164 ANNUAL OF SCIENTIFIC DISCOVERY. 



time there was a lively effervesence owing to the disengagement of 

 nitrous gas during the disappearance of the silver. As soon as he 

 judged the engraving deep enough he w r ashed the plate well in water. 

 By this means he obtained very delicate engravings, from which as 

 many as forty copies could be taken ; they were, however, deficient in 

 vigor, and had a gray tint, almost uniform. 



Attempts have been since made to take copies by the battery, 

 placing the daguerreotype in an acid, or metalliferous bath communi- 

 cating with the carbon pole of a cell of Bunsen's battery, which is the 

 pole of oxidation or departure. There were produced engravings of 

 a high finish, but of a texture that might be called impalpable, and 

 from which copies could not be taken by a copper-plate press. To 

 remedy this defect, M. Fizeau thought of covering an engraving which 

 had undergone the first biting process, with an oily substance that 

 would fill up the smallest cavities and leave untouched the prominent 

 parts, which he cut out with the greatest care ; in this state it was 

 gilded by means of the battery, and then stripped of its oily coating 

 by a suitable dissolvent. After this operation, the part already bitten 

 was. strongly acted upon by the nitric acid, which left untouched all 

 the parts that had been gilt. By means of this improvement, M. 

 Fizeau succeeded in obtaining a few engravings, possessing a certain 

 vigor, of casts illuminated by the sun. Delicate views subjected to 

 the same operation have always been far inferior to photographs on 

 paper. The increasing progress of these latter, have led to the neglect 

 of engraving daguerreotypes ; indeed, the small number of indifferent 

 copies that can be taken, is a great obstacle to this mode of employ- 

 ment. It might be remedied by taking pictures on hardened steel 

 silvered by the battery. I silvered a sheet of hardened steel, by 

 rubbing it with a solution of chloride of silver dissolved in the hypo- 

 sulphite of soda. The daguerreotype was successful, but not the 

 engraving, from deficiency, no doubt, of the silvering. With the 

 resources at present offered by the battery, it is certain that the copy- 

 ing of engravings in a similar manner would be much increased. 

 There would be required however great manual strength ; it would 

 be a very delicate operation, which could be executed only with a 

 diamond graver. No attempts have been made, that I know of, to 

 copy daguerreotypes by means of lithography, yet the art might, not- 

 withstanding, furnish all the required vigor, for the shades depend in 

 lithography only on the chemical nature of the surface, and not at all 

 on its confirmation. I propose, however, to do this ; Cover a piece 

 of silk, waxed, of the size of the engraving to be lithographed, with an 

 exceedingly thin coating of lithographic ink dissolved in alcohol. On 

 this waxed silk take by pressure a copy of the daguerreotype merely 

 washed with hyposulphite of soda and rinsed w r ith distilled water. 

 With the waxed silk alone, the operation has succeeded very well ; it 

 is a precedent of flattering promise. If the coating of lithographic 

 ink is exceedingly thin, the catching property of the waxed silk Avill 

 be only increased, and the taking of the impression will be easier. 

 The taking of the impression having been successful is a great step 



