Lectures On Mining Delivered At the School of Mines Paris volume 01
Lectures On Mining Delivered At the School of Mines Paris volume 01
J Callon
The book Lectures On Mining Delivered At the School of Mines Paris volume 01 was written by author J Callon Here you can read free online of Lectures On Mining Delivered At the School of Mines Paris volume 01 book, rate and share your impressions in comments. If you don't know what to write, just answer the question: Why is Lectures On Mining Delivered At the School of Mines Paris volume 01 a good or bad book?
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Thus, when a working area is cut up into pillars by two systems of drifts at right angles to one another, it often happens that a dis tinction is made between the two systems ; the drifts that are most important in number or extent are driven across the cleat, and the others are simple cross drifts, or headways, for ventilation. The appearance of the working face is very different in those two cases : in the first, the coal presents great flat shining surfaces; in the second, a granular structu...re. Example of a working place in a thick seam of coal. It often happens in a thick seam (we mean a seam decidedly thicker than the usual height of a mine level which rarely exceeds 6ft. Gin. To 8 feet (2 metres to 2 m -50) that the levels are only driven in the lower part of the seam; the upper part is left as the roof and is taken away at the same time as the pillars that are first of all left between the drifts. These levels are carried on like the working places just described, and only differ from them by their width which is less, and their height which is greater.
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