which are evolved in Coal-Mines. 151 



with sixteen parts of atmospheric air, even when two strong 

 sparks were transmitted from the Leyden jar. 



2. One part of inflammable gas from S. detonated, though 

 feebty, with sixteen parts of atmospheric air. 



3. When these experiments were repeated the following 

 day with the gases still contained in the bottles, both deto- 

 nated with sixteen times the quantity of atmospheric air. 



4. One part of each of the two inflammable gases taken 

 from a fresh bottle, detonated with sixteen parts of atmo- 

 spheric air. 



5. One part of inflammable gas from W. did not detonate 

 with seventeen parts of atmospheric air. 



6. One part of inflammable gas from S. still detonated, 

 though very feebly, with seventeen parts of atmospheric air. 



Perhaps the dissimilar result in the experiments of the two 

 days was caused by the unequal temperature of the water 

 used for keeping the gases ; for on the second day it was 

 79° F., and on the first only 70°. 



7. One part of each of the inflammable gases detonated 

 very powerfully with seven parts of atmospheric air. 



8. One part of each of the inflammable gases no longer de- 

 tonated with six parts of atmospheric air. 



Notwithstanding the dissimilar result of the experiments 

 1-6, it was nevertheless invariable that the inflammable gas 

 from S. was somewhat more easily ignited than that from W., 

 and this agrees very exactly with the results of the analysis. 



The inflammable gas from Gerhard's Stollen ceases to form 

 explosive mixtures, when one part is mixed with more than 

 ten parts, and with less than seven parts, of atmospheric air. 

 This also agrees with the chemical analysis, according to 

 which 15 per cent, of nitrogen is contained in this inflam- 

 mable gas. 



Principal results of the previous investigations. 

 1. The chief component part of inflammable pit-gases is 

 carburetted hydrogen gas, mixed with unequal quantities of 

 olefiant gas, carbonic acid gas, and nitrogen. The similarity 

 of these gases to marsh gas is much in favour of their being 

 also a product of the decomposition of organic substances, pro- 

 bably of the coal itself. 



