I have said above, that the bank of Amsterdam puts forth, from time to time, what regulations they think fit, as to the rate at which they receive the different species of coin. These regulations are formed according to the fluctuation of the value of the metals. When silver rises above the proportion it had before, with respect to gold, then the silver species is received at a higher rate than formerly. When gold rises in proportion to silver, then the gold coins are received at a higher rate than formerly. This regulation produces the same effect as that, which I formerly recommended in the third book, would do, in fixing a standard for the unit of the money of Great Britain, according to the mean proportion of the metals: and it was for this reason, that [Book III. part I. chap. 1.] I asserted the bank money of Amsterdam to be an invariable unit, which the art of man had invented; that it stood like a rock in the sea, immoveable by the fluctuating proportion between the metals. It is no objection against this, to allege the variation of the agio, and the fluctuation of the value of bank money according to demand. These variations ought to be referred to the coin, not to the bank money: the bank money is to be considered as fixed, because it has all the characters of invariability. If, indeed, the affairs of the bank came to be ill administred, and that the credit written in the bank were allowed to swell so far beyond the demand for it, as to sink the value of bank money so far below the rate of coin as to make it impossible to recover itself; then I should allow that the bank money was no longer an invariable standard: but in this case, I should consider the bank as in a kind of political disease, because it would then be withdrawn from under the influence of its own principles, which hitherto has never been the case.