102 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



clear from Figs. 52 to 56 showing the phials, guide tubes 

 and clinometer. The phials contain liquid gelatine. Clear 

 glass phials (Fig. 52) nearly filled with a hot solution 

 of gelatine and each containing a magnetic needle in 

 suspension, free to assume the meridian direction, are 

 encased in a brass protecting tube, let down to the required 

 depth and allowed to remain for several hours until the 



Fig. 52. — Gelatine phials. 



gelatine has set. On withdrawal the phials are replaced 

 at the same angle, at which they cooled, by means of the 

 congealed surface seen through the sides of the phial; 

 this is brought to the horizontal. Revolving the phial 

 upon the part where the magnetic needle is seen embedded 

 in the gelatine, until the needle is again in the meridian, 

 the phial is then in the same position, both as regards 

 inclination and azimuth, as it was when its contents con- 

 gealed. Thus we get the gradient and bearing of the bore- 

 hole at that spot, and these are measured by means of an 

 angular instrument constructed by the inventor. The 

 mean of the several phials gives a more accurate result. 

 By repeating this operation at measured intervals through- 

 out the borehole, its course is mapped. 



