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GENEBAL CONCLUSIONS.
Seventh. We believe that the conclusions adduced from the tests made, and the calculations and tabulations based thereon, are reasonably reliable; yet we desire to record the opinion that there are conditions existing in the mines to which they might not apply—for instance, in localities where several seams of coal are separated by a thin layer, or layers, of shale and slate, or even sandstone, and the pillars in the several seams are not over one another, and it is proposed reclaiming all or any part of the pillars.
Even though an application of the above tables might appear to fit the conditions, we believe that the only permissible procedure would be to first fill with flushed material all of the openings in the lowest bed of the series and then fill upward until all the beds are filled, care being taken to have the flushed areas over one another. After all of the openings in all of the seams have been filled, the pillars in the uppermost seam may then be attacked; as each pillar is removed, the space should be at once filled. No pillar reclamation should be permitted in any of the other beds until all of the pillars in the upper bed have been removed and the overburden has come to rest on the flushed material; then the pillars in the next lower seam may be attacked and handled in like manner.