I had also to deal with the question of prepayment, on which difficulties had been raised both in the office and by some persons without; the former taking alarm lest its establishment, however attained, should greatly diminish the amount of correspondence, and the latter objecting that it would enable the clerks in the Post Office to become possessed of information relative to parties corresponding which might be used for the commercial injury of one or other, and also pointing out that servants or others intrusted with money for the payment of postage might be tempted to keep this for their own use, destroying the letters to conceal their dishonesty. While giving various reasons, which I need not repeat, for declining to share in the alarm of the Post Office, I suggested, as a means of obviating the other difficulties, the use of stamped covers, a device which, as I have already mentioned,[128] had been originally recommended, not, indeed, for letters, but for newspapers, by Mr. Charles Knight; and I take occasion to remark that the mention of this expedient, as applied to letters, occurred for the first time in this supplementary paper. I pointed out at the same time that, to whatever extent the covers might be used, to that extent, or nearly so, the revenue would be collected in large sums instead of small, a change obviously tending to the simplification of accounts in the department concerned. I submitted at the same time that mode of gradual introduction of my plan which appeared almost immediately afterwards in the second edition of my pamphlet; and, as time would be required for the preliminary arrangements necessarily extending over the whole country, I suggested its experimental application, in the meantime, to the local correspondence of the London District, containing, as I pointed out, one-twelfth part of the whole population of the United Kingdom.