108 Mr. J. Tatiim on Electro-Magnetism. 



Exp. 4. When removed to the upper side of the wire, it ro- 

 tated to the left. 



These movements of the needle may be represented by Fig. 1, 

 in which A may represent a section of tlie horizontal negative 

 wire, and the heads of the arrows the direction in which the 

 needle rotated. 



■h 



I 



Fig. 3. 



2c_ 



T 



X 



I now wished to see what effects would be produced oil the 

 needle by the positive wire; for which purpose, 



Exp. 5, It was brought near the left side of GH, Fig. 13 

 (see last Number), in which situation it ascended. 



Exp. 6. It was then removed to the imder part of the wire, 

 when it turned to the left. 



Exp. 7. It was next placed on the right side: here itdescended. 



Exp. 8. And finally, when it was brought above the wire, it 

 passed off to the right : which may be represented by Fig. 2, 

 in which it will be seen that the motions of the needle at the 

 positive wire are the reverse of those at the negative wire: and if 

 the south end of the needle be made use of, all the above effects 

 are reversed ; from which it must appear, that there was an 

 evident tendency of the needle to rotate round the positive and 

 negative wires, but in opposite directions. 



Exp. 9. Having shown, in a lecture which I delivered be- 

 fore the above Society, that when an electrical discharge of a 

 battery of five jars, equal to twenty-one coated feet, was made 

 to traverse a helix which was coiled from left to right, and 

 which contained pieces of steel, it not only communicated to 

 them magnetic properties, but their north poles were directed 

 towards the positive side of the battery. 



Exp. 10. But when a helix coiling in a different direction 

 was used, the north poles of the pieces of steel were directed 

 towards the negative side of the battery. 



I was desirous of showing the analogous effects of common 

 and Voltaic electi'icity, not only in conimimicating magnetism 



to 



