Dr. Mac Culloch on the Lignites. 227 



comparison that this investigation is principally concerned, the 

 object being to discover the differences between woody lignite and 

 coal, it is necessary to state more particularly the circumstances 

 in which they differ. 



In the distillation of bistre, or of the vegetable compound of 

 carbon and hydrogen, a considerable proportion of acid is always 

 obtained, indicating the presence of oxygen ; but in the distillation 

 of bitumen, it is either not obtained, or is in a quantity so small 

 as to bear no comparison with the produce in the former case. 

 Thus the bitumens seem principally compounded of carbon and 

 hydrogen, while the bistre, and the tar of vegetables, and peat, 

 contain a notable proportion of oxygen. As the different varieties 

 of lignite, therefore, approximate on the one hand to coal, and, on 

 the other, to peat, or unchanged vegetable matter, so they will be 

 found to yield, on distillation, mixed products, varying in quality 

 according to the position of the specimen between those two 

 extremes. The ultimate analysis of such products proves that 

 which may easily be inferred from the preceding remarks, namely, 

 that the greatest proportion of oxygen is found in those lignites 

 which are the least removed from submerged wood or peat, and 

 the least in those that approach nearest in their aspect to coal. 

 Thus the pale lignite of Bovey yields a larger proportion of 

 oxygen ; while the analysis of jet differs but in a slight degree 

 from that of bituminous coal. 



These differences, indeed, can be rendered perfectly visible by 

 much ruder experiments ; as, without the necessity of a complete 

 decomposition of all the products, the first results of distillation 

 are sufficiently indicative of the relative place of any specimen 

 towards peat or coal, or of the extent to which the process of bitu* 

 minization has taken place in the lignite under trial. There is, 

 in the first place, an easy, though a rude test, to be derived from the 

 odour of the volatile matters : that of wood, or of peat, in burning, 

 is well known, as is that of coal ; and the peculiar smell of either 

 of these substances is most highly sensible in the volatile fluids 

 which may be condensed from their distillation. In the lignites, 

 it will be found that the odour, on burning, differs in the several 



