334 



THE CARBONIFEROUS SYSTEM. 



the third are also inferior, while in this part of the mine the upper 

 three feet of fall coal have disappeared, or been reduced to an insig- 

 nificant thickness, by thinning out or being replaced by shaly matter. 

 The following table gives the composition of all the varieties of 

 coal in the whole thickness of the seam, as ascertained by an elaborate 

 series of assays made by the writer in 1854 : — 



Assays of Samples of Albion Coal, taken at distances of one foot in 



thickness, in the main seam. 



