Archive image from page 268 of Deep borehole surveys and problems. Deep borehole surveys and problems deepboreholesurv00hadd Year: 1931 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.

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