NO. 7.] TOTAL INTENSITY. 167 



It is true that in Hamburg, after the return, on March 6th, 1897, a series 

 of observations were also made by Captain SCOTT-HANSEN with needle B de- 

 flected by means of only the one deflector N, the result yielded being 



Vi = 31 43-5' 



at a temperature of 6"6 C. Assuming, for the place of observation in Ham- 

 burg on that day, an inclination of 67 21' and a horizontal intensity of 

 0-1812, we obtain 



B 1 (l + Ci<) = 0-2474. 



I have already pointed out, however, that the constant-determinations made 

 in Hamburg after the return, cannot be considered thoroughly reliable, owing 

 to the proximity of the electric tramway. Considering also the uncertainty 

 prevailing with regard to the changes that the magnetic moment of the 

 magnets may have undergone during the voyage, it seems to me hardly fair 

 to make this one uncertain constant-determination the basis for a calculation 

 of the absolute value of the total intensity, the more so as the determinations 

 of the angle of deflection t//, with the one deflector, were made in tempera- 

 tures varying between -\- 6V2 and 36V2, while no notice can be taken of 

 this fact, there being no material forthcoming for the determination of the 

 temperature-coefficient. 



It might perhaps be thought that out of the values of the angle of 

 deflection T//J found when drifting with the ice, a few data might be picked 

 out, to which there were corresponding values of the horizontal intensity and 

 inclination sufficiently well determined to justify an attempt at an approxi- 

 mate calculation of .B, and t , according to formula (1), by the method of 

 least squares, when the formula will become 



1 . cos I y. cos I 



RI Hsinip! Hsmipi' 



But to this it must be remarked that the observation-material that would 

 then be employed, would have to be selected within sufficiently narrow time- 

 limits for .R! to be supposed to have remained constant, which, in its turn, 

 would occasion the risk of there being too little variation in the temperature 

 in which the observations were made. 



I have nevertheless made some experiments in this direction, but unfortu- 

 nately without success. I am therefore convinced that it is best to make 

 direct use of the determinations of horizontal intensity and inclination made 



