Geographic Positions at Sea 



225 



Summary of Magnetic Observations on August 23, 1913. 



There have been included in the following summary of results of magnetic observations 

 made in the afternoon of August 23, 1913, also the declination observations in the morning 

 of the same day at station 1336 C II. 



'Course, NNE ; roll from side to side, 6° ; sea, S ; weather, be. 



'Course, NNE; roll from side to aide, 8°; sea, MS; weather, 

 be. 



'Course, NNE ; roll from side to side, 8° ; sea, S ; weather, be. 



*This is the combining weight when taking the weighted 

 mean of individual values. It is not to be confused with the 

 "weight" (wt.) which appears in the Table of Results. The 

 latter is intended to give an approximate measure of the relia- 

 bility of a result according to conditions encountered. Thus, 

 to the results on August 23, 1913, a weight of 3 was assigned 

 in the table. (See explanation, pp. 258-259.) 



'Marine coUimating-compass 1. 



'Sea deflector 4. 



'Sea dip-circle 189, regular dip needles 5 and 9, and inten- 

 sity needle 7 deflected by intensity needle 8 ; for summary of 

 individual values, see bottom of Form 28a, p. 220. 



'Marine earth-inductor 3. 



•Sea dip-circle 189, deflection observations with needles 7 

 and 8. 



'"Sea dip-circle 189, loaded-dip observations with needle 8. 



GEOGRAPHIC POSITIONS AT SEA. 



In ordinary navigation the position of the ship is required at the earliest moment 

 possible, particularly in the vicinity of land, rocks, reefs, and like dangers. For this pur- 

 pose a smgle Sumner line is often sufficient for the immediate needs of the navigator. For 

 the geographic positions of sea-stations, where magnetic results have been obtained, the 

 promptness of acquiring the geographic coordinates is not so important as the attainment 

 of the highest precision, which necessarily involves delay to secure the data and make 

 additional computations. The navigational work of the Carnegie has been planned to 

 meet both requirements. The dead-reckoning is advanced as quickly as is practicable, 

 and the new navigational methods are freely used when advantageous, but upon the high 

 seas the usual work of navigation on the Carnegie is computed on forms which become a 

 permanent record, and permit application of subsequent corrections for current effects or 

 similar causes that may affect the course and distance run. 



