MARYLAND COLLIERY. 271 



years ago had 8-yard Lords, and 4-yard pillars. The latter not 

 being strong enough, the roof has collapsed, and the surface 

 in places looks like a gigantic ploughed field. Fig. 174 gives 

 an idea of the appearance of the surface, at a place where 

 there is about 30ft. of cover. The direction and position of 

 the Lords and pillars can be readily distinguished. The creek 

 has broken into and flooded a portion of the old workings. 

 Now both Lords and pillars are made 6 yards wide. The fol- 

 lowing is a section of the seam : 



Hoof, shale, does not stand well. 

 Little tops (coal: this 



is left, as it makes 



a good roof) 1ft. 



Penny Land lin. 



Big tops (coal) .. .. 2ft. / ) second 



Penny Land lin. ' working. 



Coal 2ft. 4 extracted. ] 



Penny band lin. 8ft. coal 



Coal 4ft, j first 



Floor hard sandstone. ' working. 



The lower 6ft. of coal only is taken out when mining the 

 Lords in the first instance : the upper 2ft. of coal is extracted 

 in the Lords at the same time that the pillars are drawn. When 

 drawing the pillars, as the roof is tender, a strip of coal is taken 

 out right across the pillar at the far end. The roof falls close 

 up to the face in spite of the timber used to support it. When 

 this happens a stump is left for three yards, and then a four- 

 yard crosscut is put through the pillar, after which they start 

 to take out the stump; if the roof does not fall again, they go 

 ahead till it does, and then proceed as before. 



The chief trouble in this mine is the water. Coffer dams 

 are built of timber and clay to about Gin. above water level, so 

 as to hold it back. The combined pumping capacity of all the 

 pumps in the mine, which can be put into commission in case 

 of emergency, is 150,000 gallons per hour. 



The Co-operative Colliery. 



This colliery, situated at Plattsburg, is owned by Messrs. 

 Laidley and Co., and has been managed by Mr. Jas. Barr for 

 the past 19 years. It is an old mine, and the miners are wow 

 chiefly engaged in extracting pillars. The pillars are worked 

 in two lifts of 4 yards each. One lift is extracted in-bye the 

 other out-bye. 



