Chemical Properties attributed to Light. 83 



as filled the tube to the height of two inches; and, 

 having poured on them as much of the aqueous solu- 

 tion of nitro-muriate of gold as nearly covered them, 

 exposed the tube, with its contents, to the action of 

 the direct rays of a very bright sun. 



In less than half an hour, small specks of revived 

 gold, in all its metallic splendour, began to make their 

 appearance here and there on the surface of the char- 

 coal ; and in six hours the solution, which at first was 

 of a bright yellow colour, became perfectly colourless, 



AND AS CLEAR AND TRANSPARENT AS THE PUREST WATER. 



The surface of the charcoal was in several places 

 nearly covered with small particles of revived gold ; 

 and the inside of the glass tube, in that part where it 

 was in contact with the upper surface of the contained 

 liquid, was most beautifully gilded. 



This gilding of the tube was very splendid, when 

 viewed by reflected light ; but, when the tube was 

 placed between the light and the eye, it appeared like 

 a thin cloud, of a greenish blue colour, without the 

 smallest appearance of any metallic splendour. 



From the colour and apparent density of this cloud, 

 I was induced to conclude that the gilding on the 

 glass was less than one millionth part of an inch in 

 thickness. 



This interesting experiment was repeated six times, 

 and always with nearly the same result. The gold was 

 completely revived in each of them, and the solution 

 left perfectly colourless: in most of the experiments, 

 however, the sides of the glass were not gilded, all the 

 revived gold remaining attached to the surface of the 

 charcoal. 



In two of these experiments, I made use of pieces 



