66 THE LAST CRUISE OF THE CARNEGIE 



From these measurements we could tell how much the "variation" 

 of the compass had changed since former cruises. 



After breakfast is over, and when time-sights on the sun have 

 been made for longitude, the observers take their places at the 

 magnetic instruments in the domes. Soule stands at the earth- 

 inductor; Torreson sits in the control-room on the quarter-deck; 

 and Paul reads aloud the heading of the ship from the standard 

 compass in the chart-room. This allows Soule to keep the 

 rotating coil properly oriented. As Soule places the coil in vari- 

 ous positions, Torreson reads the ammeter or potentiometer in 

 the control-room. From here he also starts and stops the con- 

 stant-speed motor which rotates the coil. These observers de- 

 termine the "dip" or inclination of the dipping-needle. 



Meanwhile, Scott is in the after dome at the deflector. He 

 places magnets of known strength near his compass and reads off 

 their effect upon it. Jones makes simultaneous readings of the 

 standard compass in the chart-room, and records for Scott. 

 These two men measure the strength of the earth's magnetic 

 field. 



The afternoon is occupied in calculating the values for the 

 magnetic elements. The observers were furnished special forms 

 for recording, and these were so printed as to make the necessary 

 tabulations as simple as possible. The formulae used in computing 

 appeared in these, together with space for entering data derived 

 from tables. By using these sheets it was practically impossible 

 to overlook essential control-records, such as air-temperatures 

 and chronometer-reading. It is very easy to make these omis- 

 sions when the observer's attention is directed primarily to the 

 operation of the instrument itself. 



For some of us the time-keeping on board was at first quite 

 confusing. The ship's routine was operated on Local Apparent 

 Time, with a resetting of clocks every morning at eleven. Many 

 records were kept on Local Mean Time, others in Greenwich Mean 

 Time. Then there was 75th Meridian Time for certain radio 

 schedules, while a Sidereal-Time chronometer later became part 

 of our equipment for gravity-observations. In addition, for the 

 most accurate time-signal comparisons, an "offset chronometer" 

 was added, that loses one second in sixty -five of mean time. 



