surplus, may deposit approved securities with the currency association
and be empowered by the Secretary of the Treasury to issue additional
circulating notes to an amount not to exceed seventy-five per cent of
the cash value of the securities. If the securities are State or
municipal bonds the issue must not exceed ninety per cent of the market
value of the bonds.
(3) The banks and assets of all banks belonging to the currency
association are liable to the United States for the redemption of this
additional currency, and the association may at any time require that
additional securities be deposited. All banks are held liable to make