Puddling machines were pioneered on the Victorian goldfields in 1854 as an affordable means of processing gold-bearing clay on a large scale.
A horse dragged a harrow repeatedly through a circular, barklined trough full of clay and water, 'puddling' the mixture into a thin sludge. Any gold freed from the lumpy clay would sink, remaining behind on the bottom of the trough after the watery sludge was drained off. A clean-up of the residue, using tin-dish or cradle, would bring the gold finally to light.
Geological map of the Maryborough gold field which shows historical features in superb detail, including reefs, leads, gullies/flats, and old workings. Originally published by the Department of Crown Lands and Survey, early 20th century. High quality, durable A1 print in a satin finish. Large, 594 x 891 mm. Go to online shop.