# Principles of Political Economy (J.S. Mill, 1871), vol. 2/Book III, Chapter X

This is the seventh edition of the Principles, which was first published 1848.
CHAPTER X.
OF A DOUBLE STANDARD, AND SUBSIDIARY COINS.
§ 1.Though the qualities necessary to fit any commodity for being used as money are rarely united in any considerable perfection, there are two commodities which possess them in an eminent, and nearly an equal degree; the two precious metals, as they are called; gold and silver. Some nations have accordingly attempted to compose their circulating medium of these two metals indiscriminately.
There is an obvious convenience in making use of the more costly metal for larger payments, and the cheaper one for smaller; and the only question relates to the mode in which this can best be done. The mode most frequently adopted has been to establish between the two metals a fixed proportion; to decide, for example, that a gold coin called a sovereign should be equivalent to twenty of the silver coins called shillings: both the one and the other being called, in the ordinary money of account of the country, by the same denomination, a pound: and it being left free to every one who has a pound to pay, either to pay it in the one metal or in the other.
At the time when the valuation of the two metals relatively to each other, say twenty shillings to the sovereign, or twenty-one shillings to the guinea, was first made, the proportion probably corresponded, as nearly as it could be made to do, with the ordinary relative values of the two metals grounded on their cost of production: and if those natural or cost values always continued to bear the same ratio to one another, the arrangement would be unobjectionable. This, however, is far from being the fact. Gold and silver, though the least variable in value of all commodities, are not invariable, ​and do not always vary simultaneously. Silver, for example, was lowered in permanent value more than gold, by the discovery of the American mines; and those small variations of value which take place occasionally, do not affect both metals alike. Suppose such a variation to take place: the value of the two metals relatively to one another no longer agreeing with their rated proportion, one or other of them will now be rated below its bullion value, and there will be a profit to be made by melting it.
Suppose, for example, that gold rises in value relatively to silver, so that the quantity of gold in a sovereign is now worth more than the quantity of silver in twenty shillings. Two consequences will ensue. No debtor will any longer find it his interest to pay in gold. He will always pay in silver, because twenty shillings are a legal tender for a debt of one pound, and he can procure silver convertible into twenty shillings for less gold than that contained in a sovereign. The other consequence will be, that unless a sovereign can be sold for more than twenty shillings, all the sovereigns will be melted, since as bullion they will purchase a greater number of shillings than they exchange for as coin. The converse of all this would happen if silver, instead of gold, were the metal which had risen in comparative value. A sovereign would not now be worth so much as twenty shillings, and whoever had a pound to pay would prefer paying it by a sovereign; while the silver coins would be collected for the purpose of being melted, and sold as bullion for gold at their real value, that is, above the legal valuation. The money of the community, therefore, would never really consist of both metals, but of the one only which, at the particular time, best suited the interest of debtors; and the standard of the currency would be constantly liable to change from the one metal to the other, at a loss, on each change, of the expense of coinage on the metal which fell out of use.
It appears, therefore, that the value of money is liable to more frequent fluctuations when both metals are a legal tender ​at a fixed valuation, than when the exclusive standard of the currency is either gold or silver. Instead of being only affected by variations in the cost of production of one metal, it is subject to derangement from those of two. The particular kind of variation to which a currency is rendered more liable by having two legal standards, is a fall of value, or what is commonly called a depreciation; since practically that one of the two metals will always be the standard, of which the real has fallen below the rated value. If the tendency of the metals be to rise in value, all payments will be made in the one which has risen least; and if to fall, then in that which has fallen most.
§ 2. The plan of a double standard is still occasionally brought forward by here and there a writer or orator as a great improvement in currency. It is probable that, with most of its adherents, its chief merit is its tendency to a sort of depreciation, there being at all times abundance of supporters for any mode, either open or covert, of lowering the standard. Some, however, are influenced by an exaggerated estimate of an advantage which to a certain extent is real, that of being able to have recourse, for replenishing the circulation, to the united stock of gold and silver in the commercial world, instead of being confined to one of them, which, from accidental absorption, may not be obtainable with sufficient rapidity. The advantage without the disadvantages of a double standard, seems to be best obtained by those nations with whom one only of the two metals is a legal tender, but the other also is coined, and allowed to pass for whatever value the market assigns to it.
When this plan is adopted, it is naturally the more costly metal which is left to be bought and sold as an article of commerce. But nations which, like England, adopt the more costly of the two as their standard, resort to a different expedient for retaining them both in circulation, namely, to make silver a legal tender, but only for small payments. In ​England, no one can be compelled to receive silver in payment for a larger amount than forty shillings. With this regulation there is necessarily combined another, namely, that silver coin should be rated, in comparison with gold, somewhat above its intrinsic value; that there should not be, in twenty shillings, as much silver as is worth a sovereign: for if there were, a very slight turn of the market in its favour would make it worth more than a sovereign, and it would be profitable to melt the silver coin. The over-valuation of the silver coin creates an inducement to buy silver and send it to the Mint to be coined, since it is given back at a higher value than properly belongs to it: this, however, has been guarded against, by limiting the quantity of the silver coinage, which is not left, like that of gold, to the discretion of individuals, but is determined by the government, and restricted to the amount supposed to be required for small payments. The only precaution necessary is, not to put so high a valuation upon the silver, as to hold out a strong temptation to private coining.