The London, Edinburgh and Dublin philosophical magazine and journal of science . r detail. The pheno-menon is beautifully shown in the globular tube, fig. 14. Fur. 12. j^\ Fiar. 13, C^) )))))))))) ) ([Qj )))))))))))) Of course, what appear to be the lines of force are not reallythe lines made visible but the effects due to the form of thefield; since if an effect is due to the field at any given point andvaries with the strength of the field, the result will take uponitself the form of the lines of force. It is known that the re-sistance to the passage of the current is less with the lines off
The London, Edinburgh and Dublin philosophical magazine and journal of science . r detail. The pheno-menon is beautifully shown in the globular tube, fig. 14. Fur. 12. j^\ Fiar. 13, C^) )))))))))) ) ([Qj )))))))))))) Of course, what appear to be the lines of force are not reallythe lines made visible but the effects due to the form of thefield; since if an effect is due to the field at any given point andvaries with the strength of the field, the result will take uponitself the form of the lines of force. It is known that the re-sistance to the passage of the current is less with the lines offorce than across them, which effect may have some influencein producing the phenomenon. The bright lines are nothingmore than bright bands very closely packed ; and the form isdue to self-induction. 254 Sir David Salomons on the Electric In fact, all points on similar lines of force in a magneticfield lying between the N. and S. poles make up a figuresomewhat like the shell of an egg ; and the appearance ofwhat I term the visible field appears to be like a vast num- Fi£. ber of transparent coloured egg-shells placed symmetricallyone within the other, although, of course, each shell is notsymmetrical with any other, the inner ones being more elon-gated and the outer ones more spherical, the centre one ofall being a straight line. By holding the tube which has been experimented with invarious positions in regard to the poles of the magnet, whetherthey be N. and 8., or both N. or both S., a variety of appear-ances are seen in the tube according to the position in whichit is held. All the effects can be traced to what I term theAmperian explanation. From the experiments which have been described it isevident that a very important opening suggests itself as tothe practical use of vacuum-tubes, viz. that of exploring themagnetic field. I have used such tubes for this purpose formany years past, and have been able to plot out in a fewminutes mentally that which takes a long time
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