Imagens das páginas
PDF
ePub

fects of the roads will not be observed and acknowledged, and, consequently, will not be remedied. The following extract from the examination of Dr. Lardner, before the Committee already mentioned, contains the opinion, on this point, of a man of science, in every way qualified to explain correctly the business of road-making.

"Is it a matter requiring much science and skill to arrange a road with reference to these objects ?— It is quite evident it requires a very unusual combination of scientific and practical knowledge. It is obviously impracticable to make a road which would be theoretically perfect; and therefore there arises an extremely delicate inquiry as to the best possible compromise which can be made between all the inevitable imperfections, the existence of which we are forced to admit. A road, to be theoretically perfect, should be, first, perfectly straight; secondly, perfectly level; thirdly, perfectly smooth ; and, fourthly, perfectly hard. If it possessed all these qualities in absolute perfection, the consequence would be it would require no tractive power at all. An impulse given to a load at one end would carry it to the other by its inertia alone. This is the ideal limit to which it is the business of a road-maker to approximate as nearly as he can, all practical circumstances being considered.

"It would appear, that the construction of a road requires a considerable degree of science and practical skill on the part of those who undertake it ?—I do not know that I could suggest any one problem to be proposed to an engineer, that would require a greater exertion of scientific skill and practical knowledge, than laying out the construction of a road. Unfortunately the original laying out of a road is an employment that is rarely submitted to an engineer; he is generally controlled by circumstances. The early road-makers were almost always obliged to follow our old horse-paths in the country, in a very great degree. To lay out and design a road between two points, the surface of the country should, in the first instance, be accurately ascertained; the engineer should make himself as well acquainted with the undulations and the surface of the country as if he had passed his hand over every foot of it; and, even supposing he has a model of it before him, it becomes an extremely delicate and difficult problem to say what will be the best course to take for a line of road joining two points; he of course must encounter the undulations in such a manner as to adapt his cuttings to his embankments; that is, where he cuts through an eminence he must take care so to arrange the course of the road as that he shall have a hollow to fill up which will just employ the stuff he cuts out of the embankment; then the quality of the crust of the earth he must know, because it is not after he has begun to make his road that he is to discover the practical difficulties which stand in his way. In fact, it requires a considerable knowledge of geology; the stratification and the angles at which different soils will not only stand at the beginning, but the angles at which they will continue to stand, subject to all the actions of the weather.

"Then, in point of fact, it does not appear that the advantage of the science of engineering has been applied very extensively to the roads in this country ?—Most decidedly not.

"With reference to general improvements, and also with reference to new roads in this country, it seems to be your opinion that the assistance of engineers should be more generally called in?— Clearly so; recourse ought to be had to the very first scientific and practical skill of the country; it requires the first civil engineers that can be found.

"If any plan were attempted by the legislature for the improvement of the roads, is it your opinion that it ought to be conducted under the management of the most experienced engineer that this country possesses ?—I am quite decidedly of that opinion.

"The surveyors generally do not belong to the profession of engineers ?—No."

If the opinion of Dr. Lardner is a correct one, that the business of road-making requires a very unusual combination of scientific and practical knowledge, it is not difficult to understand why the roads are still so imperfect; for certainly those persons who have had the management of them have not possessed this knowledge.

The following is an extract from the examination of Mr. M'Niel before the same Committee:—" In your former answer, you said that you thought it would be of advantage if the trustees of the roads were assisted by civil engineering; I wish to know whether road-making ought not to be considered as a branch of the science or art of civil engineering ?— I am of opinion that the laying out a good line of road, in some parts of the country, is perhaps as difficult a subject as comes before an engineer; and it is quite impossible for country surveyors and land surveyors, who have not been accustomed to engineering pursuits, to run out a line of road with advantage to the public.

"Or short lines for improvements?—I know instances in which lines of road that are said to be improved are not so good as the old line of road.

"Now, in regard to the construction of a road, is it not necessary a person who undertakes to construct and make a new road should have that sort of education that makes him acquainted with the science of civil engineering ? — It is quite necessary, and that is shown in France to a very great extent; and I believe wherever roads are made here by civil engineers, they bear a very different character to the roads in other parts of the country; and also that there is a saving in the wear of materials on a well-constructed road, and well laid out road. If a line of road has not rates of acclivity greater than 1 in 40, there will be 20 per per cent, saving over one that rises 1 in 20; this is a fact not generally known, but it is quite certain; that is to say, a road that has acclivities of 1 in 20 will cost 18 or 20 per cent, more than the one that has acclivity of 1 in 40.

"As a matter of course, a civil engineer looks to the appearance his road has, as well as to the fitness to draw carriages; is it not always a rule with them to have it uniform as to breadth and shape ?—Yes; there are certain rules which an engineer would always adopt, that is, a certain uniform width and a certain curvature, a certain height of footway, and a certain width of waste and fences, according to the description of road he was to make.

"To acquire that degree of uniformity, is it not necessary to use instruments, and to have that sort of habitual method of managing works that can only be acquired by a regular education ? — I conceive so; I do not think a road can well be laid out, except by a professional person.

"Have you found it the practice to appoint engineers as surveyors of roads ? — No; I do not know an instance of it, except on the road between Shrewsbury and Holyhead, and there the effect is very apparent.

"What class of persons are they commonly ?— Generally farmers; in some instances they have been tradespeople.

"May not a great deal of what may be considered to be imperfect in the roads of this country be attributed to the want of having more assistance from the profession?—Yes; I think the fact I have stated, that a saving of 20 per cent, in repairing a road might be made in a very slight alteration of declivity in a road, will prove that principle, and also that there will be a saving when the road has the appearance of uniformity and neatness about it; for the men who put out the stone can see when it

« AnteriorContinuar »