But, secondly, a drain may be produced by the failure of some staple article of food or manufacture, and the consequent importation of an adequate substitute. The most calamitous case of this kind which has occurred in recent times, was the general failure of the potato crop in 1846, which necessitated the transmission of more than £8,000,000 of treasure in payment for bread-stuffs, chiefly to America. In this and similar cases the efflux of gold is not produced by any excess of circulating medium, with its attendant rise in prices and fall in the rate of interest; the recovery of the gold, therefore, should be effected with the smallest possible diminution of currency, reduction of prices, or enhancement of the rate of interest, and any unnecessary aggravation of either of these is a perfectly gratuitous evil. Yet here, as in the previous case, the provisions of the Act of 1844 require that the circulating medium should contract, at least by the difference between the amount of the available reserve and that of the exported gold. For example, should the drain commence when the available reserve should amount to only £4,000,000, which is about the average, and should it extend to six, eight, or even ten millions, the amount of the circulating medium must inevitably contract, at the very least by two, four, or six millions. And yet, there can be little doubt that in such a case as this, a contraction of one or two millions would be amply sufficient for the recovery of the treasure.