Fire-damp from the Coal Mines near Neiocastle. ■$' 



drogen, or marsli gas of chemists, whicli issues in a state of 

 purity from coal, wholly free from atlmixture with hydrogen, 

 carbonic oxide, or olehant gases, and but rarely containing 

 a trace of carbonic acid gas*'. The sole difference in the ex- 

 plosive gas of different mines must hence be referred to the 

 degree of admixture with air. If diluted with nineteen or 

 twenty times its volume of air, the mixture does not detonate 

 or take fire at all ; on diminishing the proportion of air below 

 this term the mixture becomes inflammable, and on the ap- 

 proach of a lighted candle, a pale blue flame appears, which 

 passes slowly through the mixture when the air is in large 

 excess; rapidly when the ratio is favourably adjusted for com- 

 bustion. The most explosive mixture, as Davy correctly 

 states in his " Essay on Flamef," is formed of one measure of 

 pure fire-damp, and about seven measures of air. Such mix- 

 ture, unlike an explosive mixture made with air and hydrogen 

 or carbonic oxide gas, is not kindled by incandescent solid 

 matter, such as a mass of hot iron; but it burns rashly [rapidly ?] 

 in contact with flame, and detonates readily with the electric 

 spark. As the proportion of pure fire-damp rises above a 

 sixth, the mixture burns less and less readily, and the tint of 

 the flame changes at the same time from blue to yellow or 

 brown. The phaenomena receive a ready explanation from 

 the well-known principles established by Davy. 



The analysis of fire-damp was performed by detonation 

 with oxygen gas over mercuiy. In successful analysis with all 

 the gases, the diminution in volume subsequent on detona- 

 tion with the electric spark, and due to gaseous matter con- 

 densed as water, was precisely twice the volume of carbonic 

 acid gas which was generated, and equal to the oxygen gas 

 whicli disa})peared. The volume of carbonic acid gas some- 

 times fell short of half the diminution due to production of 



* Extract of a letter from Major Enimett, Royal Engineer, to Mr. 

 Ihitton, dated Hull, 19th February, 1836. 



" I send you the following extracts from a letter from Dr. Dalton of the 

 13th. As regards Wallsend Pit, they are important, and to nie conclusive. I 

 sent him three bottles Mr. Buddie had collected for me about three months 

 ago, also one of water from the old working at Gateshead Park Pit for- 

 warded to me by Mr. Wood. Respecting the Wallsend gas he says: *I 

 received your letter and bottles of gas jafely, and soon after opened the 

 bottles under water. The air in each bottle was very much alike. It was 

 constituted of some two or three per cent, of carbonic acid, about one 

 tenth common air rather short of oxygen, and the rest, about eiglU3-five 

 per cent., was pure carburetted hydrogen, or pond gas, without a trace of 

 either pure hyilrogen or olefiant gas.' Respecting the Gateshead water 

 he says, ' The bottle of water from the old waste I also examined • it 

 contained about one per cent, of soluble niatter, chiefly coinmon salt, with 

 some carbonic acid, sulphurous acid, sul|iluiietted hydrogen and lime.'" 



{\ See Phil. Mag. First Scries, vol. xlxvi. p. 448.] 

 B2 



