large rocks at the bottom and small ones at the surface, laid
on drained soil and with a camber to allow drainage. His revolutionary
roads were inexpensive, flexible, almost waterproof and
silent. Years of research and work saw him spend thousands of
pounds of his own money before his ideas were finally accepted
and put into general use. The terms macadamised
and macadamisation were used to describe the new
roads and their building.
More About John Loudon McAdam. It isn't trivial to build roads. People made the very first roads by tramping the same way over the undergrowth year after year. The Chinese built them, the Egyptians built them, the Greeks built them and the Romans certainly built them. General Wade built them in Scotland, to put down the mutinous Highlanders.
John London McAdam really built them, because he made them work. Roads fall apart when chariots, wagons and stagecoaches overload them, but not McAdam's roads. In 1770, at the age of 14, the lad from Ayr emigrated to New York where he made a fortune in a counting house. He came home to enjoy his rich retirement before he was 30. McAdam spent the next 20 years or so
idling, before roads started to obsess him. When he put his mind to it he becante the great inventive road man. He got a job in Bristol in charge of the city's roadworks, and he later became boss of Metropolitan Roads with an award of £10,000. That trick alone was sufficient to make him a millionaire in today's terms.
He must have been a big spender because he went broke now and again. But he had literally paved the way. His very simple discovery was that if people made roads by heaping stones together, traffic threw the stones aside and the whole thing collapsed. Yet if the stones were arranged in size, large ones at the bottom, smaller ones on top, and the surface covered with cinders or gravel, the weight of traffic would not scatter them, it would keep compacting them, thus constantly improving the roads.
People who followed McAdam improved on his scheme by adding tar to the stones, which bound them together even more firmly. We now have concrete roads and runways that have nothing to do with McAdam's stone arrangement or his genius, but John McAdam was the man who started the whole thing and made the surface of the earth safe to drive on. John London McAdam's simple innovation revolutionised road building and won him the post of surveyor general of roads.