50 ANNUAL OF SCIENTIFIC DISCOVERY. 



depth of tint produced by the fibre of the paper is desired to be in- 

 creased in those impressions on metal which are treated in the man- 

 ner of mezzotinto engravings, the paper is coated, before commencing 

 the drawing or design, with the composition formula No. 1, mixed 

 with water to the consistency best adapted to produce the desired 

 effect, and after the same is dry, and properly fixed by time or the 

 action of light, the drawing or design is made upon the surface thus 

 produced. 



The drawing or writing, executed as described, presents, when the 

 material is dry, a surface in relief which is capable of impressing or 

 engraving a metal surface ; and such impression or engraving is capa- 

 ble of giving an impression, according to the artistic method of execu- 

 tion, either in the manner of copper-plate printing, or in that of print- 

 ing from wood blocks, or for the purpose of transfer to lithographic 

 stones or zinc plates, for the purpose of printing from in the manner 

 of lithography or zincography, or for the transfer of designs to por- 

 celain, earthenware, or Japanware. To obtain an impression which 

 will print in the manner of copper-plate printing, that is to say, an 

 impression in intaglio, the patentee executes the lines or touches of 

 the drawing he desires to impress or engrave upon a suitable material, 

 such as paper, the parts when impressed or engraved in the metal 

 surface being capable of retaining the printing ink, and thus giving 

 an impression. To obtain an impression which will print in the man- 

 ner of a wood block, that is to say, in relievo, he paints or draws 

 upon those portions which it is desired should not be printed from, 

 and thus these parts being depressed in the operation of impressing 

 upon a metal plate or surface by suitable machinery, those parts 

 which it is desired to print from are in relief, in the manner of a 

 wood block. Drawings, writings, and designs are also prepared by 

 making the drawing-materials sufficiently glutinous by the addition of 

 a large proportion of gum arabic ; and after the drawing, writing, or 

 design has been damped, it is supplemented by the addition of a fur- 

 ther quantity of the powdered solid, leaving out the glutinous sub- 

 stances and the chromic salt. In this case, when the drawing is com- 

 pletely finished, it is floated with the back downward upon water in 

 a suitable vessel ; and when, upon examination, the glutinous material 

 has become sufficiently damp, it is taken from the water and placed 

 upon a flat board, and the material which already constitutes the 

 drawing is supplemented by dusting it with powdered glass, peroxyd 

 of tin, or emery. 



OENAMENTAL BOOKBINDING. 



An interesting process in ornamental bookbinding has been recently 

 patented by Mr. Charles Tuckett, of London. This is a method by 

 which various colored designs are produced on the sides and backs 

 of books, according to taste and pattern, by means of numerous acids, 

 alkalies, salts, mineral and neutral, and their compounds, acting in 

 such a manner as to cause a permanent change of color on the founda- 

 tion leather. That is to say, the volumes being first bound in leather 

 of a uniform color, as red, olive, blue, or green, any other color or 

 colors may be superadded at will by the new process, and with little 



