~Electronite.~--This is a high explosive designed to afford safety in coal getting. This important end has been attained by using such ingredients, and so proportioning them, as will ensure on detonation a degree of heat insufficient under the conditions of a "blown-out" shot, to ignite fire damp or coal dust. It is of the nitrate of ammonium class of permitted explosives. It contains about 75 per cent. of nitrate of ammonium, with the addition of nitrate of barium, wood meal, and starch. The gases resulting from detonation are chiefly water in the gaseous form, nitrogen, and a little carbon dioxide. It is granulated with the object of preventing missfires from ramming, to which nitrate of ammonium explosives are somewhat susceptible. This explosive underwent some exhaustive experiments at the experimental station near Wigan in 1895, when 8 oz. or 12 oz. charges were fired unstemmed into an admixture of coal dust and 10 per cent. of gas, without any ignition taking place. It is manufactured by Messrs Curtis's & Harvey Ltd. at their factory, Tonbridge, Kent. ~Sprengel's Explosives.~--This is a large class of explosives. The essential principle of them all is the admixture of an oxidising with a combustible agent at the time of, or just before, being required for use, the constituents of the mixture being very often non-explosive bodies. This type of explosive is due to the late Dr Herman Sprengel, F.R.S. Following up the idea that an explosion is a sudden combustion, he submitted a variety of mixtures of oxidising and combustible agents to the violent shock of a detonator of fulminate. These mixtures were made in such proportions that the mutual oxidation or de-oxidation should be theoretically complete. Among them are the following:-- 1. One chemical equivalent of nitro-benzene to equivalents of nitric acid. 2. Five equivalents of picric acid to 13 equivalents of nitric acid. 3. Eighty-seven equivalents of nitro-naphthalene to 413 equivalents of nitric acid. 4. Porous cakes, or lumps of chlorate of potash, exploded violently with bisulphide of carbon, nitro-benzol, carbonic acid, sulphur, benzene, and mixtures of these substances. No. 1 covers the explosive known as _Hellhoffite_, and No. 2 is really oxonite, and No. 4 resembles rack-a-rock, an explosive invented by Mr S.R. Divine, and consisting of a mixture of chlorate of potash and nitro- benzol. Roburite, bellite, and securite should perhaps be regarded as belonging to the Sprengel class of explosives, otherwise this class is not manufactured or used in England. The principal members are known as _Hellhoffite_, consisting of a mixture of nitro-petroleum or nitro-tar oils and nitric acid, or of meta-di-nitro-benzol and nitric acid; _Oxonite_, consisting of picric and nitric acids; and _Panclastite_, a name given to various mixtures, proposed by M. Turpin, such as liquid nitric peroxide, with bisulphide of carbon, benzol, petroleum, ether, or mineral oils.