COPPER.

325

leverberatory hearth. If there be 3; 2 of them are placed between the vertical bindingrs upon one side, and a third upon the opposite side of the furnace; if there be 4, 2' r e placed upon each side, facing one another. These openings are 12 inches square,n aie bound with iron frames. The chimney is about 22 feet high, and is placed atne angle of the hearth, as at f, fig. 298, being joined by an inclined flue to the furnace,i or charging it with ore there are usually placed above the upper part of the vault 2toppers, E e, in a line with the doors; they are formed of 4 plates of iron,.supported inhearth* 1 ^ rame ' Beneath each of them there is an orifice for letting the ore down into the

These furnaces serve for calcining the ore,, and the malts or crude coppers : for the latterEJn^e, indeed, furnaces of two stories are sometimes employed, as represented in fig. 301.

e dimensions of each floor in this case are a little less than the preceding. Two doors,nS, e0rres P 0lw ' each hearth, and the workmen, while employed at the upper story, standI’ on s raised moveable platform.

2. Melting furnace, figs. 299 and 300. The form of thehearth is also elliptical, but the dimensions are smaller thanin the calcining furnace. The length does not exceed 11 or lljfeet, and the breadth varies from 7 to 8. The fire-place ishowever larger in proportion, its length being from 3J feetto 4, and its breadth from 3 to 3J; this size being requisiteto produce the higher temperature of this furnace. It hasfewer openings, there being commonly three; one to thefire-place at d, a second one, o, in the side, kept generallyshut, and used only when incrustations need to be scrapedoff the hearth, or when the furnace is to be entered forrepairs; and the third or working-door, G, placed on thefront of the furnace beneath the chimney. Through it thescorire are raked out, and the melted matters are stirred andpuddled, &c.

The hearth is bedded with infusible sand, and slopesslightly towards the side door, to facilitate the discharge ofch; m the metal. Above this door there is a hole in the wall of the

bott,/ 5 .^?- 300) for letting the metal escape. An iron gutter, o, leads it into a pit, K,filled ■ W ' t * 1 an ' ron receiving-pot, which may be lifted out by a crane. The pit m is"tellin^f 1 Water > an( l the metal becomes granulated as it falls into the receiver. The8 furnaces are surmounted by a hopper, L, as shown in fig. 299.

Melting furnaces are sometimes used also for calcination.There are some such near Swansea, which serve this doublepurpose; they are composed of 3 floors (fig. 301.) The floorA is destined for melting the calcined ore; the other two,n c, serve for calcination. The heat being less powerful,upon the upper sole c, the ore gets dried upon it, and beginsto be calcined — a process completed on the next floor.Square holes, d, left in the hearths B and c, put them incommunication with each other, and with the. lower one A ;

- iron r . these perforations are shut during the operation by a sheet

, The hea'm, Ve ? ble at P' easu re.

. ne ath. A “ s “ an( l c are made of bricks; they are horizonal at top and slightly vaultedr ‘or I'eanh* 1 ^ are 2 bricks thick, and their dimensions are larger than those of the infe-tbe f«rna ce \ as tbey exten< l above the fire-place. On the floors destined for calcination*,bcy are tWo fi°°fs on one of its sides : on the lower story there are also two ; but

dra wing of p a ,en tly collocated. The first, being in the front of the furnace, serves for"Jwkrnen to ' S f cor “ B > for working the metal, &c.; and the second, upon the side, admitsPlaced, whici ma <e neces sary repairs. Below this door the discharge or tap-hole A is~‘'nensio ns 0 ’ f communicates by a cast-iron gutter with a pit filled with water. The? ellin g furnne! furnac e in length and breadth are nearly the same as those of thec ' at| s of on _ ® above described; the total height is nearly 12 feet. It is charged by3. J) 0ast ( r tWo hoppers.

??. u ? to the cirir'- nace ' — The furnaces employed for this purpose are in general analo-lv )an, th cse f * ning ones ; but in the smelting works of Hafod, the property of Messrs,(j- Jrt tr°r] Uc j n ^ Paces, alluded to above, present a peculiar construction, for the purposecuiem. r fhic C ° ntInUOUS current of air upon the metal, in order to facilitate its oxy-- ent fight to M 1,roce ^. was originally invented by Mr. Sheffield, who disposed of his

mu

jv air* x tendj|

,re holt

—ng by a channel, c c, through the middle of the fire-bridge, fig. 302, and

® length; it communicates with the atmosphere at its two ends c ,9 left at right angles to this channel, conduct the air into t ie