1869.] Fhysics. 467 



experiment can be repeated over and over again with tlie same 

 tube. The bromide, and probably also the cyanide of silver, behave 

 in the same manner ; the iodide of silver blackens only after having 

 been rendered sensitive to hght by pyrogallic acid. 



Dr. Thudicnm has recently published some investigations on 

 Luteine. By luteine Dr. Thudicum understands a yellow crystal- 

 line substance occurring in various parts of animals and plants, as, 

 for instance, the corpora lutea of ovaries, serum of blood, yolks of 

 eggs, in seeds, as maize (Indian corn), in annatto, in carrots, and 

 the stamina and petals of a great many flowers. Luteine is easily 

 soluble in alcohol, ether, and chloroform ; insoluble in water. These 

 solutions are yellow ; but that in chloroform, when concentrated, 

 has an orange-red colour. The spectrum of its solutions is distin- 

 guished by great brilliancy of the red, yellow, and green jDart, and 

 by three absorption bands, which are situated in the blue, indigo, 

 and violet part of the spectrum. The crystals of luteine are appa- 

 rently rhombic plates, of which two or more are always superposed 

 in a curious manner. The crystals are microscopic yellow when 

 thin, orange to red when thick, and have no resemblance to any 

 other known animal or vegetable substance. Luteine combines with 

 few substances, mercury-acetate being perhaps the only reagent by 

 which it is immediately and completely precipitated as a yellow 

 deposit ; mercury-nitrate produces a yeUow precipitate, which on 

 standing becomes white. Nitric acid, poured over the crystals, 

 produces a blue colour, which immediately passes into yellow. The 

 blue is not produced when nitric acid is added to either the alco- 

 holic, ethereal, or chloroformic solution of luteine, but appears with 

 the acetic-acid solution, and disajjpears again rapidly. Luteine has 

 great afiinity for fatty matters and for albumen. 



The Paris correspondent of the 'British Journal of PhotograjDhy ' 

 reports that the oxyhydi'ogen-zirconia light has been such a success 

 at the Tuileries, having been worked without interruption since the 

 21st of January, that the Emperor has ordered measures to be 

 taken to render that mode of illumination permanent in front of 

 his palace. In connection with this fact, we may mention that 

 M. Tessie de Mothay has had the Order of Chevalier of the Legion 

 of Honour bestowed upon him. The learned Abbe Moigno, while 

 referring to this subject in 'Xes Moiides,' says, " Our readers will 

 imdoubtedly hear with pleasm'e that the production of oxygen in a 

 cheap manner from manganate of potassa, and that of pure hydi'ogen, 

 by means of a hydrocarbon fuel on the large scale, have become a 

 decided success ; that moreover, the reduction of the earths baryta, 

 magnesia, and alumina to the metals barium, magnesium, and 

 aluminium, by means of hydrogen under high pressure and a very 

 high temperature, is successfully carried out ; while lastly M. Caron 



