122 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



measurer and, crude as it appears, therefore deserves a 

 place of regard in our remarks. Here it was decided, 

 after the borehole had gone down 200 ft,, to connect it by 

 a mine with a neighboring well 18 ft. 3 in. distant, center 

 to center. A mining engineer was then sent down, and he 

 showed where the hole ought to have been, but as it was 

 not to be found at that spot, it was evident that it had 

 diverged from the vertical. The ground had already been 

 cut away all round the place, and an unsuccessful attempt 

 had been made to locate the hole by the device of listening 



,4 = Vertical Base of Borehole 

 E=Aciual 



Fig. 67. 



while the rods were shaken within it. Mr. Haddow cut 

 a space of 3 ft. all round this spot, and the mine extended 

 6 ft. farther before he attempted to indicate the position 

 of the hole by the device of passing a magnet down it, and 

 noting its effect on a compass stationed in the mine. He 

 procured four 8-in. bar magnets, which he put end to end 

 and secured between two laths of wood. These were 

 lowered into the bore with the south pole downwards. 

 The north end of the compass needle moved first to the 

 west, then to the east of zero, which showed that the mag- 

 nets were on the west side of the compass, and led to the 

 mine B being cut (Fig. 67). While this was proceeding 

 he set the compass on a table and passed the magnet 

 round it; finding a number of points on the floor where the 

 deflection of the needle equaled 3^^ deg., he then drew a 

 line through the points found. He did the same for other 



