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heavier than common air. The heat of the air 
during the trial of this experiment was 45 0 . 
By another experiment of the fame kind, made 
when the thermometer was at 65°, fixed air feemed 
to be about 563 times lighter than water. 
Experiment IX. 
Fixed air has no power of keeping fire alive, as 
common air has; but, on the contrary, that property 
of common air is very much diminifhed by the mix- 
ture of a fmall quantity of fixed air ; as appears from 
hence. 
A fmall wax candle burnt 80" in a receiver, which 
held 1 90 ounce meafures, when filled with common 
air only. 
The fame candle burnt 51" in the fame receiver, 
when filled with a mixture of one part of fixed air to 19 
of common air, i. e. when the fixed air was of the 
whole mixture. 
When the fixed air was of the whole mixture, 
the candle burnt 23'' . 
When the fixed air was T *_ of the whole, it burnt 
iT'. 
When the fixed air was JL or -L of the whole 
9-r 
mixture, the candle went out immediately. 
Hence it fhould feem, that, when the air con- 
tains near^. its bulk of fixed air, it is unfit for fmall 
candles to burn in. Perhaps indeed, if I had ufed a 
larger candle and a larger receiver, it might have burnt 
in a mixture containing a larger proportion of fixed air 
than this ; as I believe that large flaming bodies will 
burn in a fouler air than fmall ones. But this is 
lufficient to fhew, that the power, which common air 
