RODMAN, Thomas Jefferson, soldier, born in Salem, Indiana, 30 July, 1815 ; died in Rock Island, Illinois, 7 June, 1871. He was graduated at the United States military academy in 1841, assigned to the ordnance department, and served at Alleghany arsenal till 1848, going to Richmond, Virginia, in 1845 to prepare machinery for testing gun-metal and supervise the manufacture of cannon, and to Boston in September, 1846, for the purpose of experimenting with Colonel George Bomford's columbiads of 12-inch calibre. He invented a method of casting guns on a hollow core, through which a stream of cold water is kept running, greatly improving their tenacity. In 1847 he supervised the manufacture of columbiads on this system at Pittsburg, Pennsylvania During the Mexican war he served as ordnance officer at Camargo and Point Isabel depots. Returning to Alleghany arsenal, he continued his experiments. He was in command of the arsenal in 1854, and of the one at Baton Rouge, Louisiana, in 1855-'6. Although columbiads made by his method showed greater power of resistance than those that were cast solid, yet they failed under severe tests, and, as the result of a series of experiments at Pittsburg in 1856, he recommended that no more guns of large calibre should be made of that pattern. Ill 1857-'8 he experimented with a pressure-gauge of his invention, consisting of a piston working in a hole bored into the wall of a gun and acting on an indenting tool, for the purpose of determining the pressure in the bore at different points, He devised a new form of columbiad which was determined on the hypothesis that the pressure is inversely as the square root of the space behind the shot. q/he first 15-inch Rod-man gun was completed in May, 1860. In the trials, mammoth (or very large-grained) powder, and powder in perforated cakes, were also tested, and in the following year the mammoth powder was adopted for heavy ordnance. The perforated cake powder for rifled cannon of large calibre was at once adopted by the Russian government, which obtained specimens from Fortress Monroe in 1860, and soon afterward came into use in Prussia, , and more recently the military authorities in England decided on using the mammoth powder, there called pebble powder, in their big rifled guns. Rodman, who had reached the grade of captain of ordnance on 1 July, 1855, and was promoted major on 1 , June, 186":I, was in command of Watertown arsenal during the civil war, being detached at intervals for various services, especially to supervise the manufacture and trials of 12-inch rifled and 20-inch smooth-bore cannon. Many 13 and 15-inch Rodman guns were made during the war for the monitors and the forts along the coast. The method of casting about a hollow core and cooling the metal from the inside was applied to shells as well as to cannon, and from 27 September, 1864, he was engaged in supervising the manufacture of ordnance and projectiles by this method. He originated the idea of making heavy guns without preponderance at the breech, on which plan all tile heavy east-iron cannon were subsequently constructed in the United States. In March, 1865, he was brevetted lieutenant-colonel, colonel, and brigadier-general for his services in the ordnance department. He was placed in command at Rock Island on 4 August, 1865, and promoted lieutenant-colonel on 7 March, 1867, served on various boards for testing inventions in fire-arms, and at the time of his death was engaged in completing the arsenal at Rock Island, which was constructed at his suggestion and under his superintendence.