1S2 ANNUAL OF SCIENTIFIC DISCOVERT. 



with the oxygen of the air. Above the blue part comes the luminous 

 part, produced by the passage of the carbon from the gaseous to the 

 solid state, giving out in the passage a considerable amount of heat. 

 The black cone surrounding the wick of the candle is formed of gas- 

 eous carburets of hydrogen, which only burn in the upper part of the 

 flame where they come in contact with oxygen. Hydrogen being not 

 very combustible but very subtle, diffusive, and penetrating, its com- 

 bustion takes place under conditions in which it would be impossible 

 for other gaseous bodies or vapors to burn. If a candle be gently 

 moved so that the ilame may be inclined and the air allowed to come 

 in contact with the vapor of the hydrocarbons which surround the 

 wick, we see the hydrogen take fire, and above the flame appears the 

 blue vapor of the carbon. The latter can only exist alone, and gives 

 its luminous reactions when it has near it the high temperature pro- 

 duced by the combustion of hydrogen. When cyanogen is burnt in 

 a current of oxygen, the high temperature produced by the interior 

 of the flame makes the vapor of carbon intensely hot, and hence very 

 luminous : consequently its spectrum is very luminous. 



PHOTOGRAPHING NATURAL COLORS. 



It has often been asserted; but never yet substantiated, that the pho- 

 tographic process was capable, under certain mysterious processes, of 

 reproducing the colors of the spectrum, and not merely the gradations of 

 black to which we are accustomed. A few years ago, an American, a 

 Mr. Hill, startled the scientific world at least that part of the world 

 which knew anything about photography- by insisting that he could 

 produce any color in the photographic image. Practically speaking, this 

 announcement came to nothing. Now we find in Milan, something at 

 least has been recently done for the furtherance of the idea. Suppose it 

 be required to color the photograph of a man, in a black coat, whose 

 hair and beard are fair, and whose figure is projected on a white back- 

 ground, slightly shaded otf; the process of the inventor is as follows: 

 Tne photograph, taken by daylight, lies in a basin of water; it is in 

 the dark, and subsequent operations are performed by candle light. 

 Two solutions are at hand, one, consisting of one gramme of chloride of 

 gold and ten of acetate of soda, dissolved in 1,000 grammes of water; 

 the other B, consisting of 20 grammes of hyposulphite of soda dissolved 

 in 100 grammes of water. There are besides two more basins of water, 

 and a quire of blotting paper. The photograph is taken out of the water 

 and put between the leaves of blotting paper: it is then laid flat on a 

 pane of glass, and the whole surface, except the face and hands, receives 

 with a water-color brush a coating of solution B. By this means the 



tf 



parts subjected to the action of the gold soon change their tints into 

 black. The photograph is then put into clean water again and left there 

 for a few minutes, during which the operator prepares a second pho- 

 tograph if required. The former one being taken out, is put in solution 

 B, where it stays for a few minutes and is then washed and rinsed as 

 u.su d. Now, as the time of immersion will influence the depth of color 

 by successive immersions, an orange-colored cravat will be obtained in 

 one minute, a coffee-colored great coat in five, violet-colored trousers in 

 ten, and a black coat in 30 minutes, while the hyposulphite of soda, or 

 solution B, gives color to the flesh and hair. Hence certain colors, 



