But the increase of revenue was so small that some of these provisions remained for many years inoperative. The increase of rate was found burdensome. Merchants resorted to every available means of avoiding the additional expense.[45] A large clandestine traffic in letters grew up. The very postboys were found carrying letters outside the mail for what fees they could obtain. In 1710 the net revenue had been £66,822. In 1721 it was £99,784, an increase of £32,962. After the deduction, therefore, of the £700 a week (or £36,400 a year), the payment of which had preference over all other payments chargeable on the Post Office revenue, excepting only the expenses of management, the actual net revenue of the Post Office available for the purposes prescribed by the Act was in 1721, £63,384, or less than the revenue of 1710 by £3,438. The Act provided that one-third of the surplus of the yield of postage over and above the sum of £147,861 (£111,461 plus the £700 a week) should be at the disposal of Parliament for the use of the public; but although the gross revenue had exceeded that sum, there was no surplus for the use of the public, the explanation being that the sum mentioned in the Act, viz. £111,461, was the amount of gross revenue, which could only serve as a basis provided the cost of management remained stationary. As a matter of fact, the cost so greatly increased that the net revenue was not sufficient to provide the sum of £700 a week and also a revenue equal to that obtained before 1711. As Mr. Joyce has pointed out, the Treasury had confounded gross and net revenue.[46] The essentially fiscal character of the rates of 1711 is evidenced by a provision of the Act that from and after the 1st June 1743 the rates charged under the previous Acts were to be restored.[47] But after 1743, although they were without legal sanction, the rates of 1711 continued in operation, and by an Act of 1763 they were made perpetual.[48]