CraNneE.| Prospecting, Mining and Milling Machinery. 223 
parts and appliances of a drill would be too lengthy for the 
intended scope of this work, so will be omitted. 
The temper for the tools is set in the copper color for very 
hard flint and is drawn out more (made softer) as the hard- 
ness of the rock decreases. 
TO ORILE 
Fig, 30. Actuating device employed in the American rope system of boring holes. 
Mine Machinery. 
No machines other than hand or power drills can success- 
fully cope with the conditions met with in the lead and zinc 
districts of Missouri and Kansas. The exceedingly irregular 
occurrence of the ore bodies allows a wide range of move- 
ment in the mining operations, which would be disadvan- 
tageous to the handling of heavy mining machinery. It is 
comparatively easy to operate machines, even of considerable 
weight, on a level surface, but when they have to be elevated 
100 feet or more, and that, too, over rough and often loose 
ground, machines other than tripod and column drills are 
rendered practically useless. 
Power Drills and Drilling. 
Compressed-air drills of the Rand and Ingersoll makes are 
beginning to take the place of hand drilling, which has been 
the practice in the district for years. These drills are prob- 
