His ordinary method of road-making in the Highlands was, first to level and drain; then, like the Romans, to lay a solid pavement of large stones, the round or broad end downwards, as close as they could be set. The points of the latter were then broken off, and a layer of stones broken to about the size of walnuts, was laid upon them, and over all a little gravel if at hand. A road thus formed soon became bound together, and for ordinary purposes was very durable. But where the traffic, as in the case of the Carlisle and Glasgow road, was expected to be very heavy, Telford took much greater pains. Here he paid especial attention to two points: first, to lay it out as nearly as possible upon a level, so as to reduce the draught to horses dragging heavy vehicles,--one in thirty being about the severest gradient at any part of the road. The next point was to make the working, or middle portion of the road, as firm and substantial as possible, so as to bear, without shrinking, the heaviest weight likely to be brought over it. With this object he specified that the metal bed was to be formed in two layers, rising about four inches towards the centre the bottom course being of stones (whinstone, limestone, or hard freestone), seven inches in depth. These were to be carefully set by hand, with the broadest ends downwards, all crossbonded or jointed, no stone being more than three inches wide on the top. The spaces between them were then to be filled up with smaller stones, packed by hand, so as to bring the whole to an even and firm surface. Over this a top course was to be laid, seven inches in depth, consisting of properly broken hard whinstones, none exceeding six ounces in weight, and each to be able to pass through a circular ring, two inches and a half in diameter; a binding of gravel, about an inch in thickness, being placed over all. A drain crossed under the bed of the bottom layer to the outside ditch in every hundred yards. The result was an admirably easy, firm, and dry road, capable of being travelled upon in all weathers, and standing in comparatively small need of repairs.