16S METHOD OF COPYING PAINTINGS UPON GLASS. 



Hence the light The confideration of thefe fads enables us readily to under- 

 through "paint- ^ an ^ tne method by which the outlines and (hades of paintings 

 ingon glafs will on glafs may be copied, or profiles of figures procured, by 

 "n U g« V on r th U e 8 the a S cn< T of Hghli When a white furface, covered with 

 paper, &c. and folution of nitrate of iilver, is placed behind a painting on 

 affbriacopy } gj a f s expofed to the folar light ; the rays tranfmitted through 

 the differently painted furfaces produce diftinct tints of brown 

 or black, fenfibly differing in intenfity according to the fhades 

 of the picture, and where the light is unaltered, the colour of 

 the nitrate becomes deepeft. 



»r profiles may When the fiiadow of any figure is thrown upon the prepared 

 be taken rrom r c , , , , • ' , . , , , 



ikadows. lurtace, the part concealed by it remains white, and the other 



parts fpeedily become dark. 



For copying paintings on glafs, the folution fhould be ap- 

 plied on leather ; and, in this cafe, it is more readily acted 

 upon than when paper is ufech 

 The tinge is After the colour has been once fixed upon the leather or 



paper, it cannot be removed by the application of water, or 

 water and foap, and it is in a high degree permanent. 

 The copies thus The copy of a painting, or the profile, immediately after 

 ableVyday- 1166 ~^ em S ta ken, must be kept in an obfeure place. It may 

 J'ght j indeed be examined in the made, but, in this cafe, the 



expofure ihould be only for a few minutes ; by the light of 

 candles or lamps, as commonly employed, it is not fenfibly 

 affected, 

 and this imper- No attempts that have been made to prevent the uncoloured 



yef b°een h reme°- P arts of the C0 P/ or P rofile from bein § aaed U P 0n ^ H S ht ' 

 died. have as yet been fuccefsful. They have been covered with a 



thin coating of fine varnifb, but this has not deffroyed their 

 fufceptibility of becoming coloured ; and even after repeated 

 warnings, fufficient of the active part of the faline matter will 

 ftill adhere to the white parts of the leather or paper, to 

 caufe them to become dark when expofed to the rays of 

 the fun. 

 Copies of tex- Befides the applications of this method of copying that 

 tures thus made. have b een juft mentioned, there are many others. And it 



invifible heat-making rays which exift on the red fide, and which 

 are leaft refrangible, though it is powerfully and diftinclly afFe&ed 

 in a fpace beyond the violet rays out of the vifible boundary. See 

 Annalen der Pbyjik, Jiebenter Band, 527.— D. 



4. will 



