GUN 



White pine ... . . . 420 



Fir, of New England ..... 553 



of Riga ...... 753 



of Mar Forest, Scotland .... 696 



Cypress ....... 644 



Lime tree ...... 604 



Filbert wood ...... 600 



Willow ...... 585 



Cedar ....... 560 



Juniper ....... 556 



Poplar, white Spanish .... 529 



common ..... 383 



Sassafras wood ..... 482 



Larch, of Scotland ..... 530 



Cork ....... 240 



GREGORIAN Calendar. See Calendar. 



GULDINUS' Property. See Solids and Surface*. 



GUNNERY, leading principles of.(Hutton.) 



1. To find the initial velocity of a shot. 



Let JP = weight of powder, B of the ball, v the initial velocity, then 



- 2000 >. 



Cor. 1. The initial velocity of a shot varies from 1600 to 2000 feet per 

 second. 



Cor. 2. B e* = (2000)*. P, i.e. the effect of a shot is nearly as the quan- 

 tity of gunpowder. 



2. If w = weight of any ball, d its diameter. 



w .5236 d 3 in pounds. 



3. To find the resistance of the air to any ball or projectile. 



Let d = diameter of ball, v its velocity, r = resistance in avoirdupois 

 pound?, then 



(ft x 2 e* N 



-1660(3600-*-) 



Ex. Resistance to a ball, whose diameter = 2.78 inches (or weight 

 31bs.), when thrown with a velocity of 1800 feet per second, 176 Iba., 

 more than 58 times ite own weight. 



4. Supposing the air to resist according to the law just assigned, re- 

 quired the height to which a ball will ascend perpendicularly, 



137 



