Figure C-10. Bringing BT aboard with a retrieving line and ring. 



it to be sure that a suitable trace has been ob- 

 tained. With a sharp instrument or pencil, write 

 the following information on the slide, being 

 careful not to obscure or touch the temperature- 

 depth trace (fig.C-13). 



Slide number and time grouf. Number slides 

 consecutively. Use Greenwich Mean Time (0000 

 to 2359 ) , giving the hour and minute at which 

 the BT entered the water. Enter a dash between 

 slide number and time. Slide number five taken 

 at 2240 is marked : 5-2240. 



Day^ month, and year. Use Eoman numerals 

 for the month. 29 November 1966 is written : 

 29-XI-66. 



BT instrument serial number. The serial 

 number of the BT is stamped near the nose of 

 the instrument. This number is very important 

 as each BT has a calibrated grid, a duplicate of 

 which is on file at the laboratory that will proc- 

 ess the slide. Without the proper serial number, 

 the information on your slide is valueless. In- 

 clude any letter which precedes or follows the 

 serial numbers; e.g., BT A-1257 or BT-1216A. 



Always enter the information on the slide in 

 the order given above. Avoid the temptation to 

 improve an apparently faint trace by enlarging 

 or tracing over it at the time you enter the data. 

 The processing laboratory can copy an actual 

 trace, however faint, by the delicate photo- 

 graphic processes it uses, but a retouched trace 

 will invariably be detected and rejected. After 

 the slide is labeled, rinse in fresh water, read 

 the slide, and record the data on the log sheet. 



C-6 Reading the BT Slide.— The BT grid 

 (fig. C-14) is connected to a magnifying grid 

 mount viewer which facilitates holding and 

 reading the BT slide. 



Clean the grid with a cloth or tissue. Place 

 the slide in the viewer with the coated surface 

 toward the grid and the beveled edge toward 

 the set screw. Gently push the slide down against 

 the spring and into place so the coated surface 

 lies flat against the grid and snugly against the 

 set screw. 



C-6 



