Chemical Examination of the Fire- Damp. 205 



present, there remain, as Oxygen gas which went 



to the production of water . . . . =11-4 



II. Analysis of a gas from the Bensham, coal seam, Jarrow 

 Colliery, collected from a Mower, which caused the accident in 

 1826. 



Specific gravity actually observed =0-6381. 

 This gas was quite free from carbonic acid gas. In two trials 

 with nitrous gas, it was found to contain 3.7 per cent, of oxygen, 

 equivalent to 18*5 of air. A gaseous mixture of 18-5 air, and 81*5 

 real marsh gas, should have a specific gravity of 0-641, since 

 0-5595+0-815+0-185=0-641. 



Of this gas 13-5 measures, inferred from the foregoing premises 



to contain 0.5 of oxygen and 11 of real marsh gas, were fired with 



30 measures of oxygen, which contained 28-8 of real oxygen gas. 



Loss of volume due to production of water . . =22-8 



Carbonic acid gas generated =11-2 



Risidual oxygen . . . . . . =6-4 



Deducting 17-6 from 29-3 there remain, as Oxygen 



gas which went to the production of water . . =11-7 



III. Analysis of a gas from the Eppleton Jane Pit, Hutton 

 Seam, Hetton Colliery, collected at a depth of 175 fathoms below 

 the surface. 



Specific gravity actually observed =0-78. 

 This gas was quite free from carbonic acid. Two experiments 

 with nitrous gas agreed in indicating the presence of 4-6 per cent. 

 of oxygen, equivalent to 23 measures of air. Analysis indicated 

 the presence of 50 per cent, of real marsh gas, leaving 27 per cent. 

 as nitrogen, independently of that already considered as atmos- 

 pheric air. 



Of this gas 11 measures, containing 0-5 of oxygen, were fired 

 with 28 of oxygen gas, which contained 26-9 of real oxygen. 

 Loss of volume due to the formation of water . =10-5 

 Carboniclacid gas generated . . . . . = 5-5 

 Residual oxygen - • • • * ' =16-4 



Deducting 5-5-{- 16-4=21-9 from 27-4 there remain as 



Oxygen gas which went to the formation of water = 5-5 

 A gaseous mixture, consisting of 50 measures of real marsh gas, 

 23 of air, and 27 of nitrogen, should have a specific gravity of 

 0-7724, since 0-5595+0.5+0-23 + 0-9727+0-27=0-7724. 



The first of the foregoing analyses supplies an instance where 

 the loss of carbon was decisive. In the second and third, as in 



