THE SMITHSONIAN INSTITUTION. 



363 



ment. A glance at the arrangements (Figs. 14 and 15) shows us that 

 we must select the fifth combination as the most suitable ; because its 

 resistance, 0.G5, is nearer to that of the closing arc, than that of the 

 other combinations. Make, for sake of brevity, the electro-motive 

 force of the element eqnal 1, and the resistance also 1, then, if we ap- 

 ply successively all of the eight combinations to the electro-magnet 

 above mentioned, the following values will be obtained for the 

 strength of the current : 



24 



=: 0.963 



24 + 0,1) 

 12 

 •6 + 0,9 



=: 1.T4 



2.666 + 0,9 — ^-^^ 



6 



1.5 + 0,9 — ^-^ 



4 



0^666 + 0,9 ~ ^'^^ 



= 336 



=: 1.85 



0.375 + 0,9 



2 

 0.166 -f 0,9 



0.012 + 0,9 



1.61 



Fig. 16. 



It is observed here that with the combination 5 the coils of the 

 electro -magnet remaining unchanged, the magnetism of the soft iron 

 will be greater than with any of the other combinations. Combination 

 4 approaches 5 very closely in its effects ; thus the exact maximum 

 should be looked for between 4 and 5. In fact the combination re- 

 presented in fig. 16 gives the strength of 

 the current 2.56. 



By charging the same elements with 

 strong acid, the resistance of the element 

 will be 5.85 ; the resistance of the closing 

 arc will be 2.3 times as great as that of one 

 element, and for this case the third com- 

 bination (eight three-fold elements) will be 

 the most suitable. 



The best combination for a given appa- 

 ratus to decompose water will be further 

 considered hereafter. 



If a given number of elements be so con- 

 bined that they will yield in a given cir- 

 cuit a maximum strength of current, an 

 increase of the number of elements will in- 

 crease the strength of the current in the most favorable cases only 



