126 Chronicles of Science. [Jan., 



process it was frequently remarked that polished copper-plates iodized 

 in a similar manner to silver ones, were also sensitive to light. 



In a paper on the crystallogenic force, M. Kuhlmann has applied 

 photography to the reproduction of some phenomena of crystalliza- 

 tion. He coats glass with a solution of sulphate of magnesia thickened 

 with gum, after the plan adopted by barbers and others, who ornament 

 their windows in this way. The prettiest effects are obtained with a 

 solution of sulphate of zinc, and the appearance may be improved by 

 painting over the crystallization with an alcoholic solution of some 

 colouring matter, such as fuchsine. In order to perpetuate these 

 appearances, M. Kuhlmann has thought of copying them by photo- 

 graphy. With Mr. Bingham's assistance, he obtained some beautiful 

 pictures on collodion plates, and also copied the crystallizations directly 

 on paper. The galvano-plastic method of reproducing these crystal- 

 line forms, so as to be able to print them upon paper or fabrics, was 

 also tried. For this purpose the crystallization was obtained upon a 

 thin plate of copper, and it was copied by putting this plate on 

 another through a powerful rolling machine. The forms were beauti- 

 fully preserved, notwithstanding the great pressure, and the plates 

 could be used for printing, as soon as they came from the rollers. 

 The designs may also be copied by pressing gutta-percha on glass 

 plates covered with the crystals ; the gutta-percha moulds may then 

 be copied by the electrotype process. It was suggested that this style 

 of ornamentation might be substituted for ordinary chasing on articles 

 of gold and silver, and a specimen so ornamented was exhibited to the 

 Academy. The author pointed out that no two crystallizations are 

 obtained exactly alike. They can only be copied by photography, 

 for the fineness of the designs would defy the burin of the most clever 

 engraver ; he therefore suggests that the designs would be useful for 

 bank-notes. Copper-plates might be obtained in the way described, 

 and if the design were printed in pale blue ink, on a bright yellow 

 ground, the photographer and the engraver would both be defeated 

 in obtaining a counterfeit. 



A very excellent substitute for yellow glass, for the purpose of ex- 

 cluding the chemical rays of light, has been suggested by Mr. W. 

 Sydney Gibbons, of Melbourne. He dissolves gelatine and bichromate 

 of potash together, and with the hot solution coats slender fabrics. It 

 leaves no pinholes, gives a clear orange tint, is perfectly weather- 

 proof, and is so firm, that it admits of the use of a slight fabric, which 

 does not itself obstruct the light. Mixed with lampblack the mixture 

 makes a good and lasting pigment, which is admirably suited for a black 

 board, as it stands any amount of washing after it has been actinized. 

 The gelatine and bichromate of potash mixture, either with or without 

 pigments, is a good material for coating bottles of substances which 

 require darkness, as the copper solution for sugar testing, chlorine 

 water, nitrate of silver solution, &c, the bottle only requiring to be 

 dipped in a' moderately strong warm solution. 



A new binocular microscope is spoken of as having been invented 

 in America, which is said, in ' Silliman's Journal,' to be in " every 

 way superior to Mr. Wenham's ingenious arrangement." The inventor 



