H A R 



Let d = diameter of ball, c the velocity of projection, 7i r= 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 llf 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, 



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 



! 

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



6 1 



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 pounds or more, 

 and reduces the velocity in a second from 2000 to 1200 feet in the first 

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



GUNPOWDER. See Gunnery and Steam. 



GYRATION, Centre of. See Centre of Gyration. 



H 



HARMONICAL Progremon.See 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 w, latitude of the place = I, moon's declination = J, 

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



t) _ m > sin, n 



"" Vco8.sin.*/ 



