macadam

1824, named for inventor, Scottish civil engineer John L. McAdam (1756-1836), who developed a method of levelling roads and paving them with gravel and outlined the process in his pamphlet "Remarks on the Present System of Road-Making" (1822). Originally, road material consisting of a solid mass of stones of nearly uniform size laid down in layers; he did not approve of the use of binding materials or rollers. The idea of mixing tar with the gravel began 1880s.