MAGNETIC DECLINATION. 



Circle. 



Scale. 



Circle. 



Scale. 



Readings; January 16, 1854. 



(Dr. Hayes, observer.) 



119° 31'-31' 

 120 48—46 

 120 48—46 

 122 09—06 



452'! 

 350 

 353 

 251 



121° 53'-55' 



123 19—18 



123 19—18 



124 42—40 



256* 



150 



149 



42 



l'i=0'.'741. 



Readings; February 16, 1854. 



127° 04'-04' 



125 55—56 



125 55—56 



124 18—17 



124 18—17 



123 00-00 



123 00—00 



121 34—34 



62d.5 

 153.0 

 136.0 

 257.0 

 259.7 

 355.0 

 354.5 

 463.0 



121° 34'-34' 



122 55—56 



122 55—56 



124 23—24 



124 23—24 



125 47—47 

 125 47—47 

 127 05—05 



453'i.0 

 356.0 

 360.0 

 249.0 

 254.0 

 150.0 

 145.5 

 42.0 



1*=0'.839. 



Yalue resulting, equal mean of all or one division of scale = 0'.804. 

 Value adopted = 0'.80. 



An ■] Jf '''"^^^^ I of scale readings indicates a movement of the north end of the magnet to the •] ^ . i 



A well rated pocket chronometer, nearly showing Greenwich mean time, was 

 used for noting the time. 



Diurnal Variation. — The observations for changes of magnetic declination were 

 made during the months of January, February, and March, 1854, at the following 

 dates: — 



and 



To these must be added the term days during the same period of the year, viz: 

 January 18-19, February 24-25, and March 22-23. The remaining three terms 

 in April, May, and June, of the same year, furnish values of the change of the 

 diurnal inequality at a later season. Readings (the mean of two extremes during 

 a vibration when the magnet was in motion) were taken every sixth minute, com- 

 mencing, with but one exception, between 4 and 5 o'clock in the afternoon. The 

 error of the chronometer has been applied and the time in the abstracts is given in 

 local mean (astronomical) time. The readings are, as stated above, uncorrected 

 for torsion, and are expressed in scale divisions. In regard to the observers. Dr. 

 Kane remarks in his narrative: " It was not until the close of the winter that I 

 was able to take my share in the preceding (the observations for variation) or the 

 term-day observations; and I desire to express my obligations to Dr. Hayes and 



