FLUID METHODS OF SURVEYING BOREHOLES 109 



the danger of premature solidifying of the gelatine in holes 

 of great depth, with the consequent fixing of the floating 

 needle, a small thermos flask (Fig. 57) is used to hold the 

 gelatine and needle, the other half of the apparatus having 

 the tube of HF. Figure 58 shows the special goniometer 

 used for checking the results. The Maas method used to 

 be popular in the Lake Superior mining fields years ago. 

 The method is fully described and illustrated by E. E. 

 White. 1 



The Modified Maas Method.— In the modern adapta- 

 tion of Maas' method HF with either gelatine or paraffin 

 wax is used. If either of the latter is adopted it is melted 

 in the hole after lowering the instrument.- This obviates 

 the thermos flask trouble of Maas and MacGeorge. 



The apparatus a (Fig. 59) is let down on a cable b which 

 carries a connection c to a dynamo aboveground. An arc 

 d in the circuit is carried through the casing, with the glass 

 vessel e inside, and when in position the current is switched 

 on and the wax or gelatine / melted, giving about three- 

 quarters of the container length of fluid. In this thinned 

 state it has a horizontal surface and the magnet of the com- 

 pass g enclosed in the very mobile liquid can easily move, 

 as seen in Fig. 59. After a given time the current is 

 switched off, the paraffin again solidifies and the apparatus 

 is withdrawn. The amount and direction of deviation 

 are now easily read. 



The apparatus is widely used today owing to its simplic- 

 ity, cheapness and reliability for most purposes. It has 

 been well tried in South Africa. 



Meine's Apparatus. — As a variation of the principle of 

 using a fluid for marking (just for the time of the survey) 

 the position of its surface in a vessel. Dr. F. Meine of 

 Berlin produced the device^ of Fig. 60. In effect it con- 

 sists of a body being automatically immersed in a fluid 



1 Bull. Amer. Inst. Min. Eng., No. 71, p. 1277, 1912. 



2 Fauck, a., Remarks at the November, 1910, Convention of Austrian 

 Mining Engineers and Architects, Organ des Verein der Bohrtechniker, p. 277, 

 Nov. 20, 1910. 



3 German Patent No. 157,879. 



