As to the transmission of letters, Sir Rowland Hill first perceived the significance of the fact that with objects of light weight the cost of conveyance, even over great distances, is small, and in his scheme of reform he consciously applied this fact to the determination of the rate of letter postage. This consideration remains; and as regards the ordinary letters of business or private communication--the average weight of which is less than half an ounce--the principle of uniformity of rate irrespective of distance, which is now the characteristic of letter postage, is well founded. Of the whole expense of conducting the postal services, the expense of the actual conveyance of a letter from place to place is not only small as compared with the cost of the terminal services of collection and delivery, but is actually so small in amount that no monetary system provides a coin of sufficiently small value to make its collection a practical possibility. The uniform rate, by making practicable the system of prepayment of postage by means of adhesive labels, has, moreover, effected great economy in the working of the service, and its simplicity is a boon to the public, the more so as it has been possible to fit the common rate to a popular coin. A low uniform rate is, however, only made possible from the financial standpoint by the Post Office monopoly of the carriage of letters, although that monopoly is justified on other grounds. With a uniform rate, owing to the varying conditions under which the service is conducted in different districts, there is inevitably a variation in the amount of profit. In certain cases, the rate is actually unprofitable; and were private undertakings permitted to compete for the more profitable traffic, such as the local traffic in large centres of population, the profits of the Post Office would be reduced to vanishing-point.