Specimen Magnetic Observations and Computations 



213 



Ocean Magnetic Observations: Declination (D) 



(Form 21a) 



Station: At sea 



Date: Sat., Aug. 23, 1913, P. M. 



Compass: CI 



Weather: be Sea: 8 



Lat: 39° 44' N 

 Vessel: Carnegie 

 Obs'T: P. and S. 

 Wind: SSW. 2 



Long: 39° 50' W 

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

 Rec'd'r: N. M. 

 Roll: 4° 8. to 4° p. 



'Adjusted for sea rate. 



On Form 26 the means are entered and the values of a and "constant + a" are deter- 

 mined in exactly the same manner as on Form 26a. The angle A, however, is obtained 

 by applying two corrections to the angle A, the first, designated "Tabular Reduction," 

 being taken directly from Table 46, page 182, and the second, "Red'n of Scale to Horizon," 

 is the product of the respective values of scale altitude and the factor obtained from Table 47. 



Observations with sea deflector. — The observations of magnetic decUnation with the sea 

 deflector (D4), made at the same time as those with the standard compass (CI), are shown 

 in the specimen on Form 21a, page 215. In all, 20 sets of readings, similar to sets I, II, III, 

 and IV given in the specimen, were taken. The computation is shown on Form 22, page 

 216. The various steps are made clear by the column-headings. The correction — 0?08, 

 applied to the observed values of D, is derived from Table 55, page 236. 



