206 ANNUAL OF SCIENTIFIC DISCOVERY. 



grains to the ounce of water. This produces a most intense black, and the 

 negative, being washed and varnished, is finished and permanent. Dr. D. 

 concludes by affirming that this process is applicable to the production of 

 photographic copies not merely of MSS. on vellum and paper, but of engravings, 

 medals, seals, oil paintings, and all similar objects. 



Artificial Light for taking Photographs. A very brilliant light has been pro- 

 duced by directing a stream of oxygen gas into the flame of coal gas which 

 had been previously made to pass through cotton and naphtha in order to 

 surcharge it with carbon. "With this light, using a reflector, a photograph of 

 an engraving could be taken by the camera in a very short tune. 



Transferring Collodion Photographs. Alexander Eollasen, of Birmingham, 

 England, has obtained a patent for an invention in photographs, the nature of 

 which consists in transferring to paper, linen, ivory, wood, metal, or stone, 

 collodion pictures taken on glass. The glass plate on which the picture is to 

 be taken is first cleansed with spirits of wine, naphtha, and tripoli, and is 

 finally buffed with buff leather, which has a slightly greasy surface. The 

 glass is then covered with iodized collodion, or albumen, and is immersed in 

 a bath of nitrate of silver, to render it sensitive. It is then placed on the 

 camera, the picture taken in the ordinary manner, and afterwards developed 

 by first washing in a solution of nitrate or acetate of iron, then with a solution 

 of hyposulphate of soda. After being well washed in pure water it is dried. 

 If the collodion be of a very adhesive quality it is sometimes necessary, before 

 drying the picture, to immerse it for two or three seconds hi a bath of dilute 

 nitric acid. The picture thus taken is removed from the glass by transferring 

 the film on which it is impressed. "When it is perfectly dry it may be 

 colored and tinted on the back, according to the taste of the artist, and then 

 covered with varnish. If it is desired not to color the picture while on the 

 glass it is covered at once with a varnish made of asphaltum dissolved in 

 naphtha to about the consistency of cream. The varnish is now allowed to 

 dry to a certain point, namely, when it does not seem sticky to the touch ; 

 but it is not allowed to dry further, lest it should crack. It is then coated 

 with a thin solution of shellac, which prevents further hardening of the var- 

 nish. The next operation is to remove this film of collodion, with the picture 

 on it, from the plate of glass. A thin mucilage, composed of two-thirds gum 

 arable and one of honey, is now laid on the varnish of the picture, and if the 

 transfer is to be made on paper, it is damped first, and also coated with 

 mucilage. The paper is now laid on the back of the picture, and both are 

 laid flat on a table, and clamped between two pieces of wood. The surface 

 of the paper is then rolled over with a small India rubber tube, to press out 

 the air bubbles between the paper and glass. "When the transfer is to be 

 taken on wood or stone care must be taken that the surface is perfectly 

 smooth, and the air bubbles may be driven out by commencing at one end, 

 and laying the picture gradually down, from end to end. "When the mucilage 

 is dry enough which may be ascertained by raising one corner of it the 

 film should begin to separate itself from the glass. When this is the case, its 

 complete removal may now be effected. A few drops of water are now 

 introduced with a feather between the glass and film, and gradually the 



