What is tar macadam?

Tarmac is a hard black material used for roads, parade grounds or anywhere that a hard, even and durable surface is needed . It is a mixture of tar (which accounts for the colour) and macadam, which consists of hundreds of tiny even-sized chips of granite pressed together.

Macadem is named after a Scotsman, John Loudon MacAdam, who first used it in the late 18^th Century. Until MacAdam’s time roads were tracks, sometimes covered with stones, which easily got muddy and waterlogged and whose unevenness made travelling by stage coach so uncomfortable that most people stayed at home. MacAdam, who was on the roads committee in his home country of Ayrshire in Scotland and wrote several books about road-building, persuaded the government to let him make experiments which resulted in vastly improved highways.

The original macadam is still used on roads and looks much better than tarmac. But tarmac and other more recently invented surfaces fare better where there is heavy traffic and when loose stones would be quickly dispersed.