(_a_) _In Roasting Practice._—=1865.= Introduction of the mechanically driven furnace (the Brückner cylinder); not, however, adopted for copper smelting till many years afterwards. Later—Arrangements for using roaster gases for sulphuric acid manufacture. (_b_) _In Reverberatory Furnace Smelting._—=1861.= Gas firing introduced, but with very little success for copper smelting, even at the present day. (_c_) _In Blast-Furnace Smelting._—Several very important changes were introduced in the construction of furnaces. =1863.= Elongation of the furnace. Rachette in Germany introduced the elliptical blast furnace. (Intended first for lead smelting; rapidly adopted for copper matte smelting.) =1875.= The water-jacketing of blast furnaces. The Piltz water-jacketed furnace was likewise first employed in lead smelting, and subsequently introduced into copper smelting practice. The principle had, indeed, been utilised in certain branches of iron smelting before this date, but for non-ferrous work the idea was new. Although the method of water-jacketing was recognised as leading to great improvement in the working of the furnace, its use was at first somewhat restricted, owing to various practical difficulties, and the ultimate great success was effected when in American practice, the plan of working the two principles of elongated furnaces and water-jacketing in conjunction, was adopted. Commencing from 1880, and onwards, however, when production in the Far West began, enormous advances have been made, both in connection with the principles of working as well as in practical operation. These include— (1) Enormous increase in the size and capacity of furnaces of both the reverberatory and the blast-furnace type. (2) The application of the Bessemer process to copper mattes. (3) The development of the pyritic smelting principle. (4) The adoption of electrolytic refining. (5) The use of mechanically rabbled roaster furnaces. (6) The manufacture of sulphuric acid from blast-furnace gases. (7) The blast-roasting and sintering of sulphide fines.