76 SCIOPTICON MANUAL. 



find the Sciopticon very useful in sketching their pictures. 

 Having first obtained a glass positive or negative of 

 the subject to be painted, it can be thrown upon the 

 canvas of the size desired, and expeditiously and accu- 

 rately traced. It saves valuable time to the good artist, 

 and it prevents the poor artist from producing distor- 

 tions. 



WOODBURT PHOTO-RELIEF EXCELSIOR LANTERN 

 SLIDES. 



By JOHN C. BROWNE. 



While it is a comparatively easy matter to produce 

 fine positives by either the wet or dry process of pho- 

 tography, yet the results are liable to vary somewhat 

 even in the hands of the most careful manipulator. The 

 Woodbury photo-relief process, as now worked in Phila- 

 delphia, has the merit of distancing all competition in 

 the uniform excellence of its lantern slides. It would 

 be a pleasure to give in detail a description of this won- 

 derful process, did space permit, commencing with the 

 sensitive gelatine tissue, resembling in appearance a 

 piece of patent leather, and following it in its exposure 

 to light under a negative, the light's action rendering 

 insoluble those parts reached through the negative; its 

 subsequent immersion in hot water dissolves out those 

 parts not rendered insoluble, producing a relief as thin 

 as writing paper, which when dry is pressed into a piece 

 of soft metal by a hydraulic press of fabulous power, 

 forcing this delicate substance into the smooth metal, 

 and leaving upon its surface a counterpart or mould of 

 all its finest lines and half tones. Strange to say this 

 flimsy gelatine relief is not crushed to atoms by this 



