The latest development in machine guns is a pocket edition weapon--a firearm weighing only 7 pounds and measuring but 22 inches over all. This little gun which is too small to be classed as a rifle and yet rather large for a pistol, has two grips so that it may be fired from the waist line, and it may be fitted with a gun butt so that it may be fired from the shoulder. It operates at the astounding rate of 1,500 shots per minute or three times the speed of the average machine gun. The cartridges are fed either from a box magazine containing 20 rounds or from a drum-shaped magazine loaded with 50 to 100 cartridges. The operating mechanism of this gun is entirely different from anything produced heretofore and depends upon a discovery made by Commander Blish of the United States Navy. He found that a wedge of a certain angle will hold a breechblock closed against the pressure of an exploding cartridge while the pressure is high, but will slide when the pressure falls. Apparently at first the adhesion due to friction is too great to permit the wedge to move, but the adhesion falls off more rapidly than the pressure does and a point is reached at which the wedge yields to the pressure. In the “submachine” gun, as the new weapon is called, the barrel (or rather an extension of the barrel) and the receiver, in which the operating mechanism is contained, are locked together by a wedge. The wedge slides in slots set at an angle of 80 degrees with the axis of the barrel. When a cartridge is fired the wedge remains fast while the bullet is traveling through the bore, but when it emerges and the pressure of the gases falls off the wedge slides, unlocking the breech mechanism. The gun is remarkable for its simplicity and the fewness of its parts. It has been adopted by the Police Department of New York City. ARTILLERY VS. ARMOR As has been stated above, gunpowder was first introduced in warfare not for the purpose of destroying men, but for smashing city walls and fortifications, so that infantry could pour through the breeches made by the heavy stone or iron projectiles. As artillery grew more powerful and the aim more accurate walls of masonry gave way to earthworks and to masses of concrete and armored steel. However the World War demonstrated the impossibility of building any fortifications above ground that would stand up against modern high-powered guns. GUNS, MORTARS, AND HOWITZERS