THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



MARCH 1891. 



XXI. On the Illustration of the Properties of the Electric Field 

 by Means of Tubes of Electrostatic Induction. By J. J. 

 Thomson, M.A., F.R.S., Cavendish Professor of Experi- 

 mental Physics, Cambridge *. 



I HAVE attempted in the following pages to develop 

 a method of expressing the various processes which 

 occur in the electric field in terms of changes in the form or 

 position of tubes of electrostatic induction which are assumed 

 to be distributed throughout the field, in the hope that it may 

 help the student to obtain a physical interpretation of results 

 which are perhaps too frequently regarded as entirely ex- 

 pressed by equations. Methods such as this, of materializing, 

 as it were, mathematical conceptions, seem to have a use even 

 where, as in the case of Electricity, the analytical theory is 

 well established ; for any method which enables us to form a 

 mental picture of what goes on in the electric field has a 

 freshness and a power of rapidly giving the main features of 

 a phenomenon, as distinct from the details, which few can 

 hope to derive from purely analytical methods. Experience 

 has, I think, shown that Maxwell's conception of electric 

 displacement is of somewhat too general a character to lend 

 itself easily to the formation of a conception of a mechanism 

 which would illustrate by its working the processes going on 

 in the electric field. For this purpose the conception of 

 tubes of electrostatic induction introduced by Faraday seems 

 to possess many advantages. If we regard these tubes as 

 having a real physical existence, we may, as I shall endeavour 

 * Communicated by the Author. 

 Phil. Mag. S. 5. Vol. 31. No. 190. Mar. 1891. N 



