79 

 APPENDIX FIRST. 



VOLCANIC ROCKS. 



APPENDIX SECOND. 



Clay, marie, and sand. Alluvia. 



Coal. Lignite and Peat, 



In introducing the last articles into this list, 

 it may perhaps appear necessary to apologize for 

 the presence of coal, which has no claims to the 

 character of a rock ; as well as for that of peat. 

 But the former is intimately connected with the 

 strata in 4 which it lies ; and as it must also be 

 treated of in any geological history of these sub* 

 stances, of which the arrangement and descrip- 

 tion alone is here attempted, it could not have 

 been omitted without inconvenience. The latter 

 illustrates, in so many important points, the his- 

 tory of that valuable mineral, that, as it must also 

 be described in any geological system which shall 

 hereafter attempt to complete this subject, its 

 adoption in the arrangement became equally a 

 matter of necessity. 



