Mr. J. Napier on Copper Smelting. 463 



will be more plainly developed. In the meantime we may refer 

 to one or two other plans that have been adopted or tried in the 

 calcination of ores. 



Some smelters have ore-calciners on the top of the ore fusing- 

 furnace, the roof of the furnace being the lowest bed of the calciner 

 aiTanged in the same manner as we have described in the case of 

 the three-bedded calciner. There being two beds for the calcining 

 operations above, the ore is put into a hopper on the roof and let 

 into the top bed ; it is then passed by a hole through the floor into 

 the second bed, and from thence in the same way to the fusing-fur- 

 nace. Thus the ore is being calcined during the time taken for 

 fusing two charges ; by this means the waste heat of the fusing- 

 furnace is taken advantage of to calcine the ore. At first sight 

 this mode may appear to be very ceconomical ; but it is subject 

 to certain practical di-awbacks, such as a greater liability in the 

 furnace to get out of repair, thereby stopping two operations : 

 the mat obtained is neither so good nor rich in copper. From 

 causes to be noticed as we proceed, these have pi-evented the 

 adoption of this method in the trade. 



Calciners have also been tried alongside of a fusing-fumace, 

 so fitted that the waste heat of the furnace passed over them as 

 through a flue ; also causing the fire from the fusing -furnace to 

 pass along a series of flues covered by fire-tiles forming the 

 bottom of close-chambers, in which the ore was put to calcine, 

 separate chambers being connected to condense the sulphur ; but 

 all schemes depending upon the employment of the waste heat of 

 the fusing-furnaces have been found ultimately more costly than 

 the ordinary calciner of one bed. The close-chamber for cal- 

 cining the ores by heating them from under the floor we have 

 seen tried in a variety of forms, but always with one result. While 

 the plates forming the floor were at a red heat sufiicient to cake the 

 ore in contact with it, the suiface of the ore was comparatively 

 cold, never at the temperature necessary to volatilize the sulphur, 

 80 that the sulphur volatilized at the bottom was condensed on the 

 surface. To prove that some of these experiments were not made on 

 a niggardly scale, or without an anxiety to succeed, we may state 

 that a patent furnace fitted up for this object under the eye of the 

 patentee measured 54 feet in length and 9 in breadth, took 30,000 

 common and 30,000 fire-bricks, 100 fire-tiles, 20 tons fire-clay, 

 12 tons cast and 2 tons wrought iron, besides the lime and 

 labour. The results of several weeks^ trial, were one ton of ore, 

 half-calcined in 54 hours, without obtaining an ounce of sublimed 

 sulphur. In many of the plans proposed there is a want of know- 

 ledge of principles. Sulphur will not sublime freely from ores 

 in an atmosphere of sulphur; there must be some means of 

 drawing off the atmosphere of sulphur whenever formed to give 



