“With regard to the line of draught, or longitudinal section of a railway, it may be stated as one of its great advantages that it is more easily accommodated to the irregularities of the ground through which it has to pass than a navigable canal; and even where the ground is so irregular as not to admit of a uniformly level track, or an inclined plane, there are several simple methods which may be resorted to for lifting the wagons from one level to another, so as to produce similar effects with lockage on a canal. In so far, however, as the present design of the Edinburgh Railway has been carried by actual survey, neither of these plans will be found necessary upon the main lines. Even on the descending line, the fall is so extremely gentle that the horses in returning may be loaded with four or five tons. But the proposed mode of lockage may with propriety be introduced on the several offset branches, such as those from Leith to the main line, and from Monkton Hall and the Cowpits to Dalkeith, and to the southern parts of the county, on which a trade may be expected to be carried both to and from the main line.
“Where the load or trade is all in one direction, it is a maxim in _practice_, that the fall should be so apportioned to the rise, that the work may be equal _down_ with the load, and _up_ with the empty wagons. But where there is to be a trade both ways, it is obviously much to be desired that a level in all such cases should be obtained. This, in the Edinburgh Railway, has been found from the declining aspect of the country towards the sea; but as there will be less return trade on this railway in merchandise and manure, etc., to the eastward, than the coal and building materials, etc., carried to the city, it becomes a question of policy how far it may be proper, in this instance, to adopt the level line at a great additional expense.
“By the level line to Edinburgh the branch to Leith becomes also somewhat more lengthened than by the descending line, which, instead of preserving the level, is always falling, or approaching towards Leith. The reporter, as before noticed, has various modes in view, by which the branch to Leith may be made of a very easy line of draught, or be thrown into a succession of levels, by a species of lockage or stepping. Where sudden acclivities occur on the line of a railway they are generally overcome by an inclined plane, of greater or less extent, according to the particular rise, and on this the loaded wagons are brought up by a steam-engine. But to render railways applicable to all situations, it seems to be necessary that the overcoming of such obstacles should be within the reach or power of the driver and his horse; by working a kind of _gin_ connected with an inclined plane, or by lifting the loaded wagons perpendicularly, which may in various ways be accomplished by the aid of pulleys, by the common lever, or the revolution of a wheel.