I 1 8 THE STATIC NEEDLE. 



in a reverse direction. These apparently opposite 

 directions are the results of bending around the 

 ends. In accordance with the preceding illus- 

 trations, the two opposite poles develop a recip- 

 rocal attraction ; for the currents move in similar 

 directions about their nearest sides. About the 

 N poles, or the s poles, of two bar-magnets, when 

 similarly brought near one another, the currents 

 move in opposite directions, with a consequent 

 reciprocal repulsion between 

 them. If two magnetic needles 

 be fastened together with their 

 opposite poles adjacent, as 

 shown in Fig. 36, their recipro- 

 cal action and reaction neutral- 

 ize one another, and the terres- 

 36 . trial currents do not turn this 



compound needle on its pivot ; hence it is denoted 



a STATIC NEEDLE. 



In Fig. 35, w, representing the section of a 

 conducting wire between the two vertical poles, 

 N s, is propelled by the two combined magnetic 

 currents in the direction denoted by the arrow, if 

 the electric current ascends through it, and in the 

 opposite direction if it descends. So delicate 

 is the combined action of the magnetic currents 

 circling between the two poles of a horse-shoe 

 magnet, that a flexible strip of gold-leaf is used, 

 as represented between the two poles N s, Fig. 

 37, for a sensitive test of slight electric currents. 



