28 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



The results obtained are very satisfactory but the 

 apparatus exhibits the same deficiencies as Lapp's appa- 

 ratus because the basis of the record is time and not the 

 revolutions of the rods, and here even in a higher degree. 

 Since the motion of the recording surface is always uniform 

 it turns too quickly in solid strata and too slowly in broken 

 strata. In this way the variations in the recorded line, 

 upon which the stratigraph depends as stated previously, 

 are weakened, while in Lapp's method where the pen 

 works by clockwork they are increased. The irregularities 

 in the velocity of rotation of the rods in working are of no 

 great importance since the expenditure of power for the 

 proper action of the crown is small as compared with the 

 movement of the rods. 



Depth Measurers. — There are many types of these, the 

 simplest being the direct types. Figure 7 shows the simple 



. Measuring 

 ^ Wheel 



Frame 



Rone K>i 



Fig. 7.— Depth measurer. 



direct depth measurer of the Lucey Products Corporation 

 of Tulsa, Oklahoma, known as the Thatcher Depth- 

 ometer. It is easily assembled on a rod frame and is very 

 portable, being only 15 to 16 lb. in weight and can be used 

 on ropes up to Ij.^ in. diameter. The measuring wheel 

 transmits its revolutions by toothed gearing for direct 

 reading, and it can be used on bailing and apparatus lower- 

 ing ropes as well; also it can be used when letting the rope 

 into the hole or when pulling it out. 



Borehole Diameter Measurers. — Decisions as to the 

 variations in the diameter of a borehole are often necessary 

 to settle difficulties arising during boring. 



