Annalen der Physik und Chemie, Ergänzung Band viii. Stück 4.—In an inaugural dissertation, with which this number opens, Dr. Less investigates the heat conductivity of some seventeen varieties of stone, and several kinds of wood, his method being a refinement on that of Hopkins, with whose results (for stone) his own generally agree, only the numbers obtained for different varieties of one rock vary much more. In general, density and compactness favour the passage of heat, though the effect evidently does not depend on this alone. Stones of crystalline texture conduct better than those mechanically mixed, and fine-grained better than coarse-grained stones. In his table, marble from the Pyrenees is put at the top, its conductivity being reckoned 1,000; then follow Saxon granite (804), Carraran marble (769), & c., down to common clay (275). Tyndall's observation of a difference in conduction in two directions (with and at right angles to the fibres) in wood is confirmed, but the differences are found considerably less. The ratios of the galvanometer deflections are much greater in the better-conducting than in the worse-conducting woods, making it very probable that these deflections are proportional, not to the conductivities themselves, but to a somewhat higher power of them.—In two papers dealing with magnetic induction and Clausius and Weber's fundamental laws of electro-dynamics, M. Lorberg, by a development of the theory of two experiments, arrives at results throwing doubt on Clausius' law, and endeavours to show that Weber's is the only possible one.—M. Sadebeck contributes a lengthy paper on the crystallisation of markasite, and its regular growths with iron pyrites; and M. Schönn describes the absorption of light by water, petroleum, ammonia, alcohol, and glycerine.