MACHINES FOR CUTTING COAL IN MINES 153 



stock. The chain is made of wrought steel, and the cutters of the best tool-steel. The 

 machine draws or " feeds " itself by means of a drum and a 7 B 3 in. chain passed round 

 a pulley fixed to a prop 100 ft. in advance. The drum shaft is actuated through n 

 toothed wheel worked by a racket motion from an excentrie cast or bevel-wheel of 

 upright shaft. The roadway on which the machine travels is of cast malleable iron. 

 The rails are keyed clown to sleepers, and are kept in condition by means of snugs 

 cast on sleepers, which fit into oblong holes in end of rails. Each machine is fitted 

 with 21 ft. or seven pairs of such rails 3 ft. long. The machines are of two designs. 

 No. 1, being 2 ft. 4 in. high, requires about 3 ft. of head room between pavement and 

 roof. No. 2 is 1 ft. 8 in. high, including roadway, and so is capable of working tho 

 thinnest seam. The gearing can be altered to speed required by the nature of the coal 

 or other material cut. They have been adapted to undercut clay band iron-stone lying 



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on hard sandy fire-clay. At work the machine is attended by three men, one driving, 

 one lifting roadway behind machine, and the other laying roadway in front, &c. 



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The cutters are sharpened at each shift, the cutting chain being brought to bank daily 

 for thjs purpose, and the cutters removed, sharpened, and dressed to a gauge. 



This description will be rendered quite intelligible by reference to the drawings. 



