Pt. II. Chap. II.] collieries — mode of working. 165 



doubt, this is mainly due to the small depth, the deepest shafts yet 



opened in this mine being only 160 feet from the surface to the bottom 



of the coal, while most pits do not much exceed 100. 



In Tapassi mine, the whole seam is 22 feet in thickness, from the 



centre of which 12 feet of coal is mined. The 

 Tapassi mine. 



colliery has not been regularly or largely worked 



until lately. In this case, both roof and sole are formed of coal, which 

 is in general finer and safer than either sandstone or shale. Indeed, 

 in some mines, as at Sirsol, 2 or 3 feet of coal are left in the roof to 

 strengthen it.* Of all the mines above mentioned, the worst condi- 

 tions for working exist at Rogonathchuk. Here a 12 feet seam of 

 coal is mined, the roof is of coarse sandstone, very irregular and unsafe, 

 and, despite the relatively large size of the pillars, huge blocks conti- 

 nually fall, sometimes almost blocking up the galleries. The mine is 

 rather deeper than the average, the two shafts at present worked being 

 138 feet and 148 feet respectively. The mode of working at Harisptir, 

 Mangalpur, and Chokidanga is similar to that at Raniganj, and the 

 seams worked are similar in thickness. 



Except in the one instance of Chinaktiri, the tools employed by the 



workmen are crowbars, hammers of large size, 

 Tools used. . 



and wedges. In Chinaktiri alone, picks are used, 



but the method of working is altogether bad. The coal, instead of 



being " holed under," or cut away at the bottom, and wedged down 



from above, is cut out above, and then broken away from below, 



mainly by crowbars and wedges. This plan was probably introduced by 



Mr. Betts ; that ordinarily pursued in all mines, except Chinakuri, was 



* This is one reason only. Another is, that it has become customary to work away a seam 

 of coal not exceeding 10 or 12 feet in thickness. If the coal is thicker, the lower part is sub- 

 sequently removed from the floor of the gallery. The mode of working employed is best 

 adapted for seams of moderate thickness, and, unless improvements are introduced, a large 

 proportion of the coal in the field will be irrecoverably lost and wasted. 



