In Canada the rate of postage on first-class matter is 2 cents per ounce or fraction of an ounce, except on postcards, for which the rate is 1 cent, and local or "drop" letters, on which the rate is also 1 cent (_supra_, p. 255). On second-class matter the rate is 1/4 cent a pound when posted by publishers to subscribers, otherwise 1 cent for each 4 ounces or fraction thereof. On general third-class matter (including samples) the rate is 1 cent for each 2 ounces or fraction thereof: a special rate of 2 cents for the first 4 ounces and 1 cent for each additional 4 ounces or fraction thereof is given for seeds, cuttings, roots, bedding-plants, scions, or grafts. The object of this privilege is evident. The rate on fourth-class matter is 1 cent for each ounce or fraction thereof. These rates have not been calculated with reference to the cost of the service in each case. Classification was introduced in the United States Postal Service as far back as 1863, but until 1906 no attempt had been made to apportion the total cost between the various classes. The estimate then made showed that the second-class mail involved a heavy loss, probably equal to six or seven times the rate of postage.[529] * * * * * V LOCAL RATES UNITED KINGDOM Local postal services, providing for the delivery of local letters at reduced rates of postage, existed in the United Kingdom over a long period. The first service was established in London in 1680. Up to this time the business of the Post Office had been restricted to the transmission of letters between the post towns, and no rate of postage existed except in respect of letters sent over appreciable distances.[530] The idea of a local service seems to have originated with a Mr. Robert Murray; but the London local post was actually established by William Dockwra, "a merchant, a Native and Citizen of London, formerly one of his Majesty's Sub-Searchers in the Custom House of London." Other citizens of London were concerned in the undertaking, which was established without reference to the authorities of the Post Office, and was intended to be purely a private commercial undertaking.[531] Under Dockwra's scheme London, with Westminster and the suburbs, was divided into seven districts or "precincts," in each of which was a "sorting house." Scattered over the City and suburbs were from four hundred to five hundred receiving houses for the taking-in of letters. Messengers called at the houses for letters every hour. Letters and parcels not exceeding 1 pound in weight or £10 in value were accepted and conveyed at the uniform charge of 1d., payable in advance.