There are cases, however, in which the _potential_ change of the precious metals affects their value as money in the same way that it affects the value of other things. Such a case was the change in the value of silver in 1876. The usual causes assigned for that serious fall in value were the greatly increased production from the mines of Nevada; the demonetization of silver by Germany; and the decreased demand for export to India. It is true that the exports of silver from England to India fell off from about $32,000,000 in 1871-1872 to about $23,000,000 in 1874-1875; but none of the increased Nevada silver was exported from the United States to London, nor had Germany put more than $30,000,000 of her silver on the market;(233) and yet the price of silver so fell that the depreciation amounted to 20-¼ per cent as compared with the average price between 1867 and 1872. The change in value, however, took place without any corresponding change in the actual quantity in circulation. The relation between prices and the quantities of the precious metals is, therefore, not so exact, certainly as regards silver, as Mr. Mill would have us believe; and thus their values conform more nearly to the general law of Demand and Supply in the same way that it affects things other than money. It is evident, however, that the cost of production, in the long run, regulates the quantity; and that every country (temporary fluctuation excepted) will possess, and have in circulation, just that quantity of money which will perform all the exchanges required of it, consistently with maintaining a value conformable to its cost of production. The prices of things will, on the average, be such that money will exchange for its own cost in all other goods: and, precisely because the quantity can not be prevented from affecting the value, the quantity itself will (by a sort of self-acting machinery) be kept at the amount consistent with that standard of prices—at the amount necessary for performing, at those prices, all the business required of it. Chapter VII. Of A Double Standard And Subsidiary Coins. § 1. Objections to a Double Standard. 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.