4- The late Dr. Turner's Chemical Examiiiatioii of the 



water, but this only took place when the combustion was in- 

 complete. Sometimes the gaseous mixture, after detonation, 

 was more or less obscured by a deposit of carbonaceous 

 matter, and in such instances, as already remarked by Dr. 

 Henry, there is always a deficiency of carbonic acid gas, 

 which deficiency is less considerable the more completely the 

 mixture at the moment of detonation approximates to perfect 

 transparency. I have occasionally observed this cloud, even 

 when ample oxygen for complete combustion was present; 

 but with a decided excess of oxygen it generally does not oc- 

 cur at all, or at most in so slight a degree as not to be appre- 

 ciable. To show the course of the inquiry, I quote three 

 analyses, in the first of which an error, from deposited carbon, 

 is apparent. 



I. Analysis oj Jirc-damp from Jarroia Colliery, isohich issued 

 from a seam of coal eleven fathoms below the Bensham seam. 



Specific gravity as found by weighing the gas = 0'6209. 

 Tested by nitrous gas it was found in one experiment to con- 

 tain 2*25 per cent, of oxygen, and in a second 2*1 per cent., 

 indicating as a mean 2-2 per cent, of oxygen, equivalent to 

 1 1 per cent, of air. This gas, which was quite free from car- 

 bonic acid gas, may be considered as a mixture of 89 mea- 

 sures of real marsh gas with 1 1 measures of air. A gas so 

 constituted, and assuming 0*5595 as the specific gravity of 

 marsh gas, should have a specific gravity 0'6079 ; lor Q'oS'dS 

 + 0-89 + 0-11 = 0-6079. Of this gas 12'3 measures, con- 

 taining 0*3 of oxygen and 11 of real marsh gas, were fired 

 with 32"7 measures of a sample of oxygen gas, which con- 

 tained 3 1 of real oxygen gas : — 



Loss due to condensed water = 22*3 



Carbonic acid gas generated and absorbed by 



potassa = 9'4< 



Residual oxygen, determined by firing with hy- 

 drogen gas = 10*5 



Deducting 10*5 + 9"4, the oxygen above ac- 

 counted for, from SI'S, the whole oxygen gas 

 originally present, there remain, as Oxygen 

 gas which went to the production of water ... = J 1*4 



II. Analysis of a gas from the Bc7isham coal scam, Jarroro 

 Colliery, collected from a bloser, tohich caused the accident 

 in 1826. 



Specific gravity actually observed = 0'6381. 

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



