138 Progress in Mechanics. [January, 



material. In some cases it is considered desirable to form the mixture into 

 hollow cylindrical blocks in order that it maybe exposed to the most favourable 

 conditions. These prepared blocks are introduced through the charging door, 

 and are gradually passed j through the furnace ; the molten mass falling into the 

 hearth at one end while a fresh charge is introduced at the other, so that the 

 furnace is constantly kept filled. It is said that the ore is first " reduced and 

 carburetted " ; then as it passes onwards and is exposed to a higher tempera- 

 ture it melts, and at length flows into the melting-hearth, near which the 

 combustible gases and heated air gain access to the furnace. 



We learn from "The Glasgow Daily Herald" that a blast-furnace has recently 

 been erected at the works of the Monkland Iron and Steel Company on a new 

 principle patented by Mr. Ferrie. The furnace is 83 feet high, and is closed at 

 the top by a bell-and-cone arrangement. On lowering the cone the raw materials 

 fall into four separate retorts at the top of the furnace, where the coal is coaked 

 before passing down into the body of the furnace, whilst the other constituents of 

 the charge become strongly heated. The combustible gases evolved are used 

 partly for heating this coking apparatus and partly for heating the blast. 



A new lead-smelting furnace has been invented by Mr. George Metcalf, of 

 the Pertusola Foundry, near Spezzia, in Italy, and is said to be working with 

 the most satisfactory results. The furnace is divided longitudinally into two 

 chambers by a vertical partition, which does not, however, reach to the grate or 

 fire-bars. These passages may be placed in communication with the chimney 

 at will, and as the draught is shut off from each compartment alternately, it 

 follows that the charge on one side will be subjected to the free current of 

 heated products of combustion, whilst the other side will be exposed merely to 

 a dead heat. The charge is worked gradually over the curved bed of the 

 furnace towards the fire-bars, being subjected to a preparatory roasting on one 

 side of the partition and finished on the other. The slag collects in the 

 chamber in front of the grate, whence it is run off and subjected to treatment 

 in a blast-furnace, whilst the metal on the bed of the furnace is drawn off 

 through the tapping-door. Each charge consists of about ii tons of ore, and 

 occupies 24 hours in its passage through the furnace ; four charges are in work 

 at the same time, one being drawn every 24 hours. 



The third volume of Dr. Percy's Metallurgy* — a volume so long expected 

 and so often promised — has at length appeared. Instead, however, of com- 

 pleting the treatise, as originally intended, or even embracing the three metals 

 lead, silver, and gold, as subsequently announced, the present volume deals 

 only with the metallurgy of lead, including, however, the processes of desilver- 

 isation and cupellation. The volume forms a goodly octavo of nearly 

 600 pages. 



It will probably be remembered that in the course of last summer Mr. Fre- 

 mantle, the Deputy Master of the Mint, in company with Mr. W. Chandler 

 Roberts, the chemist, and Mr. J. M. Napier, as engineer, made a rapid 

 continental tour with the view of inspecting the chief European Mints, and of 

 reporting upon their organisation. The report of this tour of inspection has 

 just been published, and contains much that is of interest to the metallurgist. 

 It is satisfactory to learn that the " waste " in our English Mint compares well 

 with that of other establishments, and that the loss on gold coinage is estimated 

 not to exceed in future 0*2 per mille ; that is to say, there will not be more 

 than ;£2oo lost on a coinage of one million. Mr. Fremantle sees no necessity 

 for altering our standard of fineness for gold coin (n Au to 1 Cu), and believes 

 that the "remedy of fineness" — that is, the margin allowed on the legal 

 standard in the manufacture of gold coin — ought not to be reduced below 

 2 parts per mille. 



In that portion of the report which has been prepared by Mr. Roberts we 

 observe many excellent suggestions relative to improvements in the metal- 

 lurgical operations of the Mint. Already he has introduced Miller's chlorine 

 process for the treatment of gold too brittle for coinage — a process which was 



* The Metallurgy of Lead, including Desilverisation and Cupellation, by John Percy, M.D., 

 F.R.S.; Murray, 1870. 





