Miscellanies. 179 



not to soften the varnish too much ; when cold, the smoke is wiped off 

 with a cloth from the parts of the glass exposed by the etching needle. 

 Another method is to cover one side of the glass with starch solution, 

 of such strength, that when dry it is transparent, and it is then to be 

 laid down with the glass side next the paintings, which can be traced 

 with a pencil on the starch, and then etched on the other side, as al- 

 ready described. From glass etchings thus procured, impressions are 

 taken in the usual way. 



This process of transparent etching is applicable to the camera 

 obscura ; for, instead of using ground glass, as is commonly done, the 

 representation may be thrown on starched glass, on which it is traced 

 and then etched on the other side, as above described. 



Before finishing this part of the subject, I may here allude to a 

 method of taking the impressions, by which I have succeeded in giv- 

 ing them a resemblance to oil paintings. 



By the method noticed, paper, or some absorbing substance, is used. 

 I have already stated that the phosphate suspended in water may be 

 employed, which suggested to me the use of the same substance along 

 with a varnish, in the hopes of being able to take the impression on 

 panel-board or metal. I have found this to answer as well as with 

 paper. The varnish I have used is Canada balsam and turpentine, 

 with which the phosphate, dried by the cautious application of heat, 

 and excluded from light, is thoroughly incorporated ; with this the 

 panel-board, previously prepared as for an oil painting, is varnished ; 

 when dry, the impression is taken on it in the usual way. It will be 

 found to have all the richness of an oil painting. 



By this process, impressions equally distinct and brilliant may be ta- 

 ken on metal. Perhaps this may be of service in saving engravers the 

 time and trouble of laying down on the metal the figure to be en- 

 graved. 



The impressions received by the modes now described are taken by 

 exposure to the solar ray. It is well known that the paper may be 

 darkened by other means, as by the oxyhydrogen blowpipe ; but there 

 is no necessity for having recourse to so intense an artificial light. I 

 have found that, by concentrating the light of a common fire by me- 

 tallic mirrors, the paper is darkened, and the same also occurs with the 

 flame of a gas lamp. Of course, the time required is much longer 

 than when exposed to sunshine. In this way I have succeeded in get- 

 ting impressions of dried leaves almost as distinct as by solar light ; 

 indeed we may dispense altogether with the mirror, for, by exposing 

 the paper with the leaf on it, in a frame, to the light of a common fish- 

 tail gas-burner, at the distance of a few inches, I have procured speci- 

 mens, some of which, though on a small scale, have all the richness of 

 those taken by solar light. 



