G.—No. 27,

INFORMATION RELATIVE TO PHOTO-ZINCOGRAPHY.

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Lithographic Transfer Ink. Lithographic Printing Ink ... ... ... ... 8 ounces. Middle Lithographic Varnish ... ... ... ... 4 ounces. Burgundy Pitch ... ... ... ... 3 ounces. Palm Oil ... ... ... ... ... Oj ounce. White Wax ... ... ... ... ... 0£ ounce. Asphaltum ... ... ... ... ... 1 ounce. The lithographic printing-ink is of a superior quality, known to the trade as " Best Chalk Litho Ink." The Ordnance Survey Department obtains it from Benjamin Whinstone, 100, Shoe Lane, City, London. Etching Solution. Pour ounces of Aleppo galls are bruised, and steeped in three quarts of cold water for twenty-four hours. The water and galls are then placed in a vessel over a fire, and allowed to boil up. The decoction is then strained. One quart of the decoction of galls is added to about three quarts of gumwater, which should be about the consistence of cream ; and to the mixture is added about three ounces of a solution of phosphoric acid, prepared as follows : —Sticks of phosphorus are placed in a pint bottle of water, the bottle being stopped by a cork in. which a small hole has been cut. The bottle is three-quarters filled with water ; and the ends of the sticks of phosphorus rise above the surface, and become oxydised by the air admitted into the bottle. The phosphoric acid, as fast as it is formed, is dissolved by the water. In a few days the solution is strong enough for use. Before adding the acid to the decoction of galls and gum-water, it should be tested on a piece of polished zinc, when it should merely effervesce. If it acts strongly on the plate it should be diluted. One of the plates sent to the Hon. the Colonial Secretary by the last mail, shows a covered van, with a man standing beside it. Sir H. James gave the plate, or print, to me as a sample of an attempt to reproduce half-tint drawings or engravings, which he said had created much interest; but he added, that the art had not been, in every sense, completed. Samples of paper, before and after being coated with the sensitizing solution, are sent herewith. E. Fox. London, Ist June, 1871. 1