as zero. The "bottom bound of the last interval with slope less than 

 -1°F/100 ft is then recorded. The slope between the upper and lower bounds 

 is computed and recorded as the first gradient. The following are except- 

 ions to this procedure: 



a. A gradient with thickness less than ko feet and slope greater than 

 -2°f/100 ft is discarded, and a new search is begun from the last interval 

 examined. 



b. If the first gradient persists to the end of the trace and the last 

 interval meets the requirements for inclusion in the first gradient, the 

 depth of the last recorded temperature is designated as the lower bound of 

 the first gradient. If the last interval of the digitized graph has a 

 negative slope but does not meet the requirements of a first gradient, and 

 the next to the last interval is included in the first negative gradient, 

 the lower depth of this interval is designated as the lower bound of the 

 first gradient. In either event, column 68 of detail card no. 3 is X 

 overpunched and the first gradient is preceded by a minus sign print out. 



17 



