By this time the question had, indeed, become acute. The prosperity of the country had undergone much expansion, but the improvement of the roads, notwithstanding the extension of the turnpike system, had in no way kept pace with the general progress and the growing needs of the nation. Parliamentary Committees were still devoting close attention to that good old stock subject, the width of cart-wheels. In 1806 there was a Select Committee appointed "to take into consideration the Acts now in force regarding the use of Broad Wheels, and to examine what shape is best calculated for ease of draught and the Preservation of the roads." This Committee presented two reports, and like Committees were appointed in the Sessions of 1808 and 1809, each of these Committees making three reports. What Parliament itself was doing at this period in the way of cart-wheel legislation has already been told.
So there was abundant scope for the activities of someone who could offer new ideas, and when, in 1811, a Select Committee was appointed "to take into consideration the Acts in force regarding the Highways and Turnpike Roads in England and Wales, and the expediency of additional regulations as to the better repair and preservation thereof,"[[16]] McAdam came forward with his proposals, as contained in the aforesaid "Observations" presented by him to the Committee in question.
McAdam began by saying that "In all three reports of Committees of the House of Commons on the subject of roads, they seem to have principally in view the construction of wheeled carriages, the weights they were to draw, and the breadth and form of their wheels; the nature of the roads on which these carriages were to travel had not been so well attended to." Proceeding to give the results of his own investigations, he expressed the view that the bad condition of the roads of the kingdom was owing to the injudicious application of the materials with which they were repaired, and to the defective form of the roads; and he assured the Committee that the introduction of a better system of making the surface of the roads, and the application of scientific principles which had hitherto never been thought of, would remedy the evil.
The basis of his system, as defined on this and subsequent occasions, was the covering of the surface of roads with an impermeable crust, cover or coating, so that the water would not penetrate to the soil beneath, which soil, whatever its nature, and provided it was kept dry, would, he argued, then bear any weight likely to be put upon it.
His method of securing the said impermeable crust was by the use of an 8 in. or 10 in. covering of broken stones, these being not more than about 1½ inches each in size, or more than about six ounces each in weight. Such broken stones, if properly prepared and properly laid on a road, would, he showed, consolidate by reason of their angles, and, under the pressure of the traffic, be transformed into a "firm, compact, impenetrable body," which "could not be affected by vicissitudes of weather or displaced by the action of wheels." The broken stones, with their angular edges, would, in effect, dovetail together into a solid crust under a pressure which, applied to pebbles or flints, would merely cause them to roll aside, in the same way as shingle on the seashore when passed over by a cart or a bathing van.
The difference between his broken stones and the more or less rounded stones with which the roads were then being repaired was, McAdam declared, the difference between the stones that were thrown down in a stream to form a ford and the shaped stones used to construct the bridge that went over the stream; while inasmuch as the road-arch, or crust, he formed would rest on the ground, and be impermeable to rain-water, there would be no need to have underneath it either a stone foundation or a system of drainage; though he held it as essential that the subsoil should be perfectly dry when the "metal," or covering of broken stone, was laid in position. Keeping the water out of the road by this means, he would prevent the road itself from being broken up by the action of frost, and he would have a more elastic surface than if there were a solid stone foundation under the metal. The thickness of his consolidated cover of broken stones would, he further argued, be immaterial to its weight-carrying capacity.
In 1816 McAdam became surveyor of roads in the Bristol district, and the object lessons in road-mending which he provided there were so convincing that his system began to be generally approved in 1818. In 1827 he was appointed Surveyor-General of Roads, and in the same year he issued a ninth edition of his "Remarks on the Present System of Road-Making."
In this publication he states, among other things, that very considerable sums were being raised annually in the kingdom, principally from tolls, on account of turnpike roads, and these funds were expended, nominally under the protection of Commissioners, but practically under the surveyors. Every Session there were numerous applications to Parliament by turnpike trusts for powers to increase their tolls in order to pay off their debts and to keep the roads in repair. In the Session of 1815 there were 34 such petitions; in 1816 there were 32, and "all passed as a matter of course." The condition of the turnpike roads was, nevertheless, most defective, and that of the parish roads was "more deplorable than that of the turnpike roads." Legislative enactments for the maintenance and repair of the parish roads were so inadequate that these roads "might be considered as being placed almost out of the protection of the law." In the result "The defective state of the roads, independent of the unnecessary expense, is oppressive on agriculture, commerce and manufactures by the increase of the price of transport, by waste of the labour of cattle, and wear of carriages, as well as by causing much delay of time."
As for Scotland, he declared that "The roads in Scotland are worse than those in England, although materials are more abundant, of better quality, and labour at least as cheap, and the toll duties are nearly double; this is because road-making, that is the surface, is even worse understood in Scotland than in England." He mentions that the Postmaster-General had been obliged to give up the mail-coach from Glasgow to Ayr on account partly of the bad roads and partly of the expense, there being ten turnpike gates in 34 miles of road.
The roads were, in fact, McAdam continued, "universally in want of repair." Ample funds were already provided; but the surveyors employed by the turnpike trusts were "mostly persons ignorant of the nature of the duties they are called on to discharge,"[[17]] and the money brought in by a continual and apparently unlimited increase of the tolls was "misapplied in almost every part of the Kingdom." In some new roads made in Scotland the thickness of the materials used exceeded three feet;[[18]] but, said McAdam, "the road is as open as a sieve to receive water"; and what this meant he was able to show by pointing to the results of weather conditions on bad roads in the month of January, 1820. A severe frost was succeeded by a sudden thaw, accompanied by the melting of much snow, and the roads of the kingdom broke up in an alarming manner, causing great loss, much delay of the mails, and endless inconvenience. The cause of the trouble was explained by McAdam thus:—