For the historical context to this story please go back to The Ploughed Ground – Part 1.
The Ploughed Ground – 2
In 2007 I had the opportunity to examine the Ploughed Ground with Dr Roy Lawrie, then a soil scientist with the NSW Department of Agriculture. Roy has worked closely with many archaeologists and I’ve known him since the dig of the First Government House site in Sydney in 1983. I had called Roy up to discuss another site I was planning to work on a bit further south, but as we chatted I thought I’d ask him whether he had any idea of what this plough marking may be and I described Mason’s and others’ descriptions of it. Without any hesitation he suggested ‘linear gilgai’, an unusual but by no means rare phenomenon that is found around the world.
Linear gilgai is a version of the more general landform gilgai, which refers to any sort of repetitive ditch and mound formed naturally within soils. The name itself comes from the Wiradjuri language, which ties it nicely into the centre of NSW, and has been adopted around the world. Its modern known distribution is from the Hunter Valley, but mainly from northern NSW and southeastern Queensland [Beckmann et al 1973]. There has been much speculation among soil scientists on the precise factors that generate gilgai, but a substantial depth of igneous-derived soil on slopes seems to be necessary. Blackburn  noted that the known distribution proposed by Beckmann had to be extended further south. He had come across Wells’s  description of the Ploughed Ground and recognised it as a linear gilgai. He further noted some of the landscape descriptions by Howitt which were possibly of linear or mounded gilgai in northern Victoria.
Gilgai forms into a range of different configurations, with the long straight plough marks of linear gilgai being one of the least frequent. More common are depressions forming a honeycomb-like pattern with dips of a metre or more, ten or so metres across, and persisting across hectares of ground. The opposite is hummocks of comparable dimension rising above the natural grade of the land. Other configurations that have been recorded as well, often with one transitioning into another, which suggests that micro-topography also has a strong influence on how gilgai appears.
Colonial settlers had their own names for these features. Apart from the ploughed ground the Australian National Dictionary records ‘dead men’s graves’, ‘melon holes’, ‘crab holes’ as three vernacular names for gilgai country. It seems likely that the examples Mason talked about in the Hunter and at the Ploughed Ground were among the first of any type of gilgai seen by most settlers. Mitchell and Sturt, seasoned explorers, do not talk about the plough marks and this is possibly because they had become familiar with the broader range of gilgai present in New South Wales and this was explicable purely as a localised topographic form, rather than a unique phenomenon.
There is still discussion about why gilgai develops, and particularly why it takes a particular form, whether linear, mounded or hollowed. There is a strong association with igneous soils, as in this case. There is an outcrop of basalt coincident with the area of the Ploughed Ground and this seems to be a common occurrence.
Observing from the roadside Roy and I were only able to spot one likely terrain feature that looked like gilgai [Figure 1]. Ironically, the rest had disappeared through farming and grazing. Hopefully in this instance the natural patterning will re-emerge, and make others marvel at the prospects it offers for alternative history [Note 1].
Throughout the 1830s and 1840s many natural scientist travellers speculated on the origin of these perplexing plouhg marks. As well as Mason’s speculations on secret visitors these included other theories of earlier farming, the Biblical flood and geological processes. Although the name and novelty of the phenomenon gradually faded and was all but forgotten by the 1850s, the early scientific recognition of this phenomenon represents one of the first attempts to come to grips with a more complex Australian history. In the case of Joseph Mason it combined with other things he saw and read and talked about to provide a potential alternative historical framework for his Australia. Mason’s memoir shows that he was able to pull together a series of facts and speculations that were readily available in newspapers, books and traveller gossip sufficiently to show that there was a potnetial for Australia to have been occupied by another people than the Aborigines. Whether these were an agricultural society who routinely farmed the land, or explorers opportunitistically growing crops during a brief stay in Australia was open to discussion, as Mason’s sources suggested either could be possible.
While we have to acknowledge that Mason was not a typical convict, it would be unlikely that he was the only person in the colony to put these facts and speculations together in the same way and come up with a secret visitor theory on his own. It would, I think, be surprising if others did not come to similar conclusions. It was definitely piquing curiosity into the 20th century. One example from the papers of Lawrence Hargrave, who received a letter from Edward Petherick . Petherick was one of the few historical professionals who admitted that they thought Hargrave was on to something. Petherick’s own pet theory about Australia’s pre-Dutch discovery was almost as outlandish and even less securely based, if possible. But, as the Commonwealth’s Archivist and the founder of the collection that became the National Library’s Australian collection he had access to much obscure literature. His letter asked ”Is the following note with consideration, as evidence of early agricultural operation in or near coast of N.S.W.?’, followed by an extract from an article by the Rev. Wilton on the Hunter District in the Australian Almanack of 1831 which includes a brief description of linear gilgai country:
the soft alluvial soil thrown up in regular ridges or furrows as if the land had undergone the action of the plough. The native blacks questioned as to the cause of this phenomenon explain it by saying that corn has grown there a very long time ago. [Wilton 1831: pp. 162-163]
Wilton felt it was a product of tremedous inundation, evidence of which he had seen elsewhere in the Hunter. It is clear that Petherick was thinking along different lines. He asked the loaded question ‘how long would furrows remain unobliterated by the weather [?200 years]. Hargrave’s answer was that he did not know, and could only offer a remembered anecdote about Saxon pploughing patterns that was not particularly useful [Hargrave 1914].
The Ploughed Ground soon became one of those cryptic names that dot the map with no remembered explanation. As European settlement filled the remainder of Australia gilgai in all its forms was encountered and the Aboriginal word eventually became the term for this pheonomon globally. However, in the beginning it was a prompt for natural scientists and even the observant, thoughtful person to speculate further on Earth’s history. This could range from the newly considered depths of deep uniformitarian time, to a catastrophic Earth, Noachian floods of a God-created Earth, or to a not too remote human earth as ephemeral evidence of secret visitors.
The speculations of Mason and Petherick used the idea of secret visitors to provide a framework within which seemingly anomalous observations of the human or natural world could be explained. It suggests that this mode of thought was not necessarily just related to scenarios created by the likes of Collingridge, Hargrave and
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1. Since that inspection with Roy Lawrie I have visited the area whenever I have had a chance when driving to Canberra, and have seen it throughout the year in different lighting conditions and stages of vegetation growth. Unfortunately the mounds and furrows remain hidden in all of them.
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The Australian National Dictionary , Oxford University Press, Oxford, 1988.
Beckmann, G.G., C.H. Thompson and G.D. Hubble 1973
‘Linear gilgai’, Australian Geographer, 12, pp. 363-366.
Blackburn, G. 1974
‘Distribution of linear gilgai: a comment’, Australian Geographer, 12, p. 564.
Breton, William Henry 1835
Excursions in New South Wales, Western Australia and Van Diemen’s Land during the years 1830, 1831, 1832 and 1833, Richard Bentley, London, 3rd edition.
Cambage, R.H. 1921
‘Exploration between the Wingecarribee, Shoalhaven, Macquarie and Murrumbidgee rivers’, Journal of the Royal Australian Historical Society, vol. 7, pp. 217-287.
Fletcher, Chrissy 2002
Arthursleigh: a history of the property 1819 to 1979, University of Sydney Press, Sydney.
Grey, George 1841
Journals of two expeditions of discovery in North-west and Western Australia during the years 1837, 38, and 39, … Describing many newly discovered, important, and fertile districts, with observations on the moral and physical condition of the aboriginal inhabitants, T. and W. Boone, London.
Hargrave, L. 1914
Letter to Edward Petherick 27 February 1914, National Library of Australia MS 325 – Lawrence Hargrave Papers, Item 8 – Papers 25.8.1913-28.5.1915.
Kent, D. and N. Townsend 1996
Joseph Mason assigned convict, 1831-1837: ‘doomed … to the earth’s remotest region’, Melbourne University Press, Carlton.
Lhotsky, John 1834
A journey from Sydney to the Australian Alps, undertaken in the months of January, February and March, 1834, Blubber Head Press, Hobart, 1979 facsimile edition, edited by Alan E.J. Andrews.
Mitchell, Thomas 1838
Three expeditions into the interior of eastern Australia: with descriptions of the recently explored region of Australia Felix, and of the present colony of New south Wales, T. and W. Boone, London, Volume 1. Second edition. Project Gutenberg transcribed copy here.
NSW Calendar 1832
The New South Wales Calendar, and General Post Office directory, Trustees of the Public Library of NSW, Sydney, 1966 facsimile edition.
Petherick, E.A. 1914
Letter to Lawrence Hargrave 25 February 1914, National Library of Australia MS 325 – Lawrence Hargrave Papers, Item 8 – Papers 25.8.1913-28.5.1915.
Sturt, Charles 1833
Two expeditions into the interior of southern Australia, during the years 1828, 1829, 1830, and 1831…, Doubleday, Lane Cove, 1968 facsimile edition.
Throsby, Charles 1819
‘Journal of a tour to Bathurst through the Cowpastures 25 April – May 11 1819”, NSW Colonial Secretary Special Bundle 1819, State Records of NSW Reel 6034.
Wilton, C.P.N. 1831
‘A sketch of the geology of the country about the River Hunter’, Australian Almanack, for the year of our Lord 1831 …, Ralph Mansfield, Sydney, pp. 156-163. Available here.