144 HOUSTOX, KEXXELLY — THE PATH OF A CURREXT. [Mar. 19, 



THE INSULATING MEDIUM SURROUNDING A CON- 

 DUCTOR THE REAL PATH OF ITS CURRENT. 



BY EDWIN J. HOUSTON, PH.D., AND A. E. KENNELLY, SC.D. 



{Read March 19, 1897.) 



Up to the commencement of the i^resent century our knowledge 

 of electricity and its action was almost entirely confined to the 

 phenomena of electric charges and their dissipation by discharge. 

 The conception of an electric current as a steady condition of dis- 

 charge had not then been clearly ai^prehended. It was observed 

 that dissimilar bodies, when placed in contact with, or rubbed 

 against, each other, manifested electric excitation. It was assumed 

 that the electric charges thus acquired resided upon the exterior 

 surfaces of the charged bodies, and that charged bodies evidenced 

 mutual electric attractions. and repulsions at a distance. The idea 

 of action at a distance was, therefore, inseparably connected with 

 early conceptions of electricity and electrical phenomena. Action 

 at a distance was explained by some on the hypothesis that an elec- 

 trified body emitted an invisible electric effluvium which acted 

 upon electrified bodies in its vicinity. It was observed that elec- 

 tric charges were transmitted through certain bodies called conduc- 

 tors, and failed to be transmitted' through other bodies called non- 

 conductors or insulators. In a similar manner the phenomena of 

 magnetism, as developed up to the commencement of the present 

 century, pointed to the seeming attraction and repulsion of mag- 

 netic poles. According to the views then existing, a magnet was a 

 skeleton of iron or steel for supporting two opposite poles at its 

 extremities. These poles manifested peculiar properties to which 

 the intervening skeleton was considered as merely subordinate. 

 This- magnetic action at a distance, by which the magnetic poles of 

 the earth were assumed to direct the compass needle, was supposed 

 by some to be effected through the medium of a magnetic effluvium 

 emitted from the poles of the magnet. Up to the commencement 

 of the present century, therefore, electric and magnetic phenomena 

 were studied apart, and each was accredited with the possibility of 

 action at a distance, except in so far as some physicists endeavored 

 to explain such action by the intervention of material electric and 

 magnetic effluvia. About the commencement of the present cen- 



