Ly ell's Principles of Geology. 185 



Both D.C. and Schouw have followed a similar plan, that 

 is, the formation of divisions or Botanical Kingdoms of an 

 arbitrary rank and uncertain number. Yet these kingdoms, 

 293 in number, only form portions of Continents. 



If such and such a proportion of genera and species consti- 

 tutes a kingdom, a higher amount of grouping would insti- 

 tute a higher division. Several of these divisions, if not the 

 generality, are in my opinion mere provinces, and if viewed 

 in this light, the scale of proportional parts may be consider- 

 ed just enough. 



4th. — Formation of Coal and Distribution of Fossil Floras. 



" Coal is said by Hatchet to be formed chiefly from the 

 resinous principles of plants, — this would account for its 

 appearance when burnt, which is the same as that of burnt 

 bitumen. But resinous principles are, even when they 

 exist, of partial extent only in plants. In good coal the 

 whole of the vegetable substance seems to be transformed, 

 a supposition barely compatible with Hatchet's idea. 



To study this, extensive examination of coal in all degrees 

 of formation would be necessary, beginning with the wood 

 so curiously changed by the Brahmapootra, i. e. brown coal 

 occurring in its sand-banks, and which has a very peculiar 

 and disagreeable odour when burning. It would also be 

 necessary to examine how far the coal-plants exhibit vege- 

 table structure: are they mere impressions or are they the 

 plants themselves changed ? To what extent do these agree 

 with coal? What particular plants, and what parts of these 

 appear to have formed coal ? Its fibrous structure would 

 hint at formation from the woody system, and it is not incom- 

 patible with the deliquescence of a thick layer of drift. 



The plants of coal fields having been drifted, can only 

 give us an idea of the vegetation along the natural drains 

 of the then former country, which may by no means have 

 had one universal character. 



2 B 



