CONCLUSIONS. 747 



15. That slags cauuot very well be compared with minerals, from which they dif- 

 fer essentially; that they contain minute quantities of carbonates which have escaped 

 destruction, and small quantities of carbon or carburets, two products which hitherto 

 had not been generally known to exist. That slags are formed of crystallographic 

 compounds of silicates of iron, manganese, zinc, lead, lime, and magnesia on the one 

 hand, and on the other of a peculiar matte which is designated by the name of calcium 

 matte, and which, like its congeners, is formed of a sulphide (sulphide of calcium) 

 and of magnetic oxide of iron, which can be isolated in the pure crystalline state. 



16. That at least three distinct metallurgical kinds of speiss, containing two dis- 

 tinct chemical arsenio-sulphurets of iron, are formed in lead smelting ; and that they 

 always contain small quantities of nickel and molybdenum entirely concentrated in 

 them, showing that the metallurgy of molybdenum could be conducted jointly with 

 that of lead with ores containing only traces of molybdenum. 



17. That a very curious and a hitherto unsuspected reaction takes place in the 

 blast-furnaces of Leadville, by means of which cobalt is completely separated from 

 nickel (nickel being concentrated in speiss and cobalt in the skimmings of the lead- 

 pots of blast furnaces), and showing that the metallurgy of both metals and their sep- 

 aration could be effected in lead furnaces by operating under conditions similar to 

 those observed in Leadville. 



18. That iron sows are a variety of speiss and present a great analogy with the 

 latter products. 



19. That lead fumes are very complicated products, characterized in Leadville by 

 the presence of no inconsiderable amount of chloro-bromo-iodide of lead and phos- 

 phate of lead, and that they contain, contrary to the opinion formed in Leadville, but 

 small quantities of arsenic and antimony. 



20. That the practice of roasting the dust in order to free it from arsenic and 

 antimony, as adopted at one smelter, is a useless and costly one, which ought not to 

 be generalized in Leadville. 



21. That accretions are products of sublimation, and that these products, which 

 line the shafts of the furnaces and interfere seriously with a regular run, might be to 

 some extent avoided, or made less troublesome, by a slight modification of the manner 

 of charging the furnaces and by the adoption of caustic lime instead of raw limestone 

 in smelting. 



22. That some accretions are characterized by the concentration, sometimes in 

 large quantities, of metals such as tin, arsenic, antimony, and zinc, which exist but in 

 small quantities in the ores. 



23. That the charcoal used in smelting is of very good and the coke of bad qual- 

 ity; but that the fuel obtained by mixing them contains 10 per cent, of ash, and that 

 it requires a maximum amount of 32 to 33 parts of this fuel for 100 parts of ore, and 

 24 parts for 100 parts of charges, to effect smelting ; but that at several smelters these 

 percentages are considerably lowered. 



24. That for every 100 parts of carbon thrown in the furnaces with the smelting 

 charges, only 40.36 l parts reach the zone of combustion at the tuyeres, the balance 

 being oxidized in the upper zones to carbonic oxide, chiefly by the carbonic acid formed 

 in the zone of combustion, involving, as is well known, an absorption of heat. 



'This figure differs from that given in the abstract of this report published in the Second Annual 

 report of the Director of the United States Geological Survey (188CM81), several clerical errors in Mr. 

 Gnyard's calculations having been discovered since that appeared. (S. F. E.) 



