on the grid is the error for which corrections 

 must be made at all depth readings. 



2-56 Disassembly of the BT.— Do not dis- 

 assemble the BT. It is a precision instrument 

 with delicate internal mechanisms, and even 

 with the greatest care possible it is difficult to 

 avoid damage if disassembling is attempted 

 aboard ship. If for any reason the BT fails to 

 operate satisfactorily, it should be turned in for 

 repair with a report indicating the symptoms 

 to aid the repair facility in correcting the 

 trouble. Standard failure reports should also 

 be submitted in accordance with current direc- 

 tives. Those BTs issued by the Hydrographic 

 Office for Navy surveys should be returned to 

 that office. 



2-57 Maintenance of the BT.— The BT is 

 an accurate measuring instrument and while 

 the construction is reasonably rugged, the in- 

 ternal mechanisms are delicate. Careful hand- 

 ling is essential to maintain the accuracy of the 

 measuring elements. 



After each period of use, the BT should be 

 rinsed with fresh water. Never store a BT that 

 is being withdrawn from use without thoroughly 

 rinsing it. 



The interior of the BT should be rinsed with 

 one-half cupful of grade III rust preventive 

 compound each week. Place the BT in a clean 

 bucket, with the tail fins down. Slide the sleeve 

 forward toward the nose, pour in the compound 

 and close the sleeve. Then cover the four ports 

 or openings in the body tube, shake the BT and 

 turn it over on its nose and back several times 

 so that every part is thoroughly covered. Let 

 the compound drain out. The compound can 

 be reused several times. Do not oil the BT — 

 fresh water or rust-preventive compound is all 

 the lubrication necessary. 



2-58 Inspection of New Slides. — Do not 

 remove the water and airtight cover from 

 around the box of slides until ready to use the 

 slides from that box. This cover is to keep 

 the oil that retains the smoke on the slides 

 from drying out. Samples of slides in a new 

 box should be inspected before using. If the 

 smoked surface of a new slide is in bad condition, 

 or if the smoked surface shows spots after lower- 

 ing the BT, all the slides in the box should be 

 tested by holding each slide under a moderate 

 stream of water. Do not use those slides on 

 which spotting or flaking of the smoked sur- 

 face appears. If more than 25 percent of the 

 slides are unusable as a result of spotting or 

 flaking, report the failure in accordance with 

 current Bureau of Ships instructions. 



2-59 Paclcaging the Slides. — Whenever a 

 full box of slides is accumulated during the 



H. O. 607 



course of a survey, it should be packed securely 

 and shipped to the Hydrographer. Be sure 

 that all slides are properly lacquered and are 

 easily removable from the box. Indicate clearly 

 the cruises contained in each box. Pad the 

 corners of each box and wrap securely with 

 heavy wrapping paper. Seal the wrapper and 

 label" "BREAKABLE— HANDLE WITH 

 CARE." Slides should always be kept in 

 the special boxes in which they are provided 

 and should not be shipped in any other type of 

 container. 



2-60 Forwarding Completed Slides and 

 Log Sheets. — At times special instructions may 

 be given for forwarding completed slides and 

 log sheets. When such special instructions 

 have not been received and when a box of 

 slides has accumulated, send in the slides, log 

 sheets, BT position charts (see sec. 14-59), and 

 any special notes to : 



The Hydrographer 



U. S. Navy Hydrographic Office 



Washington 25, D. C. 



Attn: Code 5430 

 2-61 Forwarding Grids from BTs Lost 

 During Operations. — All grids from BTs lost 

 during operations at sea shall be forwarded to 

 the Hydrographer upon return to port or at the 

 end of a survey cruise. 



2-62 INSTRUCTIONS FOR OPERATING 

 THE SPILHAUS-MILLER SEA SAMPLER.— 

 The Spilhaus-Miller sea sampler is an instru- 

 ment resembling the bathythermograph and 

 operating in a similar fashion, with the ad- 

 ditional ability of obtaining water samples at 

 discrete depths within the limit of operation 

 (fig. 2-14). Basically a bathythermograph to 

 which 12 small sea water sampling bottles are 



Figure 2~H. The Spilhaus- .Miller sea sampler. 



25 



