214 Intelligence and Miscellaneous Articles. 



Our method requires the employment of iodine and bromine, and 

 is easily performed by persons who are accustomed to employ those 

 substances separately. It consists in polishing and iodizing the 

 plate in the ordinary manner, and afterwards causing it, by any 

 convenient means, to absorb three times as much vapour of bromine 

 as is usually thought sufficient to render the plates as sensitive as 

 possible. Whilst the ordinary quantity of bromine does not visibly 

 alter the tint of the iodized layer, that which we recommend causes 

 it to assume a deep bluish violet tint. 



The sensibility of the plates thus surcharged with bromine is re- 

 duced to a third of what it would be if the ordinary quantity only 

 were used ; but at the same time they are rendered capable of pro- 

 ducing a perfect picture of subjects presenting the greatest variety 

 of shade. This will be seen by inspecting a small picture, presented 

 herewith, which was produced when the sun was shining. There 

 will be perceived the clouds in the sky, white houses, with the sha- 

 dows well-defined, and trees, the foliage of which is delineated much 

 in the same manner a? if executed by an artist. 



We recommend the ordinary quantity of bromine to be exactly 

 tripled ; as if less than this quantity be used, the picture will not be 

 properly brought out ; and if more than this quantity were used, the 

 mercury would not be properly condensed and the image would not 

 be so well-defined. 



This new property, communicated to the iodized plates by an 

 excess of bromine, may be very usefully applied ; and besides, as 

 it appeared to us that this statement might be useful to the chemical 

 world, we have been induced to make this communication to the 

 Academy. — Comptes Rendus des Seances de VAcademie des Sciences, 

 (^as inserted in the London Jmirnal.) 



OBSERVATIONS ON THE EXPERIMENTS OF MESSRS. FOUCAULT 

 AND FIZEAU, RELATIVE TO THE ACTION OF THE RED RAYS 

 UPON DAGUERREOTYPE PLATES. BY M. EDMOND BECQUEREL, 



Messrs. Foucaultand Fizeau, at the sitting of the Academy on the 

 5th inst. (October 184G), presented some observations concerning 

 the action of the red rays upon Daguerreotype plates, from which it 

 would appear that the least refrangible part of the solar spectrum 

 acts upon the iodide of silver in an inverse manner to the most 

 refrangible portion. As it appears that these gentlemen are not 

 acquainted with the experiments which have been made during the 

 last few years on this subject, and as the results stated by them do 

 not appear to me to lead to the conclusions which they deduce, I 

 take the liberty of submitting some remarks thereon to tlie Academy. 



Dr. Draper (Philosophical Magazine, Nov. 1842), on examining 

 the image produced by the action of the spectrum upon iodized plates 

 of silver, made known, before these gentlemen, the existence of pro- 

 tecting rays modifying the influence of the solar rays, and even acting 

 negatively upon the iodide of silver. Sir J. F. W. Herschel examined 

 the pictures on that occasion, and in a very interesting experiment 



