John Loudoun McAdam, a Scottish inventor, traveled almost 19,000 miles from 1798—1814 to form a method of making roads less susceptible to water.
Stagecoaches and wagons got stuck on muddy roads, adding to the difficulty of traveling. As surveyor general, McAdam devised a way to greatly improve roads and wrote of it in his Remarks on the Present System of Road-Making (1816).
To aid in water drainage, McAdam first recommended that roads be higher than the ground beside it. A layer of large broken stones then covered the road. Smaller stones were then laid over them. A fine layer of gravel was the last component.
This design reduced wear and tear on the road. Water drained to ditches on the side.
His recommendation was a great improvement over traveling on muddy roads. His idea spread to the United States.
Construction started in 1811 on the National Road, which began in Cumberland, Maryland, and wound through Pennsylvania and Virginia into Ohio. McAdam’s principles weren’t yet known.
His methods grew in popularity so that road makers used it on a new section of the National Road between Canton and Zanesville, Ohio, in 1825-1830. They broke stones small enough “to pass through a two-inch ring.”
At a width of twenty feet, the road contained the three layers of stone suggested by McAdam. Each layer was compacted with a cast-iron roller. This created the Macadamized road, making travel easier and safer for the pioneers settling in Ohio and farther west.
-Sandra Merville Hart
Bellis, Mary. “John Loudon McAdam – The History of Roads and Asphalt,” About.com, 2017/04/20 http://theinventors.org/library/inventors/blJohnMcAdam.htm.
Edited by Raitz, Karl. A Guide to The National Road, The Johns Hopkins University Press, 1996.
“John Loudon McAdam”. Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2017. Web. 20 Apr. 2017.
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