Its importance arose thus. To estimate the increase in correspondence required for my purpose, it was obviously necessary to know the amount of loss per letter involved in the proposed reduction of postage; in other words, the difference between the proposed rate and the average of the rates actually paid, which average had therefore to be arrived at. This I placed at sixpence farthing, the Post Office authorities at a shilling. Actual knowledge, however, did not exist, and each party had resorted to calculation, dividing the gross revenue by the supposed number of letters. That number I then estimated at eighty-eight millions,[158] the Post Office authoritatively declared it to be only forty-two or forty-three millions;[159] hence the difference in our results as to the actual average of postage, and consequently as to the required increase in correspondence, which I fixed at five-and-a-quarter-fold, the Post Office at twelve-fold. Of course it would have been easy for the Post Office authorities to correct their calculation, before the appointment of the committee, by an actual counting of letters; nor have I ever learned why this corrective was not applied. I had indeed to thank the department for obligingly supplying me with a fact essential to my calculation, viz., the number of letters, general and local, delivered in London in one week; and had this fact been dealt with by the Post Office as I myself dealt with it (a process, however, pronounced incorrect by the office),[160] the same result, or nearly so, must have been arrived at by both parties; but, as already intimated, had the counting process been applied to the whole country, as was afterwards done on the requisition of the committee, the whole question would have been settled at once.