THE NEWSLETTER OF THE SYDNEY DIVISION OF ENGINEERS AUSTRALIA
MARCH 2013
PRESIDENT’S MESSAGE
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I recently spent an enjoyable day north of the Hawkesbury River retracing the path of the original Sydney to Newcastle road, originally called The Great North Road. For those interested in Engineering Heritage, walking and the Australian bush, it’s a fascinating and beautiful discovery. The first road to Newcastle was built between 1826 and 1836 by convict labour and there’s a ten kilometre abandoned and well preserved relict located north of the Hawkesbury River at Wisemans Ferry. It contains the oldest mainland bridge in Australia at Devines Hill, built in 1830 (beating the three Lennox Bridges: Glenbrook 1833, Lansvale 1836 and Parramatta 1839). The 1820s was a turbulent time in engineering with revolutionary changes created from the work in England of Thomas Telford on pavement construction and drainage, and John McAdam in Scotland on pavement matrix, and both these avant-garde theories were put into practice on this site for the first time in Australia. Leading the design was Major Thomas Mitchell with his assistant Lieutenant Percy Simpson as construction engineer, along with their construction force of 350 recalcitrant convicts (who didn’t want to be there). In the pecking order of convicts the bad were sent to the road gangs with the worst in iron chains. They cut a precipitous mountain goat track from the sheer cliffs of Hawkesbury sandstone, hewn with their bare hands. There is still much evidence of the convict construction with numerous hand quarried stone retaining walls, culverts, drains, kerbs and gutters. Many of the individual stone blocks weigh 600kg were shaped by hand drill, sledge hammer and gunpowder blast, trimmed by hand hammer and chisel, and then moved to position by human hand and back.
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Closer inspection of the numerous relict drill holes left in the rock faces reveal a very interesting aspect which you don’t see in modern blast drill holes: they’re a triangular shape in plan. This comes from hand drilling, with the convict on the bottom holding the hand drill and then rotating the bit 60 degrees after each sledge hammer impact. Sarcastically, the convict on the bottom holding the drill was called the “bottom dog”, while the convict with the sledge hammer on the top was called the “top dog” which is still a linguistic relict in our language today, meaning to be the “best in the trade”. There’s still an open forest gum clearing remaining which was the camp site for the construction crew, excavated stone safes for the storage of gunpowder, abandoned stone quarry source sites and a curious stone formation which is still called Hangman’s Rock. Worthy of mention is that the site is identified by a National Engineering Landmark brass plaque placed by Engineers Australia’s Heritage Group. The Great North Road is one of many fascinating Engineering Heritage sites marked and conserved by our Heritage Committee, and each one tells a unique and heart wrenching story of the triumph and failure of the engineering mind and hand. John Nichols BE (Civil), CPEng, FIEAust President, Engineers Australia Sydney Division