. Factory and industrial management . 4,000 pounds of dynamitewere used for blasting, and more than 300,000 cubic feet of rock weretaken out. The greatest depth is 900 feet. By means of the tunnel200 tons of ore and waste are now daily taken out with the minimumof power, and the various properties are drained, by natural gravity, tothe extent of 400 gallons per minute, the estimated saving in operatingexpenses being from 50 to 60 per cent. As a further illustration of the mineral wealth of the general dis-trict in which the Lamartine mine is located, it may be stated thatsince 1859 a little st
. Factory and industrial management . 4,000 pounds of dynamitewere used for blasting, and more than 300,000 cubic feet of rock weretaken out. The greatest depth is 900 feet. By means of the tunnel200 tons of ore and waste are now daily taken out with the minimumof power, and the various properties are drained, by natural gravity, tothe extent of 400 gallons per minute, the estimated saving in operatingexpenses being from 50 to 60 per cent. As a further illustration of the mineral wealth of the general dis-trict in which the Lamartine mine is located, it may be stated thatsince 1859 a little strip of country, 4 miles long by 2I2 miles wide,around Central City, Gilpin county, has produced over $80,000,00aof mineral, mostly gold, while the adjoining section of Clear Creekcounty around Idaho Springs has been a proportionate Central City there are ten mines which have passed the mill-ion-dollar mark in their production. There are five to ten shaftsreaching a depth of from 1,200 to 2,200 feet, and perhaps twenty. MINING TUNNEIS IN COLORADO. 777 mines ranging from 700 to 1,200 feet in depth, with many of lesserdepth. In consequence of the excessive cost of pumping and hoist-ing, the working of some of these mines has been temporarily aban-doned. In view of the fact that Idaho Springs on the main stream ofClear Creek, while less than four miles in an air line from CentralCity, is about 1,100 feet lower in altitude, it was simultaneously de-termined by various parties to run long tunnels, at a slight up grade,practically from the line of railroad below and above Idaho Springs,in the direction of the rich mines, and, by tapping them from below,not only to drain them automatically, but to take out the ore by natu-ral gravity to the railroad tracks. The first of these is the Newhouse tunnel, commenced in January,
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Keywords: ., bookcentury1800, bookdecade1890, booksubj, booksubjectengineering
