70 AKSEL S. STEEN. TERRESTRIAL MAGNETISM. [NORW. POL. EXP. 
All these determinations of « and C refer to cases in which the small needle 
has been used as deflected magnet, and may therefore be directly compared. 
It will be seen from the two tables that in the case of magnet V, the 
values found for «, which is proportional to the magnetic moment of the 
deflector, exhibit such slight differences, that the moment of this magnet 
may be assumed to have remained unchanged throughout the expedition. 
On the other hand, it appears as if the moment of magnet VI has undergone 
a weakening, which cannot be left altogether out of consideration. On Sep- 
tember 30th, 1893, Capt. Scorr-Hansen makes the following remark in his 
magnetic journal: “Inadvertently allowed a steel knife to come near magnet VI”. 
This may perhaps explain the above-mentioned weakening of the moment of 
the magnet, and in the absence of other particulars, there may be reason 
to suppose that as regards magnet VJ also, « has remained constant in each 
of the two periods marked by the above-mentioned contact, and that thus 
the value found in Hamburg in 1893 may be considered as applicable for 
the time before the 30th September, 1893, and the value found in Wilhelms- 
haven in 1897, for the time after the 30th September, 1893. 
As both w and C, as formule (6) and (2) show, are determined 
separately by a combination of the time of vibration and the angle of 
deflection, and the double needle was also used during the expedition as 
deflected magnet for the determination of the angle of deflection, the value 
of the two constants in question must be known in this case also. With 
this object, a series of deflection observations were taken in Wilhelms- 
haven, with the double needle both in position P, and in position P, as 
deflected magnet. If « and C are calculated by these observations combined 
with the corresponding determinations of the magnets’ time of vibration, the 
following values are obtained: 
Wilhelms- 
haven 
1897 
April 17 0°11617 | 0:076082] 0:26805 | 0°17554 
— 18 | 011618 | 0:075932} 0:26804 | 0°17518 
Mean 0°11618 | 0:076007] 0:26805 | 0°17536 
VI | April 17 0:091922} 0°38552 | 0°21961 
Fo WAL = ike) 0:091916} 0°33590 | 0:21959 
Mean 0:091919 | 0°38571 | 0°21960 
