No description of a cable transfer having been given in the preceding description of different kinds of exchange, it may be explained briefly that a "cable," so-called, differs from a sight draft only in that the banker abroad who is to pay out the money is advised to do so by means of a telegraphic message instead of by a bit of paper instructing him to "pay to the order of so and so." A, in New York, wants to transfer money to B, in London. He goes to his banker in New York and deposits the amount, in dollars, with him, requesting that he (the New York banker) instruct his correspondent in London, by cable, to pay to B the equivalent in pounds. The transfer is immediate, the cable being sent as soon as the American banker receives the money on this end. To be able to instruct its correspondent in London by cable to pay out large sums at any given time, a bank here must necessarily carry a substantial credit balance abroad. It would be possible, of course, for a banker to instruct his London agent by cable to pay out a sum of money, at the same time cabling him the money to pay out, but this operation of selling cables against cables is not much indulged in--there is too little chance of profit in it. Under special circumstances, however, it can be seen that a house anxious to sell a large cable and not having the balance abroad to do it, might easily provide its correspondent abroad with the funds by going out and buying a cable itself. But under ordinary circumstances foreign exchange dealers who engage in the business of selling cables carry adequate balances on the other side, balances which they keep replenishing by continuous remittances of demand exchange. Which in itself constitutes an important form of foreign exchange activity and an operation out of which many large houses make a good deal of money. All the parties involved being bankers there is little risk in business of this kind; but, on the other hand, the margin of profit is small, and in order to make any money out of it, it is necessary that very large amounts of money be turned over. The average profit, for instance, realized in the New York exchange market from straight sales of cables against remittances of checks is fifteen points (15/100 of a cent per pound sterling). That means that on every £10,000, the gross profit would be $15.00. A daily turnover of £50,000, therefore, would result in a gross profit of $75 a day.