JOHNSON, Walter Rogers, chemist, born in Leominster, Massachusetts, 21 June, 1794; died in Washington, D. C., 26 April, 1852. He was graduated at Harvard in 1819, taught in Framingham and Salem, Massachusetts, and in 1821 became principal of the academy in Germantown, Pennsylvania In 1826, when the high school was established in Philadelphia, under the auspices of the Franklin institute, he was given the chair of mechanics and philosophy, and at the same time delivered a public course of lectures on those subjects, which were largely attended. In 1836 he begum a series of geological investigations, with special reference to the coal formations and iron ores of Pennsylvania, and a year later was given charge of the department of magnetism, electricity, and astronomy on the United States exploring expedition, but soon resigned this office, owing to changes in the original plan. From 1839 till 1843 he held the professorship of physics and chemistry in the medical department of the University of Pennsylvania. In 1843 he was appointed by congress to investigate the character of the different varieties of coal, with reference to their absolute and relative values for generating steam and heat and producing illuminating gas, and he published a report on that subject during the following year. Subsequently he made scientific researches for the navy department, and in 1845 was appointed by the city authorities of Boston to examine the sources from which pure water might be brought to the city. In 1848 he became connected with the Smithsonian institution in Washington, and in 1851 he was sent to the World's fair in London. Professor Johnson was active in the organization of the Association of American geologists and naturalists, and when it gave place to the American association for the advancement of science he was its first secretary. His publications include "Natural Philosophy," originally entitled "Scientific Class Book, No. 1" (Philadelphia, 1835); "Chemistry," originally entitled "Scientific Class Book, No. 2" (1835); "Notes on the Use of Anthracite in the Manufacture of Coal" (Boston, 1841); Knapp's "Chemical Technology," translated (Philadelphia, 1848); Weisbach's "Mechanics," translated (1849); and "Coal Trade of British America" (Washington, 1850).