366 
Tim 
grain tin at least, I found that a cubic foot of the spe- 
cimen I examined, weighed 7246 ounces ; but even this 
sort exceeds in purity any of the kinds examined by the 
authors above mentioned* Chemistry affords certain me- 
thods of discovering the quantity of lead with which tin 
is alloyed, but these methods are often troublesome in the 
application ; an enlarged table, of the kind of which I 
have here given a specimen, will enable us to judge with 
sufficient precision of the quantity of lead contained in any 
mixture of tin and lead, of which we know the specific 
gravity, Pewterers, however, and other dealers in tin, 
use not so accurate a method of judging of its purity, but 
one founded on the same principle ; for the specific gra- 
vities of bodies being nothing but the weights of equal 
bulks of them, they cast a bullet of pure tin, and another 
of the mixture of tin and lead, which they want to exa- 
mine, in the same mould ; and the more the bullet of the 
mixture exceeds the bullet of pure tin in weight, the more 
lead they conclude it contains, 
Pewter is a mixed metal $ it consists of tin united to 
small portions of other metallic substances, such as lead, 
zinc, bismuth, and the metallic part , commonly called, 
regulus of antimony . We have three sorts of pewter in 
common use ; they are distinguished by the names of 
plate— trifle— ley. The plate pewter is used for plates 
and dishes ; the trifle chiefly for pints and quarts ; and 
the ley- metal for wine measures, See. Our very best sort 
of pewter is said to consist of 100 parts of tin, and of 1 7 
of regulus of antimony,* though others allow only 10 
parts of regulus to 100 of tinf ; to this composition the 
French add a little copper. Crude antimony, which con- 
sists of nearly equal portions of sulphur and of a metallic 
# Med. Trans, vol. I. p. 286, 
t Perrib. Cliem. p, 322* 
