Under the old system the rates of postage were for the most part nominal, that is to say, no attempt was made to adjust the rates to the actual cost of providing the service, although in allocating between the different States the total amount of postage, a rough assignment as between land and sea services was made.[694] The usual 6d. rate for single letters to and from the various colonies illustrates this. The actual cost of service must have varied greatly. In the case of the colonies other considerations, mainly political, were allowed to enter. In the case of foreign countries the whole arrangements for the interchange of correspondence were based on such agreements as could be arrived at, and the actual rates of postage were determined in that way.[695] The chief difficulties in negotiations occurred in connection with the division between the contracting parties of the postage collected. The packet service was often conducted at a loss, and the rates of postage on foreign and colonial letters were not, in general, fixed with a view to rendering the service self-supporting, although this was regarded as a condition to be aimed at.[696] By the Consolidating Acts of 1837 (1 Vict., cap. 34 & 36) the Postmaster-General was empowered to require the masters of outward-bound vessels to accept mails, and to deliver them without delay on arrival at the port of destination, under penalty of £200. The general character of the foreign packet service was entirely changed by the introduction of steam propulsion, which greatly shortened the length of voyages and introduced a degree of punctuality and regularity hitherto undreamt of. Until this time the Post Office had, for many long-distance services, relied on its own packets; i.e. packets sailing under contract expressly for the conveyance of the mails and under the control of the Post Office. In 1818, with the introduction of steam vessels, this policy was changed and that of Crown ownership of the packets adopted. This method was found extremely costly, and the Commissioners of Revenue Inquiry reported emphatically against it.[697]