Dr. Mac Culloch on the Lignites. 209 



in strictness, to rank in this place ; but being unimportant as a 

 deposite, it may be neglected among the following more con- 

 spicuous examples of the substance. 



The lowest in order is that which belongs to the lias and oolithe 

 series, which, for the present purpose, may rank as one. Though 

 some geologists have been unwilling to admit of more than one 

 such deposite beneath the chalk, there can be no question that there 

 is a second, which may be referred to the green sand. The third 

 is situated above the chalk, in the plastic clay, and the last is 

 that which occurs in the ancient alluvia. I might indeed refine 

 on this division, by separately enumerating those which have 

 been described in the red marl, in the muschelcalk, and in other 

 positions, through the whole series above the magnesian lime- 

 stone ; as we might also find other deposites in the strata above 

 the plastic clay. But such refinement appears unnecessary, except 

 for local purposes, and it will be sufficient to have thus indicated 

 such less important and marked examples. To these, however, 

 must be added those lignites, which, if they do not form extended 

 deposites, are important from their characters and positions, while 

 they do not easily fall into any of the preceding divisions. These 

 occur among the trap rocks. They have been called basaltic coal ; 

 but as this term has also been applied to the ordinary coal series, 

 where interrupted by trap, the name of basaltic lignite will be 

 preferable. Volcanic lignites, such as that of Iceland, need not 

 be distinguished from this kind. 



From the confusion which has been made between the coal beds 

 here classed with lignite, and those of the proper coal series, it is 

 not possible, or not safe, to quote examples in illustration of some 

 of them ; nor is it even in my power to produce adequate descrip- 

 tions. A more perfect set of observations is yet wanting, and 

 until then, this sketch must be doubtful, or imperfect. The stu- 

 dent who may choose to adopt this arrangement, and follow the 

 track of accurate observation, will hereafter be enabled to separate 

 these from the genuine coal, and complete what I must leave im- 

 perfect. It must be always remembered, that as these deposites 

 can be distinguished by the strata in which they are found, so, 



