Not yet has the most important element in modern barter been mentioned. I refer to the "clearing-house" arrangements of the stock and produce exchanges. Under these arrangements, brokers who have sold ten thousand shares of Westinghouse El. and M. Common during the day, and bought seven thousand shares, buying and selling being in smaller lots, with a number of different houses, no longer are obliged to deliver ten thousand shares, receiving therefor $700,000, and to receive seven thousand shares, paying therefor $490,000. Instead, they deliver three thousand shares only to the clearing house, and receive from the clearing house only $210,000 when the transaction is, from the standpoint of the particular broker involved, completed. This is a far remove, in technical perfection, from primitive barter, but it is barter, and it saves the using of a vast deal of bank-credit as between brokers. How important it is, from the standpoint of the stock exchange, may be judged from the following statement in Sprague's _Crises Under the National Banking System_: "A much more fundamental change in the organization in the New York money market came with the establishment of the stock exchange clearing house in May, 1892. It led to a very considerable reduction in the _clearing-house exchanges of the banks_ and also, and more important, in the volume of certified checks. [Italics mine.] Overcertification of checks ceased to be a factor of the first magnitude in the banking methods of the city. Had not this arrangement for stock-exchange dealings been set up, it is probable that it would have been necessary to close the stock exchange in 1893 and in 1907, and it is also probable that the volume of business transacted in the years after 1897 could not have been handled." (P. 152.) The same arrangements have been widely introduced in other stock exchanges, and in the produce exchanges.[201]