208 INTERESTING SCIENTIFIC WORK IN THE ARCTIC 



gitude (approximate) and the difference between watch time and 

 sun time (equation of time), which gives the time as shown by 

 the sun; that is, its angle from the meridian at the observation. 

 With this "hour angle" and the declination and approximate alti- 

 tude, the sun's altitude is computed by a simple formula of trigo- 

 nometry. 



The altitude of the sun thus obtained is then compared with the 

 observed altitude after correction, and the difference is the dis- 

 tance in miles the observer is from the assured position given by 

 the latitude and longitude used in the computation. 



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Method of determining the position of the North Pole with a sextant. 



His direction from the assumed position is toward or away 

 from the sun, according to whether his observed altitude is 

 greater or less than the altitude obtained by computation. By 

 marking on the chart the assumed position in the latitude and 

 longitude used and drawing a line through this point in the di- 

 rection of the sun's bearing (the direction which would be indi- 

 cated by the shadow of an upright staff), the correct position can 

 be found by measuring off on this line, away from the assumed 

 position, a distance equal to the difference between the observed 

 and the calculated altitudes. 



In view of the many questions raised as to the accuracy of Dr. 



