Hill's pamphlet, "Post Office Reform: its Importance and Practicability", referred to above, was circulated privately in 1837. The report called for "low and uniform rates" according to weight, rather than distance. Hill's study reported his findings and those of Charles Babbage that most of the costs in the postal system were not for transport, but rather for laborious handling procedures at the origins and the destinations. Costs could be reduced dramatically if postage were prepaid by the sender, the prepayment to be proven by the use of prepaid letter sheets or adhesive stamps (adhesive stamps had long been used to show payment of taxes, on documents for example). Letter sheets were to be used because envelopes were not yet common; they were not yet mass-produced, and in an era when postage was calculated partly on the basis of the number of sheets of paper used, the same sheet of paper would be folded and serve for both the message and the address. In addition, Hill proposed to lower the postage rate to a penny per half ounce, without regard to distance. He first presented his proposal to the Government in 1837.