12 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93 



honeycomlj wind-straightener. The air speed was estimated to be 

 40 feet per second. 



The balance was based on the principle of using the normal pres- 

 sure on a plane surface to measure the lift of an airfoil. The wing 

 model and the normal plane were mounted on separate horizontal 

 cross-stream bars so linked together that the wind lift on the model 



Fig. 6. — Schematic drawing of the Wright Brothers' balance, based on a photograpli. 



tended to move it across stream. The drag on the normal plane would 

 tend to resist this movement. When the two were exactly balanced, 

 the ratio of lift to the resistance of the normal ])lane was indicated 

 by a pointer. 



A balance of similar construction was later used by Orville Wright 

 in his wind tunnel in Dayton.'" 



'"Warner and Norton, Wind tunnel balances. U. S. Nat. Adv. Comm. 

 Aeronautics, Rep. no. ~2, pp. 39-40, 1920. 



