Mu. Napiek on Copper Sheathing. 



169 



The ores referred to are from Chili, and the localities on that coast. 

 There are some of these ores very pure, but the following analyses of two 

 samples will show their general character : — 



Copper, 30-6 



Sulphur, 29-3 



Iron, 21-4 



Siliceous matter, 16'8 



Antimony, I'G 



99-7 



A. Thomas. 



Copper, 28-50 



Iron, 25-83 



Sulphur 23-70 



Silver, 0-06 



SUica, 18-70 



Antimony and arsenic, 2-80 



John Cameron. 



99-59 



Poorer ores of Chili, and which would not pay transit, undergo an oper- 

 ation of calcining and fusing near the mines which takes away the matrix, 

 and the product is brought to this country under the name of regulus. 

 The following two analyses will give an idea of the general composition of 

 this compound: — 



Copper, 596 



Sulphur, 19-1 



Iron, 15-4 



Antimony, 1'2 



Siliceous matter, 2"8 



98-1 



Copper, 52-8 



Sulphur, 20-3 



Iron, 18-6 



Silver, 0-1 



Antimony, 1*4 



Silica, 4-2 



97-4* 



The ores and regulus are mixed with the Cornish ores during their pro- 

 gress of smelting. Previous to the introduction of these ores, the average 

 of the ores smelted did not exceed eight per cent. The operations of 

 smelting are a series of calcining, fusings, and roastings, amounting to 

 about seven or eight operations, during which the greater portion of 

 impurities are scorified. The introduction of these richer ores shortened 

 and lessened the number of operations, and also the chance of so com- 

 pletely slagging off the deleterious matters. About the same time these 

 South American ores were introduced, Muntz's yellow metal came into 

 use, an alloy of two equivalents of copper and one of zinc. The success 

 of working this alloy depends much upon the purity of the copper used ; 

 heace, with an increased supply of impure ores, came an increased demand 

 for good quality of copper to make this alloy, which copper was con- 

 sequently taken out of the copper market. This was obtained by the 

 process termed selecting, and to show the bearing of these circumstances 

 upon the subject under consideration, I must briefly describe the pro- 

 cess and principle of smelting and selecting. The ore is first calcined 

 by being placed on tlie floor of a large high roofed reverberatory 



* Some of llic iron existed as oxiilc, wliich accounts for the loss. 



