8 DEEP BOREHOLE SURVEYS AND PROBLEMS 



fresh deposits will become more common. In these daily- 

 growing cases, especially in those situated near property 

 boundaries, legal disputes will be settled by the results of 

 borehole surveys. Again the deep borehole being the most 

 straightforward and direct verification for any completed 

 geophysical survey, any doubt which may arise as to (1) 

 mapped lenses being missed in the borings, (2) the nature 

 of the body surveyed aboveground (3) its extent, etc., can 

 only be verified by a thorough instrumental survey of the 

 boreholes concerned. Since deviation of a string of tools 

 may take place in the ultimate up to and beyond 60 deg. 

 from the originally intended direction,^ and boreholes are 

 now attempting the enormous depth of 10,000 ft. and more, 

 the great significance of deflection surveys is obvious. 



Horizontal and inclined boreholes, particularly upward 

 inclined holes, deviate sooner and to greater extent than 

 vertical ones.^ They also give rise to a special set of 

 deflection apparatus, but, generally speaking, results of 

 surveys of such holes are not so reliable as those of vertical 

 ones. Thus most of our remarks will apply to deep vertical 

 boreholes. 



There is no doubt that the best evidence of initial or 

 subsequent deflection in boreholes is to be obtained from 

 the precision with which the working of the entire system 

 of boring is checked. The onus rests almost entirely upon 

 the boring master and personnel, chiefly because the site 

 is usually situated far from the headquarters of the boring 

 company and its direct command. Thus the master borer 

 should be selected mainly on his experience, skill and 

 ability, other qualifications notwithstanding. There is 

 more responsibility upon him than in any other sphere of 

 technical work. This applies more in foreign and remote 

 lands. Thus it is important that all hands graduate in 

 the actual school of practice from the meanest position 

 upward. 



^ Kitchen, op. cit., mentions one deflection of 66 deg. 

 ^ Justice, J. N., Channing, Park, Trans. Inst. Min. and Met., Vol. 12, 

 p. 319; Proc. Lake Superior Min. Inst., Vol. 2, p. 23, 1894. 



