Fig. 9. Sectional view of a 3-inch Stokes mortar showing a shell at the instant of striking the anvil
Fig. 10. A 6-inch trench mortar shell fitted with tail-vanes
Curiously enough, there is no breech-block, trigger or fire-hole in this mortar. It is fired merely by the dropping of the missile into the mouth of the barrel. The shell carries its own propelling charge, as shown in [Fig. 9.] This is in the form of rings, A, which are fitted on a stem, B. At the end of the stem are a detonating cap and a cartridge, to ignite the propellant, A. At the bottom of the mortar barrel, there is a steel point, E, known as the "anvil." When the shell is dropped into the mortar, the cap strikes the anvil, exploding the cartridge and touching off the propelling charge, A. The gases formed by the burning charge hurl the shell out of the barrel to a distance of several hundred yards.
The first Stokes mortar was made to fire a 3-inch shell, but the mortar grew in size until it could hurl shell of 6-inch and even 8½-inch size. Of course, the larger mortars had to have a very substantial base. They were not so readily portable as the smaller ones and they could not be carried by one man; but compared with ordinary artillery of the same bore they were immeasurably lighter and could be brought to advanced positions and set up in a very short time. The larger shell have tail-vanes, as shown in [Fig. 10], to keep them from tumbling when in flight.
[CHAPTER III]
Guns that Fire Themselves
Many years ago a boy tried his hand at firing a United States Army service rifle. It was a heavy rifle of the Civil War period, and the lad did not know just how to hold it. He let the butt of the gun rest uncertainly against him, instead of pressing it firmly to his shoulder, and, in consequence, when the gun went off he received a powerful kick.