 ... circulars, to which the replies appear to have been exceedingly disproportionate, although the viva voce evidence which they obtained was sufficient. In brief, their conclusions are as follows : — The workable depth of coal mines depends upon human...  Manual of Geology: Theoretical and Practical - Page 276by John Phillips - 1885Full view - About this book
 | John R. Leifchild - 1873 - 194 pages
...workable depth of coal mines depends upon human endurance of high temperatures and the possibility of reducing the temperature of the air in contact with heated strata. The mechanical difficulties connected with increased depth, and the cost of steam power for hoisting... | |
 | John R. Leifchild - Coal - 1873 - 198 pages
...workable depth of coal mines depends upon human endurance of high temperatures and the possibility of reducing the temperature of the air in contact with heated strata. The mechanical difficulties connected with increased depth, and the cost of steam power for hoisting... | |
 | 1873 - 610 pages
...workable depth of coal mines depends upon human endurance of high temperatures and the possibility of reducing the temperature of the air in contact with heated strata. The mechanical difficulties connected with increased depth, and the cost of steam power for hoisting... | |
 | Sandra Peart - Biography & Autobiography - 2003 - 472 pages
...workable depth of coal mines depends upon human endurance of high temperatures and the possibility of reducing the temperature of the air in contact with heated strata. The mechanical difficulties connected with increased depth, and the cost of steam power for hoisting... | |
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