HENRY, JOSEPH, LL.D., 1797-1878; b. N. Y.; educated in Albany academy, where he was professor of mathematics in 1826. His attention was turned to electrical experi• meats, and he published in 1829 results of modifications in the appliance of electro magnetism which attracted wide attention, particularly in the application of magnetic force at long distances. About this time he invented a machine worked by magnetism, in which he showed that an oscillating iron bar inclosed in insulated copper wire which was automatic in action would oscillate as long as the magnetic force was applied. Ile demonstrated the remarkable power that might be produced by a small galvanic appa ratus, exhibiting in 1829 electro-magnets which possessed a far greater power than any before tried. One such, occupying only a cubic foot of battery space, is capable of supporting 3,500 lbs. In 1831 was successful in an attempt to make a bell ring at the end of mile of wire. In the same year he published his observations, and claimed to be the originator of the idea that communication with distant places might be made feasible by magnetism, some years before Morse reduced the matter to ractiee. In
1832 lie became professor of natural philosophy in Princeton college. 7 here and in Europe he pursued his investigations and experiments, and made the acquaintance of distinguished scientists. On the establishment of the Smithsonian institution (1834), lie was selected as secretary and chief director, holding the position through life. In 1840 he was chosen president of the American association for the advancement of science, and in 1868 he was president of the National academy of sciences. In 1871 he was head of the lighthouse board, in which capacity he introduced valuable improvements in the service. Among his publications are Contributions to Electricity and .+Iagnetisan,. and a great number of papers in the scientific journals, and the reports of the Smith sonian institution. Among his chief contributions to science are the electromagnet (indispensable to telegraphy), improvements in fog-signals and in coast lights. his observations were also of great service in the lately established signal service. Ito spent his life in scientific research, without thought of pecuniary profit for himself.