468 ELECTRO-MAGNETIC EXPERIMENTS AND OBSERVATIONS. 



% Zinc South. 



1. Needle placed below the wire, deflected to the E. 



2. - above - W. 



3. Zinc West. 



No sensible effect either above or below the wire. 



4. Zinc East. 



No sensible effect either above or below the wire. 



In these experiments, there appears to be a maximum of 

 deflection when the connecting wire is in the magnetic meri- 

 dian ; but when it is at right angles to that meridian, the 

 effect is imperceptible. This, however, is evidently owing to 

 the small portion of the connecting medium, which, in this po- 

 sition, can act on the needle ; for when a broad piece of metal 

 was substituted for the connecting wire, the needle was power- 

 fully acted on, as was evident by its short oscillations ; and the 

 same thing was observed with Von Buch's apparatus above 

 described. 



In order to ascertain how far the influence of the connecting 

 wire depended on the supposed direction of a galvanic current 

 or currents, passing from one metal to the other, a connecting 

 wire was bent several times at right angles, as is shewn in per- 

 spective in Fig. 3., and the following effects were observed on 

 applying a needle to different parts of the wire, in different po- 

 sitions of the plates. 



1. Zinc North. 



When the needle was presented to those portions of the 

 wire in the magnetic meridian 1, 2, 3, the deflection was as 

 follows : 



1. Above the wire, deflection - to W. 



2. Below - - to E. 

 but in other parts of the wire there was no deflection. 



% Zinc 



