288 GREAT MEN OF SCIENCE 



mainly upon its agreement with the energy principle, recog- 

 nised somewhat later and always found to hold strictly; this 

 agreement could be demonstrated by the aid of Ohm's law. 

 The three laws thus brought into connection with one 

 another mutually support one another in the best possible 

 manner, so that every new confirmation of one also reacts 

 upon the other two. Nature is a connected whole; every new 

 part that is rightly grasped always fits perfectly into what is 

 already known, and thus actually simplifies our general view 

 of the whole of knowledge.^ 



Joule had carried out these investigations on the heating 

 effects of currents, with the special intention of seeing 

 whether heat was thus actually generated, as in Rumford's 

 friction experiment, or whether heat might possibly pass 

 from the sources of current, the Voltaic cells, into the path of 

 the current, in which case the elements should cool down. 

 The result contradicted the latter view; the cells also became 

 warm, in exact accordance with the resistance and the cur- 

 rent. Joule already concluded from Faraday's electrolytic 

 laws, that the total heat produced by the current in a closed 

 circuit fed by Voltaic cells of any kind is proportional to the 

 number of atoms chemically changed in the cells. He 

 thus arrived at setting the heat of combustion, for example 

 of zinc, in parallel with the current heat, which is connected 

 in this way with the oxidation of zinc taking place in the 

 cells. 



It was therefore for Joule an obvious step, and one which 

 followed directly from his line of thought, to proceed to 

 find out whether the currents generated by induction ac- 

 cording to Faraday's method produced cold anywhere in the 



^ It appears to be an increasingly popular device, unconscious or con- 

 scious, but in any case objectionable, to talk of 'classical' and 'modern' 

 science, with the result that by introducing a division or opposition be- 

 tween two parts of our knowledge by means of such nicknames, the newer 

 receives an apparent recommendation, instead of our admitting a want of 

 clarity to be the simple cause of the appearance of a division or oppo- 

 sition. 



