Mineral Substances of Organic Origin* No. III. Ozocerite. 395 



A glance at the second column of this table shows that se- 

 veral of these substances are obtained from the products of 

 the distillation of coal ; and though it has not been demon- 

 strated that any of them actually exist ready formed in the 

 mass of the coal itself, yet the very low temperature at which 

 some of them are given off lends to this opinion a considerable 

 degree of probability. Reichenbach states that bituminous coal, 

 by distillation with water, yields 1 •320,000th of an aethereal oil, 

 which is identical with native naphtha; and he concludes that 

 the naphtha and petroleum springs of Persia, India, Italy, and 

 South America, have their origin in the slow distillation of 

 large beds of coal, by the ordinary heat of the earth. The 

 fossil wax of Moldavia, and the hatchetine of England, are 

 probably derived from vegetable matter by a like agency. 



Naphtha is a comparatively dense fluid, requiring a tem- 

 perature of upwards of 173° Fahr. to boil it; and, therefore, 

 unless present in large quantity, it will rarely escape from the 

 coal so rapidly, as alone to render the atmosphere combust- 

 ible; but, suppose the very light liquid discovered in oil gas 

 to exist in the coal, it will at once escape as a highly inflam- 

 mable gas, and materially injure the atmosphere. Because 

 such substances have not hitherto been observed in the air of 

 mines, we ought not hastily to conclude that they do not exist, 

 ready formed, in the great laboratory of nature. The diffi- 

 culty of detecting them in a limited portion of gaseous mat- 

 ter will, probably, long present insuperable obstacles to the 

 analytical chemist, while the more we learn of the carbo- 

 hydrogens the more likely it appears that several of them 

 should be occasionally present in the air which circulates 

 through mines of bituminous coal. 



The common fire damp requires, for its perfect combustion, 

 ten times its bulk, the vapour of Faraday's light liquid thirty 

 times, and that of naphtha forty-five times its bulk of common 

 air. A very small portion of either of the latter, therefore, 

 would render an atmosphere dangerous. The sudden out- 

 burst of a small reservoir would pollute a working previously 

 considered safe, and give rise to an explosion where none was 

 considered possible. In a district of country like the north of 

 England, where rich bituminous coal is so abundant, where 

 mines are worked at the very verge of the inflammable state, 

 and where the most serious accidents from explosions occa- 

 sionally occur, it is of importance, I think, that the probable 

 presence of such substances, in the state of vapour, should be 

 taken into account. Where the coal is richer than usual, and 

 where troubles occur in which these compounds, as at Urpeth, 

 may exist in a liquid or solid state, the rapid escape of com- 



