850 



Sir. J. Napier on Copper Smelting. 



The best Newcastle and Stourbridge bricks are equal in qua- 

 lity for any of the purposes for which the above or Lysnewydd 

 are used, and often preferable, but they are not so generally em- 

 ployed. However, none of the ordinary fire-bricks can replace 

 the Dinnas in the uses to which they are applied. 



The fire-clay used for making these bricks should possess 

 similar properties to the brick. It may be considered the same 

 materials unaltered by fire ; and the same rule applies, viz. the 

 more silica they contain consistent with their solidity and binding 

 qualities, the better they answer the purposes of standing high 

 temperatures. Dinnas clay, that used for binding Dinnas brick, 

 is simply the materials of which the bricks are formed, made 

 moist by water. 



The following table of analyses of fire-clays from three locali- 

 ties far apart, will serve as an illustration of quality. 



Such, then, is the general chemical character of the fire-brick 

 and fire-clay used in lining the fusing-furnaces in copper smelting. 

 Chemical investigation and practical experience have not yet 

 been sufiiciently and simultaneously carried on to enable ana- 

 lysis to supersede an actual trial; neverthelcp^ it is a very good 

 guide ; and that it is not now more certain, is owing rather to the 

 paucity of such investigations with a due observation of facts in 

 relation to analyses than to any discrepancy between principle 

 and practice. 



These fire-bricks and clay are only used to line the side walls 

 and form the roof of the furnace, but they are not for the bottom 

 of hearths. When bricks, however refractory, are used for a 

 bottom, the melted stufi" finds its way under and x'aises them up. 

 The bottom of a fusing-furnace, however large, must be one solid 

 piece, and this is obtained by using sand. A fusing-furnace, as 

 it is now biiilt, stands upon an arch running the whole length and 

 breadth of the furnace, and brought up square ; upon this rise 

 the side walls, which we have been describing as being lined with 

 fire-bricks ; the intervening space is where the sand bottom is 

 laidj which averages from 18 inches to 2 feet in depth. When 



Ml-. C. Cowper. 



t Dr. Penny. 



