"The ground was covered by some dark stuff that silenced all the wheels. ...It was like magic."
Laura Ingalls Wilder, children's writer
In the early nineteenth century, road maintenance was carried out by road gangs, who were often more interested in profit than in keeping roads in good condition. Scot John London McAdam (1756-1836) was a self-taught engineer, who had been appointed trustee of a turnpike. His neighbor suffered rickets and found traveling on potholed roads extremely painful, so McAdam began to experiment with different methods of road construction.
Since the days of the Roman Empire, roads had been constructed with a bottom layer of heavy stone, topped by several layers of finer stone and a top layer of gravel. McAdam took this method, but used a compressed heavy roller to compact the layers of
rocks together. McAdam's roads had graded layers of broken chippings, with a center higher than the edges and drains on either side. This meant that roads were not only more stable but needed less maintenance.
McAdam's method greatly increased the speed of road travel, but macadam had to be adapted with the arrival of the motor car. To reduce dust caused by the vacuum created under fast-moving vehicles, E. Purnell Hooley used hot tar to bond the broken stones together and patented tarmac in 1901.
