A tar cry

More than a week has elapsed and none of your readers has challenged Michael Fry's erroneous claim (Opinion, 19 June) that Scots invented the steam engine and tarmacadam.

The first patent for a steam-powered device was lodged by Thomas Savery (1650-1715), more than a century before James Watt's birth, and Watt merely improved on the design of Thomas Newcomen's "Atmospheric steam engine" by devising a condensing system.

Newcomen died some seven years before Watt was born.

Sign up to our Opinion newsletter

Sign up to our Opinion newsletter

Nor did John Loudon McAdam "invent" tarmacadam, but promoted the idea of using carefully graded stone ("macadam") to produce a firm, free-draining foundation without the use of tar as a binding agent.

"Tarmac" was in fact patented in 1902 by Edgar Purnell, county surveyor of Nottingham, and it was used on the first recognisable tarred road laid in Paris around 1854.


North Street