DOVE ON THE ELECTRICITY OF INDUCTION. 135 



however, the unenclosed bundle acts in a contrary direction to 

 an enclosed bundle, powerful shocks are obtained. In the gal- 

 vanometer a solid iron cylinder more than overpowered 140 thin 

 iron wires, whilst thirty-six were sufficient to retain it in physio- 

 logical equilibrium. The physiological series for the following 

 substances was ascertained by drawing out the rods which were 

 opposed to each other. The following is the series, beginning 

 with the substance that exerted the most powerful action : — 



Unenclosed iron bundle of wire. 



The same bundle in a longitudinally cut tube. 



Cut tube of tinned sheet iron. 



Entire tube of tinned sheet iron. 



Cut gun-barrel. 



Entire gun-barrel. 



Soft iron cylinder. 



Cylinder of white and gray pig iron. 



Soft steel. 



Hard steel. 



Tube of nickel and square bar of nickel. 



Bundle of iron wire in an entire tube of brass. 



This series, as also the whole of the phaenomena observed, are 

 analogous to those which were obtained when the iron was mag- 

 netized by means of a galvanic battery. 



42. The two other modes of excitation of the current, on the 

 one hand by means of an empty wire keeper, and coils of wire 

 connected in the same direction, and on the other hand by means 

 of compensating coils, in one of which was placed a bar of iron, 

 gave analogous results, namely, a shock when an unenclosed 

 bundle of wire was opposed to an enclosed bundle which com- 

 pensated it galvanometrically. 



Uniform results are therefore obtained when the primary cur- 

 rent is — 



1. That of a galvanic battery. 



2. That of a thermo-battery. 



3. That of a Saxton's machine. 



4. That excited by the approach of a closed conductor to a 

 magnet. 



5. That excited by magnetizing iron in an enclosing wire by 

 means of a steel magnet. 



