A written order from A. to B., directing B. to pay to C. a certain sum of money therein named. Byles, Bills, 1. An open (that is, unsealed) letter addressed by one person to another directing him, in effect, to pay, absolutely and at all events, a certain sum of money therein named, to a third person, or to any other to whom that third person may order it to be paid, or it may be payable to bearer or to the drawer himself. 1 Daniel, Neg. Inst. 27. A bill of exchange is an instrument, negotiable in form, by which one, who is called the “drawer,” requests another, called the “drawee,” to pay a specified sum of money. Civil Code Cal.