hii Vertical Fire. '293 



jected to a greater height than 523 feet ; and it is evident that 

 all above this is unnecessary. 



" The indentation which a musket-ball, moving with a velo- 

 city of 1 80 feet per second, makes on a piece of elm timber, is 

 about -i^jjth of an inch : this might, perhaps, be sufficient to 

 knock a man down, if by great chance it were to fall upon his 

 head ; but in no other case would it put him " hors de combat." 



" Now, as to the four-ounce balls. The diameter of a French 

 four-ounce ball, is one inch, two lines, five points ; which, re- 

 duced to English measure, is 1.28038 inches. 

 Its content is 1 "09909 inches. 



The weight is 4"72247 ounces, if made of cast iron, 

 and 4*8624 if of wrought iron. 



The terminal velocity of the cast-iron ball, is about 201 feet. 



The terminal velocity of the wrought-iron ball, is about 204 

 feet. 



The potential altitude of the cast-iron ball, is about 631 feet. 



Ditto ditto wrought ditto ditto 650 



" M. Carnot recommends that the balls should be made of 

 hammered iron ; but adds, that as the charge of powder for a 

 mortar is small, balls of cast-iron may resist the explosion 

 without breaking, and will answer as well. Now this obser- 

 vation shows that the author had not considered the effect of 

 the air's resistance, nor doubted a sufficiency of force in his 

 vertical fire ; for the weight of a ball of hammered iron, is 

 greater than that of a ball of cast-iron of equal diameter ; and 

 the superior weight, or urging force, of the former, would gene- 

 rate greater terminal velocity than a lighter ball, of the same 

 size, could acquire ; the momenta of the two balls in question, 

 would be as 19 to 18. 



" Four-ounce balls, discharged at elevations even considerably 

 above 45°, to the distance of 120 yards, would not inflict a 

 mortal wound, excepting upon an uncovered head. They 

 would not have force sufficient to break any principal bone ; 

 there would be no penetration, but merely a contusion. This 

 certainly would not oblige the besiegers to cover themselves 



