30 CEMENTS, LIMES, AND PLASTERS. 



'' Unfortunately, the adit was driven so nearly level as to render 

 drainage very difficult, and much water stands in depressions on the 

 limestone floor. 



" The adit is lined with rough-hewn oak, walnut, and red-elm timber, 

 except the last 300 feet, which has round timbers of similar material. 

 Three-quarter sets that is, sets with posts and caps only are em- 

 ployed. The posts and caps are 6 feet 2 inches and 6 feet 4 inches 

 long, respectively, both being 8X8 inches in section. They are spaced 

 36 inches. The posts stand on a limestone stratum 2 feet in thickness, 

 and therefore require no sills. The sets for the first 700 feet are lagged 

 with 2 X 12-inch oak plank; the remaining 300 feet has plank lagging 

 on the caps and pole-lagging on the posts. A single track of 36-inch 

 gauge is laid in the middle of the tunnel for the mine-cars, which are 

 drawn by mule-power. The cars have a capacity of from 800 to 1000 

 Ibs. gypsum. 



"The gypsum mined is 8.5 feet thick and is won by shooting it from 

 the face or sides of the rooms, holes being bored by hand-operated 

 post-augers, Hardscop make. The holes are 1.5 inches in diameter and 

 range from 3 to 6 feet deep. Black powder of C grade is usually em- 

 ployed, the charge ranging from 6 to 14 inches per hole. Squibs are 

 employed in firing the charges. The cost of explosive per ton of gypsum 

 extracted is about four cents. 



A 4 X 6-foot air-shaft connects the end of the adit with the surface, 

 96 feet above." 



Working gypsum-earth deposits. Deposits of gypsite or gypsum 

 earth, being purely surface deposits of a soft, granular material, can 

 be worked best by methods entirely different from those used in ex- 

 cavating rock gypsum. The gypsum earth is not only soft, but frequently 

 carries a large percentage of moisture: and as it freezes deeply because 

 of this moisture, the Kansas deposits can be worked only during warm 

 weather. If the gypsum earth is covered by soil or sand, this is stripped. 

 The gypsum earth is then loosened by disk harrows or plows, and taken 

 up by wheeled scrapers. It is then taken to drying-sheds, in order 

 to get rid inexpensively of as much of the water as possible. The cost 

 of working a gypsum-earth deposit, under average conditions, may 

 fall between 10 and 25 cents per ton. 



