42 Dr BREWSTER on the Construction of Polyzonal Lenses 



Sciences on the 29th July 1822 ; and the New System of ' Illumi- 

 nation for Lighthouses which it describes, is, with the exception of 

 the lamp * (which is a combination of the inventions of Count 

 RUMFORD and M. CARCEL), the very same as mine. The com- 

 pound lens which M. FRESNEL gives as an invention of his own, 

 is the same as that which I had invented eleven years before ; 

 and the combination of lenses and lateral reflectors for widening 

 the main column of light, is exactly the same as mine. In 

 1815, 1 had transmitted to the Library of the Institute of France, 

 and also to M. BIOT, one of its most distinguished members, a 

 copy of the EDINBURGH ENCYCLOPEDIA, containing the article 

 Burning Instruments, in which these inventions were not only de- 

 scribed, but distinctly engraven ; and it certainly seems strange, 

 that, during the seven years which preceded the publication of 

 M. FRESNEL'S memoir, the eyes of none of his colleagues in the 

 Institute should ever have fallen upon the above article, or up- 

 on the engravings by which it is illustrated. M. FRESNEL, how- 

 ever, has the honour of being the first who actually applied the 

 built up lenses to lighthouse illumination ; and M. BECQUEY, Rear- 

 Admiral HALGAN, Baron ROSSELL, M. PRONY, M. ARAGO, and the 

 other Commissioners for French lighthouses, are entitled to no 

 slight praise for the liberality with which they seconded his views, 

 and the promptitude with which they have adopted the valu- 

 able improvements which he submitted to their consideration. 



Under these circumstances, I lost no time in calling the pub- 

 lic attention to the history of these lenses, and to their great 

 utility for lighthouses f ; but although this appeal was made in 

 December 1822, it excited no notice, and the compound lenses 



* This lamp has been brought to a high degree of perfection by MM. ARAGO 

 and FRESNEL, and is a most valuable addition to the apparatus for lighthouses. 



f See Edin. Phil. Journ. vol. viii. p. 165. 



