 | 1906 - 1190 Seiten
...Methods and costs of gravel and placer mining in Alaska: Bull. I". S. Ueol. Surrey No. 263, 11)03. OPEN-CUT MINING. The ground is generally stripped...Gravel is hoisted by derrick, by automatic trolley, or sometimes by a rock pump. When the last method is used a set of boxes is placed on the bottom of the... | |
 | Geological Survey (U.S.) - 1906 - 232 Seiten
...Purington, CW, Methods and costs of gravel and placer mining in Alaska: Bull. US Geol. Survey No. 263, 1905. OPEN-CUT MINING. The ground is generally stripped...Gravel is hoisted by derrick, by automatic trolley, or sometimes by a rock pump. When the last method is used a set of boxes is placed on the bottom of the... | |
 | Albert Foster Crider, Edwin Clarence Eckel - 1906 - 328 Seiten
...Purington, CW, Methods and costs of gravel and placer mining In Alaska: Bull. US Geol. Survey No. 263, 1905. OPEN-CUT MINING. The ground is generally stripped...Gravel is hoisted by derrick, by automatic trolley, or sometimes by a rock pump. When the last method is used a set of boxes is placed on the bottom of the... | |
 | Dwight T. Randall, H. T. Weeks, H. W. Weeks - 1909 - 692 Seiten
...has been done by open cut. The ground is generally stripped first of all by ground sluicing; then a cut of sufficient width for one or two sets of boxes is opened, and a bed-rock drain several hundred feet in length is constructed. The pay gravels have generally... | |
 | Geological Survey (U.S.) - 1909 - 66 Seiten
...has been done by open cut. The ground is generally stripped first of all by ground sluicing; then a cut of sufficient width for one or two sets of boxes is opened, and a bed-rock drain several hundred feet in length is constructed. The pay gravels have generally... | |
 | Cecil Clement Longridge - 1910 - 510 Seiten
...in ravines, where the water is transient. They are mostly worked by pans, cradles, toms, &c. 2.— Open-cut Mining:. The ground is generally stripped...the valley. In some cases the gravel is hoisted by steam-power entirely out of the cut to boxes set above the surface and to one side of the workings.... | |
 | 1908 - 648 Seiten
...says that the ground is generally stripped first of all by sluicing off the overlying muck. A bed rock drain is then constructed, and an open cut of sufficient...is hoisted by steam power entirely out of the cut of boxes set above the surface and to one side of the workings. By this method a frequent resetting... | |
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OPEN-CUT MINING. The ground is generally stripped first of all by sluicing off the overlying muck. A bedrock drain is then constructed, and an open cut of sufficient width for one or two sets of boxes is carried gradually up the valley. In some cases... 