

Dr. Mac Culloch on the Lignites, 213 



here to draw the conclusions which will follow, without even an 

 inference, from the facts on this subject that appertain to the 

 history of Peat, and of which I have treated in another journal. 



Having thus given such localities as seemed sufficient for ex- 

 amples, and for indicating both the general positions of these de- 

 posites and the errors which have been committed respecting them, 

 I may add a sketch of what little is known with regard to the 

 general characters of each class or division. 



The lowest deposite, which is called that of the oolithe, and 

 which may include all that are found, from the magnesian lime- 

 stone upwards to the green sand, is more frequently perhaps akin 

 to coal than to the woody lignites, though the latter substances 

 occur also in various forms. In some places it exists in the strata, 

 in groups of different dimensions, or in scattered fragments, or else 

 in thin and partial beds. In others, it forms regular beds of coal, 

 of various, and sometimes of considerable thickness ; and where 

 these alternate with the shales, sand-stones, and lime-stones of the 

 series, the superficial aspect is so much like that of the regular 

 coal series, that it is not surprising if it should have been mistaken 

 for that deposite. This coal is, however, generally, or perhaps 

 always, accompanied by woody lignites, commonly in the state of 

 charcoal, dispersed through the accompanying rocks. In the 

 example in Sutherland, one of the beds is three feet or more in 

 thickness, while another does not exceed an inch. The animal 

 remains yet discovered are not numerous, but they are marine ; 

 and hence one of the essential distinctions between this and the 

 proper coal series. It is probable that the supposed existence of 

 marine shells in this last, has generally arisen from confounding 

 it with the lignite coals under review. Oysters and ammonites 

 have been found among them ; and, in Sutherland, the shells, 

 though often obscure, appear to be in addition to those, madre- 

 porites, the spines of echini, beleranites, terebratulae, and frag- 

 ments that may belong to myae and mytili, and to cardium or 

 some similar shell. It is obvious, however, that whatever ob- 

 scurity there may be as to individual specimens, the shells to be 



