148 ANNUAL OF SCIENTIFIC DISCOVERY. 



placed face downwards on the subject to be copied in an ordinary 

 pressure frame, such as is used for printing photographs. 



The subject must be a positive picture on glass, or else on paper 

 rendered transparent by waxing or other mode, and an exposure to 

 the light will, in a few seconds, according to the state of the weather, 

 show, on removing the coated glass from the pressure frame, a faintly- 

 indicated picture in a negative condition. To bring it out, an enamel 

 color, in a very finely-divided powder, is gently rubbed over with a 

 soft brush until the whole composition or subject appears in a perfect 

 positive form. It is then fixed by alcohol in which a small quantity 

 of acid, either nitric or acetic, has been mixed, being poured over the 

 whole surface and drained off at one corner. 



AVhen the alcohol has completely evaporated, which will generally 

 be the case in a very short time, the glass is quietly immersed hori- 

 zontally in a large pan of clean water, and left until the chromic so- 

 lution has dissolved off, and nothing remains besides the enamel color 

 on the glass ; it is then allowed to dry by itself near a heated stove, 

 and when dry is ready to be placed in the kiln for firing. 



It may be stated that enamel of any color can be used, and that by 

 careful registering, a variety of colors can be printed one after the 

 other, so as to obtain a perfect imitation of a picture ; also that bor- 

 ders of any description can be subsequently added, such as those shown 

 in the specimens exhibited, without any liability to remove or even 

 diminish the intensity of the color in the first firing. 



It will be easy to perceive that this mode of obtaining an image on 

 glass, in an absolutely permanent substance, and of any description, 

 color, or size, may prove of considerable advantage and utility for the 

 decoration of private houses, and also for public buildings. Now that, 

 by means of the photographic art, the most correct views of any object 

 or of any building or scene even portraits can be faithfully and 

 easily obtained, I need only point out the usefulness of the mode of 

 fixing those images, in an indelible manner, for ornamental as well as 

 for scientific purposes. 



In large cities, where houses are built so close to one another, in 

 how many places may not the process become available, by enabling 

 any one to introduce, for a very moderate expense, pleasing or in- 

 structive images where common plain ground glass is now used, to 

 shut out the sight of a disagreeable object, a dead wall, or an unpleas- 

 ant neighbor, without diminishing the amount of light more than is 

 convenient. Even for domestic purposes, for lamps or screens, or any 

 object in glass, the process will be found useful, especially on account 

 of its rapidity, which will enable the manufacturer to execute and to 

 deliver an order at a very few days' notice. 



Discussion. Mr. Harvey inquired whether the method now em- 

 ployed for coloring daguerreotypes was applicable to the process just 

 described, provided the colors used were such as to stand the firing. 



M. Joubert replied in the affirmative ; mineral colors being used 

 instead of vegetable colors, as in the case of photographic coloring. 

 The difference between the two was this: where they applied the 

 color to a photograph, or drawing upon paper, the color remained as 

 applied ; but any one acquainted with glass painting knew that vari- 

 ous colors were acted upon differently under the action of heat in the 



