Jto5 On the Component Parts of Iron-Jlones. 



1 8, 20 to 24 inches, the determination of its height 

 depending upon circumftances. The furface is a fecond 

 time levelled, by introducing fmall pieces of iron-ftone 

 betwixt the interftices occafioned by the angles of the larger, 

 ^his again receives a covering; of fmall coals, feldom ex- 

 ceeding % inches in thicknefs. Upon this is reared the 

 fubfequent building, always gradually narrowing itfelf till 

 it has aflumed the fhape of a flout wedge, with its bafe 

 refting upon the ground. After this is effected, the whole 

 of the external furface receives a complete covering of the 

 fmalleft fort of coals. The pile is kindled by applying 

 burning coals to the ground ftratum. This creeps ilowly 

 along; heats the ftone upwards; kindles the fecond layer 

 of fmall coals, and ultimately inflames the whole mafs from 

 top to bottom. 



When the coals are confumed, the pile gradually cools, 

 and in 8 or 10 davs may be wheeled away to the furnace. 



The quantity of iron-ftone burnt at one time is various 

 at different and even at the fame places; fome kinds re- 

 quire to be burnt in fmaller heaps, owing to their nature 

 and fufibilily. At fome works the fires extend from 50 to 

 60 yards; and it is not uncommon to fee fkilful workmen, 

 at one end, adding frefh materials to the burning pile : 

 while others, at the oppofite end, are employed wheeling 

 away that which the fire has left fufficiently burned for the 

 purpofe of the furnace. Fires that extend from 30 to 60 

 feet in length are more common; from 10 to 16 feet widej 

 and about 5 feet high. 



At nioft iron-works a local opinion exifts, to what degree 

 of heat iron-ftone ought to be expofed before it is properly 

 fit for the blaft-furnace. • All, however, agree that burning 

 is neceffarv ; though few give an accurate reafon why. The 

 onlv one I have heard adduced is, that iron-ftone is calcined 

 in order to burn out the fulphur and other heterogeneous 

 mixtures. Hence arife a diverfity of opinions, chiefly 

 founded upon individual notions of the fixity or volatility of 



fulphur, 



