specific Gravity, and comparative Wear of Gold. 85 
were alloyed with eighteen pennyweights and twenty-one grains 
of granulated Swedish copper, which was taken from another 
parcel. 
The bar was cast in a mould of iron, and was found to be, 
in a small degree, less ductile than the metal formed by the 
foregoing experiments. 
Experiment v. 
The same bar was melted again, and was cast in sand, 
faced in the usual manner by charcoal dust; it then proved 
slightly brittle. 
Experiment vi. 
The bar was melted as before, and was cast in the mould of 
iron. 
The metal was now found to have recovered the same duc- 
tility which it possessed in Exper. iv. 
Experiment vn. 
Eleven ounces one pennyweight and three grains of fine gold, 
were alloyed with eighteen pennyweights and twenty-one grains 
of Swedish dollar copper, which being well mixed, the whole 
was cast in a mould of iron. 
The colour of this bar resembled the former ; but it did not 
possess the smallest degree of ductility, for it broke like glass. 
Experiment vm. 
The bar was melted again, and was cast in sand ; but not 
any alteration was thus produced. 
Experime?it ix. 
The foregoing bar was melted once more, and was cast in 
the mould of iron ; but it still remained as brittle as at first. 
