THE PRINCIPAL FLOOR. 
34 
solidification of the superficial crust, which was then removed in 
the form of a thin circular plate or rosette ; more water was then 
thrown on the fused mass, and other discs were successively 
obtained, until the whole of the charge had been removed. 
By the side of the German specimens is a small group 
illustrating the process of Copper smelting at Falun, in Dalecarlia, 
Sweden. 
Tin-Smelting. 
Table Case 38. — In this Case will be found some ancient 
blocks of Cornish tin, known ns Jews’ tin, while the rude furnaces, 
which are not unfrequently discovered in connexion with them, 
are termed Jews’ houses. This arises from the fact that during 
the reign of John, and subsequently, the tin mines of Cornwall 
were farmed by the Jews, Those blocks, and the furnaces 
named, are, however, probably very much older than this period. 
A model of a remarkable block of tin, which was fished up from 
off St. Mawes, at the mouth of Falmouth harbour, will also be 
found in Case 10. The original block is in the Museum of the 
Koyal Institution of Cornwall, at Truro. The late Sir Henry 
James showed, with much ingenuity, that the form of this 
block was peculiarly adapted for its transport, both by land and 
water. 
Tin smelting is a simple operation, conducted either in the 
reverberatory furnace, or in the blast furnace : in Cornwall the 
former method is now always employed. The tin ore, having 
been roasted and washed, is mixed with small anthracite or 
culm ; and a small quantity of either slaked lime or fluorspar, 
which serves as a flux for its siliceous impurities, is mixed with 
it previously to its being placed in the furnace and smelted. 
The crude tin is refined by liquation, or sweating, in a rever- 
beratory furnace, and the resulting product is then generally 
poled, or stirred with green wood. 
During more than six centuries the tin paid a tax to the Earls 
and Dukes of Cornwall. The blocks of tin were subjected to a 
process called “ coining,” and certain towns were fixed upon as 
■coinage towns. The blocks of tin — rectangular masses — weighing 
about 3 * 34 cwts. each, were sent to the coinage Hall ; a corner 
of each of the blocks was struck off, and some of the Coinage 
'pieces are in this Case : these were examined by Duchy officers 
appointed for the purpose, in order to see that the tin was of 
proper quality ; the blocks were then stamped with the Duchy 
seal, the dues paid, and the blocks permitted to be sold. By an 
Act of Parliament of 1838, the duties payable on the coinage of 
tin in Devon and Cornwall were abolished. 
The finer varieties of tin, known as grain tin, which are used 
principally by the dyers, are usually prepared by heating blocks 
of tin to a certain temperature, and then breaking them by a 
blow from a heavy hammer, or by a fall from a small height. 
