The commissioners state that this plan has been repeatedly tried, and the experience is, that it has barely succeeded in a temporary trial by one engineer who had the entire control; but that it has in most instances failed, owing to the deterioration produced by the shifting of the mineral conveyed; though no expense was spared in the erection of proper machinery for effecting the transference of the loose boxes; and these failures occurred in a traffic which is comparatively regular, namely, that of coal. In traffic of a more varied character, the liability to failure would be much increased.
Expedient for a Combination of two gauges on one line, by placing one or two intermediate rails between those on the broad gauge, so as to enable the use of theengines and carriages of both gauges, would also be productive of many difficulties, and the expense be enormous. If two rails were placed between those of the broad gauge, so as to form a narrow gauge track, the carriages of each gauge might travel together, without any alteration of their buffers, as the distance of these from the centre is precisely the same in both. The cost of such an alteration has been estimated at even more than entire change of gauge, including engines, and carrying stock. The complication which it would introduce at the crossings would be attended with increased danger, or a loss of speed. It would also be difficult to pack and adjust such rails properly. In the case of a single rail being inserted at 4ft. 8 1/2in. distance from one of those on the broad gauge, the difficulties just mentioned would be in a certain degree lessened, but it would introduce another, which seems to have escaped the attention of the commissioners; namely, that of causing the double traffic upon only one of the original broad gauge rails, and the single traffic on the other broad gauge rail.
If we consider the enormous difference between the operating forces on the rails in a double train, the effect of the concussions of such an unbalanced force would be rapidly destructive of far more stable substructures than have hitherto been found necessary. It would at least render it necessary to make the single rail which sustains the double traffic much stiffer, and the supports more solid; otherwise a disruption would speedily ensue, and it would always be dangerous to travel upon. Besides, the narrow gauge traffic on the broad gauge line would probably continually increase, and thereby increase the disparity of the resisting powers of each rail, and never attain that uniformity of vibration and resistance, that appears to be essential to the stability of the structure.
The commissioners lay it down as the first principle, that intercommunication of railways throughout the country ought, if possible, to be secured. If, to obtain the last-mentioned object, it should be necessary to alter or make a change in any existing railways, they think that it may be left as a matter of ulterior consideration for the legislature, whether in these limited instances the combination of gauges may not be allowed.
After giving to all the plans submitted to them, the most mature consideration, the commissioners came to the conclusion, that none of them were adapted to effect an adequate remedy for the inconveniences incident to a break of gauge; and hence they entered upon the following