THE CONQUEST OF NATURE 



multipolar type, rests upon a steel carriage, which forms 

 the bearing for the main shaft ... A reversing switch 

 is provided, so that the truck can travel in either di- 

 rection, and when the machine has reached its stopping 

 point, either forward or backward, it is checked by an 

 automatic cut-off. The return travel is made in about 

 one-fourth of the time required to make the cut." 



In veins of coal of a thickness from twenty-eight to 

 thirty inches, such a machine will cut about one hun- 

 dred tons of coal in a day. The cost of production 

 with such machines has been estimated at about 

 sixty- three cents a ton, as against ninety cents as the 

 cost of pick mining in rooms, a saving of about 

 twenty-seven cents a ton. Since it is estimated that 

 for a cost of $10,000 an electrical equipment can 

 be installed capable of working four such machines 

 besides affording power for lighting, pumping, venti- 

 lation of the mine, etc., thus saving something like 

 $100 a day for the operator, the great popularity of these 

 machines is readily understood. 



After such a machine has been placed in position, 

 a cut some four feet wide, four or five inches high, and 

 six feet deep can be made in five minutes, with the ex- 

 penditure of very little energy on the part of the work- 

 men. One of the largest cuttings ever recorded by 

 one of these machines is 1,700 square feet in nine and 

 one-half hours, although this may have been exceeded 

 and not recorded. 



Among the several advantages claimed for the chain 

 machine over the older pick machines is the small 

 amount of slack coal produced, and the absence of 



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