from the Coal Mines, near Newcastle. 



393 



In these experiments the error is very uniformly such, that more oxygen 

 was indicated than was actually present. The causes of error appear to be 

 especially two-fold, — agitation, and a large excess of nitrous gas. By per- 

 mitting the action to ensue tranquilly, and avoiding much excess from ni- 

 trous gas, the indications in my trials were uniform, and very nearly true. 

 Applying the same method to fire-damp, I found that in two or more trials 

 with the same gas, the indications hardly ever differed so much as 1 per 

 cent, of oxygen ; and in general, as in several instances already given, the 

 coincidence in different experiments was exact. 



Having now mentioned all that appears necessary to elucidate the che- 

 mical nature of the different samples of fire-damp from the mines of New- 

 castle, I conclude this account of the examination by inserting a tabular 

 view of the composition of all the gases which have been analyzed. 



Mine in which the Gas was collected. 



Bensham Coal Seam, Wallsend Colliery, 



Yard Coal Seam, Burraton Colliery, 



High Main Seam, Killingworth Colliery, 



Low Main Seam, Killingworth Colliery, 



Marquess of Londonderry 's Pensher Colliery,from 

 the Hutton Seam waste, 125 fathoms deep, 



Mar. of Londonderry 'sPittingtonColliery, Adelaide 

 Pit, Hutton Seam, 45 fathoms below the surface, 



Eppleton Jane Pit, Hutton Seam, Hetton Col- 

 liery, 175 fathoms below the surface, 



Blossom Pit Main Coal Seam, Hetton Colliery, 

 100 fathoms below the surface, 



Bensham Coal Seam, Jarrow Colliery, 



Jarrow Colliery Seam, 11 fathoms below No. 9,... 



Bensham Seam, Willington Colliery, 145 fathoms 

 from the surface, 



Specific 

 observed. 



gravity 

 calculated 



Marsh 

 Gas. 



Air. 



Nitrogen. 



Carbonic 

 Acid. 



0-6024 

 0-600 

 0-6196 

 0-8226 



0-6991 

 0-5903 

 0-6236 

 0-8325 



91 

 93 

 85 

 37 



9 

 7 

 8 



46-5 











7 



16-5 





 

 

 



0-966 



0-9662 



7 



82 



11 







0-866 



0-8755 



28 



67-5 



4-5 







0-747 



0-7677 



50 



6 



44 







0-78 



06381 



0-6209 



0-7724 



0-641 



0-6079 



50 



81-5 



89 



23 



18-5 



11 



27- 













 

 



0-7278 

 I 



0-7175 

 ]• 



68 

 



28-7 

 100- 





 



3-3 



9. 



10. 

 U 



12. 



The gas, No. 12, proved to be unmixed air. I have no remarks to offer 

 respecting the nitrogen found in some samples of the fire damp, beyond 

 what will readily occur to other chemists, who, I apprehend, will consider 

 its presence as a simple consequence of oxydizing processes, especially of 

 metallic sulphurets, abstracting oxygen from atmospheric air. 



