346 J\Ir. J. Napier on Copper Smelting. 



nace, when calcined, by means of holes in the floor of the furnace 

 or hearth through the roof of the arches. 



Each calcining-furnace has generally a shaft or chimney of its 

 own about 40 feet high, except where there is one general shaft. 

 When the fumes from the calciner are led tlirough a culvert 

 under ground to the main shaft, which, as will be shown in the 

 sequel, is the best and most oeconomical, much stuff is caught in 

 these culverts that is useful. 



It need hardly be mentioned, that these furnaces have to be 

 firmly tied or bound together by means of iron, having large 

 upright east iron studs opposite each other round the furnace, 

 and these held together by means of iron rods passing over and 

 through the building, which the men have to watch and tighten 

 up or ease as the expansion or contraction requires ; otherwise 

 the furnace is liable to crack, or, as sometimes takes place, the 

 bindings break and the furnace splits in tAvo. The furnace is 

 lined inside with fire-brick built in with fire-clay, so is the fire- 

 place and bridge. The shaft or chimney has also to be lined 

 with fire- or flintsliire-brick. The cost of an average-sized cal- 

 cining-furnace without shaft is about £150. 



A Fusing-furnnce is constructed differently from the calciner, the 

 object being to get a high heat concentrated in the hearth. The 

 ordinary size of the hearth of a fusing-furnace is 13 feet long by 

 8 wide inside measure, of an oval form, resembling the section 

 of an egg. Generally these furnaces have each a stack or chim- 

 ney of its own. The inside of the hearth and fireplace is lined 

 with the best fire-brick ; so is the inside of the lower part of 

 the chimney, passing into flintshire-brick as it ascends. These 

 ai'e also bound about with iron studs and bars, and some are 

 cased all round with east iron. A furnace of the size above 

 named with stack attached will cost about £130 before anything 

 be fused in it. 



The Roasting -furnace differs little from the fusing-furnace. 

 They are generally larger in size, and have an opening or door in 

 the side of the hearth for the purpose of charging, as the matters 

 are put into it in large pieces which could not pass through a hop- 

 per. This door is also occasionally opened during the roasting 

 to admit air to the fused materials. The roasting-l'arnace is also 

 furnished with air-holes through the bridge, similar to what is 

 used in the calciner ; the materials iised in the construction of 

 these furnaces must also be of the best quality. 



The Refining-furnace is similar to the roasting-furnace, but is 

 generally a little more oval ; it has also a side door for the intro- 

 duction of the metal, and there is a well left iu the bottom of 

 the hearth close to the front door to allow the metal to be ladled 

 out to the last portions. 



