Prof. Graham on the Composition of Fire-Damp. 437 



agent is produced that forms on mixing hyponitric acid with 

 water; and it appears also that tin engenders with dilute nitric 

 acid a deoxidizing matter, i. e. a nitrate of protoxide of tin. 



LXXII. On the Composition of the Fire-Damp of the 'New- 

 castle Coal Mines. By Thomas Gylkh am, Esq., F.R.S.* 



SOME years ago I examined the gas of these mines, with 

 the same result as Dr. Henry, Davy and Dr. Turner had 

 previously obtained, namely, that it contains no other com- 

 bustible ingredient than light carburetted hydrogen. But the 

 analysis of the gas of the coal mines in Germany, subsequently 

 published, showing the presence of other gases, particularly 

 of defiant gas, has rendered a new examination of the gas of 

 the English mines desirable. The gases were, — 1, from a seam 

 named the Five-Quarter seam, in the Gateshead colliery, 

 where the gas is collected as it issues, and used for lighting 

 the mine ; 2, the gas of Hebburn colliery, which issues from 

 a bore let down into the Bensham seam — a seam of coal which 

 is highly charged with gas, and has been the cause of many 

 accidents ; and 3, gas from Killingworth colliery, in the neigh- 

 bourhood of Jarrow, where the last great explosion occurred. 

 This last gas issues from a fissure in a stratum of sandstone, 

 and has been kept uninterruptedly burning, as the means of 

 lighting the horse-road in the mine, for upwards often years, 

 without any sensible diminution in its quantity. The gases 

 were collected personally by my friend Mr. J. Hutchinson, 

 with every requisite precaution to ensure their purity, and 

 prevent admixture of atmospheric air. 



The usual eudiometrical process of firing the gases with 

 oxygen was sufficient to prove that they all consisted of light 

 carburetted hydrogen, with the exception of a few per cent. 

 The results were as follows : — 



Gateshead Gas. — Specific gravity 0*5802. 



Carburetted hydrogen .... 94*2 



Nitrogen 4-5 



Oxygen 1*3 



100-0 

 The density of such a mixture is, by calculation, 0'5813. 

 Killingworth Gas. — Specific gravity 0*6306. 



Carburetted hydrogen .... 82*5 



Nitrogen 16*5 



Oxygen 1*0 



100-0 

 * Communicated by the Chemical Society ; having been read November 

 3, 1845. 



