that a very extensive difference was produced. They would see at once that this was a very decisive experiment to prove that the great source of resistance was to be found in the bulk, and not the mere section or the form, whether of the front or the back of a train; but simply in the general bulk of the body carried through the air. It was very likely to arise from the successive displacements of a quantity of the atmosphere equal to the bulk of the body; or still more probably, from the fact of the extensive sides of the train; and indeed there was little doubt that the magnitude of the sides had a very material influence; for if they consider what is going on in the body of air extending from either side of a train of coaches, they would soon see what a mechanical power must be exercised upon it. Thus, when a train is moving rapidly, the moving power had not only to pull the train on, but it had to drag a succession of columns of air, at different velocities, one outside the other, to a considerable extent outside the train; and it did more, for it overcame their friction one upon the other; for as these columns of air were at different velocities, the one would be rubbing against the other; and all this the moving power had to encounter. This would go far to explain the great magnitude of resistance found, and its entire discordance with any thing previously suspected.” * * * * * GILDING OF METALS BY ELECTRO-CHEMICAL ACTION.--M. de la Rive has succeeded in gilding metals by means of this powerful action. His method is as follows: he pours a solution of chloride of gold (obtained by dissolving gold in a mixture of nitric and muriatic acid) as neutral as possible and very dilute, into a cylindrical bag made of bladder; he then plunges the bag into a glass vessel containing very slightly acidulated water; the metal to be gilded is immersed in the solution of gold, and communicates by means of metallic wire with a plate of zinc, which is placed in the acidulated water. The process may be varied, if the operator pleases, by placing the acidulated water and zinc in the bag, and the solution of gold with the metal to be gilded in the glass vessel. In the course of about a minute, the metal may be withdrawn, and wiped with a piece of linen; when rubbed briskly with the cloth, it will be found to be slightly gilded. After two or three similar immersions the gilding will be sufficiently thick to enable the operator to terminate the process.--_Athenæum._----[By referring to the article on the Electrotype which appeared in No. 20 of the Irish Penny Journal, the reader will be enabled clearly to understand the mode in which the gold is separated from the acid, which holds it in solution, and forced, or attracted, to deposit its particles upon the metallic surface; the solution of gold bearing in this case a precisely similar relation to the metal plate, as the solution of copper in the other.]