John Loudon McAdam in the context of "Coal tar"

Tarmacadam or tarmac is a concrete road surfacing material made by combining tar and macadam (crushed stone and sand), patented by Welsh inventor Edgar Purnell Hooley in 1902. It is a more durable and dust-free enhancement of simple compacted stone macadam surfaces invented by Scottish engineer John Loudon McAdam in the early 19th century. The terms "tarmacadam" and "tarmac" are also used for a variety of other materials, including tar-grouted macadam, bituminous surface treatments and modern asphalt concrete.

Macadam is a type of road construction pioneered by Scottish engineer John Loudon McAdam c. 1820, in which crushed stone is placed in shallow, convex layers and compacted thoroughly. A binding layer of stone dust (crushed stone from the original material) may form; it may also, after rolling, be covered with a cement or bituminous binder to keep dust and stones together. The method simplified what had been considered state-of-the-art at that point.