| http://www.w3.org/ns/prov#value | - Invention of CERTAIN IMPROVEMENTS IN THE PROCESS OF ENGRAVING ON METALS BY MEANS OF VOLTAIC ELECTRICITY; in which said Letters Patent there is contained a proviso, obliging us, the said Thomas Spencer and John Wilson, by an instrument in writing under our hands and seals, or under the hand and seal of one of us, particularly to describe and ascertain the nature of our said Invention, and in wh
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