The names of Richard Edgeworth, F.R.S., and John M’Adam, are well known in connection with roads—Mr. Edgeworth writing in 1813, Mr. M’Adam in 1816. Both men had, it appears, given attention to the subject before the end of the last century. Mr. Edgeworth says:—“I have visited England, and have found, on a journey of many hundred miles, scarcely twenty miles of well-made road. In many parts of the country, and especially near London, the roads are in a shameful condition, and the pavement of London is utterly unworthy of a great metropolis.”
Mr. M’Adam had been much struck by the entire want of system that existed in the management of roads at that early period, and strongly urged the necessity of a reform in road management as a pre-requisite to road improvement. He urged the laying out of the roads of the country into separate districts, with the appointment of road trustees to manage them—the appointment of chief and assistant road-surveyors to superintend them—and a new system of accounting and finance,—all under statutory regulations; and it cannot be doubted that in all this Mr. M’Adam did good service, which was recognised in 1823 by Parliament voting a sum of money to him for having introduced a system of “repairing, making, and managing turnpike roads and highways, from which the public have derived most important and valuable advantages.”
It appears to me, however, that all that is said in Mr. M’Adam’s first edition of his book on road-making, in 1816, is of so general and vague a nature that he cannot have known of Mr. Stevenson’s work at an early part of the century.
From Mr. Stevenson’s reports it appears that he was much employed in road-engineering in the counties of Edinburgh, Stirling, Linlithgow, Perth, and, indeed, generally throughout Scotland, extending as far north as Orkney and Shetland; and without raising any claim to priority of design, I give the following extracts from reports made by him in 1812 and 1813, after he must have had at least several years’ previous study and practice of road-making, which I think clearly show that Mr. Stevenson, if not the original, was at least an independent inventor of the system of road-making which is termed “macadamising.”
In a report to “The Honourable the Committee of the Trustees for the Highways and Roads within the county of Edinburgh,” dated 1812, he says:—
“It may not, however, be considered altogether out of place to notice that the pieces of stone composing the road-metal in common use are perhaps one-half, and in some instances two-thirds, larger than is suitable for the best condition of a road. Road-metal of a small size consolidates by the pressure of weighty carriages, when stones of the size commonly used are either pounded under the wheel or forced into the road. It would therefore be desirable, as an experiment upon the large scale, to lay one of the most public roads in the county to the extent of one fourth of a mile with stones broken much smaller than is customary.
“In some instances, especially within a few miles of Edinburgh, it might be worthy of consideration by the Honourable Trustees of this county how far cast-iron cart-tracks might not be advantageously laid upon the roads. Some years since the reporter got two or three yards’ length of these iron tracks brought from the Shotts ironworks, where they have been used for years with much advantage, and, it is believed, with economy. These cart-tracks would cost about £2000 per statute mile, including upholding by the iron-founder for one year. It would be interesting to have also a trial made of these in some very public road, although it were only to the extent of two or three hundred yards.”
Again, in a report to “The Honourable the Trustees for the Bridge of Marykirk,” also in 1812, he says:—
“In the annexed specification of road-makers’ work, the reporter makes some alterations upon the common and ordinary method of breaking and laying road materials, by reducing the road-metal to a more uniform size, and using a course of gravel, if it can be procured, or even of clean sharp sand, as a bottoming for the broken stones. A road composed of stones of various sizes can never be brought into that smooth and uniform surface, which is so much to be desired, for the moment the pressure is brought upon one of these out-sized stones, it must either be crushed under the wheel or be forced by repeated attacks into the road, and thereby it displaces the surrounding stones, and in either case admission is given to the surface-water; a pit is immediately formed, and every succeeding wheel widens the breach, until the road is rendered impassable. To counteract this very common effect, arising chiefly from the very vague manner of defining the dimensions of road-metal by bulk or even by weight, the reporter provides that the Trustees shall furnish a riddle or screen, the meshes or openings of which are to be of such dimensions that a stone measuring more than one inch and a half upon any of its sides cannot pass through it.”
Fig. 12.—Section of one half of Roadway.