. St. Nicholas [serial]. MINING BY GRAVITY. THE WHOLE MASS IS ORE. CARS ARE LED BY TUNNELS TO THE BOTTOMOF THESE DEEP PITS AND ARE FILLED THERE. That is what gravity mining does. It consistsin digging a hole under a mine, running a carunder, and letting the mine fall into the is literally what it amounts to. Fig. 5 shows what seems to be a yawningchasm, with four or five conical holes in the pit. These holes, or chutes, converge to a commoncenter, or chamber, deeper down, from whichan inclined tunnel runs to the surface of theground somewhere out beyond the train ofcars. Notice partic
. St. Nicholas [serial]. MINING BY GRAVITY. THE WHOLE MASS IS ORE. CARS ARE LED BY TUNNELS TO THE BOTTOMOF THESE DEEP PITS AND ARE FILLED THERE. That is what gravity mining does. It consistsin digging a hole under a mine, running a carunder, and letting the mine fall into the is literally what it amounts to. Fig. 5 shows what seems to be a yawningchasm, with four or five conical holes in the pit. These holes, or chutes, converge to a commoncenter, or chamber, deeper down, from whichan inclined tunnel runs to the surface of theground somewhere out beyond the train ofcars. Notice particularly the finely dividedcharacter of the ore. This is characteristic of. FIG 6. OKE-DOCKS AT DULUTH, MINNESOTA. i9o4.] THE STORY OF A BAR OF IRON. 433 the Messaba mines. Much of it comes as fineas coarse gravel, not at all like the usual hard,stony ore lumps. Even the larger pieces breakand crumble readily,which greatly aids thework of the steamshovel and especiallythe process of the easy-going gravity mining. TRANSPORTATION. It is this character-istic that makes it aseasy to transport andhandle this ore as tomine it. Fig. 4 showed theore dropping into thecar at the mine. Fig. 6shows the cars on oneof the great ore-docksat Duluth, the ore is dumpedinto chutes and conveyed by them to the holdsof the waiting vessels, which are to carry itthrough the famous waterways of the GreatLakes. Fig. 7 shows the ore being mined, as one might say, from the hold of a vessel whichhas arrived at its destination. The ore hoistshave just lowered the great shovel, and in Fig. 8
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Keywords: ., bookauthordodgemar, bookcentury1800, bookdecade1870, bookyear1873
