Mr. W. Sturgeon on Electro-Magnetism. 97 



Exp. 4. The semicircle adjusted as before, the lamp was 

 now applied at D. The wire was projected to the right. 



Exp. 5 and 6. In these experiments the lamp was applied 

 as before, but the south pole of the magnet was now presented 

 to the wire. The motions were the reverse of the two former 

 experiments. 



I have tried rectangles instead of semicircles, but there is 

 no difference in the results. 



If a semicircle or rectangle be made of platinum and silver 

 wires, the former supplying the place of the copper, and the 

 latter be substituted for the zinc, in the above thermo experi- 

 ments, the results of the two machines are exactly alike ; 

 hence the copper and platinum wires are possessed of the 

 same kind of electricity, and so are the zinc and silver each to 

 each ; but of the contrary kind of the other two wires : so if 

 the copper be positive to the zinc, by this magnetic test we must 

 necessarily conclude that the platinum is positive to the silver. 



But this is not all that is to be observed in these experi- 

 ments ; we must compare the results of the chemico with those 

 of the thermo experiments, and endeavour to trace the rela- 

 tion that subsists in the phenomena exhibited by those two 

 modes of exciting the electrical influence. 



We will therefore compare our chemico experiment 1, with 

 our thermo experiment 3. We here find the wire projected 

 to the left in both cases. 



We will now suppose the immersed plates of the chemico 

 apparatus to correspond with the heated union of the thermo 

 wires ; and the most remote extremities of the chemico con- 

 ducting wires, with the coldest junction of the thermo machine. 

 It will follow, that as the copper wire (by the supposition) is 

 as evidently ascending in the thermo machine, as the zinc 

 wire is ascending in the chemico cylinder ; and as they are 

 both propelled hi the same direction (left), by the approxi- 

 mation of the north pole of the magnet ; the forces of the 

 two galvanized wires must of necessity be exerted in contrary 

 directions. For although they are both propelled the same 

 way, yet they are of contrary kinds or names. 



Again : Let us now suppose the immersed plates of the 

 chemico apparatus to correspond with the coldest union of 

 the thermo wires ; and the most remote extremities of the 

 chemico conducting wires, with the heated junction of the 

 thermo machine. In this case, the two wires nearest the magnet, 

 of the chemico and thermo machines, will in all respects cor- 

 respond with each other; for they are now both descending from 

 the copper, or both ascending from the zinc (by the supposi- 

 tion). Hence the forces of the two galvanized wires are ex- 



Vol.G.'i. No. 310. Feb. 1824. N erted 



