258 Mr. Tredgold'on a ?iew Theory of the Resistance 



The equation rendered applicable to this case is 



v* (-242 d (3 z — 1*1629 r) -f 0-0032 ^? I) = the resistance in 



pounds ; and as d = '89 ; z = 13 8 ; r = 27*32, and p I = 540, 



it becomes 3*79 if = the resistance in pounds. 



Considering the complex form, the resistance is expressed very 

 well by the equation, and quite as nearly as a general rule 

 could be expected to give it ; and every one is aware of the 

 advantage of being able to anticipate practical effects so nearly. 

 29. The most important experiments on the resistance of 

 air appear to be those conducted by Dr. Hutton*, for the 

 improvement of the theory and practice of Gunnery. In or- 

 der to ascertain the effect of giving different inclinations to the 

 same surface, he fixed a rectangular plane 32 inches in area s 

 at different angles to the direction of its motion ; the velocity 

 was twelve feet per second. 



The resistance of the plane when set at an angle of 90° and 

 moving at the rate of twelve feet per second, was 0*841 ounce. 

 By my mode of calculation it comes out 0*896 ounce. In an- 

 other set of trials with a triangular plane, the resistance cor- 



* Tracts, vol. iii. p. 202. 



responding 



