10 MINING CONDITIONS UNDER CITY OP SCRANTON, PA.
mines, and after tabulating and considering the information gained by these investigations, the conclusions we have reached are as follows:
Although some other devices are locally useful, the only method that combines the necessary qualities of strength, ease of application, and reasonable cost is filling the underground openings by what is known as the “Hushing” method, using for flushing culm, sand, crushed rock, and other fine material that can be washed into the mines with water. This method was originated in the anthracite region of Pennsylvania, and has been extensively adopted in European mines, where, at great expense, sand, loam, and crushed rock are flushed into the mines following the removal of the coal by the longwall method of mining.
The tables and estimates of cost contained in the body of the report give in detail the results of our investigations and conclusions.
We therefore offer as our only recommendation that the flushing method be adopted, under the plans and specifications contained in the body of the report and in plates 1 to 24. From the report the following general conclusions are drawn:
1.	Speaking broadly, the surface of the city can be supported by the methods recommended, and at a cost not in any sense prohibitory when considered with relation to the value of the property and operations for which support is absolutely essential.
2.	Although in our judgment there are points in the city, as indicated in the detailed report, where at the present time there is distinct and immediate danger to life and property, yet the total area immediately threatened constitutes but about 15 per cent of the entire area of the city, and the danger is mainly from workings in surface beds.
3.	On the west side the beds of the middle series are thick and close together, and the pillars are not columnized, creating a dangerous situation where the workings have not been closed by previous caves. Particular areas thus threatened can not be definitely speci fied on account of the inaccessibility of much of the mined-over area. Detailed investigation should be made of the portions of the mines not already closed. Relatively, we do not believe that a large part of the territory mentioned is threatened on account of so much ground having been already closed by caves.
Special attention is called to the conditions under schools Nos. 13, 23, and 29. They should be attended to promptly.
The lower series of beds, namely, the three Dunmores, are so thin and so far below the surface that with the usual system of mining we do not think they constitute a serious menace to the improvements on the surface, except along the margin of solid blocks of unmined coal and near the outcrops. In the deep-lying parts of the Dunmore beds we believe these solid blocks should be mined.