30. For my part, I find no difficulty in interpreting the arrangement made by the bill of lading and its acceptance by the consignor as providing that if, in fact, the appellant stevedored the cargo, leaving aside for the moment what the stevedoring involved, the appellant should have the benefit of the clauses of the bill including the benefit of the time limitation expressed in cl. 17 of the bill of lading. I am unable to treat the clauses of the bill of lading as in any respect an unaccepted but acceptable offer by consignor to stevedore. Indeed, I do not think the bill can be interpreted as containing an offer at large by the consignor. The consignor and the appellant as stevedore were ad idem through the carrier's agency upon the acceptance by the consignor of the bill of lading as to the protection the stevedore should have in the event that it stevedored the consignment. But this consensus lacked the essential of consideration. The appellant through the bill of lading made no promise to stevedore the cargo. Thus, whilst I would not analyse the situation obtaining on the acceptance of the bill of lading as an exchange of promises, I would not analyse it as merely the making of an offer susceptible of acceptance by an act of the stevedore done in purported acceptance of the offer. For this reason I have described the bill of lading in so far as the carrier there purports to act for the appellant as an arrangement. To agree with another that, in the event that the other acts in a particular way, that other shall be entitled to stated protective provisions only needs performance by the doing of the specified act or acts to become a binding contract. Whether or not the arrangement is susceptible of unilateral disavowal before the stated act is done need not be discussed. Here the act was done. The performance of the act or acts at the one moment satisfied the need for consideration and attracted the agreed terms. For myself, and with due respect to those who find comfort in them, I find the descriptions "unilateral and bilateral" or "mutual" unhelpful in the resolution of this case. Indeed, the use of them seems to assume that they are mutually exclusive terms and together cover all are mutually exclusive terms and together cover all possibilities. But I do not think they do. Indeed, this bill of lading, as I read it, indicates in my opinion that they do not. As I see it, we have here an arrangement, a compact with agreed conditions to attend the performance of certain acts, which are not promised to be done. True enough that, until such performance, the consensus has nothing upon which to operate. But that is its essential characteristic, to provide an agreed consequence to future action should that action take place: to attach conditions to a relationship arising from conduct. If one desires to use the terms, it could be said that the arrangement is mutual: it is bilateral: to it there are two parties both agreeing to the terms of the intended consequence, on the one hand the consignor and on the other the stevedore acting through its authorized agent, the carrier. The performance of the contemplated act both supplies the occasion for those conditions to operate and the consideration which makes the arrangement contractual. The document containing the basic terms and conditions for stevedoring at Sydney to which I earlier referred is another instance of an arrangement made between parties to regulate their relationship in the event that one of them in fact became the stevedore of the other's ship. Neither promised the other anything: the ship did not engage to employ the stevedore or the stevedore to discharge the ship and stevedore its cargo. (at p244)