So confident was the reverend patentee that he wrote the following challenge: "I have no fear that either science or practice can effectually controvert the following remark: Supposing, in a stage-coach as at present, that the centre of gravity be four feet above the main axle, and the width on the ground the same in two cases, then the higher the wheels the greater will be the danger of an overturn from an equal cause. It is not so with me, for the higher the wheels the deeper may the luggage box be, so that the antidote follows the growth of the danger; and here, from the full conviction I have of its truth, I wish to offer the following opinion: Let seven or eight parts in ten of the total load be within the hind wheels, and let them be at least six feet high, on horizontal cylindric arms, by this disposition, compared against the present, more than one horse in forty would be saved or spared, for the goodness of the draught would come out even through the intricacy of the medium, the fore-carriage; but in many coaches the door at the middle of the side does not permit so advantageous a hind wheel, and that at the expense just mentioned." The invention was not accepted by the Postmaster-General, although it was, to some extent, admitted to combine a principle of safety with the celerity required in mail carriages. The cost, however, of such a change in the mail coaches would have been very heavy, which, no doubt, had a good deal to do with its rejection. The fact, however, is that these inventions were not wanted, clever as they might have been and effective where required. The mail coaches were not called upon to travel over "dangerous and side-long ground," but upon fairly good roads at the worst, for which the coaches, as then constructed, possessed quite sufficient stability, and the idle wheels, however great the security they would have imparted to heavily-loaded stage-coaches, were not required on the mails, where the sustaining power was so great in proportion to the comparatively light loads which they carried, that a broken axle was unknown among them, and it was impossible for a wheel to come off with Mr. Vidler's axle and boxes; and, of course, the idle wheels must have added to the weight. Although these patent-safety coaches were rejected by the Post-office, they did find favour in one or two quarters. One worked for some time between London and Stroudwater, and several were in use in Reading, as the following certificate will prove:--