... to the question of taxing the correspondence of the thickly settled parts of the country for the purpose of raising means to defray the expense of sending mails to the new and distant parts of ... many of them the treasury is amply remunerated, and more, by the increased sale of the public lands, the increase of population, and the consequent increase of the revenue from the custom-house. ... charge on the general treasury, which has not been the case heretofore. The post-office tax was the only one in which the North and the East bore their share equally with the South and the West....