Mr. H. L. Pjttinson on Smelting Lead Ore, §c. 167 



A pipestone g, Figs. 1 and 3, being a prism 10 inches square, and 28 

 incheslong, with an opening to admit the bellows-pipe, as in Fig. 6, where 

 it is shewn separate, and lying upon what is its upper part when pro- 

 perly placed in the hearth. 



An upper backstone a, Figs. 1 and 3, a parallelopiped 28 inches 

 long, 4 inches deep, and 5 inches wide, which completes the back part 

 of the hearth. 



A forestone c, Figs. 1 and 3, 26 inches long, 6A inches deep, and 5 

 inches broad, and 



Four keystones being exact 10-inch cubes of iron b, b, b, b, Fig 1. 

 The two cubes nearest the back of the hearth, are placed upon the 

 bearers d, d, so as to correspond with them on the inside, and are thus 

 22 inches apart ; but the two cubes in front are made to lie against the 

 ends of the forestone, and are consequently 26 inches distant from each 

 other. 



The forestone itself is moveable to a certain extent. It can be placed 

 at the distance of 10 inches from the backstone, by being put in con- 

 tact with the two keys nearest the back, and it can be lowered down so 

 as to rest upon the two bearers d, d, if necessary, and in that case would 

 be only 6 inches above the upper edge of the workstone. In Figs. 1 

 and 3, it is represented 12 inches from the back of the hearth, and sup- 

 ported by a fire brick at each end, placed upon the bearers ; its under 

 edge being thus 11 or 12 inches above the workstone, which is its usual 

 position. The various castings are secured in their places by brick-work, 

 and the top of the hearth is finished level with masonry, to receive any 

 particles of ore, called hearth ends, that may be expelled by the blast. 

 Each hearth is placed under a chimney supported by an arch (as shewn 

 in Figure 1), and communicating with the horizontal flues already refer- 

 red to, by passages through which the fume and smoke are conveyed 

 away. 



In Figure 3, the pipe of the bellows is represented to enter the hearth 

 6i inches above the level of the upper edge of the workstone, which 

 regulates the surface of the lead when the hearth is in a working state, 

 but it more frequently happens, that by the bearers and hearth -bottom 



