Mr. R. Phillips on Volta-Electric Induction. 263 



The battery circuit was completed through B, and then the 

 needle was placed in the indicator and the circuit broken, 

 which made the eye end the marked pole. 



Finally, a needle was placed in the indicator, the battery 

 circuit closed and the needle removed ; the point of the needle 

 was the marked end. In these two last experiments the mag- 

 netism was much stronger than in the one preceding them. 



The copper plate was now removed, and a plate of zinc the 

 T i n dth of an inch thick was substituted for it ; on closing and 

 opening the battery circuit once, the eye end of the needle 

 became as the marked magnetic pole. I have thought it rather 

 unnecessary to examine every plate as I did the copper, and 

 I have therefore taken the most easily obtained case as a re- 

 presentative of the others. I should observe, too, that in all 

 these experiments care was taken to place only unmagnetized 

 needles in the indicator. 



A plate of lead ^th of an inch thick being substituted for 

 the zinc, produced the same effect ; so also did a plate of tin 

 of similar thickness; but when a glass plate jj%tb of an inch 

 thick was used instead of the metal plates, I could obtain no 

 effect on the indicating needle, although I closed and opened 

 the battery circuit through B many times. 



When a plate of iron ^th of an inch thick was placed 

 between B and C, the same effect as if it was a copper plate 

 was produced on the indicating needle, but with the iron plate 

 the induced current was evidently much more powerful. 



I now proceeded to examine if a specific force belongs to 

 each metal, or whether they all similarly effect the volta- elec- 

 tric induction. 



Between A and B I placed a plate of lead ^th of an inch 

 thick, and between B and C a plate of copper of similar thick- 

 ness ; the battery was then closed and opened once through 

 B as before; the indicating needle had its eye end as the 

 marked end of a magnet. 



A needle was now placed in the indicator, the circuit through 

 B completed, and the needle removed ; in this case the point 

 was the marked end. 



The battery was now closed through B, the needle placed 

 in the indicator, and the circuit broken ; this gave the eye end 

 of the indicating needle as the marked magnetic pole. h\ 

 these two last experiments the magnetism was stronger than 

 in the experiment next going before. 



When a plate of copper was substituted for the lead, no 

 effect could be obtained in the indicator, even when this plate 

 of copper was only ^th of an inch thick. 



From the last experiment it follows that lead is much in- 



