 

 on the part nearest th(^ wind is iiu'r(Mis(>d and the pressure on the other 

 part decr(>ased, so that the c(Miter of pressui-e is now located, not in 

 the center of the surface, but a little toward the side which is in 

 advance. If tho plane be still further inclined the center of pi'essure 

 will move still farther foiward, and if the wind blow a little to one 



