The plus-silver is due to the fact that in assaying the base bullion by cupellation, the silver lost by volatilization and cupel-absorption is neglected.
His reports on smelting and assaying were remarkable for their detail and for the comparisons drawn between Swedish and other methods.
The other volumes dealt with (a) iron and steel, (b) copper and brass, their smelting, conversion and assaying, and chemical experiments thereon.
Seigniorage was abolished for both gold and silver in 1666, when it was provided that no charge should be made at the Mint for coining and assaying.
The ingots are valued by weighing and assaying, and a calculation is made as to the amount of copper required for melting with them to produce the standard alloy.