It began in July 2007, when Gerry and Theta Brentnall took us up into the mountains to see the results of gold sluicing there, and told us about the court cases that resulted, cases which stopped sluicing, because of the environmental damage caused downstream. That shot was taken in the Malakoff Diggins State Historic Park.
We never did that in Australia, I told them with a high degree of confidence. I said there probably wasn't enough water to use huge hoses to undermine cliffs, sending stuff tumbling down. But when I realised there was a story to tell, I started to look into sluicing, found some hints, did some checking, and came away amazed. We did it, sure enough! But then I found out where this sort of thing happened first, when the Romans went to "ruin the mountain" near Las Medulas in Spain, which area I visited last June.
The name was coined by Pliny the Elder, who was Procurator in the area in 74 AD: "alio modo puteorum scrobibus effoditur aut in ruina montium quaeritur", he wrote. What you see above is all that was left after a couple of centuries of breaking down a mountain and collecting about seven tons of gold a year, across that time.
|This is scanned from a copyright-free source.|
That is why I didn't really expect anything like the arch you see above, which is in the Golden Gully, just outside Hill End, not that far from the Turon River. It turns out that some diggers diverted water through a tunnel that has, bit-by-bit, collapsed until there is just this section left standing.
Somewhere along the way, I became aware of the Oriental Claims site near Omeo in Victoria, and we headed off there last Friday, driving 1584 km, just under 1000 miles, in 55 hours.
As at the Malakoff diggings, the idea was to carry water around mountains and hills in high channels, before the water was fed into iron pipes or toughened hoses that could withstand the pressure. The idea was to use high pressure water jets to loosen and erode paleogravels, washing them down to a point where the usual Long Tom style device could be used to take out the gold. There was a bit more to it than that, but that's a reasonable amount of free information: for the rest, buy the book!
And here is the sort of result you get. You have now seen photos taken in Spain, California, Victoria and New South Wales: make of the common factors what you will.
Now here is some evidence:
The hydraulic system is another great improvement in mining. By means of hose, the force of one hundred and fifty to two hundred feet head of water is turned upon the hills, which in this way are dissolved and run through sluices, and thus diggings, which in the ordinary mode of mining would not pay the working, are made extremely profitable. The necessity of scientific explorations is felt by every practical miner. Frequently in running tunnels into the hills, the labour of months or years has been made unavailing through ignorance of the geology of the location. But when science is brought to aid labour, we shall bear no more of tunnels started too high or too low, and thus rendered useless.
Somebody at the Empire cared about this method, because here is more, some three yeares later:
HYDRAULIC MINING.-It affords us rare pleasure (says the Mountain Messenger), at times, to stroll through the mines and see the gigantic operations which are there carried on to procure the precious metal. A few days ago we wended our way over fallen logs and down deep banks to where the workmen were piping down the high gravelly deposit into sluice boxes. The large hose was conducting about fifty inches of water, and as it escaped from the nozzle at the end, it sounded to us like the "rush of many waters," mentioned by St, John. A playful desire overcame us to use the hydraulic, and with the consent of a friend we stood for two mortal hours, pipe in hand, watching and sometimes retreating in hot haste from the gigantic masses which would come thundering down.
Oh! it was rare sport, and to a person who has never seen such or indulged in it, but little idea can be formed of the excitement attendant thereon. In hydraulic mining the mode adopted by the miners is to work from the bed-rock. A sufficient force of water is let on, and so soon as an excavation is made by its power, the bank commences crumbling piece by piece, as a sort of providential warning for those at work to get out of the way. A wise man will take tho necessary precautions and run, for there is no tolling the extent of the cave, or where it is going to spread to; but we are sorry to say this is not always the case.
We have begun to destroy the beauty of this creek. It will no longer run clear between its banks... We diggers are horribly destructive of the picturesque.
— William Howitt, Land, Labor and Gold, volume I. Boston: Ticknor and Fields, 1855, 219. (That is the edition available through Google Books. As the English edition probably has different pagination, this is at the head of Letter XIII, written from Yackandanda, February 28, 1853.)That's enough on gold. I will revert to natural history, once I have finished with my notes and photographs.