INTRODUCTION. THERE are very few arts, if any, whose history is perfectly comprised within Patent Specifications; it is to supply the gaps which occur in the specifications relating to plating or coating metals with metals that the following chronological arrangement of non-patented inventions in this department of practical science is given. Each discovery or invention has a separate paragraph devoted to it, and has the titles of works affording information upon it explicitly stated; by this arrangement the utmost facility of reference is obtained, and the reader is enabled to extend his knowledge of any particular point to the full amount, from original sources. The processes that have been employed to coat metals with metals are very numerous; modern practical science has added to their number and at the same time rendered many of them obsolete and out of date. The peculiarities of the principal processes may be classified as follows: 1st. By amalgamation—using mercury as the means of ensuring contact between the underneath metal and the coating metal, the mercury being finally driven off by heat. This method is principally applicable to gilding and silvering. 2nd. By simple immersion of the article to be coated in an aqueous solution of a salt of the metal to be deposited. 3rd. By fusing a thin sheet of the coating metal on to the underneath metal with the assistance of a flux or intermediate fusible metal, the underneath metal being heated. 4th. By immersion of the article to be coated in a bath of the melted metal or alloy. 5th. By pressure and heat, as in the manufacture of tinned lead pipes. 6th. By casting a considerable thickness of the coating metal round the article to be coated, the article being placed in a suitable mould. 7th. By electro-deposition. The operations of nature in relation to this branch of applied chemistry are highly instructive, and therefore must not be overlooked. These agencies were active long before man could understand their workings. A notable example of this occurs in the deposition of copper upon spare pieces of iron immersed in a stream passing through a copper mine; the ancients were much puzzled at this circumstance, and for some time believed that a real transmutation of iron into copper took place. The forces concerned in the production of this simple natural result were for a long period unknown, and their laws unexplored, and it was not till the advanced chemical knowledge of the present century was brought to bear upon this and other departments of the subject that the network of causes was fully and profitably investigated; this investigation culminated in the use of electric force in the arts and manufactures which involve the deposition of metal upon metal. A.D. HOLY WRIT Contains no account of gilding or otherwise covering metals with metals, although frequent mention is made of gilding wooden structures. The EGYPTIANS are proved by Herodotus to have been "accustomed to gild wood and metals.” (See Bohn's edition of Beckmann's History of Inventions, vol. ii., p. 290; also Herodotus, lib. ii., 63.) ·- The ancient MEXICANS and PERUVIANS appear from the following paragraph to have been in possession of the art of silver plating :- "The silver-plated discs and also the "embossed silver-plate, supposed by Dr. Hildreth to have "been a sword ornament, have been critically examined, " and it is beyond doubt that the copper boses " [bosses?] are absolutely plated, not simply overlaid with silver, "and has been done by heat." (See Silliman's Journal, vol. ii.; also The Ancient Workers and Artificers in Metal by James Napier, p. 70.) 66 77. PLINY in A.D. 77, in the 33rd book of his Natural History, chap. 20, states that the most convenient method of gilding copper is to employ quicksilver. (See Bostock and Riley's translation of Pliny's Natural History, vol. vi., |