166 Intelligence and Miscellaneous Articles. 



the phosphorescence, disengages an equal quantity of carbonic acid. 

 The phosphorescence of this plant is therefore probably connected 

 with the production of a larger quantity of carbonic acid, and may 

 be considered as a phaenomenon of combustion. 



8. Nevertheless no elevation of temperature has been observed in 

 the phosphorescent parts. — Comptes Rendus, Dec. 31, 1855, p. 1248. 



ON A PROCESS OF ENGRAVING IN RELIEF ON ZINC, 

 BY J. DEVINCENZI. REPORT BY M. BECQUEREL. 



Zincography, or the art of drawing upon zinc so as to print from 

 it, has already been practised for some years. In England and Ger- 

 many zinc has long been substituted for stone in lithography, but 

 in France this substitution has not been adopted. M. Devincenzi, 

 wishing to obtain plates in relief on zinc for the purpose of typo- 

 graphy, has arrived, after many trials, at the process which will be 

 hereafter described. But in the first place we may observe, that 

 M. L. P. Dumont has since tried a very different process. M. Du- 

 mont's process consists in drawing on a plate of zinc with an inso- 

 luble chalk of his invention, or with lithographic chalk or ink, 

 liquefying the fatty matter of the drawing by heating it slightly, 

 spreading over the plate a powder composed of resin, burgundy 

 pitch, and bitumen, removing the portion of the powder which does 

 not adhere by means of the bellows, and heating afresh to fix that 

 which covers the drawing. The plate when prepared in this manner 

 is immersed in a bath of sulphate of zinc, and connected with the 

 negative pole of a battery, whilst the liquid is in relation with the 

 positive pole. In this manner a relief is obtained, which serves for 

 the formation of a gutta-percha mould, and from this a plate in 

 relief is produced by electrotype. 



M. Devincenzi's process is different from the preceding. The sur- 

 face of an ordinary zinc plate is grained by means of sifted sand, and 

 the drawing is made upon this with lithographic chalk or ink. It is 

 then passed into a weak decoction of galls, and afterwards into gum- 

 water, in order to hinder the portions of the zinc which are not 

 covered with the drawing from taking the varnish, which will be 

 mentioned hereafter. The plate is washed with water, and the 

 chalk or ink is then removed with oil of turpentine, as in the pre- 

 paration of lithographic stone. When these operations are completed, 

 the plate is moistened, and a varnish composed of asphaltum, drying 

 oil and turpentine, thinned with oil of lavender, is applied to it with 

 a roller. The varnish only adheres to the portions which were 

 covered with chalk or ink. It is left to dry for twelve or fifteen 

 hours, when a brush soaked in a very weak solution of sulphuric acid 

 is passed over the plate to clean the surface which is not covered 

 with varnish, and the plate is then immersed in a solution of sulphate 

 of copper of 15°, at the same time that a plate of copper of the same 

 dimensions is placed parallel to it at a distance of 5 millims., and 

 connected with it by a copper rod. The portion of the zinc not 

 covered by the varnish is chemically acted upon by the solution of 

 sulphate of copper, and electro-chemically by the action of the voltaic 

 couple, whilst the solution has no action upon the varnish. The 

 zinc plate is taken out every minute to remove the copper deposited. 



