248 Mr. J. E. Cullum. Report of Absolute Magnetic [Apr. 12 r 



of only 0'*2. The meridian of the circle is determined in January of: 

 each year, the value so obtained being used throughout the current 

 year. 



The intensity observations are made in the usual manner of vibrations, 

 and deflections, the same magnet being used as in the declination 

 observations. Two observations are made on the same day, one 

 before noon (11 A.M.), and the other afternoon (3 P.M.), so that the- 

 mean time of the two observations used in calculating the forces i& 

 1 P.M., which very nearly agrees with the mean time for the inclina- 

 tion, with which they are combined in the formula (V.F. == H.F. x tan 

 inclin.) and (T.F. = H.F. x sec. inclin.). The strength of the magnet 

 considerably diminished during the first year, which may be attributed 

 to its want of age ; the magnetic moment (m) falling in 1899 from 770 

 to 728 units; in 1900 to 714; and in 1901 to 700, a decrease which 

 will probably become less each year. The value of P (distribution of 

 magnetism) in the reductions is calculated for the yearly series, in 

 1899 being 8'2 ; 1900, 7*0 ; and in 1901, 7-5. 



Below are given monthly values of each element for the three 

 years. 



Year. 



Month. 



Declination. 



Inclination. 



Intensity. 



Vertical F. 



Total F. 



1899 



Jan. . . . 



2°1 39 -1 



68 34 -9 



0-17739 



-45220 



-48548 





Feb. . . . 



40-8 



35 -3 



•17715 



•45176 



•48525 





March . 



33 -8 



34 -2 



•17734 



•45392 



•48538 





April .. 



32 -3 



34 -9 



•17741 



•45227 



•48571 





May . . . 



35-6 



35 -2 



•17732 



•45216 



•48568 





June. . . 



33 -5 



32-0 



•17741 



•45115 



•48479 





July. .. 



34 -6 



33 -5 



•17742 



•45175 



•48534 





Aug. 



31 -7 



31 -5 



•17737 



•45086 



•48450 





Sept. .. 



37 -2 



31 -8 



•17736 



•45095 



'48459 





Oct 



32-8 



32 -1 



•17736 



•45107 



•48469 





Nov. .. 



33 -7 



30 '4 



•17747 



•45068 



•48436 





Dec 



35'4 



29 -7 



•17768 



•45095 



•48469 





Means . 



21 35 



68 33 -0 



-17739 



-45164 



-48504 



