On Fire Damps in Coal Mines. 303 



he rcnowad every two years, and East Iiidiamen require a re- 

 neu-al every voyage. In jwiiit of ceconomy, therefore, as v;ell 

 as safety, iron cables are far preferable to those of hemp. T. 



XL VI II. On Flie Damp in Coal Mines. 



To Mr. Tdlach. 



!^iR, — A. VALU.'^r.i.F jnijier at t!ic (.•omniencement of the thirty- 

 fifth volume of t!ie Philosopliical Magazine, on the subject of 

 Duirps in Mines, has made nic ;nid others very anxious to hear 

 further from the verv intolligeut and practical author of that pa- 

 per, particularly since the dreadful accidents which have suc- 

 cessively happened at Felling Colliery near Newcastle. I am 

 induced to troui/le \o\\ on this subject at present, in conseqiu;nc« 

 of having just read in a periodical work, the recent opinion of a 

 gentleman at Newcastle, ascribing the copious generation of 

 hydrogenous gas in Felling Colliery, to the decomposition of tha 

 \vatcr, brought in contact with a large surface of bad and py- 

 ritic small coals, that are dug from under the marketable seam 

 of that colliery ^in the process of holing or undermining the 

 coals, as I undertand), and are left in the old workings. 



To which very probalde source of the evil, as it appears to 

 me, the editor oftiiework alluded to, has opposed the following 

 remarks : vix. " I do not see how the presence of pyrites in 

 coal should occasion or increase the evolution of carburetted hy- 

 drogen, which there is every reason to consider as the only fire 

 damp that ever makes its appearance in coal mines:" and then 

 he goes on to state, that fire-damp is pecidiar to deep coid-pits, 

 and is unknown in shallow ones ! : and that fron; the comparative 

 levity of inflammable air, explosions would be unknown, "if the 

 mines were ventilated according to the well known principles of 

 hydraulics ;" that is, if this gas was let or drawn off a^ the higliest 

 pomf : without his seeming to be avv-are, that the accidental and 

 progressive falling of the roofs of most coal-pits, occasions nu- 

 merous higher places or dome-like cavities, above the old hollows, 

 and even over the gates and passages in too many instances. 

 wherein it is impofcsible to prevent the lighter gases, where they 

 abourd, from accumulating. It is often to the falling of a 

 large flake from the roof of a work, and driving the hydrogenous 

 gas down before it to the candles of the workmen, tiiat explosions 

 are to be attributed. Hoping, through your Magazine, to hear 

 the opinions of i^ome well informed practical miners on thet«f 

 subjects, 1 remain, your*. 6lC. 



Oct 13:4. An Engjnekr. 



XLIX. On 



