762 



T. E. SAVAGE 



had some of the original inorganic content renioved in solution. It 

 is also probable that some coals which locally contain more than 

 the original amount of inorganic content, as pyrites lenses, etc.? 

 have been situated in places favorable for deposition of minerals 

 rather than solution, and in this way have become enriched in their 

 mineral content. It is also probable that in many places a small 

 percentage of the inorganic constituents of the coal, above that 

 originally present in the plants, may have come from wind-blown 

 dust that settled over the coal basin during the long period of accu- 

 mulation of the vegetable matter. The amount of ash in a coal 

 bed varies very considerably at dififerent levels and in different 

 places even in the same mine. Among the possible causes of such 

 variation are differences in the proportions of the kinds of plants 

 that formed the coal, removal and deposition of mineral matter by 

 solutions, and wind-blown dust. Hence, in the absence of definite 

 evidence of sediment contributed by water, such as black shale 

 or mud partings, it is thought that, as far as the bearing on the 

 conditions of accumulation of the vegetable matter is concerned, 

 not much significance can be attached to the variation in the 

 amount of ash in a coal bed of a small percentage above or below 

 the original amount that may have come from the plants that 

 formed the coal. 



The analyses given on p. 761 show that the mineral charcoal 

 contains a smaller percentage of volatile matter and a larger per- 

 centage of fixed carbon than the average coal of the same bed. The 

 proximate analyses (Table II) of the bright and dull laminae of 

 the bituminous coal bed, cited by Pringle,' indicates that the dull 

 laminae are similar in composition to mineral charcoal, as regards 

 the smaller percentage of volatile matter, and the larger percentage 

 of fixed carbon compared with the bright or the average coal. 



TABLE II 



John Pringle, Trans. Edin. Geol. Soc, X, Ft. i (1912), ^^. 



