f the customer by means of the
pass-book, and not objected to by him, but in the present attitude of the
courts towards the pass-book some further recognition would seem necessary.
Such system of charging interest, even when fully recognized, only prevails
so long as the relation of banker and customer, on which it is founded,
continues in force; the taking a mortgage for the existing debt would put
an end to it.

[Sidenote: Lien.]

The main point in which advances made by bankers differ from those made by
other people is the exceptional right possessed by bankers of securing
repayment by means of the banker's lien. The banker's lien is part of the
law merchant and entitles him, in the absence of agreement express or
implied to the contrary, to retain and apply, in discharge of the
customer's liability to him, any securities of the customer coming into his
possession in his capacity as banker. It includes bills and cheques paid in
for collection (_Currie_ v. _Misa_, 1 A.C. 564). Either by virtue of it, or
his right of set-off, the banker can retain moneys paid in by or received
for the credit of the customer, against the customer's debt to him. Goods
deposited for safe custody or moneys paid in to meet particular bills are
exempt from the lien, the purpose for which they come to the banker's hands
being inconsistent with the assertion of the lien. The existence of the
banker's lien entitles him to sue all parties to bills or cheques by virtue
of sec. 27, subs. 3 of the Bills of Exchange Act, and to the extent of his
advances his title is independent of that of the previous holder. Moreover,
the banker's lien, though so termed, is really in effect an implied pledge,
and confers the rights of realization on default pertaining to that class
of bailment. But with regard to the exercise of his lien, as in many other
phases of his relation to his customer, the banker's strict rights may be
curtailed or circumscribed by limitations arising out of course of
business. The principle, based either on general equity or estoppel and
independent of definite agreement or consideration, requires that when
dealings between banker and customer have for a reasonable space of time
proceeded on a recognized footing, the banker shall not suddenly break away
from such established order of things and assert his strict legal rights to
the detriment of the customer. By the operation of this rule, the banker
may be precluded from asserting his li