H A R 



Let d diameter of ball, c tho velocity of projection, It height as- 

 cended, then 



Ex. A ball of 1.05 Ibs., discharged with a velocity of 2000 feet, will 

 ascend to the height of 2920 feet j in vacua it would have ascended to the 

 height of 1 If miles. 



5. If a body descending in the atmosphere has acquired such a velocity 

 that the resistance is equal to its weight, the accelerating and retarding 

 forces being equal, its motion will become uniform; to find this termi. 

 nal velocity, 



o 7 ,s 



.556 



a quadratic equation, from whence v may be found. 



Ex. For an iron ball of 1 Ib, the terminal velocity 244 feet ; for one 

 of 42 Ibs. it is 456. 



6. The best charge of powder is about or of the weight of the 



1 

 ball j for battering : a 24-pounder with 16 pounds of gunpowder at 



o 



an elevation of 45 ranges 20,250 feet, about ~ of the range that would 



take place in a vacuum. The resistance is at first 400 poands or more, 

 and reduces the velocity in a second from 2000 to 1500 feet in the first 

 1500 feet. (Young's Nat. Phil.) 



GUNPOWDER. &?e Gunnery and Steam. 



GYRATION, Centre of. See Centre of Gyration. 



H 



HARMONICAL Progression. Sec Progression, 



HARVEST Moon.(MaddyJ 



To find the retardation of the Moon's rising on successive nights. 



Let the moon's daily motion = m, the inclination of the moon's orbit 

 to the horizon , latitude of the place = /, moon's declination = o t 

 then the difference of the times of rising on succeeding days (D) is 



_^ __ m. sin, n 



Vcos.*3 sin.*; 

 133 



