ight of the engraving. fect benot diminished toward the end of the work; or perhaps, The effect of this was tovibrate a rock shaft, the lower one more accurately, so that the amount of force expended in per- in both. forming the operation shall increase in direct ratio with the represented, and so… … been adhered to, are pressed in- description of the mechanism, as a reference to the engrav- two engines, instead of but one, are employed, and these ward and, by the shape of the frame, cleaily shown in our en- are so arranged that a cylinder of comparatively small di- ing will clearly indicate…
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