Specimen Obsebvations on the Galilee 



37 



temperature at the beginning and at the end of the set of readings on that heading. The 

 following 5 columns give number of magnet, deflecting distance used, which letter, A or B, 

 on case containing deflecting magnet is turned towards observer (O), whether prism is south 

 or north, and finally whether north end of magnet is east or west. Then follows the column 



Magnetic Observations on Swing: Horizontal Intensity {H) 



Station: San Francisco Bay 

 Date: May 25, 1908, A. M. 

 Instrument: Sea Defl'r 2 (D2) 

 Weather: b 

 Sea: S 



(Form 24) 



Lat: 37° 51' N 

 Vessel: Galilee 

 Obs'r: D. C. S. 

 Wind: 

 Roll: 0° 



Long: 122° 23' W 

 Com'd'r: W. J. P. 

 Rec'd'r: W. J. P. 

 Temp: 13° C. 

 Helm: Port 



" Lubber-line reads," which gives the two readings of the forward and aft lubber-lines on the 

 deflected compass-cai'd, for each of two positions (for example, heading west: prism south, 

 north end of magnet east; prism north, north end of magnet west). The means of the two 

 opposite readings, for each position of prism and magnet, are formed next, counting con- 

 tinuously from south (0°) through west to north. The difference of the two means, e.g., 

 heading west, 109?85-69?90 = 39?95 is twice the deflection angle, hence, 2m. The mean 

 value of the two means, e. g., heading west, S 89?88 W, is entered in the last column, and 

 gives the ship's heading or course by the deflector compass. 



The procedure is similar for each heading, the positions of prism and north end of 

 deflecting magnet being readily followed by the letters in the respective columns. 



Form 25, page 38, contains first an abstract of the results derived from the preceding 

 form (No. 24) . The values of the single deflection-angle, u, expressed in degrees and hun- 



