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SUMMARY.
4.	It would seem, therefore, to be not only the part of wisdom, but absolutely obligatory, to immediately commence supporting the points menaced, and thereupon proceed upon a general policy of giving support to the entire area of the city, for it must be borne in mind that with the mining activities that are constantly going on other and additional points of danger are not only liable to, but in all probability will, develop with each passing year—it might almost be said with each passing month.
5.	Where the owner of the surface has undoubted right to the support thereof by coal pillars, in our opinion he could permit the removal of such pillars; the value thereof would under average conditions pay for such artificial support as we have recommended, if it be assumed that the pillars were mined and the support constructed by the same operating company. This observation, however, is based upon the assumption that in such case the operating company is one of the■ large transportation companies, inasmuch as although there might not be a profit in the immediate transaction of mining the pillars and installing the support, there would, of course, be a profit to such companies in carrying the coal to market.
6.	Culm flushing should be used only in coal beds having light cover, up to 200 to 500 feet, according to the settlement expected. But sand, being four or five times as strong as culm, is better, and, being suitable for filling all beds under Scranton, is to be preferred.
7.	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. Such might be the case, for instance, in localities where several beds of coal are separated by thin strata of shale and slate or even sandstone, and the pillars in the two or more beds are not over one another, and it is proposed to reclaim all or any part of the pillars.
Even though an application of the above-mentioned 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 beds have been filled the pillars in the uppermost bed may be attacked, and the space occupied by each pillar filled as soon as the pillar is removed. 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; after which the pillars in the next lower seam may be attacked and handled in like manner.
8.	Harmonious plans and procedure between the coal companies, the city, the school authorities, and the public are essential to the