508 Dr . FORDYCE, See. 
produced on the outer furface appears, if we take a fm all- 
rod of glafs, and put the end of it in the blue flame on 
the furface ; it will he heated white-hot and melt. Im- 
merfe the rod into the flame, fo that the point lhall be 
in the center, it will melt and bend, where it is in the 
blue flame on the furface; whereas, if the flame be 
large, the point which is in the center will hardly be 
heated red-hot. That the empyreumatic oil is decom- 
pofed is proved by burning a candle with a very fmali 
wick in diftilling veflels, no condenfation of empyreu- 
matic oil takes place. We may conclude, therefore* 
that light is produced by the decompofltion, as well as by 
the ignition, in inflammation. 
1 will not take up the time of this learned Society in. 
applying thefe principles to the explanation of various - 
appearances in burning bodies; or ground upon them, 
any practical rules for producing ftrong or faint, white, 
or coloured light, thefe being lufliciently obvious. I 
have chofen to illuftrate this fubjeeft by experiments that 
may be the moft eaftly tried; but, left the manner of 
powdering pbofpborus fliould not be known, I will give the 
procefs. Take pbofpborus of urine two drachms;, put it 
into a four-ounce phial; pour upon it three ounces of 
water; heat it gently, by immerflon in warm water, tilL 
the pbofpborus melts; ftiut the phial with a cork; take, 
it out of the water, and fhake it brifkly till it be cold ; the 
pbofpborus will be found in powder* 
XXXI. Ex- 
