152 MACHINES FOR CUTTING COAL IN MINES 



' But there is no reason why the machines should be restricted to a single shift 

 daily ; indeed, it is far more economical to work double shifts, there is no additional 

 outlay of capital, and so far as depends iipon the machinery, the output might be easily 

 increased to 8,000 tons .per week. 



' Wo now come to the relative costs of cutting the coal, by hand and by machine, 

 and the following figures may be taken as representing a somewhat favourable state 

 of things for the latter. 



' The seam is the " Middleton Main " or " Silkstone Bed." The depth of the mine 

 is 160 yards, and the coal four feet thick ; there are two bands of shale, with a thin 

 layer of coal between them. 



' The bottom portion is not always wholly merchantable, but when it is so, it yields 

 one ton and a third of a ton per running yard. For the purpose, however, of this 

 comparison, I take 60 tons only per day (which would come out of 45 yards of machine 

 working.' 



The Cost by Hand. 



30 Men cutting, filling, timbering, drilling, road-laying, blasting, 



and all other needful work ready in the corves for the " hurrier," * <* 



at 4s. b\d. per ton ..1389 



By Machine. 



1 Machine man at 8s. 6d .086' 



} ^th at 5s.6d.-l equal to 1 man . . . ./J { J 

 1 boy at 3s. 6. / \0 3 6 



3 men clearing and packing at 8s. 4d 150 



6 men filling, 10 tons each man at 85^. per ton .213 



3 men timbering at 6s. lOd 106 



th portion of cost of steam and air expenses . . . 1 14 

 Maintenance at Id. per ton . . . . . .050 



[Redemption of capital at 2d. per ton . . . . 10 



8 13 9 

 Difference in money in favour of the machine : or Is. Id. 



per ton . .4150 



13 8 9 



It is necessary now to bring under notice some of the other coal-cutting machines 

 which have been introduced of late years. 



Baird's, or the Gartsherrie Machine. One of the machines which has claimed the 

 largest share of attention is the ' Gartsherrie coal-cutter ' of the Messrs. Baird. This 

 appears to be a modified form of a machine which was patented many years since by 

 Mr. Gleadhill. 



The cutting in these machines is done by an endless chain with cutters attached, 

 driven round a jib or arm, which extends underneath the coal. The machine is actuated 

 by air compressed on pit bank to 35 or 40 Ibs. per square inch, and conveyed there- 

 from in cast-iron pipes. The machine at work draws or "feeds " itself along the coal 

 face, with the jib projecting underneath the coal 2 ft. 9 in. or 3 ft. as required. The 

 present work done (1874) is 300 to 350 ft., cut 2 ft. 9 in. deep, in a shift of eight to 

 ten hours, and as the seam worked is 2 ft. 10 in. thick, this yields 75 to 90 tons. 

 This rate includes all stoppages, and, of course, if it were possible to drive along 

 without interruption, the figures would be very much higher. The speed also is 

 capable of considerable increase by extra pressure of air, and when it is stated that 

 even in the hard Gartsherrie coal the machine has frequently been timed at about 

 6 ft. in four minutes, an idea may be formed of what it would do in soft English coal 

 with a good pressure above. The machine at work is attended' by three men. The 

 working parts 'of the machine are carried upon a strong cast-iron soleplate 6 ft. long 

 by 2 ft. 6 in. broad, set upon four wheels. On the soleplato is bolted the cylinder, 

 8 in. in diameter, with a 12-in. stroke. The crankshaft is fixed in bearings cast on 

 soleplate. On' this "shaft is the fly-wheel and cxcentric, which is reversible. On one 

 end of the shaft, overhanging the soloplate, is attached a spur-wheel, which by means 

 of another shaft and bevel-gearing, is connected to an upright shaft, on under end of 

 which is the chain-wheel, communicating motion to the cutting chain. The whole of 

 these wheels are of Bessemer steel, and, so far as proved, appear to give the greatest 

 satisfaction in wear. The cutters, nine in number, and 2| in. broad on face, are 

 secured to the chain by means of two bolts passing through cutter and link. The jib, 

 which distends the chain, is bolted to side of soleplate, and consists of two parts, the 

 stock and point, adjustable by means of a nut and screw working against a bridge in 



