. Standardization of mining methods; a series of important articles reprinted from Engineering and mining journal. e canvas tubing, coil it up along the drift, and moveit back a reasonable distance. At times some of thesmaller pieces from the blast flew back and cut holes inthe canvas, which damaged it considerably, and in addi-tion, the tubing was subjected to the ordinary wear andtear of rolling it along the drift and coiling it up inplaces where there was frequently mud and water. Some time ago experiments with small blowers anddifferent kinds and sizes of ventilating pipe in 100 and200-fc.
. Standardization of mining methods; a series of important articles reprinted from Engineering and mining journal. e canvas tubing, coil it up along the drift, and moveit back a reasonable distance. At times some of thesmaller pieces from the blast flew back and cut holes inthe canvas, which damaged it considerably, and in addi-tion, the tubing was subjected to the ordinary wear andtear of rolling it along the drift and coiling it up inplaces where there was frequently mud and water. Some time ago experiments with small blowers anddifferent kinds and sizes of ventilating pipe in 100 and200-fc. lengths were made under my supervision. Itwas found that the velocity and volume delivered at the VENTILATION OF METAL MINES 43 end of 200 ft. of 10-in. canvas tubing were consider-ably less than when delivered, under similar conditions,at the end of 200 ft. of 10-in. iron pipe. This made itevident that in order to deliver the same volume of airat the working face through canvas tubing that it ispossible to deliver through the iron pipe, it is necessaryto have a much larger size of canvas tubing, or else, if. Fig. 3. Door for Both Hand and Mule Team the same size tubing be used, the blower must be speededup or a larger blower be installed. In places where thecost of power must be considered, the extra expenseis important. Metal rings inserted in the canvas tub-ing at frequent intervals restore more nearly the con-dition effected through the use of the iron pipe, as theyhelp to support the canvas, which otherwise would have 44 STANDARDIZATION OF MINING METHODS only the air pressure as support. However, all theseimprovements add to the cost of the tubing, and there
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