that to work the bed with a rock cover of probably 50 feet will prove possible, as has been found possible in other collieries.

Suggestions for second mining.—At present there is no intention of conducting second mining in this territory, for there is considerable danger that a roof break extending upward to the water-bearing sands of the buried valley might cause the flooding of the mines. The possibility of second mining this territory has been considered, however, and one method suggested by the company engineers is that rock holes be driven through the parting from the Bottom to the Top Twin bed.

As the parting spalls readily, these rock holes would have to be carefully timbered along the edges, possibly with cogs or rows of props; then, second mining would start from the upper end of the chamber in the Top Twin, and the Bottom Twin would be worked simultaneously. The coal from the Top Twin would be sent down through the borehole to the waiting mine car or sheet-iron chute underneath, and the coal from the Bottom Twin would be shoveled either into the mine car or to the chute and taken to the gangway.

The company engineers have also advanced the idea that it may be possible to shoot down and gob the parting rock between the two beds and take a slice from the pillar advancing, then to stow the parting or enough of it in this space so that a roadway can be cleaned up in the.room. The coal in the Top Twin would thus be made accessible and the recovery of coal from both pillars permitted. Recovery of the coal from the pillar in the Bottom Twin on the opposite side of the room would necessitate clearing up short roads across the room to each one of the pillars. These rock holes or roadways would need to be placed in alternate rooms only, as two pillars could be recovered for each roadway or set of rock holes.

Of course, in work like this great care must be taken in order that the utmost amount of coal may be recovered consistent with furnishing ample support to the roof, that no breaks endangering the colliery may occur, and that the place will be left in such a condition that more of the coal will be obtained by second mining if a method that will give enough final support to the roof is found.

ROCK FILLING TWO BEDS MINED SIMULTANEOUSLY

Beds mined.—In many parts of the anthracite region the parting between two beds becomes very thin, too thin to allow either of the beds to be mined separately; then both have to be taken at once. Such a condition exists in the No. 17 slope district, road 415 of the colliery, where the Top and Bottom Skidmore beds are separated