1813.] 0/2 the Diurnal Magnetic Declination. 9j 



which had been touched acquired at its extremity a south pole, 

 instead of the north pole which it formerly had. The needle 

 turned round, and the touched end pointed towards the south. 



+ m 



— m < — > — m 



This needle presented a remarkable phenomenon. All the 

 other needles that had been magnetized placed themselves in the 

 magnetic meridian (which points 1S° or 20° towards the west); 

 but this needle turned its poles precisely to the north and south, 

 its direction coinciding exactly with the meridian line of Stutt- 

 gardt. (Its true position and its exact deviation from the meri- 

 dian line require, in order to be determined with precision, a 

 more numerous set of experiments than I possess.) The oscil- 

 lations of this needle were also extraordinary ; they extended 

 from 2° — 45' to 3° ; but they proceeded, like the others, in 

 the evening and morning to their maximum towards the east, 

 and about two o'clock to their maximum towards the west. 



I afterwards communicated to this needle magnetism in the 

 ordinary way by the double touch, and observed it in the same 

 circumstances. It then assumed the direction of the magnetic 

 meridian ; the extraordinary oscillations disappeared, and the 

 small oscillations of the common needle again made their 

 appearance. 



Ex per. V. 



To obtain the result of the fourth experiment in a more 

 simple manner, I took another iron needle, placed on its middle 

 the north pole of the magnet, and touched it, as in the first 

 experiment, drawing it ten times towards one pole, and ten 

 times towards the other, without returning. Both the poles (as 

 I expected) were south poles, and in the middle of the needle 

 there was a north pole. This needle took the position of the 

 magnetic meridian, and not the true meridian, as was the case 

 with the needle with two south poles in the fourth experiment. 

 Its daily oscillation amounted to 50 or GO minutes, being similar 

 in this respect to the needle with two north poles of the first 

 experiment, with this difference, that at ten in the morning it 

 began to oscillate towards the w>t, while the needle which had 

 two north poles oscillated at that time towards the east, but its 

 maximum west was at two o'clock. 



Two other needles, magnetized in the same way, exhibited 

 exactly the same phenomena. 



Exper. VI. 



I took another new needle, and communicated to it the magnetic 

 virtue exactly in. the manner described in the fourth experiment. 



