262 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



2. Those which have to hit a given point in a known 

 seam, lode, workings, etc., the problem being to find the 

 required initial inclination and bearing of the hole. 



Fig. 175. — Borehole assisting subsequent sinking. 



The practical problems connected with these important 

 groups of problems arise when it is desirable 



1. To tap known bodies of water, gas, mineral, etc. 



2. To assist in sinking a shaft to known workings and 

 thus remove the debris by borehole with trams spotted 

 beneath (Fig. 175). 



3. To aid ventilation of seams being worked simul- 

 taneously. 



4. To conduct haulage ropes, electric cables, com- 

 pressed-air lines or stowage pipes. 



5. To explore for new deposits, etc. 



1. Given a Definite Angle for the Hole and Two Known 

 Points in the Stratum to Find Where the Borehole Will 

 Strike the Stratum. — A and D (Fig. 176) are imagined as 

 being in the same plane as the borehole but need not 

 necessarily be as long as they are in the seam or stratum 

 being investigated by the borehole; their positions can be 

 projected into the borehole plane and a lateral term included 

 in the computation finally. 



