THE FORMATION OF COAL BEDS.^ 

 IV. 

 By JOHN J. STEVENSON. 

 (Read April iS, 191 3.) 



CONTENTS. PAGE. 



Explanation of terms 32 



Extent of coal deposits 35 



Are coal beds continuous ? 38 



The floor of a coal bed 41 



The coal S3 



Variations in structure 55 



Bifurcation of coal beds * 58 



Relations of benches in coal beds 62 



Relations of coal to black shale 64 



Occurrence of cannel 67 



Distribution of coal 68 



Macroscopical structure of coal 69 



Foreign bodies in coal 73 



Microscopic features of coal 89 



Variations in chemical composition 96 



Inorganic content of coal 100 



The roof 108 



Irregularities in the roof 114 



Flexed strata 117 



The hypotheses iii 



AUochthon y 1 20 



Autochthony 142 



Cannel and Boghead 142 



Conditions during Coal Measures Time were Favorable to Accumulation 



of Peat 154 



The Peat Deposits Resemble Coal Beds 158 



In Conclusion 162 



The Coal Beds. 



Coal beds are intercalated between rocks of different composition 



and apparently of different origin. The deposit may cover only a 



few square yards or thousands of square miles ; its changes in 



thickness may be abrupt or may be so gradual as to be unimportant 



in a considerable district ; the structure may be variable or it may be 



* Part I. appeared in these Proceedings, Vol. L., pp. 1-116; Part II., in 

 the same volume, pp. 519-643 ; Part III., in Vol. LI., pp. 423-553. 



31 



