For the method of proving shells. See [Proof].
To find the Weight of a Shell of Iron.
Take ⁹/₆₄ of the difference of the cubes of the external and internal diameters for the weight of the shell.
To find how much Powder will fill a Shell.
Divide the cube of the internal diameter of the shell in inches by 57.3, for the pounds of powder.
To find the size of a Shell to contain a given Weight of Powder.
Multiply the pounds of powder by 57.3, and the cube root of the product will be the diameter in inches.
The Germans do not name their shells from the diameter of the bore which receives them, but from the weight of a stone ball that fits the same bore as the shell. Thus a 7 lbs. howitzer admits a stone ball of that weight; the shell for this weighs 15 lbs. and answers to the English 5½ inch. The 30 lbs. howitzer shell weighs 60 lbs. and is rather more than 8 inches in diameter.
Note.—Shells were till lately made thicker at the bottom than at the fuze hole; but are now cast of the same thickness throughout, and are found to burst into a greater number of pieces in consequence.
SHOT.—Rules for finding the Number in any Pile.