49 
feet two inches in the middle of the hearth, five feet eleven 
inches at two feet distance from the chimney, and two 
feet ten inches at the place where the flame enters the chim- 
ney at two apertures each ten inches square. These aper- 
tures terminate in the oblique part of the chimney, the 
section of which is sixteen inches square, which commu- 
nicates with the main chimney, the section of which is 
twenty inches square. Supposing a straight horizontal 
line drawn from the lower plane of the throat of the chirm 
ney to the opposite side of the furnace, the lowest part of 
the concave hearth which is in the middle of this cavity, 
is nineteen inches below this line, the roof of the furnace 
being seventeen inches above the same line. 
On each side of the furnace, are three openings, each 
about ten inches square for lead, but larger for copper ; 
provided with iron doors to be removed as occasion re- 
quires, They are arranged at equal distances from each 
other, between the commencement of the hollow hearth, 
and the entrance into the chimney. The lower part of 
these apertures is on a level widi the horizontal line above 
alluded to : being for the purpose of stirring and raking 
the ore, &c. Besides the larger openings, there are two 
small apertures, one below the large middle opening, and 
nearly on a level with the bottom of the furnace ; the other 
under that opening which is nearest to the chimney, at 
some distance above the first aperture. The first, is a 
tap hole for the metal ; the second for the scoriae The 
ore is introduced by a vessel in the shape of a hopper, 
placed in the roof of the furnace. 
The preceding descriptions seem to me clear enough 
to render a plate unnecessary. 
6. The smelting must be continued and repeated, till 
the black copper appears of its proper colour and fit for 
the refining ; and most of the mixed metals are calcined 
and fused with the slag. I do not know a finer road, than 
G 
