1st. The difficulty of entirely protecting the fast trains from interfering with or coming into collision with the slow trains.

2d. The difficulty of seeing signals, especially in foggy weather in time to enable the engine drivers to stop the fast trains.

4th. The relative Economy of the different gauges. - In the first construction of a railway, the narrower the gauge, the smaller will be the cost of the works. This applies to tunnels, bridges, viaducts, embankments, cuttings, sheds, workshops, turntables, transverse sleepers, and ballast, and the purchase of land; but it does not affect the rails, fences, drains, and station-houses. The exact difference, however, must depend in a great degree upon local circumstances.

As to the cost of the maintenance of way, that of the broad gauge must be rather the greater of the two.

The cost of the engines and carrying stock is generally more expensive on the broad than on the narrow gauge. But it is asserted by the advocates of the broad gauge, that as the engines will draw greater loads, the work can be done at a less charge per ton; and that a compensation is thus obtained for the increased outlay. How far this is practically the case is the next subject for inquiry.

The average weight of a passenger train on the Great Western railway (independent of the engine and tender, which weigh 33 tons) appears to be 67 tons; and the average number of passengers per train for the half-year ending the 30th of June, 1845, is only 47.2, whose weight, including their luggage, may be estimated at about 5 tons.

Mr. Gooch, the locomotive superintendent on the Great Western, estimates each carriage and its passengers on the broad gauge to weigh about 9 1/2 tons, and therefore there would be seven carriages to make up the 67 tons above specified. The most commodious carriages on the narrow gauge lines, such as those on the South Western, weigh less than 5 tons; seven such carriages would therefore weigh about 34 tons, and being capable of containing 126 first-class passengers, weighing, with their luggage, 12 1/2 tons, the total load would be only 46 1/2 tons. Now we find, that even with a traffic as large as that of the London and Birmingham railway, the average per train would only be 84.9 passengers, weighing about 8 tons; so that, under the supposition of a traffic of this extent, the load of the seven narrow gauge carriages so occupied would only be 42 tons.

But Mr. Gooch estimates, from his own experiments, the relative powers of traction of the broad gauge engines, and of the narrow gauge engines, of the South Western railway, when working at the same speed, as 2,067 to 1,398, or as 67 per cent., and the load of the broad gauge in tons, to 45 tons, which would be the corresponding load for the narrow gauge; so that the narrow gauge engine has more power over the 42 tons it would have to draw, than the broad gauge has over its average load of 67 tons, both exclusive of the weight of the engine and tender; the narrow gauge carriages in this supposition being supposed to contain 84.9 passengers, and the broad gauge only 47 . 2.

It is obvious, from the foregoing statement, that the narrow gauge engine of the class we have been considering, has more power over the seven narrow gauge carriages, and a load of 126 passengers, than the broad gauge engine has over the seven broad gauge carriages, and the load of the same number of passengers; and that, therefore, if the Great Western had been a narrow instead of a broad gauge line, the South Western engines would have had the same command over the existing passenger traffic of the Great Western, as its own engines now have with the present construction of that railway.

The commissioners conclude their investigation of this question, by determining that the work would be performed at about the same expense for locomotive power.

Mr. Gooch has asserted that the Great Western company work their passenger trains at half the expense per ton, at which the London and Birmingham company work their passenger trains. The fact is, however, that Mr. Gooch's calculations refer to the gross, and not to the net loads; and, therefore, the comparison is not applicable, so far as regards the profits of these companies, and affords no proof of economy in working the passenger traffic on the Great Western system.

In the case of "goods traffic," the circumstances are not the same; railway conveyance for merchandise seems only to be required a few times in each day, and the trains are generally large. The "through" waggons have for the most part a full load, and the disproportion between the gross and nett weight is consequently much less than in the passenger trains; still, however, it frequently happens on the London and Birmingham railway, that waggons are forwarded to a considerable distance to "road side stations" containing not more than a ton of goods; which must happen on any long line of railway. The same occurs also in waggons coming in from branches along the trunk line, and in all such cases, the heavy large waggon of the broad gauge must be disadvantageous; but although the evil is not so great with goods waggons of the broad gauge as with their passenger carriages; still the loss by dead weight is greater with these than by the smaller waggons, and we do not perceive any advantage in the broad gauge to counterbalance it; for where speed is not an object, we believe that engines of nearly the same tractive power are to be found on many narrow gauge lines, as those in use on the broad gauge.

Thus far the question has been considered with reference to the railways as they now exist, and composed in a great measure of trunk lines of considerable traffic; but the railways to be made in future will in some degree be branches, or lines, in districts having less traffic than is to be provided for in the existing railways; and hence, if for the greater trunk lines a superiority were due to the broad gauge system, that superiority would be less for lines yet to be constructed, of a smaller amount of traffic; and necessarily, if the preference were given to the narrow gauge for the existing lines, that system would be still more entitled to the preference for the railways of smaller traffic to which we look forward.