In April, 1862, J. J. Andrews, a citizen of Kentucky and a spy in General Buell's employment, proposed seizing a locomotive on the Western and Atlantic Railroad at some point below Chattanooga and running it back to that place, cutting telegraph wires and burning bridges on the way. General O. M. Mitchel authorized the plan and twenty-two men volunteered to carry it out. On the morning of April 12th, the train they were on stopped at Big Shanty station for breakfast. The bridge-burners (who were in citizens' clothes) detached the locomotive and three box-cars and started at full speed for Chattanooga, but after a run of about a hundred miles their fuel was exhausted and their pursuers were in sight. The whole party was captured. Andrews was condemned as a spy and hanged at Atlanta, July 7th. The others were confined at Chattanooga, Knoxville, and afterward at Atlanta, where seven were executed as spies. Of the fourteen survivors, eight escaped from prison; and of these, six eventually reached the Union lines. Six were removed to Richmond and confined in Castle Thunder until they were exchanged in 1863. The Confederates attempted to destroy the locomotive when they evacuated Atlanta. [Illustration: BATTLE BETWEEN THE MONITOR AND MERRIMAC. _Painted by E. Packbauer._ _Copyright, 1901, by Perrien-Keydel Co., Detroit, Mich., U. S. A._] [Illustration: THE BIGGEST GUN OF ALL--THE 20-INCH MONSTER FOR WHICH NO TARGET WOULD SERVE COPYRIGHT, 1911, PATRIOT PUB. CO.] A photograph of the only 20-inch gun made during the war. It weighed 117,000 pounds. On March 30, 1861, a 15-inch Columbiad was heralded in _Harper's Weekly_ as the biggest gun in the world, but three years later this was exceeded. In 1844 Lieutenant (later Brigadier-General) Thomas Jefferson Rodman of the Ordnance Department commenced a series of tests to find a way to obviate the injurious strains set up in the metal, by cooling a large casting from the exterior. He finally developed his theory of casting a gun with the core hollow and then cooling it by a stream of water or cold air through it. So successful was this method that the War Department, in 1860, authorized a 15-inch smooth-bore gun. It proved a great success. General Rodman then projected his 20-inch smooth-bore gun, which was made in 1864 under his direction at Fort Pitt, Pittsburg, Pennsylvania. It was mounted at Fort Hamilton, New York Harbor, very soon afterwards, but on account of the tremendous size and destructive effect of its projectiles it was fired only four times during the war. It was almost impossible to get a target that would withstand the shots and leave anything to show what had happened. These four shots were fired with 50, 75, 100 and 125 pounds of powder. The projectile weighed 1,080 pounds, and the maximum pressure on the bore was 25,000 pounds. In March, 1867, it was again fired four times with 125, 150, 175 and 200 pounds of powder, each