352 



PALEOZOIC SYSTEM OF ROCKS. 



Fortunately, our own country is supplied with almost inexhaustible 

 stores of this source of industrial prosperity. 



V Origin of Coal, and of its Varieties. 



That coal is of vegetable origin is now no longer doubtful. We 

 will only briefly enumerate the evidences on which is based the present 

 scientific unanimity on this subject : 



1. The remains of an extinct vegetation are found in abundance in 

 immediate connection with coal-seams ; stumps and roots in the under- 

 clay, and leaves and stems in the black slate in contact with the seam 

 and even imbedded in the seam itself. 2. These vegetable remains are 

 not only associated with the coal-seam, but have often themselves be- 

 come coal, though still retaining their original form and structure. 

 3. Not only these easily-recognizable imbedded vegetable fragments, 

 but the imbedding substance also, the whole coal-seam, even the most 

 structureless portions, and the hardest varieties, such as anthracite, 

 when carefully prepared in a suitable manner and examined with the 

 microscope, show vegetable structure. Even the ashes of coal, carefully 

 examined, show vegetable cells with characteristic markings. The fol- 

 lowing figures show the results of such examination. 4. A perfect gra- 



Fig. 456.— Section of Anthracite: a, natural size; 

 b and c, magnified (after Bailey). 



Fig. 45? 



-Vegetable Structure in Coal 

 (after Dawson). 



dation may be traced from wood or peat, on the one hand, through brown 

 coal, lignite, bituminous coal, to the most structureless anthracite and 

 graphite, on the other, showing that these are all different terms of the 

 same series. In chemical composition, too, the same unbroken series 

 may be traced. 5. Lastly, the best and most structureless peat, by 

 hydraulic pressure, may be made into a substance having many of the 

 qualities and uses of coal. 



We may, with perhaps less confidence, go further, and say that all 



