464 Prof. D. E. Hughes. [May 27, 



Table III. 



Influence of an Iron Tube upon an Interior Insulated Wire. 



Iron gas tube, 

 90 cm. in length., 

 10 cm. diameter, 



2 mm. thick. 

 Wires 1 metre in 



length, 3 mm. 

 diameter. 



Comparative 

 force of the 

 extra 

 currents. 



Resistance 

 in ohms, 

 stable 

 period. 



Resistance 

 in ohms, 

 variable 

 period. 



Per 



centage of 

 increased 

 resistance 

 in variable 

 period. 



A IiqaI nf a 



increase of 

 resistance 

 in ohms. 



Copper wire alone 

 Copper wire insu- 



82 



] 



0-00460 



-00482 



7 



-00022 



lated in the in- 

 terior of the iron 



j. 410 



-00460 



-03220 



600 



-02760 



Brass wire, ditto. . 

 Iron wire, ditto . . 

 Lead wire, ditto. . 

 G-erman siJver 



410 

 615 

 410 



| 410 



0-01380 

 -02944 

 -05750 



07636 



-03974 

 0-05888 

 -08682 



-10384 



188 

 100 

 51 



36 



-02594 

 -02944 

 -02932 



-02748 



the magnetic reaction of the tube upon the primary current passing in 

 the wire produces a marked effect upon the different metals, the 

 force of the extra currents as measured by the induction balance rise 

 in value from 82 to 410, this being a constant for all metals except 

 iron, which alone shows the higher force of 615 ; the force of the extra 

 currents, however, has no direct relation to the extra resistance 

 shown in the variable period, but the latter must be in direct relation 

 with the duration or length of time required to pass from an infinite 

 to the stable resistance. 



The table shows on comparing the resistance of a metal in its stable 

 period with that found in the variable, that copper has the highest 

 percentage of increased resistance, being 600 per cent, increase, or 

 seven times that found for its stable resistance, each metal in the 

 order of their specific resistance having a less percentage of increased 

 resistance until we arrive at the German silver wire, which shows only 

 36 per cent, against the 600 per cent, of the copper ; we have also here 

 the remarkable fact that iron even with a circular section stands 

 simply in its order of specific resistance, showing only one-sixth of the 

 increased resistance experienced by copper; the percentage of 

 increased resistance of a metal when under the influence of an 

 insulated magnetic sheath is directly as its conductivity or inversely 

 as its specific resistance. 



If we regard the phenomenon from a different point of view, 

 confining ourselves simply to the additional resistance above that of 

 its specific stable resistance, all metals whether magnetic or non- 



