UPON SOME OF THE PHENOMENA OF COMBUSTION, 
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1. The rate of burning of candles and other similar combustibles, whose flames depend 
upon the volatilization and ignition of combustible matter in contact with atmospheric 
air, is not perceptibly affected by the pressure of the supporting medium. 
2. The rate of burning of self-supporting combustibles, like time-fuses, depends 
upon the rapidity of fusion of the combustible composition, which rapidity of fusion is 
diminished by the more rapid removal of the heated gases from the surface of the com- 
position. Hence the rate of burning of combustibles of this class depends upon the 
pressure of the medium in which they are consumed. In the case of time-fuses, the 
increments in the time of burning are proportional to the decrements in the pressure of 
the surrounding medium. 
3. The luminosity of ordinary flames depends upon the pressure of the supporting- 
medium ; and, between certain limits, the diminution in illuminating power is directly 
proportional to the diminution in atmospheric pressure. 
4. The variation in the illuminating power of flame by alterations in the pressure of 
the supporting medium depends chiefly, if not entirely, upon the ready access of atmo- 
spheric oxygen to, or its comparative exclusion from, the interior of the flame. 
5. Down to a certain minumum limit, the more rarefied the atmosphere in which 
flame bums, the more perfect is its combustion. 
