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called because of its smell. Tills comes only in summer, 

 and is common in the Peak of Derbyshire. They who 

 have seen the third sort of damp describe it thus. In 

 the highest part of the roof of those passages in a mine 

 which branch out from the main grove, a round thing 

 hangs about as big as a foot-ball, covered with a thin 

 skin. If this be broken, the damp immediately spreads, 

 and suffocates all that are near. But sometimes they 

 contrive to break it at a distance ; after which they 

 purify the place with fire. The fourth is the fire-damp, 

 a vapour, which if touched by the flame of a candle, 

 takes fire, and goes off like gunpowder, And yet some 

 who have had all their clothes burns off by one of these, 

 and their flesh torn off .their bones, at the very time felt 

 no heat at all, but as it were a cool air. 



Sir James Lowther having collected softie of the air 

 in bladders, brought it up to London. Being let out 

 at the orifice through a tobacco-pipe, it would take fire 

 at the flame of a candle. And even this is imitable by 

 art. Most metals emit sulphureous vapours, while they 

 are dissolving in their several menstruums. Iron for in- 

 stance, while it dissolves in oil of vitriol, emits much 

 sulphureous vapour. If this be received jnto a bladder, 

 and afterwards let out in a small stream, it takes fire 

 just in the same manner as the natural vapour. 



This experiment explains one cause of earthquakes and 

 volcanos ; since it appears hence, that nothing more is 

 necessary to form them than iron mixing with vitriolic 

 acid and water. Now iron is generally found accom- 

 panied with sulphur ; and sulphur consists of an inflam- 

 mable oil, and an acid like oil of vitriol. 



This acid in the bowels of the earth being diluted 

 with a little water, becomes a menstruum to iron, with 

 a violent effervescence and an intense heat. The air 

 coining from this mixture is extremely rarified, and the 

 more it is compressed by the incumbent earth, so much 

 the more its impetus will be increased to an unlimited 

 degree. Nor does there need fire to set these vapours 

 to work. The air in the bladder, if it be much heated, 



