SOME AERONAUTICAL EXrEEIMENTS. 



143 



hoi'izontal pull; hut when the wind l»ecanic still stronger it took the 

 lower position shown in the ligure, witli a strong- downward ])ull. It 

 at once occurred to me that here was the answer to our problem, for 

 it is evident that in the tirst case the center of pressure was in front of 

 the center of gravity, and thus pushed up the front edge; in the second 

 case they were in coincidence and the surface in e([uilibriuni, while in 

 the third cas(^ the center of pr(>ssure had reached a ])oint e\ en behind 

 the center of gravity, and there was therefore a downward })ull on the 



Fk;. 1. — 1', ceiitor of i)ressuro; G, center of gravity. 



cord. This point having been delinitely settled, we proceeded to truss 

 down the ribs of the whole machine, so as to reduce the depth of 

 curvature. In tig. 2 line 1 shows the original curvature; line 2, the 

 curvature when supporting the opei'ator's weight, and line ;>, the curv- 

 ature after trussing. 



On resuming our gliding, we found that the old conditions of the 

 preceding year had returned, and after a few trials made a glide of 

 3G6 feet and soon after one of 881) feet. The machine with its new 



Fiii. '2. — Diagrams of i)rL'ssurL's and curves 



curvature never failed to respond promptly to even small movements 

 of the rudder. T1k» operator could cause it to almost skim the ground, 

 following the undulations of its surface, or he could cause it to sail 

 out almost on a level with t\\v starting point, and passing high above 

 the foot of the hill, gradually settle down to the ground. The wind 

 on this day was blowing 11 to 14 miles per hour. The next day, the 

 conditions lacing favorable, the machine was again taken out for trial. 



