The charges made by banks upon their loans and the interest they pay on deposits are vitally connected with the topics which have been discussed in the preceding chapters, and must be considered before our account of the mechanism and principles of exchange is closed. Of the former, three may be distinguished: the charge on bills discounted, known as the rate of discount; that on promissory notes; and that on loans payable on demand, usually called the rate on "call loans." These three rates have much in common and are also related to the interest paid on deposits, but they may be profitably treated separately.