Mr. J, Napier on Copper Smelting, 345 



fiuitions of the direction, or, as it may be termed, polarity, of a 

 tetrahedron corresponding to a given reading, whether as taken 

 each in itself or compared one with another, give rise to, or rather 

 imply a considerable number of interesting theorems included 

 in our intuitions of space, and probably belonging to the, in my 

 belief, inexhaustible class of primary and indemonstrable truths 

 of the understanding. 



7 New Square, Lincoln's lun, 

 October 2, 1852. 



LIV. On Copper Smelting. By James Napier, F.C.S* 



[Continued from p. 2/1.] 



Construction of the Furnaces, ^c, 



IN my last communication I mentioned that the kind or qua- 

 lity of the fuel has often to be regulated by the nature of 

 the materials forming the furnace; for while it is the object of 

 the smelter to get his charge fused in the shortest possible time, 

 it is also necessary to prevent fusing the bricks and other mate- 

 rials composing the furnace. It is therefore a matter of great 

 consequence that the best materials be used in its construction : 

 they should not be easily acted upon by heat, nor by the matters 

 fused upon or in contact with them ; such materials not only 

 last longer, but they allow the smelting operations to be done 

 vAih greater facility and perfection. 



It may be necessary, in the first place, to endeavom* to describe 

 the nature of the common furnaces in use, reserving any remarks 

 upon peculiarity of construction for particular operations until 

 describing these operations. 



Calcining -furnace. — The object of this furnace is to keep the 

 ore, or whatever matters are operated upon, exposed to a red heat 

 in a free current of air, for the purpose of burning off or volatilizing 

 the sulphur, arsenic, antimony, or other volatile matters, and oxi- 

 dizing the iron. This furnace is never used for fusion, and the 

 materials composing it arc not so carefully selected or so refrac- 

 tory as for a fusing-fumace. The mode of construction is gene- 

 rally adapted to the object of it, and whether for ore or metal. 

 The common calciner ranges from 18 to 22 feet in length, and 

 from 11 to 14 feet in breadth outside measure, independent of 

 fire-place ; the roof of the chamber internally above the floor of 

 the hearth is from 2 to 3 feet. The whole furnace is built upon 

 arches, the vaults of which serve to receive tlie ore from the fur- 



* Communicated l)y the Author, who reserves to himself the copyright, 

 any infringement whereof will invoke legal proceedings. — Eds. 



