PNEUMATICS. 277 



and the resistance in avoirdupois pounds, or 



~ 1000 (,300 " 



For this theorem, so useful in gunnery, and so well 

 accommodated to practice, we are indebted to Dr 

 HUTTON of Woolwich, ubi supra. 



A ball is often resisted by a force that is many times 

 its own weight. An iron ball 3 Ib. weight has its 

 diameter 2.78 inches, and when it is thrown with 

 a velocity of 1800 feet, it is resisted by a force 

 equal to 176 Ib., more than 58 times its own 

 weight. 



373. Supposing the air to resist according to the 

 law just assigned ; the height to which a ball of 

 the weight w 9 and the diameter d, will ascend, 

 when projected perpendicularly upwards with any 

 velocity c, will be, 



2 n w 



m md? 



met* 



If this expression be reduced, by substituting for m 

 its value -5236 d 3 , and using the common loga- 



