466 ELECTRO-MAGNETIC EXPERIMENTS AND OBSERVATIONS. 



very sensibly affected, whenever the strength of the acid li- 

 quor in the cup was sufficient to cause such an effervescence 

 with the zinc as to render the liquid turbid. 



The most striking phenomena of this galvanic arrangement 

 are, the different effects produced on the magnetic needle by 

 the relative positions of the platina and zinc, in regard to the 

 magnetic meridian, and the opposite influence of the outer 

 and inner sides of the slip of zinc, as will be seen in the tabu- 

 lar results below. 



1. Cup North. 



1. Compass at O. See PI. XXX. Fig. 1. deflected to the E *. 



2. - I 



- 



- 



W. 



3. - i 



- 



- 



W. 



4. - o 



- 



- 



E. 



2. Cup South. 









1. Compass at 



o, 



deflected to W. 





2. 



I, 



E. 





3. 



h 



E. 





4. 



o, 



W. • 





3. Cup West. 









1. Compass at 



o, 



not sensibly deflected. 





2. 



I, 



inversion of Poles. 





3. 



h 



inversion of Poles. 





4. 



o, 



not sensibly deflected. 





4. Cup East. 









1. Compass at 



0, 



inversion of Poles. 





2. 



I, 



not sensibly deflected. 





3. 



h 



not sensibly deflected. 





4. 



o, 



inversion of Poles. 



In 



* In this paper, where it is not otherwise specially indicated, the deflection, to 

 either hand, means the deflection of the North Pole of the needle. 



