in Cornwall and Devonshire. 
363 
operations in dressing without much waste ; and they are therefore 
applied until the whole is generally so clean, as to yield a produce 
of metal equal to from 50 to 75 per cent. In this state they are 
sold by the miner to the smelter, who determines their value by 
assaying a sample, carefully taken from the whole quantity. 
The furnaces for smelting Mine Tin are all of the common 
reverberating kind, and are of sufficient size to hold twelve to 
sixteen hundred weight of ore. 
The charge is prepared by mixing it with a proportion of stone- 
coal, or Welch culm, to which is added a moderate quantity of 
slaked lime ; these are turned over together and moistened with 
water, which prevents the too rapid action of the heated furnace, 
and which would otherwise volatilize some of the metal before 
fusion commenced. 
The heat employed is a very strong one, and such as to bring 
the whole into perfect fusion ; it is continued seven or eight hours, 
when the charge is ready to draw. For this purpose, the furnace 
is furnished with a tap-hole leading from the lowest part of the 
bottom, which during the process is stopped with clay or mortar, 
and under which is placed an iron kettle to receive the metal. 
The furnace has also a door at the end opposite the fire-place, 
through which the slag or scoria may be raked out from the 
surface, while the tin is flowing out, by unstopping the tap-hole. 
They are thus divided, and the tin is laded into moulds, so as to 
form plates of a moderate size, and put by for a further refining. 
The slag, which rapidly hardens into a mass, is removed to a 
dressing-floor, where being broken up and stamped, it is washed, 
and a quantity of tin taken from it, which is called Prillion y and 
which is afterwards smelted again. 
No operation in smelting is more easy than that practised for 
