" The pitching or paving the bottom of a road is a subject which has often been discussed, and though generally approved of by scientific men, has met with sonic decided opponents. On the old part of the Shrewsbury and Holy head road, which extends from Gobowen to III swestry, as well as in some other places, the foundation of the road had been paved, but in an irregular and pro miscuous manner, some of the stones standing near a foot above others, and in some places holes were left without any stones; upon this a coat of gravel had been laid, and necessarily of very unequal thickness, some of the points of the stones being scarcely covered. This road having afterwards been much neglected, the upper gravel, where thin, was worn quite away, or else forced from its bed by being in so thin a coat that it could not bind, and the road's surface was thereby made a continued succession of hard lumps and hollows, with water standing in every hole after a shower, and no means of getting off but by soaking through the road. Any stranger, on passing over such a road, would condemn the principle on which it was made. But here seems to be the great error,—that the principle is condemned, instead of the abuse of it. When the paving is put down carefully by hand, of equal or regular height, with no large smooth-faced stones for the upper stratum to elide upon, and the whole pinned so that no stone can move, I have no hesita tion in saying that in many cases it is highly beneficial, and in none detrimen tal. Whenever the natural soil is clay, or retentive of water, the pavement acts as an under-drain to carry off any water that may pass through the surface of the road. The component stones of thepavement having broader bases to stand upon than those that are broken small, are not so liable to be pressed into the earth below, particularly where the soil is soft. The expense of setting this pavement is less than one-fourth of that of breaking an equal depth of stones to the size generally used for upper coating; and therefore, in point of economy, it has also a material advantage. Mr. Telford in all cases recom mends this mode of paving ; and the opinion of a man of such experience can not be treated slightly. He has made more miles of road than any engineer in the kingdom; and having myself studied for nearly fifteen years in his school, and made a considerable extent of road under Ins direction, I may venture to say that his practice is not unsupported by experience. I should not have said so much on this subject, but from the circumstance of other road improvers having asserted that paving was useless ; and I think that assertions on one side Should be met with firmness on the other, whenever an important prin ciple is attacked, the correctness of which can be established by reasoning and by facts." We have endeavoured, by the extracts we have thus given, to place before our readers the comparative merits of a firm, or of an elastic substratum ; for ourselves we confess we are disciples of Mr. Telford's school ; and to believe with Mr. Wingrove, whose practical experience was unquestionable, " that, with respect to these opinions on iroa&making, nothing but the complete ignorance of the public, upon all matters concerning road-making, could ever have suffered rules, so contrary to every thing like sound principles, to have had a single moment's favourable consideration." With this remark we dis miss this part of the subject, which we have been induced to treat at greater length than we originally intended, by our anxiety to place beyond dispute the correctness of the principles on which all our subsequent directions are founded.
Drainage.—In properly conducting this part of the business of road-making, great care is necessary. The utmost judgment of the skilful surveyor will be called into action to enable him to make the beat use of the natural facilities of the country, and to overcome the obstructions that he will sometimes meet with. In passing over fiat land, open main drains, cut on the field side of the fences, must communicate with the natural watercourses of the country ; they should be three feet deep below the level of the bed of the road, one foot wide at bottom, and five feet wide at top. If springs rise in the site of the road, or in the slopes of deep cuttings, stone or tile drams should be made into them. In cutting, small drains, technically called mitre drains, should be formed ; the angle, depending on the inclination of the road, should not exceed one inch in 100. They should be 9 inches wide at bottom, 12 inches at top, and 10 inches
deep. According to the inclinations of a road, and the form and wetness of the country, cross-drains of good masonry should be built under the road, having their extremities carried under the road fences. One of these should be built wherever water would lie ; and when the road passes along the slope of a hill, great numbers are necessary to carry off the water that collects in the channel of the road on the side next the high ground. Various descriptions of drains are made in every situation where necessary, and the preservation of the surface of the road secured by giving it a proper convexity in its cross section, as shown in the annexed section, designed for the regulation of the surfaces and wastes between the fences of the Holyhead Road.
The proper convex form is particularly essential on hills, in order that the water may have a tendency to fall from the centre to the sides. The side channels, and all the road drains should be repaired at the approach and at the end of the winter, and daily attention given to their being free from obstruction. If roads, by a proper system of drainage, be kept dry, they will be maintained in a good state, and at proportionally less expense.
Cuitings.—When it is necessary to make a deep cutting through a hill, the slopes of the banks should never be leas, except in passing through gone than two feet horizontal to one foot perpendicular; for though several kinds of earth will stand at steeper inclinations, a slope of two to one is necessary for admitting the sun and wind to reach the road. The whole of the green sod and fertile soil on the surface of the land cut through, should be carefully collected and reserved, in order to be laid on the slopes immediately after they are formed. If enough of these cannot be procured, the slopes should be strewed with mould, and sown with hay-seeds. When stones can be got, the slopes should be sup ported by a wall raised two or three feet high, at the bottom of them. These walls prevent the earth from falling from the slopes into the side channels of the road, and add very much to the finished and workmanlike appearance of • road. It is sometimes advisable, particularly if an additional quantity of earth be wanted for an embankment, to make the slopes through the cuttings on the south side of a road of an inclination of three horizontal to one perpendicular, in girder to secure the great advantage of allowing the sun and wind to reach Mae freely the surface of the In districts of country where stones abound, expense in moving earth and purchasing land may be avoided, by building retaining walls, and filling between them with earth. In rocky and rugged countries, this is generally the beat way of obtaining the prescribed in clinations. In forming a road along the face of a precipice, a wall must. be built to support it. The difficulty of forming a road in such a place, is not so great as may be imagined, for the face of a precipice is seldom vertical, and if the inclination should be half a foot vertical to one foot horizoatal, this will admit of a retaining wall being built. By building such a wall, say 30 feet high, and cutting 10 feet at that height into the rock, and filling up the apace within the wall, a road of sufficient breadth will be obtained. In forming the bed for the road, material care should be taken, except where cutting into the surface is wholly unavoidable, in order to obtain the proper longitudinal incli nations, to elevate the bed with earth, two feet at least, above the natural surface of the adjoining ground : by following this course, the road will not be affected by water running under or soaking into it from the adjoining land. In arrang ing the inclinations, they should be obtained by embanking, where that is prac ticable, in preference to cutting. Almost all old roads across fiat and wet land are sunk below the adjacent fields : this has arisen from the continued wearing of them, and carrying away the mud. No improvement is more generally wanting, than new forming these roads, so as to raise their surfaces above the level of the adjoining land. This would greatly contribute to the hardness of them, to economy in keeping them in repair, and to enabling horses to work with the advantage of having sufficient air for respiration.