Report (as ordered by the Treasury) on various methods of ascertaining the purity of copper, and the deficiencies of most methods
In obedience to your Lordships command I have made the strictest enquiry possible among Artists skill'd in the nature and Working of Copper in order to find out the best and most certain method of Assaying the finess thereof and Humbly represent to Your Lordship.
That Copper cannot be assayed on the Test as Gold & Silver are, thô it will sett on the Test, when fine, as they do, but the intensness or remissness of the Fire destroying more or less of it, and indeed the whole Copper being to be destroyed by a Sufficient quantity of Lead of the Test, there can be no dependance on that way of Assaying it.
That the finess of Copper may be guessed at by the grain and colour of it by those who are used to refine it especially by a microscope, yet neither is this agreed to have any certainty in it.
That fine Brass wch. is made of fine Copper and Lapis Calminaris and is th{illeg}|e| toughest of all Compounds wth. Copper and indeed almost as maleable as fine Copper it selfe when cold, is almost as brittle as flass when {illeg}|red h|ott.
That some argue that if Copper will draw into Wire it must necessarily be fine, which is indeed very true, yet is that no true way of Assaying the finess of Copper, because tho' Copper be never so fine unless it be melted to a due heat for that purpose, it will not draw into fine wire.
That some will have it That if Copper will bear to be hamer'd hot with Smiths hammers, and to be bent when cold without cracking, it must necessarily be fine, but tho' this be the least uncertain of all the {illeg}|former| ways, yet it has oftentimes fail'd in experience.
That there is no other certain way of {illeg}|k|nowing that Copper is perfectly fine but by it's bearing to be milled under the great Hammer red hot; All Artists agreeing, that there is no mixture with Copper (except Gold and Silver) that will bear the great Hammer red Hott, and consequently the Copper must be perfectly fine before it will bear to be Hammer'd into Plates
<415r>That fine Copper requires so great a heat to meet it, that it cannot be cast into Fillets in sand in quantities (whatever may be done in little for a Sample) wth.out running Spongy & burning the sand, except a little Tin be thrown into it, just at powring it off to Cool it wch. I am told was the method used in making most of the present Copper mony, but that little wch. was not a pound to an Hundred weight, together wth. the paleness it contracted from the Land, so discoulour'd the Copper and debased it, that the best of those Half pence are hardly so must worth to meet down as fine Copper by two pence ꝑ pound and gave occasion to the Counterfeits, of wch. 'tis computed there are above 60 Tuns, Some of 'em not worth 6d. ꝑ pound to melt down, for the Courser the Mettal is the more solid it runs in Sand.
Therefore I humbly conceive the only way to prevent the {illeg}|p|ossibili{illeg}|t|y {illeg}|of| {illeg}|a|dulterating the Copper Halfe pence & Farthings is by making of them of Hammer'd Copper whereby they must necessarily be of the same finess as those made in King Charles the 2ds. Reign which were never attempted to be counterfeited.
This way of Working is not only 3d. ꝑ pound weight dearer than casting, but the metal will be almost 3d. ꝑ pound of more Intrinsick value and of equal colour & goodness with those Coyn'd in King Charles the 2ds. Reign Yet I am willing to Vndertake this at the rate I formerly proposed to your Lordship, but Humbly crave leave to remind your Lordship that since the last Coynage a Vote was made in the House of Commons that the Farthings should be made {illeg}|a|s near the Intrinsick value as possible
All which is Humbly submitted to
Your Lordships great wisdom.
<415v>Mr Bertie's Memorial about assaying Copper.
R Apr: 24: 171{6}|4|
26 Aprill 1714
Send this to ye Offrs. Mint
