In fact the danger that is run by those who lend to foreign debtors who are cursed with an unstable currency is so great that ingenious efforts are made by issuing houses to secure, as a collateral pledge, some asset which is sure of a market abroad and so is equivalent to so much foreign currency. This device has been successfully carried out in the case of loans to the State of San Paulo and to the Brazilian Government secured on holdings of coffee which had been taken over from the growers in order to prevent its price being wrecked by sales at a time when the market was gorged. The coffee was gradually sold as consumption overtook supply and the proceeds were used to meet interest and redeem the loans. But the circumstances under which any foreign debtor is in a position to pledge such a "sterling asset" are evidently rare, and a system by which Governments undertake such wholesale purchases of commodities is not one to be encouraged, even though it provides a convenient form of collateral, if the operation is well and successfully thought out and concluded.
As to other forms of liens and pledges, such as special assignations of the Customs duties, or the profit of a tobacco monopoly or the revenues of railways, the limitations on their
