PROBLEMS 



257 



Let 



i = the inclination of the drill hole XX i from the 



horizontal. 

 di = the angle between the bedding and the axis of the 



hole which is obtained from an examination of the 



drill cores. 

 d = the difference in strike of the bedding and the drill 



hole. 

 8 — the true dip of the strata. 



Fig. 172. 



Let 



Fig. 173. 



A = any point on the drill hole — in our figures it is 

 the point at which the drill hole enters the bed 

 or seam — from which a perpendicular can be 

 erected on to the plane of the bedding. Call 

 this perpendicular Ab. 



