305) with further details on processes for testing copper

Author: Isaac Newton

Source: MINT 19/2/312-13, National Archives, Kew, Richmond, Surrey, UK

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  Report on copper coinage [MINT 19/2/305]

<312r>

To the most Honourable the Earl of Oxford & Earl Mortimer Lord High Treasurer of great Britain.

May it please your Lordship

I humbly beg leave to lay before your Lordship that the Master & Worker of her Majestys Mint is not obliged to receive all the gold & silver brought into her Majestys Mint to be coyned. If any gold be brought in which is not tough, he returns it back to be toughned at the Importers charge tho it be standard. If any gold or silver be not eavenly mixed he returns it back to be remelted at the Importers charge. If it be not neare to standard he returns it back to be refined at the Importers charge. And to judge whether it be fit to be received or returned back is left to his discretion. And by parity of reason he should not be obliged to receive all sorts of copper to be coyned. If it be not fine or not tough & malleable or ill coloured or otherwise faulty, he should be at liberty to return it back to be made fit for the Mint at the Importers charge. Otherwise it will be difficult to coyn the money of good malleable copper, without allowing for the charge loss & hazzards of such an undertaking.

There is an assay of copper by refining a small parcel & thence recconing what will be the wast charges & trouble in refining a Tunn of such copper. And such an Assay is usefull in buying coarse copper to be refined, but is of little or no use in buying fine copper. The price of fine copper depends upon the malleability & two parcels of copper equally fine may differ very much in their malleability, & by consequence in their price. Copper refined to that degree & in that manner as to be malleable without cracking when red hot is the fittest material for manufacturing into all sorts of copper vessels & by consequence for money. The Swedish copper money is of this standard. And such copper is usually valued at about 11 $\frac{1}{2}$ ^d per pound weight. And if it be made still more soft & malleable the wiredrawer may value it at 2 or 3^s per pound weight because of its fitness for his use. Tis the ductility that makes it usefull & the usefulness that sets a price upon it & the triall by hammering & bending hot & cold that determins the ductility. This is the assay by which the Refiners of copper know when their copper is fully fine & ready to vitrify & by consequence the proper assay for receiving fine copper into the Mint. For it determins the fineness & the malleability at once, no coarse copper being malleable.

By the estimates of Workmen the charges of repairing & fitting up the houses in the Irish Mint for a coynage of Copper will amount to about 146^li . And the putting up a furnace in the melting house with all things answerable for making an experiment in casting will cost about 32^li more. And a small parcel of copper <313r> for making an experiment may cost about 20^li more. If your Lordship please to impress 200^li to me for this service upon account, it may be repaid out of the copper coynage. All which &c

Mint Office
12 Mar 1713