ON THE ORIGIN OF COAL. 189 



water, and it must have remained in a state of re- 

 pose for a long period, so as to allow of the growth 

 of sufficient vegetable matter to form the two feet 

 of Coal. After the production of this Coal seam, 

 the surface slowly and gradually subsided, and 

 the vegetable matter being partially decomposed, 

 a portion of its carbon mingled with the fine clay 

 composing the Black Shale, brought by a current 

 caused by such slow and gradual subsidence. 



The subsidence then increased, and caused a 

 quick current, which brought the sand now con- 

 stituting the " Rabbit-hole Rock." Again the 

 subsidence diminished during the formation of the 

 Black Shale with ironstone nodules, and then 

 gradually increased during the formation of the 

 Black Bind, Rock Binds, and White Rock. The 

 dark gray Soapstone indicates a period of ap- 

 proaching rest. The Floor-Dirt was then formed, 

 on which grew the vegetable matter composing 

 the six-inch seam of Coal. A slight and partial 

 subsidence then appears to have taken place, and 

 formed the four feet of Fire clay whereon grew a 

 fresh crop of Sigillarise that formed the one foot 

 three inches of Coal. The subsidence then 

 appears to have been very gradual, so as to 

 allow of the decomposition of vegetable and 



