Dr. Frankland on Combustion in Rarefied Air. 

 3rd Series. 



551 



Pr. of air in in. of mercury. 



Ilium, power of exp. flame. 



30-2 

 29-2 



28-2 

 27-2 



100* 



95-0 

 897 

 84-4 



It is thus evident that the combustion of an amount of gas ■which 

 would give a light equal to 100 candles when the barometer stands 

 at 31 inches, would give a light equal to only 84*4 candles if the 

 barometer fell to 28 inches. 



An inspection of all the above results shows that the rarefaction 

 of air, from atmospheric pressure downwards, produces a uniformly 

 diminishing illuminating power until the pressure is reduced to about 

 14 inches of mercury, below which the diminution of light proceeds 

 at a less rapid rate. The above determinations give approximately 

 5*1 per cent, as the mean reduction of light for each diminution of 

 1 inch of mercurial pressure down to 14 inches. The following 

 Table exhibits the actually observed light, compared with that 

 calculated from this constant. 



1st Series. 



Pressure. 



Illuminating power. 



Observed. 



Calculated. 



29-9 



100' 



100 s 



24-9 



75-0 



74-5 



19-9 



52-9 



49-0 



14-6 



20-2 



22-0 



9-6 



5-4 



- 3-5 



6-6 



•9 



-18-8 



2nd Series. 



30-2 



100 s 



100 s 



28-2 



91-4 



89-8 



26-2 



80-6 



79-6 



24-2 



73-0 



69-4 



22-2 



61-4 



59-2 



20-2 



47-8 



49-0 



18-2 



37-4 



38-8 



16-2 



29-4 



28-6 



14-2 



19-8 



18-4 



12-2 



12-5 



8-2 



10-2 



3-6 



- 2-0 



3rd Series. 



30-2 



100- 



100- 



29-2 



95-0 



94-9 



28-2 



897 



89-8 



27«2 



84-4 



84-7 



