264 Mr. J. Napier on Coppet- Smelting. 



the proprietor : but it is always of considerable importance 

 that both qualities of coal should be used ; therefore a judicious 

 mixture of the two is a matter where ceconomy in the production 

 of copper can be practised, and, as we shall have occasion to 

 notice, is often necessary for the protection of the materials of 

 the furnaces. 



The first question which naturally arises is. What constitutes 

 the strength of the coal as applied to the purposes of copper 

 smelting ? Are strong coals those which have been found to give 

 the strongest heat in a blast or cupola furnace, or the greatest 

 evaporating power when under a boiler ? Anthracite coal, which 

 is ranked highest in a blast or for evaporating purposes, is ranked 

 amongst the weak coal in the copper-works. These coals give no 

 flame ; the heat is not carried over the chamber or bed of the 

 furnace ; the part nearest the fire may be at a smelting heat, 

 while that furthest ofi" is only of a dull red. All good coals for 

 smelting are capable of giving a certain amount of flame, although 

 wherever there is much flame there is not much heat ; neither is 

 the heat great while the flame is passing over the, furnace, it 

 being absorbed by the expansion of the burning gases constitu- 

 ting flame; but while these gases are burning ofi" the coals are 

 expanding, becoming porous and spongy, admitting air freely 

 through the mass ; so that when the blaze of flame is past, the 

 fire gives the strongest and most equable heat over the materials 

 in the hearth. 



In selecting a coal for smelting purposes, there are several 

 circumstances to be attended to as well as the mere heating 

 power — the sulphur present, which for some operations would 

 render the coal useless — the ash and the composition of the ash, 

 which should be such as to partially fuse or cake, for purposes 

 to be afterwards noticed. Some of the Newcastle coals we have 

 found equal, if not superior to the strongest Welsh coal, both in 

 their heating quality and absence of sulphur ; but owing to the 

 small quantity of ash, and that not caking, but passing off" as 

 dust, they are by this cause unsuitable without the addition of 

 matters to make up the defect. 



All the conditions referred to are combined in the coal which 

 the smelter designates strong coal, and one or more of the con- 

 ditions are more or less absent in that of the weak coal. The 

 following analyses of a few of these two qualities were made in 

 hopes of finding how far a chemical examination would assist in 

 determining the best quality of coal for smelting copper. 



