Proceedings of the Polytechnic Association. 813 



began to appear, growing like stars on the screen. As tliey were 

 enlarged, a circle or oval appeared in the middle of each star. These 

 beautiful and symmetrical flowers become visible, becanse water 

 refracts light differentlj from ice. But, as water between thirty-two 

 degrees and thirty-nine degrees Fahrenheit is less dense, and conse- 

 quently occupies less space than the ice from which it is made, a 

 vacuum is formed in the middle of each star by virtue of the melting 

 ice, which is the cause of the circular or oval appearances. 



Geeanosine. 



This new dye is made by dissolving one kilogramme of any salt of 

 roseanaline in 1,000 liters of boiling v/ater ; when this solution has 

 cooled to 113 degrees Fahrenheit, it is mixed with another consisting 

 of four and a half kilogrammes of binoxyd of barium with thirty- 

 five liters of cold water and ten kilogrammes of sulphuric acid. The 

 mixture instantly becomes a lemon color, but in a short time is nearly 

 colorless. After being filtered, to separate the sulphate of baryta, 

 the solution is gradually heated to the boiling point, when it assumes 

 a red color, which reaches its greatest intensity after boiling for two 

 minutes, and is then ready for use. Tlie shade of color produced by 

 this dye is known &,s ponceau, and is equal in brilliancy to that made 

 by cochineal. The application of acid strengthens the color, and 

 ammonia discharges it. 



Naphthyl-Carmine. 



M. Yohl prepares this dye by first dissolving twelve parts of naph- 

 thaline in 109 parts of sulphuric acid, and adding, by degrees, eighty- 

 nine per cent of bichromate of potash. After the reaction has termina- 

 ted, boiling water is added, and carbonic acid is disengaged. Carbonate 

 of soda is employed to neutralize the solution, which, after being 

 boiled for a quarter of an hour, is filtered to separate the oxyd of 

 chromium. The solution has now a beautiful golden color, but on 

 adding hydrochloric or sulphuric acid an abundant precipitant is 

 obtained, which is naphthyl-carmine. This product is an acid, giving, 

 with alkalies, a yellow solution, which dyes silks and wool, with mor- 

 dants, either orange or violet. 



Coffee used in Photography. 



Mr. Ottavio Baratti, editor of Za Camera Oh.scura, Ivre Piverone, 

 Italy, has invented a coffee dry process, by which plates prepare(J 



