Macadam
2 of the 6 encyclopedias on this shelf carry an entry for Macadam. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
a durable roadbed built of crushed rock. The bed of the proposed road is first of all graded and given a slight roll toward the sides. The road builder proceeds to apply several layers of metal, as the broken rock is called. The first consists of pieces four or five inches in diameter. Each successive layer is of smaller pieces. The road is finished with gravel and clay rolled or stamped into a smooth, compact roadway. The name is that of a celebrated Scottish engineer, John Loudon Macadam, 1756-1836. He spent several thousand pounds of his own money in demonstrating the value of this method of road building. Parliament voted him a gift of $50,000 in honor of his services. The macadam system of road building has spread all over Europe. No wayside sight is more common in Switzerland or along the Rhine than that of peasants on their knees, stone in one hand and hammer in the other, breaking metal to mend roads with. Stone crushers operated by power are now in use, especially in many American cities and in localities ambitious to have good roads. Granite is the most durable road metal.
Collier's New Encyclopedia (1921)
JOHN LOUDON, a Scotch engineer, inventor of the system of road - making known as " macadamizing "; bo born in Ayr, Scotland, Sept. 21, 1756. He began in 1810 to make experiments in the construction of roads, which became a passion with him. In 1815 he was appointed surveyor to the Bristol Turnpike Trust, and remade the roads there cheaply and well. Impoverished through his labor he petitioned Parliament, and he was voted $50,000 and appointed Surveyor-general of Metropolitan Roads in 1827. He declined knighthood. He published "A Practical Essay on the Scientific Repair and Preservation of Public Roads" (1819); and "Observations on Roads" (1822). He died in Moffat, Dumfriesshire, Nov. 26, 1836.
What Has Changed in the Last Century
Aiton's 1910 description of a road finished with gravel and clay "rolled or stamped into a smooth, compact roadway" describes water-bound macadam, which the motor car was already destroying as it wrote: fast pneumatic tyres sucked the binding dust out of the surface. The remedy had been patented in 1902 by Edgar Hooley of Nottingham, who bound the crushed stone with tar to make tarmacadam, or tarmac; asphalt concrete, in which the stone is bound with bitumen, now surfaces the great majority of the world's paved roads. Macadam's principle of graded, compacted, well-drained crushed stone survives inside those roads as the base course beneath the black wearing surface, and unsurfaced "macadam" lanes remain in rural use. The peasants Aiton saw kneeling by Swiss and Rhineland roads with hammer and stone have gone entirely, replaced by the powered crushers he mentions as a novelty.
Written for this edition, 2026.