Mr Johnston on a solid form of Cyanogen. 75 



I conceive to be the cause why coals so exposed are so much 

 deteriorated in quality, and make so dull and cheerless a fire ; 

 and we know that no coals give so much flame and heat as 

 when drawn wet from the mine and put into the fire. 



This striking difference in coal-fields as to inflammable ga*? 

 abounding in one district, and not being found in another, is 

 a matter upon which no satisfactory theory has as yet been 

 formed. 



In some of the Newcastle coals, the inflammable gas is so very 

 easily disengaged, that there have been several instances where 

 coals recently drawn from the mines and instantly shipped, 

 have, by the fall and breaking of the coals descending into the 

 ship's hold, disengaged such a quantity of inflammable gas, as 

 to ignite from the flame of candle, by which the hatches were 

 violently blown up, and the sailors severely scorched. This 

 circumstance shows how very easily this gas is in some instances 

 emitted from coal, and it must be in great abundance when we 

 know that one pound weight of some coals, will yield five cubic 

 feet of this gas when exposed to fire in a retort. 



The analysis of the gas issuing at Bedlay is interesting, and 

 the more so from the dependence which can be placed on Dr 

 Thomson's accuracy. 



Art. XII. — On a solid form of Cyanogen or its ElementSy 

 and a new compound of Carbon and Azote. By James F. 

 W. Johnston, M. A. Communicated by the Auchor. 



I. When cyanide of mercury is employed in the preparation 

 of cyanogen, there remains in the tube after the gas ceases to 

 come over, a blackish residuum resembling charcoal. The 

 weight of this substance obtained from a given quantity of the 

 pure dry salt is at all times small, though it varies much in 

 apparent quantity. Sometimes it is exceedingly light and bul- 

 ky, at others it has a fused appearance, and where it has been 

 in contact with the tube, a shining metallic lustre. It varies 

 also in hardness and density, occurring in all states from that 

 of a " light charcoal," as described by Gay Lussac, to that of 

 a hard, dense, and sonorous body. In the mass it is of a black 



