622 



EEPOET — 1891. 



Table shoicing the Output of Coal in the South Wales District in the years 

 1880 and 1890. 



Total Output for the United Kingdom. 



Dr. E. Hull refers to the increased production in the South- Welsh coal-field, 

 together with remarks on other fields and the future supply and working of coal, 

 in the ' Transactions of the Edinburgh Geological Society,' vol. vi., part 2, 1890, 

 where also Mr. EL. M. Cadell follows with valuable notes on the probable future of 

 the coal-trade. 



7. Varieties of Coal. — The coal of the British coal-fields exhibits every variety 

 of composition between anthracite, which is nearly pure carbon, and the so-called 

 bituminous coals, such as ordinary coal and cannel coal (liydrocarbons), rich in 

 hydrogen. Anthracitic beds are rarely seen except in districts where the strata 

 have been much disturbed, or peculiarly att'ected by other circumstances. Heat, 

 whether direct or induced by pressure, vertical or lateral, has probably been the 

 important agent in depriving coal of its hydrogen with some of its carbon, and 

 thus changing it into antbracite. Neither in this latter nor in the compact cannel 

 coal are the laminar structure and symmetrical jointing so distinct as in the 

 ordinary coals. The last lose their volatile hydrocarbons also by exposure to the 

 air, at outcrops and in open faults ; hence they are not nearly so good for burning 

 as those got at a greater depth. As it is well to have definite notions as to the 

 appearance and structure of the different kinds of coal, some notes on the several 

 sorts will now be ofiered.^ 



Anthracite is glossy or semi-lustrous, sometimes iridescent ; it ignites with 

 difficulty, and burns without smoke, and with little flame, on account of no volatile 

 hydrocarbons being formed during combustion. This purely carbonaceous material 

 differs f)om ordinary coal by its Ijrilliant, semi-metallic lustre, its greater density, 

 hardness, and brittleness, and by its massive and conclioidal fracture with sharp 

 edges. Some of it can be cut or turned on the lathe into fancy articles. 



Called anthracite (from civBpa^, coal) by Karsten and the older mineralogists, 

 it is also known as mineral carbon, blind-coal, stone-coal, culm, glance-coal, and 

 non-bituminous coal. It is mentioned by mineralogists and geologists as having 

 been found at many places in the Alps, Pyrenees, France, Germany, the United 

 States, and the British Isles, under various geological conditions ; but in regular 

 and extensive beds it occurs chiefly in Pennsylvania, and largely also in South 

 Wales. It is reported to have been found in China and elsewhere. 



' Much information as to the constitntion of coal and its varieties is given in 

 Eoland and Richardson's Chemical Technology. 



