Although there has been diversity of opinion regarding the nature of Post Office revenue, there has been remarkable unanimity as to the propriety of raising a net revenue for the State on the service for the transmission of letters. In the days of high rates and relatively high revenue it was not challenged.[752] Sir Rowland Hill's reform took away any sort of feeling that the revenue obtained from the Post Office lay as a burdensome tax, but the amount of surplus revenue was still so considerable that it could fairly be regarded as containing an element of tax.[753] It has, moreover, steadily increased, and its existence been made the justification for claims for further reductions of rate.[754] The use of the Post Office for the purpose of taxation, that is, the refusal to give away in improvements of service, or by reduction of rates, the net surplus of revenue, is accepted by economists as justifiable[755] and the public acquiesces. The surplus is obtained with the minimum of sacrifice on the part of those who pay, and it would be difficult to discover a tax in substitution which would fall as lightly. Apart from the fact that rates higher than would be necessary for defraying the actual cost of the service must of necessity operate to some extent to the disadvantage of trade and commerce,[756] there is little to urge against the raising of revenue from the Post Office, especially as it is obtained from such popular charges as a penny and a halfpenny, which are well within the reach of the poorest. Payment is, moreover, in a large degree voluntary. The number of letters which a private individual must write, and cannot avoid writing, in the course of a year is very small. If he has anything of importance to write, he does not think a penny an excessive sum to pay for its transmission. If he has nothing to write, there is no law to compel him to pay postage. The profits of postage are, however, large; and the existence of the State monopoly, and the essentially fiscal character of the rates charged, should not be overlooked.[757] * * * * * VII. GRAPHS [Illustration: UNITED KINGDOM _INLAND RATES OF POSTAGE 1914, AND NEW RATES INTRODUCED 1^ST NOVEMBER 1915._] [Illustration: UNITED KINGDOM (1725-1851)] [Illustration: UNITED KINGDOM (1820-1914)] [Illustration: UNITED KINGDOM] [Illustration: UNITED KINGDOM _MOVEMENT OF STATISTICS OF POSTAL TRAFFIC 1870-1914_] [Illustration: UNITED KINGDOM _NUMBER OF LETTERS DELIVERED PER HEAD OF POPULATION (1854-1914_)] APPENDIX B DOCUMENTS AND EXTRACTS ILLUSTRATING ASPECTS OF POSTAL HISTORY (i) ANCIENT POSTS. _Persia_ (_circa_ B. C. 500).