Fig. 



16. 



+ 











"~ 







,__ 



— 







_ 



+ 



— 



+ 



— 



+ 



~ 



+ 



to Electricity and Magnetism. 561 



figure, falls in the j)liis region of the primary current, and m 

 the minus region of the secondary, and hence the two actions 

 neutralize each other, and no apparent result is produced. 



J 32. Fig. 16 indicates the method in which the neutralizing 

 effect is produced in the case 

 of the secondary and tertiary 



currents. The wire con- H — r- — — ~- ^ 



ducting the secondary cur- 

 rent is represented by &, 

 that conducting the tertiary 

 by c, and the other wire, to 

 receive the induction from 

 these, by d. The direction 



of the influence, as before? is indicated by + , &c., 



and the third wire is again seen to be in the plus region of 

 the one current, and in the minus of the other. If, however, 

 d is placed sufficiently near c, then neutralization will not 

 take place, but the two currents will conspire to produce in 

 it an induction in the same direction. A similar effect would 

 also be produced, were the wire c, in fig. 15, placed sufficiently 

 near the conductor h. 



133. Currents of the several orders were likewise produced 

 from the excitation of the magneto-electrical machine. The 

 same neutralizing effects were observed between these as in 

 the case of the currents from the galvanic battery, and hence 

 we may infer that also the same alternations take place in the 

 direction of the several currents. 



134'. In conclusion, I may perhaps be allowed to state, 

 that the facts here presented have been deduced from a la- 

 borious series of experiments, and are considered as form- 

 ing some addition to our knowledge of electricity, independ- 

 ently of any theoretical considerations. They appear to be 

 intimately connected with various phaenomena, which have 

 been known for some years, but which have not been referred 

 to any general law of action. Of this class are the discoveries 

 of Savary, on the alternate magnetism of steel needles, placed 

 at different distances from the line of a discharge of ordinary 

 electricity*, and also the magnetic, screening influence of all 

 metals, discovered by Dr. Snow Harris of Plymouth t- A 

 comparative study of the phaenomena observed by these di- 

 stinguished savantSi and those given in this paper, would 

 probably lead to some new and important developments. In- 

 deed every part of the subject of electro-dynamic induction 



* Annales de Ckimie et de Physique, 1827. 



f Philosophical Transactions, 1831, [noticed in Phil. Mag. and Annals, 

 N. S. Vol. X. p. 297-298.] 



