363 
Tin . 
are mixed with it ; and hence the reader may understand^ 
that, without any fraudulent proceeding in the tin smelter, 
there may be a variety in the purity of tin* which is ex* 
posed to sale in the same country ; and this variety 3s still 
more likely to take place, in specimens of tin from differ- 
ent countries, as from the East Indies , from England , and 
from Germany . This natural variety in the purity of tin 3 
though sufficiently discernible, is far less than that which 
is fraudulently introduced* Tin is above five times as 
dear as lead; and as a mixture consisting of a large por- 
tion of tin with a small one of lead, cannot easily be dis- 
tinguished from a mass of pure tin ; the temptation to 
adulterate tin is great, and the fear of detection smalk In 
Cornwall , the purity of tin is ascertained, before it is ex- 
posed to sale, by what is called its coinage «• the tin, when 
smelted from the ore, is poured into quadrangular moulds 
of stone, containing about 320 pounds weight of metal$ 
which, when hardened, is called a block : of tin ; each block 
of tin is coined in the following manner : — > u the officers 
appointed by the duke of Cornwall, assay it, by taking off 
a piece of one of the under comers of the block, partly by 
cutting and partly by breaking; and if well purified they 
stamp the face of the block with the impression of thfc 
seal of the Duchy, which stamp is a permisssion for the 
owner to sell, and at the same time an assurance that the 
tin so marked has been purposely examined, and found 
merchantable*.” This rude mode of assay, is not wholly 
improper, for if the tin be mixed with lead, the lead will 
by its superior weight sink to the bottom, | and thus be 
liable to be discovered, when the bottom comer of the 
block is examined. But though the seal of the Duchy 
may be some security to the original purchasers of block 
tin, it can be none at all to those foreigners who purchase 
* Borlase’s Nat. Hist, of Corn. p. 183. 
1 1 doubt this. T. C* 
Vol. 111. Y y 
