' or Aurora Borealis and Australis. 341 



thus united in pairs they neutrahze each other, and their electric 

 power disappears. But in this neutral state they perhaps ap- 

 pear as elastic fluid elementary magnets, which so surround 

 the surface of the polar wire that all north poles are turned 

 on one side, and all south poles on another: and the axis of 

 every elementary magnet is the tangent of the circular section 

 of the conducting wire. Owing to the constantly aggregating 

 quantity of electricity from both ends of the wire, and the ex- 

 pansive nature of electricity, these elementary magnets are 

 forced out of the surface of the wire with a velocity equal 

 perhaps to that of light itself. As long, therefore, as the cir- 

 cuit is uninterrupted, the wire is. surrounded by a cylindrical 

 atmosphere of neutralized molecules combined in pairs, each 

 pair of which has a magnetic north pole and south pole, and 

 a neutral point. Let ABCD (fig. 5.) represent a section of a 

 conducting wire turning towards the zinc pole of a galvanic 

 apparatus. The neutralized electric pairs of molecules NS 

 flow from all points of the circle ABCD towards the direction 

 of the jadii ZE, ZF &c., (like the circular waves round a 

 stone dropt into the water,) in a manner that on imagining 

 oneself to be in the point Z, all the magnetic north poles N 

 will lie to the left, and all the south poles S to the right. By 

 this means an innumerable quantity of circular elastic fluid 

 magnets is formed round the conducting wire, in which mag- 

 nets every point may be considered as the neutral, every north 

 pole being immediately touched by a south pole, which im- 

 pedes its free action. One might obtain such a circular mag- 

 net without free poles by forming a connected steel ring, 

 touching it at the same time in several points of the circum- 

 ference with the south poles of different magnets, and then 

 moving these poles round the ring from right to left. This 

 steel ring would then have no perceptible poles ; but if it were 

 any where broken hi two, the surface of the fracture on the left 

 hand would appear as a free south pole, and that on the right 

 hand as a north pole. In this manner it may be easily ex- 

 plained, why the intensity decreases in the ratio of the simple 

 distances from the axis of the conductor : for if the radius ZE 

 is double the size of Ze, the same quantity of electricity which 

 first filled the circle ef,, must afterwards fill the doubly large 

 circle ESF, and consequently the intensity must decrease in 

 the same pioportion as the distance increases. Hence it may 

 also be easily explained why the electro-magnetic action 

 freely penetrates the conducting bodies as well as the non- 

 conducting. For the un-neutralized electric molecules excite 

 in every body instantaneously the opposite state, and are there- 



Ibic 



