36 Sir John Conroy. [May 15, 



thermo-electric and voltaic action at the cathode and external 

 junction, very different amounts of resistance, large in some cases, 

 remain, and are exercised by different metals as cathodes, and those 

 differences of resistance are only to a small extent due to heat and 

 current absorbed in liberating hydrogen, and can only in a few cases 

 be partly accounted for by chemical action, films, or absorption of 

 gases at the cathode. 



I ara now investigating the nature of this resistance, and the 

 relations of the resistance to various circumstances. 



May 15, 1884. 

 THE PRESIDENT in the Chair. 



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

 for them. 



The following Papers were read : 



L " Some Experiments on Metallic Reflection. No. V. On 

 the Amount of Light reflected by Metallic Surfaces. III." 

 By Sir JOHN CONROY, Bart., M.A. Communicated by Pro- 

 fessor G. G. STOKES, Sec. R.S. Received May 6, 1884. 



Professor Stokes recently communicated to the Royal Society 

 (" Proc. Roy. Soc.," vol. 36, p. 187) an account of some determina- 

 tions I had made of the amount of light reflected by steel and 

 speculum metal mirrors when polarised light was incident upon 

 them. 



I have repeated these experiments with films of silver chemically 

 deposited on glass, as such films approximate more closely to 

 theoretically perfect metallic surfaces than any metallic mirror, 

 however carefully polished, and also because very different state- 

 ments have been made as to the reflective power of such films ; one 

 observer having said that silvered glass mirrors reflect about 90 

 per cent, of the light incident upon them, whilst another made their 

 reflective power only equal to that of speculum metal. 



