MECHANICS AND USEFUL ARTS. 109 



charges of English large-grained rifle powder, such as is used in 

 our 7^-inch and 9-inch rifled guns. Fifteen rounds altogether 

 were fired, and sufficed to give a valuable character to the weap- 

 on. The practice on such occasions as the present is to train the 

 gun upon some definite object, such as a target, in a nearly hori- 

 zontal direction, in this case two degrees of elevation taken with 

 a spirit-level quadrant, and then to fire with various charges of 

 powder, noting. the spots at which the shots first grazed, and the 

 time, in seconds, from the discharge in which they do so. The 

 rest of the flight of the missiles in their ricochets is only incident- 

 ally noted. The object is not to hit the target, but to find out the 

 distances certain charges will project shots of the same weight, 

 the amount of deflection those shots experience, and the velocities 

 they attain in their flight. 



"The first seven rounds were with the American mammoth 

 powder, very coarse but strong, the individual grains being as 

 large as horse-beans, and roughly angular like the coarser flint 

 gravel met with just below our sea-beaches. The velocity in all 

 the following cases was taken at 50 yards from the gun : 



"Round No. 1: Charge, 35 pounds; weight of shot 452 

 pounds 12 ounces; recoil of gun-carriage, 5 feet; time of flight 

 to first graze, 2.7 seconds ; distance of range to first graze, 696 

 yards ; deflection of shot to the right, 1.6 yards. 



*' Frame of screen cut by shot, and velocity consequently not 

 obtained. 



" Round No. 2 : Charge, 35 pounds ; shot, 451 pounds ; recoil, 

 4 feet 11 inches ; flight, 2.5 seconds ; range, 740 yards ; deflection, 

 right, 0.6 yards ; velocity, 917 feet per second. 



"Round No. 3: Charge, 35 pounds; shot, 455 pounds; re- 

 coil, 5 feet; flight, 2.7 seconds; range, 737 yards; deflection, 

 right, 0.6 yards ; velocity, 926 feet per second. 



"Round No. 4: Charge, 50 pounds; shot 453 pounds 4 

 ounces; recoil, 8 feet 5 inches; flight, 3 seconds; range, 963 

 yards; deflection, right, 2.8 yards;' velocity, 1,110 feet per sec- 

 ond. 



"Round No. 5: Charge, 50 pounds; shot, 454 pounds; re- 

 coil, 8 feet 7 inches ; flight, 3 seconds ; range, 1,003 yards ; deflec- 

 tion, right, 2 yards; velocit}^, 1,120 feet per second. 



"Round No. 6: Charge, 50 pounds; shot, 453 pounds 8 

 ounces; recoil, 8 feet 9 inches; flight, 3 seconds; range, 987 

 yards; deflection, right, 3.2 yards; velocity, 1,133 feet per sec- 

 ond. 



"Round No. 7: Charge, 60 pound-s ; shot, 453 pounds 4 

 ounces; recoil, 10 feet; flight, 3.3 seconds; range, 1,138 yards; 

 deflection, right, 1.4 yards: velocity, 1,210 feet per second. 



" The next six rounds were fired with the English service large- 

 grained rifle powder, the grains of which are far smaller than the 

 American, and in appearance much like very fine coal dust. The 

 combustion is also much more sensitive, and the powder stronger : 

 roughly, probably, in the proportion of 40 pounds to 50 pounds. 



"Round No. 8: Charge, 35 pounds; shot, 450 pounds 12 

 10 



