220 Prof. Faradaij, on Lighthouse lUummation— [March 9, 



G€nh}e, SocitTt^ dePht/siqve, &-c.— M^moires. Tome XV. Partie 1. ^ 4to. 1859. 



Geological Socie^/— Quarterly .Toiarnal, Nos. 60*, 61. 8vo. 1860. 



XiM»jea»Sot'icfj^— Proceedings, Vol. III. No. 16. 8vo. 1860. 



Mackie, S. J. Esq. F.G.S. (the Editor)— The Geologist, Feb. 1860. 



Neu^fon, Mesffrs.— London Journal (New Series), for Feb. 1860. 8vo. 



Novello, Mr. {the Publisher)— The Musical Times for Feb. 1860. 4to. 



Photographic SociVfy— Journal, No. 94. 8vo. 1860. 



TYfe, W. Esq. M.P. (the Author)— AAdiVe^ to the Members of the Royal Institute 



of British Architects, Nov. 7, 1 859. 8vo. 1 859. 

 Vincent, B. {Keeper of Library, i?./.)— Haydn's Dictionary of Dates. Ninth 



Edition, revised and greatly enlarged. 8vo. 1860. (Two copies.) 

 Wells, T. Spencer, Esq. il/.Ti./.— Cancer-Cures and Caucer-Cureis. 16mo. 1860. 



WEEKLY EVENING MEETING, 



Friday, March 9, 1860. 



The Lord Wenslkydale, yicE-pRESiDE.\T, in the Chair. 



Professor Faraday, D.C.L. F.R.S. 

 On Lighthouse Illumination — the Electric Light. 



The use of light to guide the mariner as he approaches land, or passes 

 through intricate channels, has, with the advance of society and its 

 ever increasing interests, caused such a necessity for means more and 

 more perfect, as to tax to the utmost the powers both of the philosopher 

 and the practical man, in the development of the principles concerned, 

 and their efficient application. P^ormerly the means were simple 

 enough; and if the light of a lanthorn or torch was not sufficient to 

 point out a position, a fire had to be made in their place. As the 

 system became developed, it soon appeared that power could be 

 obtained, not merely by increasing the light but by directing the 

 issuing rays : and this was in many cases a more powerful and useful 

 means than enlarging the combustion ; leading to the diminution of the 

 volume of the former with, at the same time, an increase in its in- 

 tensity. Direction was obtained, either by the use of lenses dependent 

 altogether upon refraction, or of reflectors dependent upon metallic 

 reflexion ; and some ancient specimens of both were shown. In modern 

 times the principle of total reflexion has also been employed, which 

 involves the use of glass, and depends both upon refraction and 

 reflexion. In all these appliances much light is lost : if metal be used 

 for reflexion, a certain proportion is absorbed by the face of the metal ; 

 if glass be used for refraction, light is lost at all the surfaces where 



