Note.—The chamber of a mortar, or howitzer, is formed of a hollow frustrum of a right cone, and of a hollow hemisphere.
Example.—Required the quantity of powder to fill the chamber of a 13-inch mortar in which the diameter A B is 9·5 inches, the diameter C E 6·5 inches, and the length D G 21·5 inches. Vide [Fig. 22]. Plate 2. Heights and Distances, and Practical Geometry.
The content of the chamber must be found by finding the content of the hollow frustrum of the cone, and that of the hemisphere (vide preceding rules): which in this example will be 999·9741875.
Then 999·9741875 × 55 1728 = 31 pounds, nearly.
To find the quantity of powder to fill a rectangular box.
Divide the content (viz., length × breadth × depth) of the box in inches by 30 for the pounds of powder.
Example.—How much powder will fill a box, the length being 15 inches, the breadth 12, and the depth 10 inches.
15 × 12 × 10 30 = 1800 30 = 60 pounds. Number required.
To find the quantity of powder to fill a cylinder.
Multiply the square of the diameter by the length, then divide by 38·2 for the pounds of powder.