CHAPTER XV. 

 SPECIAL PROBLEMS. 



Shooting. - - The practice of "shooting" - exploding a charge 

 of nitroglycerine or other explosive in a well has long been suc- 

 cessfully employed in the oil regions, and has in late years been 

 used to increase the flow of water wells, in which dynamite is 

 more commonly used. The action of the dynamite is to shatter 

 the surrounding rock, with the result that connection is fre- 

 quently established with other crevices, in some wells largely 

 increasing the water supply. The dynamite is most effective in 

 hard, brittle rocks, such as limestone, which are as a rule com- 

 pletely shattered by the explosion, and is least effective in soft 

 tough shales, which are bent and compressed rather than broken. 



Use of Steam Jet. Shooting, owing to the character of the 

 materials, is not usually practiced in unconsolidated deposits, in 

 which the steam jet is sometimes used instead of dynamite. The 

 steam is forced down a small pipe inside a larger one and, com- 

 ing into contact with the water at the bottom, turns it quickly 

 into steam, the resulting explosion loosening the material or mak- 

 ing a pocket about the bottom of the pipe. Where the materials 

 are dense and clayey the action of the steam jet may considerably 

 increase the influx of water; in the more porous deposits it has 

 less effect. 



Screening the Well. Wherever the well is sunk in uncon- 

 solidated materials in which the grains are small enough to be 

 moved by the water entering the well, the use of some sort of 

 screen is essential. The method of forming a natural screen by 

 pumping the finer particles from amongst the coarser materials at 

 the bottom of the well, of inserting and packing gravel about the 

 lower end of the pipe, and the nature and use of the common 



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