from the Coal Mines, near Newcastle. 389 



The first of the foregoing 1 analyses supplies an instance where a loss of 

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

 successful analyses, the carbonic acid gas may be taken as exactly equal to 

 half the condensation due to the formation of water, and as containing half 

 the oxygen which was required for complete combustion. The quantity of 

 marsh gas present was equal to half the oxygen required for its complete com- 

 bustion, to half the condensation due to generated water, and to the volume 

 of carbonic acid gas which was produced. As this was a uniform result in all 

 the samples, it is manifest that the constitution of the inflammable princi- 

 ple of fire-damp is identical with that of marsh gas or light carburetted hydro- 

 gen. The proportion of carbon and hydrogen indicated by analysis, sufficiently 

 demonstrate the absence of such gases as hydrogen, carbonic oxide, and 

 olefiant gas. Their absence, however, was proved by other methods. A 

 portion of fire-damp was mixed in a tube with chlorine of known purity, and 

 the mixture kept for a quarter of an hour in a dark place, when the 

 chlorine was absorbed by milk of lime : the original quantity of fire- 

 damp was always recovered, except a slight loss due to the mere washing 

 to absorb the chlorine. The absence of olefiant and carbonic oxide 

 gases was also proved by means of spongy platinum. In 1824, soon 

 after the curious action of spongy platinum in causing the combination of 

 oxygen and hydrogen gases was made known by Doebereiner, both Dr. 

 Henry and myself pointed out the obstacles to that action, occasioned by 

 carbonic oxide, olefiant gas, and some other gases. — (Philosophical Tran- 

 sactions, and Edinhrd Philosophical Journal for 182 4. J— And Dr. Henry 

 at the same time shewed that marsh gas differs remarkably in this respect 

 from carbonic oxide and olefiant gases, as it offers scarcely any impedi- 

 ment to the action of platinum. Agreeably to those researches, it follows 

 that if fire-damp contained merely marsh gas, oxygen, and nitrogen, spongy 

 platinum introduced at common temperatures, or even heated to 300° F., 

 would not produce any sensible effect ; and that if a small quantity of an 

 explosive mixture,* made with 1 measure of oxygen, and 2 measures of 

 hydrogen gases, were added to the fire-damp, spongy platinum should cause 



* By the expression " explosive mixture," I hereafter mean a mixture made with 1 

 measure of oxygen, and 2 measures of hydrogen gases. 

 VOL. II. 4 A 



