4>G6 Mr. Hunt on Thermography, 



calorific rays, or to artificial heat. I then, speculating on the 

 probability of our being enabled by some such process as the 

 one I then named, to copy pictures and the like, proposed the 

 name of Thermography, to distinguish it from Photography. 



18. I now tried the effects of a print in close contact with a 

 well-polished copper plate. When exposed to mercury, I 

 found that the outline was very faithfully copied on the metal. 



19. A paper ornament was pressed between two plates of 

 glass, and warmed ; the impression was brought out with tole- 

 rable distinctness on the under and warmest glass, but scarcely 

 traceable on the other. 



20. Rose leaves were faithfully copied on a piece of tin plate, 

 exposed to the full influence of sunshine, but a much better 

 impression was obtained by a prolonged exposure in the dark. 



21. With a view of ascertaining the distance at which bodies 

 might be copied, I placed upon a plate of polished copper a 

 thick piece of plate glass, over this a square of metal, and se- 

 veral other things, each being larger than the body beneath. 

 These were all covered by a deal box, which was more than 

 half an inch distant from the plate. Things were left in this 

 position for a night. On exposing to the vapour of mercury 

 it was found that each article was copied, the bottom of the 

 deal box more faithfully than any of the others, the grain of 

 the wood being imaged on the plate. 



22. Having found by a series of experiments that a black- 

 ened paper made a stronger image than a white one, I very 

 anxiously tried to effect the copying of a printed page or a 

 print. I was partially successful on several metals, but it was 

 not until I used copper plates amalgamated on one surface, 

 and the mercury brought to a very high polish, that I pro- 

 duced any thing of good promise. By carefully preparing 

 the amalgamated surface of the copper I was at length enabled 

 to copy from paper, line-engravings, wood-cuts and litho- 

 graphs, with surprising accuracy. The first specimens pro- 

 duced (which I have the satisfaction of now submitting to 

 your inspection), exhibit a minuteness of detail and sharpness 

 of outline quite equal to the early Daguerreotypes and the 

 photographic copies prepared with chloride of silver*. 



The following is the process at present adopted by me, 

 which I consider far from perfect, but which affords us very 

 delicate images. 



A well-polished plate of copper is rubbed over with the ni- 

 trate of mercury, and then well washed to remove any nitrate 



* The first faithful copy of the lines of a copper-plate engraving was ob- 

 tained by Mr. Cantabrana, who has since succeeded in procuring some to- 

 lerable specimens on unamalgamated copper, which cannot be rubbed off. 



