362 Mr. Taylor on the Smelting of Tin Ores 
sufficient to remark that, after being stamped, the tin ores are 
washed according to the usual mode, so as to separate the earthy- 
mixture and as much of that of a metallic nature as is possible. 
All these operations are conducted with more than common care 
and accuracy ; for as tin ore holds such a large proportion of 
valuable metal, it is of course treated with every precaution to 
guard against waste. 
Some metallic substances will be found, however, which, from 
their specific gravity approaching nearly to that of tin ore, or rather 
exceeding it, cannot be removed by any process of washing; 
these are mostly decomposible by a red heat, which the oxide of tin 
will bear without alteration. Therefore, after as much has been 
done as possible to render the ores clean on the dressing-floors, 
they are taken to the burning-house , which is furnished with small 
reverberatory furnaces, on the floor of which the ores are spread 
and submitted to the action of a moderate and regular fire : they 
are frequently turned over by an iron rake to expose fresh surfaces, 
and a considerable volatilization of sulphur and arsenic takes place ; 
the former seems principally to be consumed, and the latter is 
condensed by long horizontal flues constructed for this purpose. 
After the ores come from the burning-house, the process of dressing 
is completed by further washing, which is rendered easy by the 
alteration which has been produced in the relative weight of the 
substances. 
Copper ore is not unfrequently present in these cases, and, as it 
is in part converted into sulphat of copper, the water which is first 
used is preserved, and a portion of copper obtained from it by 
means of iron. 
The great specific gravity of the tin ore, as I have before 
remarked, renders it possible with eare to subject it to many 
