DANIELL, JOHN FREDERICK, wee born in Essex-street, Strand, on the 12th of March 1790, and was the son of Mr. George Daniell, of West Humble, Surrey, beucher of the Middle Temple. At an early ago he became a pupil of Professor-Brande, in whose society he made several tours. Mr. Daniell entered originally into business as a sugar refiner, but his fondness for scientific investigations, manifested at a vi ry early age, prevailed, and he soon relinquished business for pur suits more congenial to his taste. In 1814 he became a Fellow of the Royal Society. In 1816, associated with Professor Braude, he com menced the Quarterly Journal of Science and Art,' the first twenty volumes of which were published under their joint superintendence.
Ile married in the following year Charlotte, youngest daughter of the late Sir W. Rule, surveyor of the navy. From this time to his death hardly a single year elapsed without the appearance of one or snore essays on chemical or meteorological subjects from the pen of Mr.
DanielL In 1820 he published the accouot of his new hydrometer, an instrument which, for the first time, rendered regular and accurate observations on the dryness and moisture of the air practicable. Iu this instrument he applied the principle of the cryophortis of Wollas ton to obtain the requisite cold for the production of dew upon a ball of dark-coloured glass containing ether. The temperature of the inclosed ether is measured by a delicate thermometer without the bulb, and corresponds with the dew-point. This instrument has been extensively employed in all climates, and has been of the greatest service to meteorology. In 1823 appeared his great work, Meteoro logical Essays ;' a second edition was published in 1827, and he was engaged in revising proofs of the third edition at the time of his death. This was the first synthetic attempt to explain the general principles of meteorology by the known laws which regulate the temperature and constitution of gases and vapours, and in which the scattered observations and isolated phenomena presented by the earth's atmosphere were considered iu their most extensive and general bearings. One of the most interesting of his theories connected with meteorology was that which he proposed to account for the horary oscillations or periodic daily rise and fall of the barometer, by which Ito predicted the occurrence of a fall near the poles coincident with the rise at the equator. Actual observations soon confirmed the accuracy of his theory, and the existence of this unsuspected phenomenon was established beyond dispute. In the year 1821 ho
published an ' Essay on Artificial Climate,' for which lie received the silver medal of the Horticultural Society. Dr. Lindley has expressed a strong opinion on the practical value of this paper in completely revolutionising the methods of horticulture till then adopted.
About this period Mr. Daniell became managing director to the Continental Gas Company, and travelled through most of the principal European cities with Sir W. Congreve and Colonel Laudmaun, making the arrangements by which many of them are lighted at the present day. He also invented a new process for obtaiuing inflammable gas from resin, which was successfully applied to the lighting of some of the large towus in America.
Ou the eatabilshment of King's College in 1831, Mr. Daniell was appointed professor of chemistry, the duties of which office be dis charged till his death. About this time he published the account of ' his new pyrometer, an instrument far superior to any that had been invented, for measuring high temperatures, such as those for fusing metals, furnaces, dm. For this simple and perfect invention, the Royal Society, in 1832, awarded him the Rumford medal. From this time his attention seems to have been principally devoted to voltaic electricity. In 1836 he communicated to the Royal Society a paper in which he described his valuable improvement in the voltaic battery . In this communication he traced the cause of the rapid decline of power in batteries of the ordinary description, and pointed out an arrangement by which a powerful and continuono current of voltaic electricity may be maintained for an unlimited period. The import *nee of this discovery was recognised immediately by the whole scientific world, and in appreciation of its merit.. the Royal Society, in 1837, awarded biro the Copley medal In 1839 he published his ' Introduction to Chemical Philosophy,' an admirable treatise on the action of molecular forces in general, though it modestly professes to give little more than a simple introduction to the discoveries of Faraday, and their applications to chemistry. He continued his researches in the same department of science till the time of his decease, communicating the results of his experiments to the Royal Society. For two of these papers. bearing most essentially on the theory of salts, he received, in 1842, one of the Royal medals.