210 Dr Fyfe on Daguerreotype. 



have in tliis way succeeded in getting impressions from en- 

 gravings, having all the delicacy of the original. For this 

 purpose it is necessary to have the engraving on thii\ paper, 

 placed on the plate with the engraving exposed to view, so as 

 not to have a reverse. They are kept together hy putting 

 them into a glass frame, and then exposed near the flame 

 either of an argand or flat burner for about twenty minutes 

 or so, according to the light and the thickness of the paper, 

 after which the plate is to be mercurialized and washed with 

 hyposulphite. 



I have already mentioned that when a polished plate, with 

 an object placed on it, is mercurialized, an image is presented 

 similar to a daguerreotype, and which, like it, is easily obli- 

 terated. It is remarkable, however, that if, instead of mer- 

 curializing at the temperature of about 160° Fahr., we raise it 

 to about 400° Fahr., not only does the mercury present a whiter 

 surface, but it adheres so fu-mly to the plate that it requires 

 the polishing powder to remove it. This affords an easy method 

 of producing and multiplyingto any extent profiles on silver. The 

 profile on paper is cut out, and, after being moistened on both 

 sides with the tongue, or with very weak mucilage, is placed 

 on the polished plate, and pressed down so as to make it ad- 

 here to it at all points ; after Avhich it is put into the mercu- 

 rializing box, and kept exposed to the vapour of the mercury 

 till the teraperatm-e reaches to about 400' Fahr. The lamp is 

 then removed, and the temperature allowed to sink before 

 taking out the plate. In conducting this process, the only 

 precaution necessary is to take care that the paper does not 

 separate from the silver, which it is apt to do when the 

 heat is'raised too high, or the plate is long kept in the box, in 

 which case the image is indistinct. To prevent this, the weak 

 mucilage is used, which is easily washed oflF from the silver by 

 keeping the plate in warm water, or rubbing it softly -with a 

 sponge. Shoidd the profile not be sufficiently sharp, the pro- 

 cess may be repeated on the same plate, by removing the mer- 

 cury with the polishing powder. 



