1884.] Some Experiments on Metallic Reflection. 



187 



in the medium, and he has given expressions which assign to each 

 part of the field a quantity of energy depending on the electromotive 

 and magnetic intensities, and on the nature of the matter at that part 

 in regard to its specific inductive capacity and magnetic permeability. 

 These expressions account, as far as we know, for the whole energy. 

 According to Maxwell's theory currents consist essentially in a certain 

 distribution of energy in and around a conductor, accompanied by 

 transformation and consequent movement of energy through the field. 



Starting with Maxwell's theory we are naturally led to consider the 

 problem, how does the energy about an electric current pass from 

 point to point ; that is, by what paths and according to what law does 

 it travel from the part of the circuit where it is first recognisable as 

 electric and magnetic to the parts where it is changed into heat or 

 other forms. 



The aim of this paper is to prove that there is a general law for 

 the transfer of energy according to which it moves at any point per- 

 pendicularly to the plane containing the lines of electric and magnetic 

 force, and that the amount crossing unit of area per second of this 

 plane is equal to the product of the two intensities multiplied by the 

 sine of the angle between them divided by 47r, while the direction of 

 flow of energy is that in which a right-handed screw would move if 

 turned round from the positive direction of the electromotive to the 

 positive direction of the magnetic intensity. After the investigation 

 of the general law several applications are given to show how the 

 energy moves in the neighbourhood of various current-bearing 

 circuits. 



II. " Some Experiments on Metallic Reflection. IY. On the 

 Amount of Light Reflected by Metallic Surfaces. II." By- 

 Sir John Conroy, Bart., M.A. Communicated by Professor 

 Stokes, Sec. R.S. Received December 15, 1883. 



In a paper which Professor Stokes did me the honour of communi- 

 cating to the Royal Society, and which appeared in the " Proceedings," 

 vol. 35, p. 26, I gave an account of some experiments I had made on 

 the amount of light reflected by polished metallic surfaces when 

 ordinary unpolarised light was incident upon them. 



The light of a paraffine lamp fell either directly, or after reflection 

 from the metallic surface, on a photometer, and the readings were 

 made by altering the distance at which another similar lamp had 

 to be placed from the photometer in order to produce an equal 

 illumination. 



I have repeated the experiments with the steel and speculum metal 



