45° Count Rumford's Inquiry concerning the 
Having found that gold, or silver, might be melted by the 
heat (invisible to the sight) which exists in the air, at the dis- 
tance of more than an inch above the point of the flame of a 
wax-candle, (see my Seventh Essay, Part II. page 350.) I 
was curious to know what effect this heat would produce on 
the oxides of those metals. 
Experiment No. 1. Having evaporated to dryness a solution 
of fine gold in aqua regia, I dissolved the residuum, in just as 
much distilled water as was necessary in order that the solution 
(which was of a beautiful yellow colour) might not be disposed 
to crystallize ; and, wetting the middle of a piece of white 
taffeta riband, i|- inch wide, and about eight inches long, in 
this solution, I held the riband, with both my hands, stretched 
horizontally over the clear bright flame of a wax candle ; the 
under side of the riband being kept at the distance of about 
i~ inch above the point of the flame. The result of this expe- 
riment was very striking. That part of the riband which 
was directly over the point of the flame, began almost imme- 
diately to emit steam in dense clouds ; and, in about 10 seconds, 
a circular spot, about -J of an inch in diameter, having become 
nearly dry, a spot of a very fine purple colour, approaching to 
crimson, suddenly made its appearance in the middle of it, 
and, spreading rapidly on all sides, became, in one or two se- 
conds more, nearly an inch in diameter. 
By moving the riband, so as to bring, in their turns, all the 
parts of it which had been wetted with the solution to be ex- 
posed to the action of the current of hot vapour that arose from 
the burning candle, all those parts which had been so wetted, 
were tinged with the same beautiful purple colour. 
This colour, which was uncommonly brilliant, passed quite 
