4541 HYDROGRAPHIC MANUAL PaGE 380 



should be removed as far as practicable from masses of vertical iron. The case should 

 have a glass top through which to read the chronometers and should be subdivided into 

 separate compartments, one for each chronometer. Each compartment should be 

 padded and lined with baize cloth, so that the chronometer fits in it snugly and to reduce 

 any jar. A chronometer should never be removed from it? individual box, except in an 

 emergency, nor should the chronometers in their boxes be removed from their padded 

 compartments except when urgently needed elsewhere. Chronometers must never be 

 adjusted or reset on board ship. 



In transporting a chronometer by hand it should first be clamped in its gimbals and 

 always placed in the carrying case provided for that purpose. It should be handled 

 with the greatest care and only set down in transit on a cushion or some shock-absorbing 

 support. 



b. Preparation for shipment. — Before a chronometer is prepared for shipment its 

 balance wheel must be stopped. This is done by allowing the wheel to strike against a 

 small piece of paper until motion ceases. A stiff object or the finger must never be 

 used for this purpose. As the balance wheel is very heavj^ compared to its supporting 

 pivots, it is imperative that it be locked motionless during transit to prevent damage to 

 the delicate pivots. The wheel is locked by inserting soft cork wedges as nearly opposite 

 the spokes of the wheel as possible. Wedges should be pressed in carefully and simultane- 

 ously to avoid a sideways pressure on the pivots. They should never come in contact 

 with any of the adjusting screws in the balance wheel. Wedges should be firmly in- 

 serted to ensure their remaining in place but must never be forced. Cork wedges will 

 be issued with most chronometers, but should none be available, a soft and resilient 

 material should be used. 



A chronometer should always be removed from its gimbal rings for shipment. It 

 should then be packed in its box, surrounded on every side and top and bottom by 

 crushed paper so that it cannot possibly move in the box during shipment. 



The chronometer box should finally be wrapped hermetically with paper to prevent 

 infiltration of dust. In the outer shipping case it should rest on and be surrounded by 

 crushed paper or other cushioning material. Excelsior must never be used as it is dusty 

 and the fine powder wUl sift through exceedingly small openings. 



c. Winding. — Chronometers must be wound at the same time each day, despite 

 the fact that they are ordinarily constructed to run for 56 hours without rewinding. 

 This regular daily winding ensures a uniform rate. To wind a chronometer, turn it 

 gently on its side and insert the key in its hole until it seats. Steady the instrument with 

 one hand and wind counterclockwise for 7K turns. The last half-turn must be made 

 slowly and gently until the stop is reached. After winding, the key is removed and the 

 chronometer gently returned to its normal position. Wliere there are several' chro- 

 nometers, they should be wound in the same order daily, and after all have been wound 

 the indicator of each should be inspected to ensure that each has been fully wound and 

 that none was omitted. 



d. Comparison. — When a survey party is engaged in operations where accurate 

 chronometer time is needed, daily comparisons of all chronometers should be made 

 with radio time signals. The daily comparisons should be begun far enough in advance 

 of their need to establish an accurate rate for each chronometer. 



