THE death of M. Becquerel, alluded to in our last issue, was followed on the 19th inst. by that of his friend and fellow-physicist, M. Regnault, whose name is associated so intimately with the elementary principles of our knowledge of heat. Henri Victor Regnault was born at Aix-la-Chapelle, July, 21, 1810. His youth was spent in a hard battle against poverty in the effort to maintain not only himself, but his sister. While still a lad he wandered to Paris, and there obtained a position as assistant in the large drapery establishment known as Le Grand Coude, a name familiar at the present day to the lady visitors of Paris. Here ability and fidelity won for him friends, and at the age of twenty he was enabled to gratify his longings for a scientific education, and enter the École Polytechnique of Paris, the Alma Mater of so many famous French savants. After a course of two years here, in 1832 he entered upon active duties in the department of mines, and was absent from Paris for the next eight years. During the latter portion of this time he occupied a professor's chair at Lyons, and had a laboratory at his disposal. Here he embraced the opportunity to enter upon the field of research in organic chemistry, which had just sprung into existence as a branch of chemical science, under the hands of Liebig, Wöhler, Laurent, Dumas, and others. While many of the chemists of the day were engaged in theoretical disputes, and the battle between the electro-chemical theory and the newly-advocated type-theory was being hotly waged, Regnault devoted himself to the accumulation of the facts so sorely needed as foundation-stones by the disputants on both sides. Among his investigations at this time may be mentioned those on the composition of meconine, piperine, canthari-dine, and other alkaloids, composition of pectic acid, identity of esquisetic acid with maleic acid, properties of naphthaline-sulpho-acid, &c. By the action of sulphuric anhydride on ethylene, he obtained the carbyl-sulphate, C2H4S2O6, which Magnus prepared later from alcohol. His most valuable researches, however, were on the halogen derivatives in the ethyl-group, especially interesting at the time of their appearance, when the theories of substitution were timidly being advocated. Among these compounds now familiar reagents to the organic chemists were mono-chloro-ethylene-chloride, CH2Cl.CHCl2, obtained by the action of chlorine on ethylene chloride, as well as the higher chlorinated derivatives, which offered one of the most striking instances of substitution. These were followed shortly after (1838) by the classical investigations on the actions of chlorine on ethyl-chloride C2H5C1, in which one by one all of the hydrogen atoms were successively substituted by chlorine, until the limit, C2Cl6 was reached. Of importance also was the change of ether, C4H10O, into perchloroether, C4Cl10O. Another interesting series of preparations gave the substituted ethylcnes by the action of alkalies on saturated halogen derivatives, ethylene-bromide for example, yielding vinyl-bromide, and hydro-bromic acid:—