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John Loudon McAdam
Macadamizer(1756 - 1836)
McAdams discovery came about when he started repair and maintenance work on the roads round his estate, which he bought after returning to the United Kingdom after making his fortune in America.
He had gone to New York at the age of sixteen and became an "agent for prizes" - an official form of dealing in stolen goods!
Formal road construction started in Britain with the Romans who relied on heavy, carefully laid foundations to withstand the dual pressures of traffic and weather. The main difficulty with this system was that it was cumbersome to install and difficult to maintain.
McAdam's theory was that with a system of properly drained foundations bare, dry soil was strong enough to bear the weight of the type of traffic using the roads at that time. His system involved raising the road - bed with adequate drainage to carry away rainfall. He then concentrated on laying tightly packed layers of small stone which the weight of traffic using the road would help compact to a smooth surface.
This was a much cheaper way of developing and maintaining roads and other engineers quickly found ways to develop McAdam's early pioneering work. One of them, Richard Edgeworth used stone dust mixed with water to fill the gaps between the stones, thereby providing a much smoother surface
It was this "water bound Macadam" that was the forerunner of the bitumen based binding that was to become tarmacadam. The first tarmac road to be laid was in Paris in 1854. With the development of the automobile in the early twentieth century tarmac roads, or "black tops" came into common use.
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