240 DEEP BOREHOLE SURVEYS AND PROBLEMS 



Oi is the mainspring and O2 is a fine adjustment spring 

 controlled by the screw F. The lever carrying the mass H 

 is extended by the light cone N. For transit the clamping 

 screw G is released and the weight H is withdrawn from the 

 tubular fitting into which it is normally fitted. The system 

 is then automatically clamped, owing to the load on the 

 spring Oi. At the end of the cone iV is a fine rod J, the other 

 end of which bears lightly on a horizontal disc in such a 

 way that any small movement of the mass H relative to the 

 base of the instrument causes a rotation of the disc. 

 A mirror is so mounted that this rotation causes a corre- 

 sponding movement of the mirror which is recorded photo- 

 graphically by a compact form of paper camera. The 

 moving mirror system, which is the only delicate part of 

 the apparatus, forms a complete unit which can be easily 

 removed and replaced, and which is disconnected from the 

 rod J by a simple automatic device. Light from a lamp 

 mounted in the camera passes through a convex lens K and 

 is reflected from the mirror so that an image of a slit in front 

 of the lamp is focused down to a bright spot of light on the 

 photographic paper. 



Malamphy^s Seismic Method of Surveying Boreholes. — 

 For localizing the work of a seismograph, i.e., concentrating 

 it upon a given spot, a form of wave detector of electric 

 line microphone or geophone may be sunk to any desired 

 depth in a borehole. This has been done by M. C. Malam- 

 phy in the western American oil fields^ and has yielded 

 hopeful results. 



The geophone is lowered into the hole to the desired spot 

 and shots (gelignite or dynamite) are located about the 

 hole with seismographs at known distances from the hole, 

 for time records. The method is much simplified and it is 

 thought that errors are distributed uniformly by this 

 method. If the hole is straight the time for each shot will 

 be proportionate to the distance of each less the strata 

 corrections, etc., for the place being considered. If the hole 



1 Seismic Method of Determining Deviation in Drill Holes, Oil Weekly. 

 p. 32, Apr. 26, 1929. 



