cedure for constructing the ZjL graph is as 

 follows : 



1. On the vertical side of the graph, lay off 

 the wire depth starting with zero at the upper 

 left for the shallow cast and the upper right for 

 the deep cast (fig. 3-6). Use a convenient 

 depth increment for each cast which will allow 

 space for the maximum wire deprth sampled. 



2. Compute the depth ratio for each ther- 

 mometric depth by dividing the thermometric 

 depth by the wire depth and record these 

 values in the Obs. (Observed) column of the 

 A-sheet. The values used for the sample in 

 figure 3-6 are : 



TheTmometric 

 Wire depth (L) depth (Z) Depth ratio {ZjL) 



Cast I: 



0.961 (cos 16°) 



200 190 .950 



300 283 .943 



400 365 .962 



Cast II: 



0. 891 (cos 27°) 



600 538 .897 



1200 1068 .905 



2000 1853 .927 



2300 2153 .936 



3. Across the top of the graph lay off the 

 depth ratio, ZjL, commencing with highest 



cosine value at the left decreasing to the right 

 in convenient increments. 



4. Plot on the graph the depth ratio at wire 

 depth and construct curves through the best 

 combination of usable points. If the wire 

 angle is small, the ratio is nearly constant and 

 approaches unity. However, if the wire angle 

 is large the ratio usually increases with depth, 

 indicating that the wire becomes more vertical 

 with depth. If the ratio curve is not reasonably 

 smooth it should be studied for errors. Er- 

 roneous values can be caused by improper 

 tripping of the bottles, malfunction of the 

 thermometers or meter wheel, etc. Values 

 that appear to be in error will fall out of the 

 smooth-curve pattern and should be disre- 

 garded when drawing the curve. 



5. After drawing the curve, pick off the new 

 ratio values for every bottle at the wire depth 

 and enter them in the Used column of the A- 

 sheet. To obtain the accepted depth for each 

 sample multiply the wire depth by the new 

 depth ratio. Example: 



(L)X(Z/L)= Accepted depth. 

 1,500X0.913 = 1,369 meters. 



38 



H. O. 607 



