IX. 



COAL : ITS NATURE, ORIGIN, POSITION, AND EXTENT ; 

 AND ITS RANGE UNDER THE SOUTH OF ENGLAND. 



By Professor T. RurERT Jones, F.R.S., F.G.S. 



A Lecture delivered at Watford, \%th November, 1892. 



PLATES I AND II. 



Contexts: — \. The Aspect of a Piece of Coal. 2. The Splitting of CoaL 

 3. The Constituents of Coal. 4. The Varieties of Coal. 5. The Origin of Coal 

 and the Area of its Formation. 6. The Materials of the Coal-measures. 7. The 

 Extent and Position of the Coal. 8. Coal uuder the South of England. 

 9. Conclusion. 



1 . Aspect of a Piece of Coal. — Tliere are t^yo or three common 

 things which may be noticed about a piece of coal which are 

 perhaps not very generally known. Have any of you ever tried 

 to take up a piece of coal without dirtying your hands ? It is ([uite 

 possible to do so. The next time you take the trouble to look 

 into the coalbox, take up a piece of coal that has no loose coal-dust 

 on it, and you will find that some parts are bright and clean, and 

 that other parts are black and dirty ; but it is dirt in the right place. 



2. The Splitting of Coal. — All parts of the coal are not the same 

 because it has been formed by the accumulation of vegetable 

 material under cUtferent conditions. When looking at a piece 

 of coal in the fire, we observe that it splits, or shows an inclination 

 to split, in two directions, either along and parallel with the lines 

 that are black and dirty, or at right angles to them. When it 

 splits along those black lines, the rent follows the bedding of the 

 coal, that is to say, the coal splits along those planes which were 

 once the surface, and on which other layers were successively 

 formed, so that they have always remained somewhat distinct. 

 "When it splits in the other direction, it is along lines of cracks 

 caused by contraction. 



3. The Constituents of Coal. — So much for the common aspect of 

 household coal ; but the subject leads us into several lines of 

 thought, only some of which can be taken up. Firstly, what is 

 coal in a chemical point of view ? Of what is it composed com- 

 pared with other things in the world ? For instance, we know 

 that a very large proportion of it is carbon, and we know that 

 it consists not merely of carbon, but also of gaseous matter, namely, 

 hydrogen ; hence we know that coal is hydro-carbon. But there is 

 a great variety of coals. Of what do the variations consist? 



In coal there is much extraneous matter which does not belong 

 to it as coal, but is due to the method of its formation, namely, 

 mud and sand. Sometimes the coal-merchant will send us what is 

 tenned " brassy " coal. There is no brass in it, but something that 

 looks like brass — a compound of iron and sulphur (iron-pyrites) ; 

 and this causes much bursting and sparkling of the coal in the fire, 

 and makes the smoke sulphurous. Again, you have possibly 

 observed white flakes on some faces of the coal ; this is sulphate of 



