William Allen, the eminent chemist, was born in London. His father was a silk manufacturer in Spitalfields, and a member of the Society of Friends. Having at an early period shown a predilection for chemical and other pursuits connected with medicine, William was placed in the establishment of Mr. Joseph Gurney Bevan in Plough Court, Lombard Street, where he acquired a practical knowledge of chemistry. He eventually succeeded to the business, which he carried on in connection with Mr. Luke Howard, and obtained great reputation as a pharmaceutical chemist. About the year 1804, Mr. Allen was appointed lecturer on chemistry and experimental philosophy at Guy's Hospital, at which institution he continued to be engaged more or less until the year 1827. He was also connected with the Royal Institution of Great Britain, and was concerned in some of the most exact experiments of the day, together with Davy, Babington, Marcet, Luke Howard, and Dalton. In conjunction with his friend Mr. Pepys, Allen entered upon his well known chemical investigations, which established the proportion of Carbon in Carbonic Acid, and proved the identity of the diamond with charcoal; these discoveries are recorded in the 'Philosophical Transactions' of the Royal Society, of which he became a member in 1807. The 'Transactions' for 1829 also contain a paper by him, based on elaborate experiments and calculations, concerning the changes produced by respiration on atmospheric air and other gases. Mr. Allen was mainly instrumental in establishing the Pharmaceutical Society, of which he was president at the time of his death. Besides his public labours as a practical chemist, he pursued with much delight, in his hours of relaxation, the study of astronomy, and was one of the original members of the Royal Astronomical Society. In connection with this science, he published, in 1815, a small work entitled 'A Companion to the Transit Instrument.' Many years before his death Mr. Allen withdrew from business, and purchased an estate near Lindfield, Sussex. Here while still engaged in public schemes of usefulness and benevolence, he also carried out various philanthropic plans for the improvement of his immediate dependants, and poorer neighbours. He erected commodious cottages on his property, with an ample allotment of land to each cottage, and established Schools at Lindfield for boys, girls, and infants, with workshops, outhouses, and play-grounds. About three acres of land were cultivated on the most approved system by the boarders, who also took a part in household work. The subjects taught were land-surveying, mapping, the elements of Botany, the use of the barometer, rain-gauge, &c., and there was a good library with various scientific and useful apparatus. Mr. Allen died at Lindfield, the scene of his zealous benevolence, in the seventy-fourth year of his age.--_English Cyclopædia_, London, 1856.--_Monthly notices of the Royal Ast. Soc._ vol. 6, Feb., 1844.