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specific Gravity , and comparative JVear of Gold. 
As, therefore, the specific gravity of metals is liable to be in- 
fluenced by such a variety of causes, it is almost in vain to expect 
absolute precision, in the results of experiments made by different 
persons; but, at the same time, it may be observed, that by 
proper care and attention to the above circumstances, a degree 
of accuracy may be attained, sufficient to answer almost every 
useful purpose, although, from what has been said, it must 
appear improper to form opinions upon small fractional varia- 
tions. By the experiments which I made, with every possible 
precaution, upon separate and intire ingots of gold, reduced to 
standard by silver, by silver and copper, and by copper alone, 
when cast in an iron mould like a cupel, it appeared, that the 
specific gravity of each of these kinds of standard gold is as 
follows. 
Gold made standard by silver - - 17,927 
Gold made standard by silver and copper - 17,344 
Gold made standard by copper - - 17,157. 
Now, as our gold coin commonly contains silver as part of the 
alloy, and as at different times this proportion of silver must have 
been various, and even considerable, particularly when the gold 
of Portugal, which is alloyed with silver, was brought to the 
Mint, it naturally follows that, exclusive of the many other 
causes of variation which have lately been enumerated, the spe- 
cific gravity of our standard gold must occasionally be different, 
according to the relative proportions of silver and copper which 
compose the alloy ; * and, as the specific gravity of gold made 
standard by silver is, in the ingot cast under the above circum- 
The first guineas which were coined, or those of Charles II. and James II. 
were generally alloyed with standard silver ; but the coins of the subsequent reigns 
have been alloyed with copper, added to compensate the deficiency of alloy, or of silver 
in the gold. 
MDCCCIII. S 
