WILLIAM HENRY, (1775-1836), a distinguished chemist, son of Thomas Henry, an apothecary and author of some works on chemistry, was born at Manchester, December 12, 1775. After completing his education at an academy in Manchester, he was for some years private secretary to a physician, and in 1795 he began the study of medicine at the university of Edinburgh. Prudential con-siderations compelled him, however, to interrupt his studies at the conclusion of his first session, and he did not resume them till 1805, two years after which he received the diploma of M.D. For some time he practised as a physician in Manchester, but on account of delicate health, caused by an accident, he was ultimately compelled to retire from his profession. He nevertheless carried on his original researches in chemistry, for which he found great facilities in connexion with his father's business, and from 1797 till his death he continued to enrich the Transactions of the Royal Society with contributions on his favourite science, especi-ally in regard to aeriform bodies. His first communication was an attempt, in opposition to Austin, Beddoes, and others, to establish the title of carbon to rank among the elementary bodies, but discovering afterwards a fallacy in his reasoning he corrected it in a subsequent paper. In 1800 he published in the Philosophical Transactions his experi-ments on muriatic acid gas, made with the view of disen-gaging an imaginary unknown element supposed to be asso-ciated with oxygen in the composition of the gas; but after the discovery of the real nature of the acid by Davy he was one of the earliest converts to the new theory. In 1803 he published his elaborate experiments on the quantity of gases absorbed by water at different temperatures and under different pressures, with the result of establishing the law that :' water takes up of gas, condensed by one, two, or more additional atmospheres, a quantity which would be equal to twice, thrice, &c, the volume absorbed under the common pressure of the atmosphere." In 1808 he described in the Philosophical Transactions a form of apparatus adapted to the combustion of larger quantities of gases than could be fired in eudiometric tubes. In the same year he was chosen a fellow of the Royal Society; and in 1809, for his valuable contributions to the Transactions of the society, he was awarded the Copley gold medal. For the next fifteen years he continued his experiments on the gases, making known the results of them from time to time to the society. In his last communication, in 1824, he claimed the merit of having conquered the only difficulty that re-mained in a series of experiments on the gaseous substances issuing from the destructive distillation of coal and oil, and proved the exact composition of the fire-damp of mines. But though Henry's experiments had reference chiefly to aeriform bodies, his acquaintance with general chemistry is proved by his Elements of Experimental Chemistry, a work which combines great literary elegance with the highest standard of scientific accuracy. He had also collected materials for a history of chemical discovery from the middle of last century, but did not live to carry out the project. It is indeed to be regretted that he did not con-tribute more to the literature of science. His biographical notices of Priestley, Wollaston, and Davy may be regarded as models in that species of composition. At intervals during his lifetime Henry suffered much from neuralgic pains. These became so severe as to render the extirpation of the principal nerves of the hand necessary, but this failed to afford the expected relief; .and ultimately the irritation of the whole nervous system deprived him of sleep, and caused his death on September 2, 1836.