Chemical Properties attributed to Light. 89 



ment, with a view to the farther investigation of that 

 matter : — 



Experiment No. 13. — Into a small pear-like phial, of 

 very fine transparent glass, I put equal quantities of 

 an aqueous solution, a crystallized oxide of gold, and 

 of sulphuric ether; and the phial, which was about 

 half filled, being closed with a good cork, well secured 

 in its place, was exposed to the action of the direct 

 rays of a bright sun. 



A pellicle of revived gold in all its metallic splen- 

 dour began almost immediately to be formed on the 

 surface of the aqueous liquid, and soon covered it 

 entirely ; and at the end of two hours the whole of the 

 oxide was completely reduced, as was evident from the 

 appearance of the ether, which became perfectly col- 

 ourless. 



On shaking the phial, the metallic pellicle which 

 covered the surface of the aqueous liquid was broken 

 into small pieces, which had exactly the appearance of 

 leaf gold, possessing the true colour and all the metal- 

 lic brilliancy of that metal. 



On suffering the phial to stand quiet, the aqueous 

 liquor and the ether separated, and most of the broken 

 pieces of the thin sheet of gold descended to the 

 bottom of the phial. The remainder of them floated on 

 the surface of the aqueous liquid, and the ether as well 

 as the aqueous liquid appeared to be perfectly trans- 

 parent and colourless. 



By the length of time which was required for the 

 ether and the aqueous liquid to separate, I thought I 

 could perceive that the ether had lost something of 

 its fluidity; but, as this was an event I expected, it 

 is the more likely, on that account, that I was deceived, 



