242 . Mr. Tatum on Electro-Magnetism. 



four north WLiCLjbur south, on each side of the equator of the 

 needle: and the above arrangement of my apparatus enabled 

 me to investigate the subject more accurately than I formerly 

 could, the results ol' which I now submit to the perusal of 

 the readers of your IMagazine. 



But first I would premise, that when I speak of attraction 

 or repulsion, as apjiiicable to the perpendicular or horizontal 

 wire, I do not mean a deviation of only three or four degrees, 

 but that of a whole revolution. 



Exp. 1. — Let A B (Plate IV. fig. 1,) represent part of the 

 perpendicular wire connected with a Voltaic apparatus (here- 

 after to be described), and CD the position of one end of a 

 magnetic needle to the wire. In such a position the needle will 

 be attracted. 



Exp. 2. — But if it be carried to the opposite side of the wire, 

 and consequently present its opposite edge to it (as in fig. 2,) 

 it will be repelled. Of course, here are two contiary poles in a 

 transverse direction. 



Exp. 3. — Let the equator of the needle be advanced a little 

 nearer to the wire, as is represented in fig. 3, but presenting 

 the same edge of it to the wire as in fig. 1 ; in this position it 

 will be repelled. Of course, here is a dissimilar polarity exhi- 

 bited to what there was in the first position. 



Exp. 4. — When the needle is removed to the other side of 

 the wire, as in fig. 4, consequently presenting its opposite edge 

 to the wire, it will in this situation be attracted. Here again 

 are two more contrary poles in a transverse direction, which 

 with the two already noticed make four poles. 



Exp. 5. — Let C D, fig. 5, represent an horizontal wire con- 

 nected with the apparatus; and E F, the under side of part 

 of a needle (now mounted on an horizontal axis) above it. It 

 will when so situated be attracted. 



Exp. G. — If its upper side be brought under the wire, as in 

 ficf. 6, it will be repelled. Consequently, here are two dissimilar 

 poles in a perpendicular direction, which with the four tians- 

 verse ones already noticed make six; and as the extremity of 

 the needle is possessed of two transverse and two perpendicu- 

 lar poles, it may be represented by N N S S, fig. 11. 



Exp. 7. — If the needle be advanced a little further, but 

 above the wire, as in fig. 7, (of course presenting the same side 

 to the wire as in fig. 5,) it will there be repelled. 



Exp. 8. — If the needle be removed to below the wire, but 

 with its point at the same distance from it, as in fig. 8, it will 

 be attracted. 



Here again are two more dissimilar poles in a perpendicu- 

 lar direction; so that there are four transverse and four per- 

 pendicular 



