最終更新日:2022/12/23

At some of the mines on the great Mother Lode, where hundreds of tons are not unfrequently thrown down at a blast, and where a wide, soft gouge along one wall enables the minder to keep two or three sides of the rock free, and give the powder the greatest opportunity to lift without waste of power, the cost of drilling and blasting per ton is so low that a reduction of one-third, even if it could be made, would not greatly affect the general count; […]

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