MACHINES FOR CUTTING COAL IN MINES 151 



When all is in readiness for work, the air is admitted to the machine, and the 

 reciprocating action commences. The piston works at a speed of sixty to ninety 

 strokes per minute, varying according to the density of the compressed air, the hard- 

 ness of the strata to be cut, or the expertness of the attendant. 



1413 



As to the qxiantity of work. In ' long-wall,' a machine can, under favourable cir- 

 cumstances, cut 20 yards in an hour, to a depth of 3 feet; but we consider 10 yards 

 per hour very good work, or say 60 yards in a shift. 



This is about equal to the day's work of twelve average men, and the persons em- 

 ployed to work the machine are one man, one youth, and one boy, who remove and 

 lay down the road and clear away the debris. 



The machines are built so strong that they rarely get out of working condition. 

 Some of those now working at West Ardsley (and other places), have been in constant 

 use for three or four years. 



At that colliery there are about eight machines in use. One of the seams is so hard 

 and. difficult to manage, that it could not be done ' by hand,' and the proprietors had 

 to abandon it, but now, by the employment of these machines, it is worked with per- 

 fect ease. It is a thin cannel seam, with layers of iron-stone, and the machines now 

 'hole' for about 1,200 tons per week. 



The groove made by the machine is only 2 or 3 inches wide at the face, and lg at 

 the back, whereas by hand, it is 12 to 18 inches on the face, and 2 to 3 inches at the 

 back, thus : 



In thick seams worked by hand, the holeing is often done to a depth of 4 feet 6 

 inches to 5 feet, and the getter is quite within the hole he has made, and where the 

 coal does not stick well up to the roof, or where there is a natural parting, there is great 

 difficulty and danger from falls of coal. In cutting coal by the ordinary method, the 

 angle is such that when the upper portion of coal falls off from the roof, that it must 

 pitch forward into the ' road,' but by the machine cutting a perfectly horizontal groove. 

 The coal, having lost its support, simply settles upon its own bed ; and has no tendnecy 

 to fall forward. 



The following statement was made by the inventor at the meeting of the British 

 Association at Bradford : 



1 The cost of applying coal-cutting machinery is an important part of the question, 

 but it frequently happens that at old established collieries there may be surplus 

 power, which can be utilised ; but supposing that everything has to be provided new, 

 then the following may be taken as an approximate estimate of the necessary outlay : 







2 Boilers at 5001. each 1,000 



1 Steam-engine 1,250 



10 Machines at 1501. each 1,500 



Pipes, Keceivers, Fixings, and sundry other outgoings . . 1,250 



say 5,000 



' This outlay would provide all necessary power and plant for the regular working 

 of eight machines, with two in reserve ; and estimating that each machine will cut 60 

 yards per day, the product in a 4-foot seam would be 85 tons per day, or per week say 

 500 tons per machine, and 8 by 500 is 4,000 tons. 



' Now at this rate of expenditure and work done, an allowance of 2d. per ton would 

 in three years liquidate the entire outlay. 



