The rate of exchange between two moneys, e. g., dollars and sterling, is measured by the amount of sterling in England that will exchange against a claim for the immediate payment of a dollar in America. It is thus a particular example of something much more general. Just as there is a rate of exchange between dollars and sterling, so there is also a rate of exchange between lead in England and iron in America, tho it does not happen that documents embodying this rate of exchange are drawn up and quoted on the market. Exchanges between the moneys of different countries are in practice affected by bills at six months, bills at three months, bills payable on demand and telegraphic transfers. When one buys with sterling a bill for dollars that will only yield dollars after an interval, the price paid must obviously include an item for interest, and is not, therefore, made up altogether of the pure sterling price of dollars.