i62 PHYSICAL SCIENCE 



part the positive ends of the tubes are also mobile. 

 Now it is this continual process of establishment 

 of aethereal strain by a battery, and the compensa- 

 ting process of its obliteration along a conductor 

 that, according to the views of Faraday and 

 Maxwell, now accepted as one aspect of the truth, 

 constitute an electric current. 



The ionic theory of electrolysis gave a clear 

 idea of the mechanism by which the slipping of 

 the ends of the tubes of force occurred in con- 

 ducting liquids, and the electronic hypothesis 

 gives us an equally vivid insight into the nature 

 of the process within metallic circuits. The tubes, 

 anchored by their ends to an ion in electrolytes 

 or to an electron in metals, drag their anchors. 

 It is the slip of the anchors that constitutes the 

 current, and the heat developed by the passage 

 of the current is to be explained by the frictional 

 resistance to the drag of the anchor, or to some 

 other means of dissipating energy, such as internal 

 radiation, not yet fully understood. 



Faraday had no skill in mathematical analysis, 

 and his insight into physical principles is one of 

 the best examples of scientific instinct found in 

 history. As was well said by Von Helmholtz in 

 the Faraday Lecture for the year 1881, *' Now 

 that the mathematical interpretation of Faraday's 

 conceptions regarding the nature of electric and 

 magnetic forces has been given by Clerk Maxwell, 

 we see how great a degree of exactness and 

 precision was really hidden behind the words, 

 which to Faraday's contemporaries appeared 

 either vague or obscure ; and it is in the highest 

 degree astonishing to see what a large number 

 of general theorems, the mathematical deduction 



