THE BAHAMA ISLANDS 105 



vations. It is desirable, therefore, that he bestow the same care upon it as 

 upon a chronometer, viz. : it should be wound up at a regular time each day, 

 so that there will be no danger of its running down, should be protected from 

 sudden temperature changes and as carefully handled as possil)le. It should 

 be set to eastern (T.lt]! meridian) standard time, then the correction to the 

 nearest fraction of a second on standard time should be obtained from the 

 noon signals on two or three days before the departure for the Bahamas. It 

 must not be reset again or regulated thereafter, unless of course necessary 

 because of its accidentally running down, and it should be compared daily, 

 preferably at some regular time, with another good watch and a record of 

 these comparisons kept. If opportunity is afforded in the Bahamas, the cor- 

 rection of the watch on standard time should be obtained whenever possible. 

 On the return of the Expedition to Baltimore the correction of tlie watcli on 

 standard time should again be obtained on two or three days. The record of 

 all comparisons should accompany the observations. With the aid of the 

 correction on standard time, the longitudes of the stations can be obtained. 



B. Magnetic Declination Observations. 



(These observations, as well as tlie other magnetic observations, should be 

 made inside the tent and the observer sliould divest himself of all articles likely 

 to have a magnetic effect and to see that no such substances are within the tent.) 

 1. With compass needle belonging to Dip Circle 56/jkHO: {a) Sight on 

 mark with aid of peep sights, passing the eye up and down the slits to 

 make sure that the mark has been accurately set upon, noting whether the 

 vertical circle of dip circle is on the left or right hand of the observer and read 

 vernier of horizontal circle and record as shown in the specimen. Mark 

 above the reading the quadrant of the horizontal circle in which the reading 

 occurs as indicated by the Roman numerals I, II, III, IIII scratched on the 

 edge of the circle, {h) Reverse circle 180°, again point on mark and record 

 as before, (c) Turn instrument until it points approximately north and 

 south, with vertical circle east. Release needle which has been kept clamped 

 throughout {a) and (/j) and move horizontal circle gently, making final 

 setting with tangent screw, until the north end of needle exactly cuts the 

 zero as Ijeheld with the small magnifying lens belonging to the dip circle and 

 held precisely vertical over the needle so as to avoid pai'allax. 



Before making the final setting, it is essential to slightly disturb the 

 needle once more with a bit of steel, e. g., pocket knife brought near. In 



