76 DEEP BOREHOLE SURVEYS AND PROBLEMS 



a and b obtained underground to take up the new positions 

 a' and b' on the surface. In both cases the parallelogram 

 of displacement gives the direction in which weights h have 

 dipped plumb needle e ; which directions are shown by lines 

 oc and oc', and, since the line is in the meridian, angle coc' 

 will be the rotation of the apparatus on extracting the core 

 box. If the core is turned with its mark from points c to c' 

 it will have its proper geographical position aboveground as 

 below. A pendulum may be used instead of the plumb line. 

 The chief objections to the appliance are: 



1. Dropped messenger weights are unreliable. 



2. In the mud rotary system the apparatus may fail to 

 function. 



3. Much time is taken up in surface orientation. 



4. Many unaccountable turning movements are not 

 provided for. 



The apparatus, particularly in respect to the methods of 

 aligning the geographical positions above and below ground, 

 has been subjected to severe criticism by Dr. Freise^ and 

 the engineer, Erlinghagen.^ 



Rapoport's Method. — The idea of this device^ is one 

 embodying the former notion of a mold, as in Wolff's 

 apparatus. It is very ingenious and though apparently 

 unsuited to the conditions of actual practice, in its present 

 form, contains the germ of an idea which may be useful to 

 investigators and inventors. We have failed to trace any 

 literature dealing with its application in the field, but 

 believe it should not be disregarded. 



Figure 41 shows the apparatus which consists of a 

 cylinder a, let down into the borehole and having an axial 

 channel b to which an upper conductor c can be joined for 

 compressed air or pressure water. Underneath, channel b 

 is closed by a valve d which opens an exit channel e on excess 

 of internal pressure. The hollow body a possesses four 

 borings / at 90 deg. to one another radially in superposi- 



^ Organ des Verein der Bohrtechniker, 1907. 



2 Gliickauf, p. 737, June 15, 1907. 



3 German Patent No. 172,179. 



