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Of Metals and their Specifick Guavities, &c.
Sect. 1. Of Gold and Silver.
PURE Gold, free from Mixture with other Metals, usually 1 called Fine Gold, is of such a Nature and Purity that it will endure the Fire without wasting, although it be kept continually melted: and therefore some of the ancient Philosophers have suppofed the Sun to be a Globe of liquid or melted Gold.
Silver having not the Purity of Gold, will not endure the Fire like it: Yet Fine Silver will waste but a very little by being in the Fire any reasonable time; whereas Copper, Tin, Lead, &c. will not only waste, but may be calcined or burnt to a Powder.
Both Gold and Silver in their Purity, are so very flexible or foft (like new Lead, &c.) that they are not so useful either in Coin, or otherwise (except to beat in Leaf-Gold or Silver) as when they are allay'd, or mixed and hardened with Copper or Brass. And altho' most Places differ more or less in the Quantity of such Allay, yet in England it is generally agreed on, that,
Standard for Gold. ? 22 Carracts of Fine Gold, and 2 Carracts of Copper, being melted together shall be esteemed the true Standard for Gold Coin, & (The French and Spanish Gold being very near of the fame Standard.) That is, if any Quantity or Weight of Fine Gold, be divided into Twenty-four equal Parts, and 22 of those Parts be mixed with 2 of the like Parts of Copper ; that Mixture is called Standard Gold.
Whence you may observe, that a Carract is not any certain Quantity or Weight, but it Part of any Quantity or Weight; and the Minters and Goldsmiths divide it into 4 equal Parts, which they call Grains of a Carract; also they subdivide one of those Grains, into Halves, Quarters, &c.*
Standard for Silver.
Eleven Ounces and Two Penny-weight of Fine Silver, and Eighteen Penny-weight of Copper being melted together, is esteemed the true Standard for Silver Coin, called Sterling Silver. And so in Proportion for a greater or lesser Quantity ; which is a less Proportion of Allay for Silver, than the other is for Gold..
Note, When either Silver or Gold is finer than Standard, it is called Better; if coarser, it is called Worfe; and that Betterness or Worseness, is reckoned by Carracts and Grains of a Carract in Gold, and by Penny-weights in Silver; and is thus discovered : The Goldsmiths or Refiners, &c. take a small Quantity of such Gold as they intend to try (which they call making an Aslay) and weigh it very exactly, then they put it into a Crucible, and melt ic in a strong Fire, so long, that if there be any Copper, or other Allay mixt with it, that Allay may be consumed or burnt away : When it is cold they weigh it very exactly again, and if it have loft nothing of it's first Weight, they conclude it is Fine Gold, but if the Lofs be it Part, they call it 23 Carracts Fine, or one Carract better than Standard: If it have lost i Parts it is 22 Carraets fine, or Standard : If Parts, it is said to be 21 Carracts fine, or rather one Carract worse than Standard, and so in Pro, portion as it happens to be better or worse.
In the same Manner they make their Affay on Silver, only they compute it's Lofs by Penny-weights, '&c.
The Author of the Present State of England, mentioned before, (page 32. ) says,
If an Ingot of Silver weighing 787 Oz. 14 Pwt. 6 Grains, be 11 Oz. 6 Pwt. fine; How much fine Silver is there in it, and what amounts it to, at 55. i į d. the Ounce? .
This Ingot is better than Standard by 4 Pwt. For 11 Ož. 2 Pwt. = 222 Pwt. the fine Silver in 12 Oz. of Standard. But 11 Oz. 6 Pwr. = 226 Pwt, the fine Silver in 12 Oz. according to the Question.
If an Ingot of Gold weighing 115 Oz. 13 Pwt. 18 Grains ; be of a Grain worse than Standard: How much Standard Gold: is there in it, and what comes it to at 31. 11 so an Ounce?
Again,' 2313,75 x 22 = 50902,5 ought to be the fine Gold in that Ingot, if it had been Standard:
Sect. 2. The Specifick Gravity of Metals, &c. I Take an Enquiry made about the different Gravities, or 1 Weights of Metals, and other Bodies, to be (not only a Work of Curiosity, but also) of very good Use upon many Occasions. Therefore several Authors have given us such Proportions, or Difference of their Weights, as they are said to have one to another; supposing every one of them to be of the fame Magnitude or Bignefs. Some of which I shall here insert.
1. Henry van Etten, in his Mathematical Recreations, printed Anno 1633, sets down the Proportion of their Weights thus; Gold 1875. Lead 1165. Silver 1040. Copper 910. Iron 810. Tin 750. Water 100.
3. The ingenious Mr Oughtred, in his Circles of Proportions, printed Anno 1660, hach their Proportions (according to the Experiments of one Marinus Ghetaldi, in his Tract called Archimedes Promotus) thus : Gold 3990 . Quicksilver 2850'. Lead 2415 Silver 2170 . Brafs 1890, Iron 1680, Tin 1554, .