treasury of the United States registered interest-bearing bonds
to an amount not less than $50,000. Those having a capital of
$150,000 or less must deposit bonds equal to one fourth of their
capital stock. Each bank may issue circulating notes to the
amount of ninety per cent. of the market value of the bonds
deposited by it, but not exceeding ninety per cent. of the par
value of the same, and not exceeding ninety per cent. of the
paid-in capital of the bank; but no bank is compelled to issue
circulating notes. No bank-notes shall be issued smaller than $5.
The notes are receivable at par for all dues to the United States
except duties on imports, and are payable for all debts owing by
the United States within the United States except interest on the
public debt and in redemption of the national currency.