Into the Leonard sump drains the water from the Boston and Molltana mines, further down on the "copper hill" where Butte's ore bodies lie, Here anolher mighty pump thrusts the water to the surface at 1,100 gallons a minute.
At the Hgh Ore and the Leonard are great precipitation plants, where the water is showcred down through a series of shelves filled with old scrap iron and tin plate. The copper in solution, as explained above, encrusts itself upon the iron, To wait until the iron is entirely supplanted by copper is much too slow, and every few clays the men who run the plant "clean up," by diverting- the water from a particular part of the "tower"-as they call the arrangement of shelves-scraping or knocking loose the copper from the iron, shoveling it into sacks or barrels, and taking it to the dryer. From the dryer the precipitates are sent to the smelters, where they are cast into ninety-nine per cent copper ingots.
But that is not all the history of the mine waters, for they are seized upon anew, when they have traversed the mine precipitation plants, pumped to the top of some old mine dump or slag dump, where great pools are formed, and left to seep through the sands or the slag into tunnels bored beneath. From these tunnels the "enriched" water is again lifted to precipitation "towers" where the iron once more begins its work, and the copper is again lured from the waters. It takes about a pound and a half of iron to precipitate a pound of copper. Scrap iron sells for one-fourth cent a pound, copper for thirteen cents-just now.
There is no limit to the number of times the precipitation process can be repeated, so long as there are dumps or tailings upon which the water can be directed. Nor need it be mine water, for all along Silver Bow creek the pumps are chugging industriously as they lift the water to the dumps and relift it to the top of the precipitation towers. There are hundreds of these, and there are miles of trestle to carry the waters out upon the dumps and the tailing piles.
It pays. The mines must be kept dry and pumping would therefore be a necessary expense under all circumstances, yet the Easton and Montana and the Anaconda companies after paying for the drainage of all their mines, realize a profit of about six cents upon every pound of copper that is recovered in this way.
The leaders who "leach" the dumps, must expend about six cents for every pound of copper obtained, but that copper brings them thirteen cents at the present market. Were it not that the big companies demand twenty-five and thirty-five per cent royalty on the net proceeds, the profits would be much higher.
Thus Butte converts what once was pure waste into an annual saving of nine million pounds of copper, worth about a million and a quarter dollars, one-half of which is clear profit.
So, as stated at the outset of this article, the people of Butte are not excited or worried over the fire which is directly under the business district of the busy camp of 70,000 people. Alarmists have declared that some day the effect of the fire will be to cause a great void under Butte and that the camp will be swallowed suddenly into this deep, hot hole in the ground. but the population is too busy to attend to such prophesies, and they seem willing to take the chance.
And the underground fire goes burning on.
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