49 AGRICULTURAL ANALYSIS 



mine shafts. In sinking these shafts great care is taken to pre- 

 serve unbroken the cap materials impervious to water, and thus 

 to prevent the highly soluble potash-bearing salts from being 

 rapidly leached or washed away. This inflow of water is made 

 impossible by sinking iron tubes or lining the shafts with con- 

 crete. Water is the great danger in potash mining, and has 

 destroyed valuable mines. Generally, potash mines have a re- 

 serve or emergency shaft, some distance from the working shaft, 

 protected by strong safety-pillars. Another mining difficulty is 

 the "pillaring" or supporting the mine-roof as its mineral sup- 

 ports are cut away. Formerly pillars of salt were left for this 

 purpose, but they disintegrated so rapidly as to be dangerous, 

 and the safer system was adopted of completely filling up the 

 excavations with the waste salts and rock salt. Within the 

 mines, potash salts are broken down by blasting as in ordinary 

 mining. In many of the works electricity is used for motor 

 power and in lighting. The mines are necessarily kept perfectly 

 dry, and visitors are free from the inconvenience and discom- 

 fort usual to underground workings. The carnallit blastings tear 

 off large blocks, which are broken up by the miners and trans- 

 ported in small cars to the shafts, thence to be hoisted to the sur- 

 face and delivered to the chemical works for grinding and fur- 

 ther treatment. 



419. Methods of Conducting the Mining Operations. These are 

 shown in the accompanying illustrations. Fig. 40 shows the 

 general appearance of the interior of a mine, especially the man- 

 ner in which the strata after deposition have been twisted and dis- 

 placed by seismic disturbances. In Fig. 41 is illustrated the 

 manner of drilling preparatory to a blast, and also the debris of 

 the blasting and other mining operations. The tunnels are so 

 driven as to support the superincumbent mass. A noon-day 

 luncheon party is shown in Fig. 42. The illustrations are from 

 photographs furnished by the German Kali Syndicate. 



420. Manufacturing the Concentrated Salts. As has been in- 

 timated, at the mine mouths are extensive and completely equipped 

 chemical works which refine the crude salts and separate their 

 constituents into products best suited^ to the various chemical in- 



