Or 



jFf 



NO. 7.] INCLINATION. 135 



I have finally represented graphically the values of z/ contained in the 

 table, as a function of /' and H, and have drawn curves through the points 

 corresponding to the same value of A for every 5th minute. I was hereby 

 enabled to take out without difficulty the value of A applicable to the case, 

 in whole minutes, for every observation of I', when I had either directly or 

 by interpolation found the value of H corresponding to the place of obser- 

 vation. 



As already mentioned, deflection observations with the employment of 

 both deflectors were only taken once with needle .B 1 during the expedition, 

 namely on May 4th, 1894. Altogether this needle has only been used 4 times 

 during the voyage, and no observations were made with it at Wilhelmshaven 

 after the return. There is thus no material upon which to base even a 

 roughly approximate determination of the temperature-coefficient f for this 

 needle, but I have nevertheless thought it feasible to make use of the deflec- 

 tion observations of May 4th, 1894, for the calculation of the constants of 

 the index-correction in the same manner as for needle B, taking for granted 

 that also in the case of needle JB 1 the magnetic axis coincides with the 

 geometrical axis. For the calculation of the total intensity, I have simply 

 employed the value of R 2 (1 -(- ) that was found in Hamburg in 1893, 

 supposing a possible weakening of the magnetic moment of the magnets to 

 be approximately compensated by the considerably lower temperature. This, 

 during the observations in Hamburg, was 13 C., whereas on May 4th, 1894, 

 it was 8 C. 



Thus, if we put R(i-\-^t) = O40024, we obtain, with the angle of 

 deflection observed t// 2 = 50 28', according to formula (3), 



W = 0-51 86. 



As the value for the horizontal intensity, I have employed the mean of 

 the values found on April 27th and May 5th, 1894, and have put H= 0'041. 

 The true inclination, calculated by W and H, thus becomes I =85 28'; and 

 as the inclination observed with the Fox apparatus is I' = 86 16', we 

 obtain 4 = 48'. Thus we have for the determination of the constants p 



and a for needle B 1 , 



J W I' 



Hamburg, June, 1893 - 23' 0'4748 68 5' 



Fram Exp., May 4th, 1894 ... 48' 0'5186 86 16' , 



