Of the various mechanical contrivances submitted to the investigation of the commissioners, was one under the foregoing denomination; wherein the running wheels of the carriages are made capable of sliding along the axles when required, permitting the wheels to approach nearer to, or separate further from each other, and thus be applicable to both gauges. By detaching the wheels from one fixed point, then pushing the carriage along converging, or diverging rails, until the wheels were brought to fit the change of gauge, and screwing the wheels to the axles again at another fixed point, the required alteration would apparently be easily managed, but it is nevertheless liable to serious objections. It is well known that a very slight degree of unsteadiness of the wheels of a railway carriage upon the axles, renders it liable to run off the rails. The safety of an entire train might thus be endangered, by one case of neglect in refastening the wheels of a carriage; and when it is considered that the attendants would have to adjust a great many carriages in succession, sometimes as many as a hundred in one goods train; that the adjustments have also to be made hurriedly; occasionally in the worst of weather, and at night; besides the attention required for loading or unloading of goods; altogether, it would become so severe and anxious a duty to the attendants that it would be scarcely possible to avoid the occurrence of very serious accidents from oversight, neglect, or forgetfulness.

But the danger attending the plan is not the only objection. On the ground of expense, the introduction of the plan is inadmissible.