down the banks

Mr. Heberton Fitzjames was (and, if he has not gone 'down the banks,' is) a gentleman such as we frequently see at the watering-places; a leader of the select parties there congregated. ... I became acquainted with Fitzjames in my way of making new friends. I had professional engagements with him, and from the name of 'the plaintiff,' I concluded it grew out of a sporting debt. Ah, Heberton, in that you were nearly gone 'down the banks!'