45-3 Count Rumford's Inquiry concerning the 
as the riband had been wetted with the solution, but no 
farther. 
I afterwards varied this experiment in several ways, some- 
times using paper, sometimes fine linen, and sometimes fine 
cotton cloths, instead of the silk riband ; but nearly the 
same tinge was produced, whatever the substance was that 
was made to imbibe the aqueous solution of the metallic 
oxide. 
Similar experiments, and with similar results, were likewise 
made with pieces of riband, fine linen, cotton, paper, &c. 
wetted in an aqueous solution of nitrate of silver ; with this 
difference, however, that the tinge produced by this metallic 
oxide, instead of being of a deep purple, inclining to crimson, 
was of a very dark orange colour, or rather of a yellowish 
brown. 
In order to discover whether the purple tinge, in the expe- 
riments with the oxide of gold, was occasioned by the heat 
communicated by the ascending current of hot vapour, or 
by the light of the candle, I made the following experiment, 
the result of which, I conceive to have been decisive. 
Experiment No. 4. A piece of riband was wetted with the 
aqueous solution of the oxide of gold, and held vertically by 
the side of the clear flame of a burning wax candle, at the 
distance of less than half an inch from the flame. 
The riband was dried, but its colour was not in the smallest 
degree changed. 
When it was held a few seconds within about of an inch 
of the flame, a tinge of a most beautiful crimson colour, in the 
form of a narrow vertical stripe, was produced. 
