Fleta minor the laws of art and nature, in knowing, judging, assaying, fining, refining and inlarging the bodies of confin'd metals : in two parts : the first contains assays of Lazarus Erckern, chief prover, or assay-master general of the empire of Germany, in V. books, orinally written by him in the Teutonick language and now translated into English ; the second contains essays on metallick words, as a dictionary to many pleasing discourses, by Sir John Pettus ... ; illustrated with 44 sculptures.

CHAP. V. How hard flowing Copper Oars are to be proved.

[Section. 1] HARD flowing Oars are not to be pro∣ved as the smooth, but in another man∣ner: thus, Take the Copper Oars, beat them as small as the Seeds of Hemp, and and mingle them together: weigh two Centners of it in the proof-weight, put it in a proof-Test, set it in a proof-Oven, give it a very gentle fire, that it may begin to roast it self, then stir it with an iron about the Test, else the Oar will turn to Ashes together in the Test, and will not rost: and when 'tis stir'd the first time, then give it a little stronger fire, that it may glow well, lift it out of the Oven, and let it cool, then put it in the Oven again, and let it roast again untill it hath done smoak∣ing (and smells not of Sulphur) then grind it a little smaller, yet not so small as Mill-dust, and roast it again till it stinks no more Sulphurish, then stir▪ it once or twice with the little hook, that it may not be ashes again.

[Section. 2] When 'tis thus ground anew, and wash'd the second time, let it cool, and set it the third time in the Assay-Oven, then roast it, and grinde it very small, then wash it once more that it may be burnt quite dead, then grinde it again very small, so is it prepared for the Proof. Then divide the Oar upon a Ballance in two equal parts, and put one part in an Assay-Crucible with 3 times so much of the foresaid Fluss, and with a fixt part of flowing Glass-Gall, mingle them well in the Crucible, and cover it with common or flowing Salt (as in the proof before)

and lute it over on the top with Clay, that the Cover be fast, so that no Coals may fall in, then set it in a little Oven, blow the Bellows, give the proof a strong sud∣den fire (a little stronger then the former proof) and when the proof hath stood in a pretty good Fluss, then lift the Crucible out of the fire, and let it cool, and break it, and so you may find in the bottom a Grain of black Copper, of such Goodness as the Oar and Flint is in the melting, and may thereby get Copper, which is the right proof of it.

[Section. 3] Yet there is of one sort of flinty Oar, fairer Copper than of another, and commonly all flints which are of an iron Nature) yields iron streamy Copper, therefore they are not to be used for making of Brass.

Of this graind Copper (as it comes out of the Proof) weigh it with a Centner weight, then you may see how many pound of black Copper, a Centner of flint or raw Coper Oar do yield, so you may easily reckon how many such Centners, do afford one Centner of Copper: and know therefore, that if you do weigh two Centners of flinty Oars to the proof, if the proof should be amiss, then you have a Centner more of the roasted Oar or flint, to make another proof, otherwise it will be a great hindrance to roast but one Centner to the Proof.

But on the contrary, the old Assayers have used this Method, and proved every Copper Oar or flint upon pure Copper, and thereby know how many Centners of it, will yield one Centner of pure Copper: this I believe to be a just proof for them, who have roasted and purifyed the Copper themselves. But those who work the Silver in it, and sell it with the Silver, it is better for them to know how many Centners of black Copper they may have in a roast, so they may know how many Loths of Silver, a Centner of black Copper contains.

And among all meltings, the Operation of Copper

(upon which is to be made a proper Account) is the most pleasant and fairest Experiment; for if the Proof be right, then what is produced will be so too.

[Section. 4] Therefore, if you will (with the old Assayers) prove the Copper-Oars upon boiled Copper, do it thus, Grind the Oars small, weigh of it two Centners: if they be unflowing or flinty then roast them (as above) in an Assay-Crucible, and weigh to it four Centner of Fluss or Lead-glass, made of Littarge and Flint-stones (as in the first Book of Silver Oars) and mingle them well, and cover it with Salt, and also cover the Crucible, and set it in a little Oven before the Bellows: and let it flow like another Copper-Proof, and when 'tis cool open the crucible, and in the Bottom is the Regulus, among which is copper, and lead together, put it upon a flat Test luted with Littarge, drive it till the copper appears to be of a clear Green, then lift the Graind-copper from the Test, and quench it in Water, and weigh it with thy Proof Weight, so you may finde how many pound of boyled copper you have from two centners of flinty-cop∣per Oar in the Proof: one may also very easily burn the copper, especially if the Oar be poor in copper (as you may finde by the Operation). Therefore I con∣ceive it better, to prove the copper Oars first upon black copper, and then upon boild copper: and this way, the Proof of the light contenty copper Oars cannot so easily be hurt.

Notes

• The manner of it.
• The Oar burnt quite dead.
• Some Cop∣per not fit for Brass.
• ☞
• To boil Oars for Copper.