186 Transfer of Energy in the Electromagnetic Field. [Jan. 10, 



VI. " On the Physiology of the Carbohydrates in the Animal 

 System." By F. W. Pavy, M.D., F.R.S. Received De- 

 cember 13, 1883. 



[Publication deferred.] 



The Society adjourned over the Christmas Recess to Thursday, 

 January 10th, 1884. 



January 10, 1884. 

 THE PRESIDENT in the Chair. 



The Presents received were laid on the table, and thanks ordered for 

 them. 



The following Papers were read : — 



I. " On the Transfer of Energy in the Electromagnetic Field." 

 By J. H. Poynting, M.A., late Fellow of Trinity College, 

 Cambridge, Professor of Physics, Mason College, Birming- 

 ham. Commnnicated by Lord Rayleigh, M.A., D.C.L., 

 F.R.S. Received December 17, 1883. 



(Abstract.) 



A space containing electric currents may be regarded as a field 

 where energy is transformed at certain points into the electric and 

 magnetic kinds by means of batteries, dynamos, thermoelectric 

 actions, and so on, while in other parts of the field this energy is again 

 transformed into heat, work done by electromagnetic forces, or any 

 form of energy yielded by currents. Formerly a current was regarded 

 as something travelling along a conductor, attention being chiefly 

 directed to the conductor, and the energy which appeared at any part 

 of the circuit, if considered at all, was supposed to be conveyed 

 thither through the conductor by the current. But the existence of 

 induced currents and of electromagnetic actions at a distance from a 

 primary circuit from which they draw their energy, have led us, 

 under the guidance of Faraday and Maxwell, to look upon the medium 

 surrounding the conductor as playing a very important part in the 

 development of the phenomena. If we believe in the continuity of 

 the motion of energy, that is, if we believe that when it disappears at 

 one point and reappears at another, it must have passed through the 

 intervening space, we are forced to conclude that the surrounding 

 medium contains at least a part of the energy, and that it is capable 

 of transferring it from point to point. 



Upon this basis Maxwell has investigated what energy is contained 



