394 TRANSACTIONS OF THE 



TALBOT— PHOTOGLYPHIC ENGRAVINa. 



Cover the plate with gelatine — that used by confectioners — a quarter of 

 an ounce dissolved in eight or ten ounces of water, by aid of heat. To 

 this solution add about one ounce of a saturated solution of bichromate of 

 potash in water, all strained through linen cloth. This mixture keeps for 

 several months. In cold weather it becomes a jelly and must be warmed 

 for use — should be kept in a dark place. Pour a little on the plate to be 

 engraved, spread it all over, then hold up the plate vertically and let the 

 superfluous gelatin riin off at a corner, then hold it level over a spirit lamp 

 and dry it ; it is then a yellowish film on the plate, with narrow borders of 

 primative colors. The object to be engraved is screwed down on it in a 

 photographic copying frame, — laces, leaves, writing, &c. Put the whole in 

 the sunshine from one to several minutes. A faint image appears on the 

 plate. Finely powdered gum copal is carefully, evenly spread over the 

 plate, then hold the plate level over a spirit lamp to melt the copal — it re- 

 quires considerable heat. Muriatic acid, commonly called hydrochloric, is 

 saturated with peroxide of iron, by heat. Strain it, then evaporate some of 

 it and bottle it. It solidifies in a brown semi-crystalline mass, — cork it 

 well. It attracts moistui-e very quickly ; place a powder of it spread over 

 the plate and it deliquesces quickly. In two or three minutes it etches the 

 plate ; then wipe all off with cotton wool ; pour a rapid stream of cold 

 water oh it ; wipe clean with linen cloth ; rub with soft whiting and water 

 to get rid of the gelatin. 



At the Royal Institution, November 2d, Mr. Malone exhibited photo- 

 lithographs, by Poitevin's process, which are very efi"ective for breadth and 

 accuracy. 



Carlon Printing is a subject to be brought before the Institution next 

 meeting. 



ENGRAVING COPIES. 



At the positive pole of a galvanic battery a plate of iron is placed, and 

 immersed in a proper iron solution, and on a copper plate placed at the opposite 

 pole and likewise immersed ; if the solution be J)roperly saturated, a deposit 

 of iron, bright and perfectly smooth, is formed on the copper plate. 



SUBMARINE CABLES. 



Mr. Hearder has patented one, coating the conductors with cotton, silk, 

 wool, hair, flax, or other suitable fibrous or porous substance or substances, 

 previous to the coat of insulating material, then the like over that, then 

 another coat of insulating material ; alternate coats as many as are requi- 

 site. 



ALUMINIUM. 



Luizi Ferrari Corbelli, of Florence, Italy. Patent for obtaining alu- 

 minium cheaply. 



100 grammes of well washed clay ; dry it, dissolve it in about six times 

 its weight of concentrated sulphuric acid, or very strong hydrochloric acid ; 



