 ... the surface, as the mineral-bearing rock did not reach a greater depth. To separate the mineral great heaps were constructed with wood intermingled with the rock. These were fired, and after the fire had done its work the heat was found to have been...  The Proceedings of the Iowa Academy of Science - Pàgina 38per Iowa Academy of Science - 1895Visualització completa - Sobre aquest llibre
 | Iowa Geological Survey - 1897 - 720 pàgines
...done its work, the heat was found to have been insufficient to melt the Galena. It had only broken the rock into small pieces. Then this was washed and...During the two years that the mines were in operation sixty-three pigs were turned out and this trifling return represents almost the entire product of this... | |
 | 1897 - 560 pàgines
...done its work, the heat was found to have been insufficient to melt the Galena. It had only broken the rock into small pieces. Then this was washed and...During the two years that the mines were in operation sixty-three pigs were turned out and this trifling return represents almost the entire product of this... | |
 | 1906 - 734 pàgines
...had done its work the heat was found to have been insufficient to melt the galena. It had only broken the rock into small pieces. Then this was washed and...During the two years that the mines were in operation Oil pigs were turned out and this trifling return represents almost the entire product of this district.... | |
 | Harry Foster Bain - 1906 - 778 pàgines
...had done its work the heat was found to have been insufficient to melt the galena. It had only broken the rock into small pieces. Then this was washed and...trifling return represents almost the entire product of this district. When the locality was visited early in 1894 some prospecting was in progress, but with... | |
 | Geological Survey (U.S.) - 1906 - 222 pàgines
...had done its work the heat was found to have been insufficient to melt the galena. It had only broken the rock into small pieces. Then this was washed and...trifling return represents almost the entire product of this district. When the locality was visited early in 1894 some prospecting was in progress, but with... | |
 | Wisconsin Geological and Natural History Survey - 1907 - 192 pàgines
...had done its work the heat was found to have been insufficient to melt the galena. It had only broken the rock into small pieces. Then this was washed and...trifling return represents almost the entire product of this district. When the locality was visited early in 1894 some prospecting was in progress, but with... | |
 | Wisconsin Geological and Natural History Survey - 1907 - 188 pàgines
...had done its work the heat was found to have been insufficient to melt the galena. It had only broken the rock into small pieces. Then this was washed and...The latter was smelted in a furnace located at the month of Mineral Creek. During the two years that the mines were in operation 63 pigs were turned out... | |
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