DANIEL, John Frederick, was born in London in 1790, and was bred to be a sugar-refiner. But having become a pupil of Mr Brande very early in life, he imbibed a strong relish for scientific investigations; and in 1814 became a member of the Royal Society. In 1817 he married the daughter of Sir William Rule, surveyor of the navy; and he now dedicated himself to science. In 1820 he published the description of his very elegant hygrometer, founded on the principle of ascertaining the dew-point by a delicate thermometer, in a very portable apparatus. Three years after this he gave to the world his valuable Meteorological Essays, a work that has gone through three large editions. In 1824 appeared his Essay on Artificial Climate, especially as it affects vegetation, a work rewarded by the Horticultural Society. In 1821 he became professor of chemistry in King's College, London, and now devoted himself assiduously to the study of voltaic electricity, its connection with chemical phenomena, and the improvement of voltaic apparatus. His Introduction to Chemical Philosophy appeared in 1839, and a second edition in 1841; in which year the University of Oxford conferred on him the honorary degree of D.C.L. In this work the doctrine of molecular forces is very ably treated. He was for several years foreign secretary to the Royal Society. This ingenious philosopher died in his lecture-room, March 13, 1845. (T.S.T.)