lo2 



ON THE FIRE-DAMP OF COAL-MINES. 



It appears, therefore, that, when the gas was entirely con- 

 sumed, 12'6 measures of the really inflammable part gave 

 11*5 measures of carbonic acid, and required for saturation 

 about 132 measures of oxigen. The average results are the 

 followiug, excluding the first experiment in which the com- 

 bustion was far from being perfect. 



Measures of oxigen required for saturating 



100 measures of fire-damp 



Measures of carbonic acid produced '• 



The second column contains the average results of two ex- 

 periments, which Dr. Thomson made over mercury; but 

 on these he places less reliance than on the foregoing series. 

 The general issue of his experiments agrees with that of 

 mine ; and the difference is chiefly in the quantity of oxigen 

 consumed by the combustion of the fire-damp, which ap- 

 peared to me not to exceed twice its volume. 

 The fire-damp I know not whether the result of the foregoing experi- 

 is not produced ments will be considered as" affording any insight into the 

 posed pyrites nature °f tne process, by which the fire-damp is generated 

 nor from water in coal mines. The entire absence of sulphuretted hidro- 

 coaT^butpro- ^ en 8 as snows J that it is not the immediate product of the 

 bably from decomposition of water by beds of pyrites ; for in that case, 

 by the heat o/ tne evolved hidrogen would undoubtedly have dissolved a 

 pyrites. portion of sulphur. Neither can it arise from the decom- 



position of water by coal ; for, besides that coal has no ac- 

 tion on water at a moderate temperature, this origin is con- 

 tradicted by the smallness of the proportion of carbonic 

 acid which is present in the fire-damp. The most probable 

 supposition is, perhaps, that it is disengaged from coal by 

 a kind of natural distillation. The heat required for this 

 purpose may be communicated by contiguous beds of py- 

 rites ; and may be excited in them by the occasional influx 

 of water. In confirmation of this opinion it may be ob- 

 served, that the fire-damp is generated most abundantly af- 

 ter long and heavy rains. The freedom, also, of some coal 

 mines fiom this destructive gas, indicates the operation of a 

 partial cause. 



It 



