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LXXXI. On Thermography, or the Art of Copying En- 

 gravings, or any printed Characters from Paper on Metal 

 Plates ; and on the recent Discovery of Moser, relative to the 

 formation of Images in the Dark. By Robert Hunt, 

 Secretary of the lloyal Cornwall Polytechnic Society*. 

 HPHE Journal of the Academy of Sciences of Paris, for the 

 18th of July, 1842, contains a communication made by 

 M. Regnault from M. Moser of Konigsberg, " Sur la forma- 

 tion des images Daguerriennest;" in which he announces the 

 fact, that " when two bodies are siifficiently near, they impress 

 their images upon each other." The Journal of the 29th of 

 August contains a second communication from M. Moser %, in 

 which the results of his researches are summed up in twenty- 

 six paragraphs. From these I select the following, which 

 alone are to be considered on the present occasion. 



" 9. All bodies radiate light even in complete darkness. 

 " 10. This light does not appear to be allied to phosphores- 

 cence, for there is no difference perceived whether the bodies 

 have been long in the dark, or whether they have been just 

 exposed to daylight, or even to direct solar light. 



" 10. Two bodies constantly impress their images on each 

 other, even in complete darkness. 



" 14. However, for the image to be appreciable, it is neces- 

 sary, because of the divergence of the rays, that the distance 

 of the bodies should not be very considerable. 



" 15. To render the image visible, the vapour of water, 

 mercury, iodine, &c. may be used. 



"17. There exists latent light as well as latent heat." 

 The announcement at the last meeting of the British Asso- 

 ciation of these discoveries naturally excited a more than or- 

 dinary degree of interest. A discovery of this kind, changing, 

 as it does, the features, not only of the theories of light adopted 

 by philosophers, but also the commonly received opinions of 

 mankind, was more calculated to awaken attention than any 

 thing which has been brought before the public since the 

 publication of Daguerre's beautiful photographic process. 

 Having instituted a series of experiments, the results of which 

 appear to prove that these phaenomena are not produced by 

 latent light, I am desirous of recording them. 



I would not be understood as denying the absorption of 

 light by bodies ; of this I think we have abundant proof, and 

 it is a matter well deserving attention. If we pluck a Nastur- 

 * Read at the Cornwall Polytechnic Society, Tuesday, Nov. 8, 1842. 

 f Comptes Rendus, tome xv. No. 3. folio 119. 



\ Translations of M. Moser's papers containing the full details of his re- 

 searches and discoveries will be published in the course of the present month 

 (December) in Part XI. of Taylor's Scientific Memoirs. 



