in Cornwall and Devonshire. 423 
The making of grain tin from the ores from stream works is 
conducted in a manner altogether different, and remains to be 
described. 
I have pointed out the purity of these ores, as regards their 
freedom from a mixture of other metals, and I do not think it 
important here to describe the mode of separating them by wash- 
ing from the sand and gravel in which they are found, because 
the processes are very similar to those in use for dressing other 
ores. The stream tin is generally made very clean, and is car- 
tied in this state, to be sold for smelting, to establishments which 
are called blowing-houses, being thus distinguished from smelting- 
houses in which mine tin is reduced, and the term is also de- 
scriptive of the process employed. 
The reduction of the ores for grain tin is performed by blast 
furnaces, and the only fuel used is charcoal. This mode of smelt- 
ing is exceedingly simple, and is probably the most ancient one, 
as would appear from relics sometimes met with of furnaces of 
rude construction, and in some of which the wind alone seems 
to have been depended on for urging the fire. 
The furnaces now in use are similar to those met with for 
smelting iron in foundries where the blast is used, and are formed 
by a cylinder of iron standing upon one end and lined with clay 
orloam. ‘The upper end is open for receiving the fuel and ore, 
which are thrown alternately, and a hole at some distance from 
the bottom, at the back of the cylinder, is provided to admit the 
blast, and another, lower down and opposite to it, suffers the 
metal to flow out regularly as it is reduced. 
A strong blast is kept up by bellows, or, in more improved 
works, by pistons working in cylinders, and the air is conducted 
by a proper pipe so as to blow into the orifice in the furnace. 
The only purification it seems to require is to separate from it 
such substances as are mechanically suspended in it, and for this 
purpose it is laded into an iron pan or kettle, where the fusion is 
kept up by a gentle fire underneath, and a complete agitation of 
the mass is effected by plunging into the melted metal pieces of 
charcoal, which have been soaked in water, and, by means of an 
iron tool, keeping them at thie bottom of the kettle. The water . 
in the charcoal is rapidly converted into vapour, which rushing 
through the metal, gives it the appearance of rapid ebullition. 
' After this is over, and the whole has rested some little time, the 
scum, which is thrown up to the surface, is taken off, and the 
tin, which is peculiarly brilliant in appearance, is removed by 
ladles into proper moulds, to form the blocks in which it is ge- 
nerally sold. 
Grain tin is, however, sometimes put into a different form by 
breaking it: for this purpose, the. blocks are heated to such a 
degree 
