On an Improvement in the Daguerreotype Process. 287 



extravasation could be seen, except the presence of the cor- 

 puscles themselves. 



I consider therefore as established, — 1st, the passage of 

 these corpuscles " de toute piece " through the capillaries ; 

 2ndly, the restorative power in the blood, which immediately 

 closes the aperture thus formed. It would lead me too far 

 at present to explain how I have obtained purulent matter in 

 these animals similar in all respects to that in the human 

 subject. 

 Kensington, Sept. 21, 1846. 



XLV. On an Improvement in the Daguerreotype Process by 

 the application of some new compounds of Bromine, Chlorine 

 and Iodine ', with Lime. By R. J. Bingham, Chemical As- 

 sistant in the Laboratory of the London Institution*. 



ALL persons who have practised the Daguerreotype must 

 have remarked, that in warm weather a considerable de- 

 position of moisture takes place upon the glass or slate cover 

 used to confine the vapour in the bromine or accelerating 

 pan. This moisture must also necessarily condense upon the 

 cold metallic surface of the plate during the time it is exposed 

 to the bromine vapour. In fact, I have been informed by a 

 number of professional Daguerreotypists (and I have experi- 

 enced the difficulty myself), that they were unable to obtain 

 perfect pictures during the excessive heat of the late season ; 

 and a very clever and enterprising operator, who last year 

 made a tour on the continent, and brought home some of the 

 finest proofs I have ever seen, entirely failed this season in 

 obtaining clear and perfect pictures, from the constant appear- 

 ance of a mist or cloud over the prepared surface. This ap- 

 pears to be caused by the deposition of moisture upon the 

 plate, arising from the water in which the bromine is dissolved. 

 To obviate this some have recommended the pan to be kept 

 at a low temperature in a freezing mixture; and M. Daguerre, 

 in a communication to the French Academy of Sciences, re- 

 commends the plate to be heated : but in practice both these 

 plans are found to be unsuccessful, (SeeLerebour's Traits de 

 Photographic.) 



It appeared to me, that if we could avoid the use of water 

 altogether in the accelerating mixture, not only would the 

 difficulty I have mentioned be avoided, but a much more sen- 

 sitive surface would be obtained on the plate. With this 

 view I endeavoured to combine bromine with lime, so as to 

 form a compound analogous to bleaching powder. In this I 

 * Communicated by the Author. 



