94 On the Diurnal Magnetic Declination. [Aug. 



examination showed me that this needle possessed two north 

 poles, and that of the two which exhibited the most energy 

 turned towards the north. In this respect the needle coincided 

 with that of the preceding experiment, 



Erper. III. 



I took the needle of Experiment II. and'placed on its middle 

 the north pole of the magnet, and drew it ten times in the 

 direction of the pole turned towards the south. The half turned 

 towards the north remained untouched. The result was, that 

 the pole previously turned towards the south became a south 

 pole ; the other pole became a north pole. The needle thus 

 treated exhibited the common diurnal variation. It appeared, 

 however, to be somewhat less regular than usual. 



Exper. IV. 



I took a needle of new iron, and communicated to it the 

 magnetic virtue in the ordinary way, by the double touch. It 

 had a north and south pole, and in the midst a point of in- 

 difference. It exhibited the usual diurnal variations of the 

 common needle. In communicating the magnetism by the 

 double touch, the north pole of the magnet was placed towards 

 the pole of the same name of the needle, the south pole of the 

 magnet towards the south pole of the needle, and the magnet 

 was drawn ten times along the needle. 



+ m |1 — m 

 + m<— ; > — m 



Upon a needle magnetized thus in the ordinary way, I placed 

 a magnet in a position precisely the reverse, as is clearly seen in 

 the following figure : — 



— mil I +m 

 + m < -> — m 



I drew it along ten times towards the north pole of the needle, 

 and as often returning to the middle, so that the south half of 

 the needle was not touched at all. The half of the needle 



