AUXILIARY REGISTRATIONS IN BOREHOLE SURVEYS 43 



of the hole at the surface, are known with respect to the X 

 and Y axes, and the depth of any point A on the wire can 

 be found, since we can get the length L of the wire direct. 



F16.5 



Plate II. — Illustrating the basket method. 



From the similar triangles SCB and BaA (Fig 1) right 

 angled at C and a, we get 



CB _ SB^ .CB _ SB 



Ba ~ BA ^^^ Ca ~ SA 



and 



Ca = m -{- X = 



CB- SA 

 SB 



Then, by coordinate geometry for the small length CB = m, 



CB = m = V(^r^^0M^7^7=^iIP (4) 



It will be seen that m is a function of the length L of the 



