The blanks, as the steel before it has teeth is called, are laid on the anvil and struck with the chisel, which rests obliquely on the blank, each blow raising a ridge or tooth. The strength of the blow depends on the hardness of the metal, and when one part is harder than another the workman alters his blows accordingly. When one side is covered with single cuts if the file is to be double cut he adds in the same manner a second series, crossing the others at a certain angle. In making fine files a good file-cutter will cut upwards of two hundred teeth within the space of an inch. The files, except those that are used for soft substances, are hardened by heating them to a cherry-red color and then dipping them in water. They are then finished by scouring and rubbing over with olive oil and turpentine. The Story of Self-Loading Pistols[8] Colt Pistols. The machine gun of the present day, the murderous weapon which has numbered its victims by the hundreds of thousands during the European war, had its origin in the mind of a man whose birth dates back to almost exactly one hundred years before this war began, that of Samuel Colt, born at Hartford, Conn., on July 19, 1814. [Illustration: CUSTER’S LAST STAND The revolver played a large part in Indian warfare.] The small arm of the previous period, the old “Brown Bess,” used in the British army for 150 years, was a muzzle-loading, flint-lock musket of the crudest make. The only important improvement made in it during that long term of service was the substitution of the percussion cap for the flint lock. This took place in the last period of its use. A breech-loading rifle was also invented about this time. This was the “Needle Gun,” of which 60,000 were issued to the Prussian army in 1841, and which was first used in 1848, in the German war with Denmark. The Colt pistol had appeared before this date. The idea of it grew in the mind of young Colt when he left his father’s silk mill and shipped as a boy sailor in the ship “Carlo,” bound from Boston to Calcutta. While on this voyage the conception of a revolving pistol came to him, and he whittled out a rude model of one with a penknife from a piece of wood. [Illustration: SINGLE ACTION ARMY AND FRONTIER REVOLVER--THE “COWBOY’S FRIEND”] [Illustration: THE ORIGINAL PATTERSON MODEL, 1836] [Illustration: OLD MODEL “POWDER AND BALL” REVOLVER USED IN MEXICAN AND CIVIL WARS] [Illustration: GUN MOUNTED ON LANDING CARRIAGE WITH SHAFT ATTACHMENT]