Mr. Barnes on Magnetic Polarity. 71 



trying these experiments, Mr. J. Dodge of the Western High 

 School of Rochester, took the (iron ?) window bar which 

 lay near it, and placing it perpendicularly found that the 

 lower end was a north pole. He inverted the bar and was 

 surprised to find the same result, that is the poles were in- 

 stantly changed by inverting the bar. He invited me to try 

 the experiments with him. I did so, and after verifying the 

 fact of the instant inversion of the poles, by the change of 

 the position of the bar, I was led to inquire at what degree 

 of elevation this change takes place. There must be some 

 point at which the poles first become inverted and there 

 must be some neutral point, or medium between polarities 

 directly opposite. The idea struck me so forcibly that I im- 

 mediately set about a series of experiments which produced 

 the following results. 



Experiment 1. An iron bar was laid on the meridian due 

 north and south. 



Result. It showed strong polarity. 



Exp. 2. The south end was raised to the Zenith. 



Res. No change took place. The needle at the bottom 

 was* steadily attracted as before. 



Exp. 3. The top of the bar was carried over from the Ze- 

 nith to the north point of the horizon. 



Res. The needle was inverted. 



Exp. 4. The north end of the bar was raised to the Zenith. 



Res. The needle was inverted. 



If then the bar, raised from the south, traverses through 

 1 80 degrees, and becomes inverted ; and the same bar rai- 

 sed from the north, traverses through 90 degrees and be- 

 comes inverted, the changing point must divide the difference ; 

 accordingly, 



Exp. 5. The north pole was slowly raised, in the progress 

 of which the needle quivered, became unsteady, and at 45 

 degrees was inverted. 



Again if the needle is inverted at 45 degrees there must 

 be a neutral point and this again must divide the differ- 

 ence ; accordingly, 



Exp. 6. The north end of the bar was raised to 22i de 

 grees; 



Res. And it exhibited no signs of polarity, being from end 

 to end simply an attracting point to either end of the needle. 



Exp. 7. The bar was laid due east and west, or at right 

 angles to the meridian. 



