THE mixers' friend. 205 



the Outside of the Boj/ler, the Flame has no otlier Effect on 

 it, than to cause the TJ^ater in it to Boyl. 



Miner. But we have often Combustable Vapours in our 

 Mines, which taking Fire from the Candhfi used there, do 

 by a sudden Explotion Destroy both the Mine, and the 

 Miner ; and therefore I am afraid that the Fire used in your 

 Engine will })e very Dangerous, and apt to Kindle those 

 Combustables more than our Candles. 



Author. To Answer this Objection, I will desire leave to 

 give you my Notion of those Combustables, which, in short is 

 this : That when your Miners come into a close Place, where 

 there is no Circulation of Air to carry off the Efiuria, or 

 Attoms constantly Eising like fine Dust in a Powder-Mill. 

 they by knocking and working do Increase to be very 

 numerous, like to those loose Particles in a Powder-Mill. 

 But it is the work of some time, for those Fapours 

 to come to Perfection ; for I liave heard several Ex- 

 perienced Miners say, That it is common to avoid the 

 Danger of those Vapours, by Eetiring as soon as they 

 see the rlame of their Candles burn longer than ordinary ; 

 which may be discerned some times long before the 

 Air is thick enough of this Combustable Matter, to 

 take Fire at once, and like Gun-powder to Destroy all. 

 I did hear one say. That from an Lich and half, once 

 the Flame of his Candle did gradually increase to two foot 

 long, and yet he escaped. Which makes it very plain. 

 That Stagnation of Air is the sole Cause of this Inconvenience 

 in Mines, which may be totally prevented by a Pipe going 

 from the Ash-Pit of our Furnace, to any part of the Mine 

 liable to Stagnation. For the Air will press, with great 

 Violence, through the Pipe into the Fire, before the Com- 

 bustable Matter can be ready to do any Hurt, and Passing 

 through the Fire, make way for fresh Air to Descend in 

 the Room of it. So that our Fire, instead of blowing up of 

 your Works, is the best Meayis that can be used to prevent 

 so Fatal an Accident; and will likewise carry off all un- 

 wholesom Vapours, Damps, or Steams which may proceed from 

 Corruption of Air, by Stagnations, or Vapours arising from 

 any Poysonous Earth, or Mineral. 



