« PreviousContinue »
horses tiring or becoming ill under their work be carefully examined into, it will often be found that it is not their muscles or limbs that fail them, but their wind; and therefore it is particularly important to have a road so circumstanced, that a horse may, on all parts of it, have the benefit of a free current of air.
It may sometimes be proper to make a road deviate from a straight line, in order to go through a town; but the expediency of such a deviation must wholly depend on the general object of the road. If it be intended to expedite the communication between two places of great trade, or otherwise of great importance, then nothing can be more erroneous than allowing the general line of road to be taken from the best and shortest direction in order to pass through a town. It is for this reason that little attention should be paid to the opposition of inhabitants of towns to new roads, when to be made for the advantage of the general communication of distant and important parts of the kingdom.
Some persons may be disposed to say, that a road should be made to deviate from a direct line in order to avoid crossing parks, or demesnes, and, to a certain extent, no doubt it should; but this motive ought not to be allowed to have much weight, where the consequence is
to add very materially to its length. It should be recollected, that, by judicious management, a road may be made, if not ornamental, at least not injurious or detrimental to the appearance or privacy of a park, by carrying it in hollow ground, or between sunk fences.
The principle of protection of private property is itself founded on the same principle that should govern the line of a road, and that principle is the public advantage; and therefore it should be laid down and acted upon as a general maxim, that private considerations ought in all cases to be made to give way, with respect to roads, to public convenience. "For let it be remembered that society is formed for the mutual and general benefit of the whole; and it would be a very unjust measure to incommode the whole merely for the convenience, or perhaps the gratifying of the whim or caprice of an individual."*
After fixing upon a general line of a road with respect to its direction, the precise line of it must be marked out, according to the smaller acclivities and declivities of the natural surface of the country it is to pass over. As moderate curves add but little to the length of a road, they will not be objectionable, if they assist the inclinations and save expense.
Bateman on Roads, p. 122.
PRINCIPLES OF ROAD-MAKING.
In this chapter, the general principles will be examined, according to which the art of constructing a road should be practised; and the particular methods will be explained, by which various kinds of roads should be constructed. The art of road-making, like every other art, must essentially depend for its being successfully conducted on its being exercised in conformity with certain general principles, and the justness of these principles should be rendered so clear and self-evident as not to admit of any controversy.*
"A knowledge of true principles is indispensably necessary in every art, and in that of making roads as much as in any other. Some preliminary species of knowledge is very necessary in every superintendant or surveyor. A beaten track of knowledge is but a bad guide in cases which very frequently occur, when, amongst several ways, the best is to be preferred."-M. S. Haldimand, Secretary to the Bailiwick of
One of the most important and most obviously correct of these principles, is that which requires a road to be made of such a degree of substance, as shall be in a due proportion to the weight and number of the carriages that are to travel over it.
But although this is, in appearance, a selfevident proposition, in practice no rule is so universally violated.
Let the construction of any turnpike road, of one commonly considered as among the best, be properly examined; that is, let measure be taken of the quantity of hard-road materials that compose the crust of the road over the subsoil, and it will almost universally be found that it consists of only from three to five, or six inches in thickness.* Whereas, instead of this weak and defective system of road
* See Mr. Telford's first Annual Report on the Holyhead Road, in 1823, where tables are given showing the result of trials made along the whole line of road from London to Shrewsbury of the depth of materials, by sinking holes into the road at short intervals. The average depth of materials was as follows on some of the trusts:
Whetstone Trust 4 inches.
making, it may be laid down as a general rule, that on every main road where numerous heavy waggons and heavy loaded stage coaches are constantly travelling, the proper degree of strength which such a road ought to have cannot be obtained except by forming a regular foundation constructed with large stones, set as a rough pavement, with a coating of at least six inches of broken stone of the hardest kind laid upon it; and further, that in all cases where the subsoil is elastic, it is necessary, before the foundation is laid on, that this elastic subsoil should be rendered non-elastic by every sort of contrivance; such, amongst others, for instance, as perfect drainage, and laying a high embankment of earth upon the elastic soil, to compress it.
The right understanding of this principle of road-making, which requires roads to be constructed with four or five times a greater body or depth of materials than is commonly given to them, is of such great importance, that it is requisite to illustrate and establish the grounds on which it rests; first, by reference to the laws of science concerning moving bodies, and secondly, by reference to experiments, which accurately prove the force of traction on different kinds of roads.