more than 17, and therefore I conclude the guinea is base metal, a mixture of silver, or copper, with standard gold.

Charles. But how will you get the proportions of the two metals?

Father. Suppose, for example, that the mass be a compound of silver and gold."Compute what the loss of a mass of stan❝dard gold would be ; and likewise the loss "which a mass of silver equal in weight to "the guinea would sustain. Subtract the "loss of the gold from that of the compound, "the remainder is the ratio or proportion

(not the quantity) of the silver: then sub"tract the loss of the compound from that "of the silver, the remainder is the pro portion of the gold." I will propose you an example.

What are the proportions of silver and gold in a guinea weighing 129 grains, whose specific gravity is found to be only 13.09; supposing the loss of standard gold 7.25, and that of a piece of silver, equal in weight to a guinea, 12.45, and the loss of the compound 9.85 ?

Charles. I first subtract the loss of standard gold 7.25 from the loss of the compound 9.85, the remainder is 2.6: I now take the loss of the compound 9.85, from that sustained by the silver 12.45, and the remainder is also 2.6.

Father. Then the proportions of silver and gold are equal to one another, consequently the false guinea is half standard gold and half silver.

Here is another counterfeit guinea, which is full weight, but I know it is composed of standard gold, adulterated with copper, and its loss in water is, as you see, 8.64: now tell me the proportions of the two metals; but you should be informed that a piece of copper of the weight of a guinea would lose in water 14.65 grains.

Emma. I deduct 7.25, the loss of a guinea standard gold, from 8.64, the remainder is 1.39: I now take the loss of the compound 8.64 from 14.65, the loss sustained by a piece of copper equal in weight to a guinea, and the remainder is 6.01. Is not the proportion of copper to gold as 1.39 to 6.01 ?

Father. You are quite right. Now, by the rule of three, tell me the quantity of each metal.

Emma. To find the weight of the copper, I add 6.01, and 1.39 together, which are the proportional weights of the two me tals. And say, as 7.40, the sum, is to 1.39 the proportional weight of copper, so is the weight of the guinea, 129 grains, to the real weight of copper contained in the counterfeit guinea: but

1.39 X 129

7.40

=24.1, therefore there is a

little more than 24 grains of copper in the compound.

Father. You have found then that there are 24 grains of copper in this counterfeit guinea. How will you find the weight of the gold?

Emma. Very easily: for if the composition be copper and gold, and there are found to be 24 grains of copper, there must be 105 of gold.

Charles. I have a question to propose. If by chance you take a bad guinea (I have

heard you say that you never attempt to pass bad money upon others), how should you be able to ascertain the value it would fetch at the goldsmith's?

Father. It is certainly very wrong knowingly to pass bad money upon the public: no man has a right to commit an injury because he has received one; if, therefore, I have taken counterfeit money, I ought to abide by the loss, rather than run the risk of injuring my neighbour: besides, în the course of circulation, a bad guinea, or a seven-shilling piece, or even coins of much less value, may fall into the hands of a poor and industrious family, which they perhaps laid by to answer the extraordinary demands of sickness; and at that period of distress, not being able to say from whom they received the counterfeit coin, they may possibly be reduced to serious and pitiable difficulties: and therefore it is better for me to put up with the loss than run the hazard of injuring the poor.

Now to answer your question. A piece of copper, of equal weight with a guinea, M

VOL. II.

loses of its weight in water 14.65 grains, 7.4 more than is lost by a standard guinea. The value of a standard guinea is 252 pence, divide therefore 252 by 7.4 and you get 34, the number of pence that is deducted, from the value of a guinea, for every grain it loses more than it would lose if it were sterling gold.

Emma. In the guinea that lost 8.64 how much must be deducted from the real value of a guinea standard gold?

Charles. I can tell that; subtract 7.25 from 8.64 the remainder is 1.39, and this multiplied by 34 pence gives 47.26 pence, or very nearly 4 shillings, consequently that guinea is worth only 17 shillings.

Father. Suppose the compound were silver and gold, how would you proceed in making an estimate of its value?

Charles. A piece of silver of the weight of a guinea would lose 12.45 grains, from which I deduct 7.25, and with the remainder 5.2 I divide the value of a guinea, or 252 pence, and the quotient is 48.4 pence,