The economy of money through the use of credit substitutes for money extends really further than the foregoing analysis indicates. Under the [now superseded] law, three-fifths of the reserves of a rural bank may be on deposit with banks in reserve cities. Thus against $100,000 of deposit liability the rural bank needs hold only $6,000 of reserve money. Against the deposit of the remaining $9,000, the reserve city bank is required in turn to hold a reserve of only 25 per cent.--$2,250. And of this required $2,250, one-half may be represented by deposits in central reserve cities, _e. g._, New York, Chicago, and St. Louis. Against the $1,125 deposited with it the central reserve bank is required to hold only 25 per cent. of reserves--$281.25. Thus at the outside limit of credit extension, $100,000 of deposit currency may be supported by only $7,406.25 of reserves in money, (6000 + 1/2 x (9000/4) + (1125/4)). one dollar of reserves upholding $13 of currency.[34] It is, of course, not true that the banks ordinarily allow their reserves to run as low as the legal limit, or make the utmost possible use of the privilege of counting claims against one another as legal reserves. Nor is it accurately true that all forms of money are of equal efficiency in the support of credit. Not all forms of money, but only those of the higher levels in the money scale, are allowed to be counted as legal reserves.... Some forms of money make demands upon other forms for redemption, or are limited in exchange power to the exchange power of the form in which redemption is to be made. The total exchange efficiency of the money of a country is, then, not accurately to be computed on the assumption that all moneys are equally efficient for all purposes--that some are not in varying degree burdens upon the money functions of the others. ~Banking Viewed in Detail and in the Aggregate.~--And one further modification is called for. The analysis so far made, while valid for any isolated bank, or for the banking system regarded as an aggregate, is not precisely accurate for the affairs of any one competing bank among other banks. When the check drawn by the borrowing depositor may be deposited in other banks and collected by them against the lending bank, its granting of credits rapidly draws down its reserves to swell the reserves of its competitors. One hundred thousand dollars of new reserves may not mean to it an increase of lending power of more than, say, $125,000. For banks in the aggregate, however, this increase of reserves brings its full several-fold increase of lending power, provided that all the reserve efficiency is utilized in whatever bank it rests. As the lending by each bank is depleting its reserves, the lending which other banks are doing is reinforcing these reserves. The aggregate possible extension of credit is not changed.