INFLAMMABLE GASES. 85 



takes place into the mine, without being found out 

 in time, and if it gets mixed with enough air to 

 burn it, a flame, that may be kindled by a candle 

 or lamp at any one point, flashes in an instant 

 through the whole of the mixed atmosphere. The 

 most fearful shocks and explosions, too often at- 

 tended with great sacrifices of human life, ensue 

 from accidents of tins kind, winch are generally 

 owing to the carelessness of some of the workmen 

 themselves. This is the so-called Fire-damp. 



The inflammable gases, which here and there 

 have been known to escape from shafts and 

 borings, and which in many places issue from clefts 

 and natural openings in the earth, have always 

 proved, whenever they have been analysed, to 

 consist chiefly of carburetted hydrogen mixed with 

 more or less carbonic acid. We are acquainted with 

 a pretty good number of natural jets or springs of 

 combustible gas. Among the best known are those 

 at Pietra-Mala, not far from the road between Flo- 

 rence and Bologna, and the Holy Fires at Baku, 

 near theCaspian Sea, winch are still objects of reve- 

 rence to some of the inhabitants of the district. 



At many spots around Baku the inflammable gas 

 has to work its way up through a mass of mud. 

 It there throws up little conical hillocks, with 

 funnel-shaped openings at their tops; these are 

 filled with liquid mud, through which the gas rises 

 in bubbles, sometimes casting up mud and stones. 



