xed figures, and which constitutes a sys- be made at the same time as the main tunnel, that we need tem that can be employed not only for the loading of coal, only consider here a length of ten milesof excavation worked but also for letting down to the bottom of the hold bricks, from one face.… … maintained of one yard per hour, or twenty-four yards per two figures may be seen how it operates when the loading nearly to the base of the bucket frame, is provided with a day, at which rate the work of excavating ten miles of tun- begins and the hull is still empty, and when, the hull being…
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