Macadam roads

   Macadam is the name of a popular road surface. It was introduced in England in the early nineteenth century by John Loudon McAdam, a Scotsman. The need for economical as well as durable road paving has always existed. McAdam's contribution in this field made him one of the leading figures in the history of road-making.
   His technique was basically simple. The roadbed was covered with layers of crushed rocks of about two inches on a side. Moving coaches and wagons packed them, the many rocks adjusting themselves to each other to give a stable, solid road.
   Variations on the basic plan utilize clay, tar, or other tar-like substances as fillers and binding agents. Today any road built of gravel or crushed rock and bound by tar or asphalt is referred to as a macadam road.
   Sometimes an over-layer of asphalt mixtures is used to give a yet smoother surface, known as black top.