While Mackenzie was in England, Joseph Hume secured the production of a number of documents relating to the Canadian post office, which the legislatures in Canada had tried in vain to obtain from Stayner. Among these was a statement showing the amount paid by the several newspaper publishers for the distribution of their papers by the post office. On looking over the list Mackenzie was surprised at the very moderate amounts paid by publishers of some of the most widely-circulated papers. _The Montreal Gazette_, for instance, distributed nearly two thousand copies by post, but paid postage on only two hundred and fifty copies. Mackenzie made some further inquiries, and found that all sorts of irregularities prevailed, which Stayner in the weakness of his position was fain to connive at. The publisher of one paper in Kingston told Mackenzie that he entered seventy-five copies as sent by post, while mailing four hundred copies; another reported sixty copies and sent three hundred. A third publisher, who objected to paying the usual charge of four shillings per copy per annum, was let off with two shillings and sixpence per copy; while a fourth publisher paid no postage at all for several years. Until that time Mackenzie had been paying the regular charges for all copies of his newspaper--_The Colonial Advocate_--which he sent by mail. But he determined to be no longer the victim of such barefaced discrimination, and he accordingly began to enter for postage only a part of the total issue distributed through the mails. In order that he might not be open to a charge of dishonesty, and perhaps also to help in the exposure of a vicious system, Mackenzie told the postmaster at Toronto what he was doing, and at the same time published the facts in his newspaper. This, of course, could not be tolerated by Stayner, and he demanded from Mackenzie the full postage on all his papers sent through the mails. Mackenzie refused to pay, but declared that if Stayner would allow the case to go before a jury in Toronto, Stayner might employ all the counsel in the colony to support his demand, and if the jury could be persuaded to render a verdict against him, he pledged himself to pay the demand and all expenses. The offer was, of course, declined and the claim was dropped. In the course of a long examination, Stayner was taken over all the points in controversy between the postmaster general and the Canadian provinces. Dr. O'Callaghan,[246] who soon afterwards acquired notoriety as a leader in the rebellion, was chairman of the committee. He and his associates in the inquiry had sat on several earlier committees and were well versed in the points at issue.