88 STEVENSON— FORMATION OF COAL BEDS. [April 21. 



apparently cementing them " consists of an amorphous and irregular 

 mass full of rounded holes, therehy giving it a spongy character." 

 It contains fragments of perhaps broken rods, the material in both 

 being the same. The source of the amorphous material is not 

 certain. 



Penhallow offers no positive hypothesis respecting the origin of 

 these coals, though he is inclined to think that it must be " sought 

 elsewhere than in modified vegetable structure." At the same time, 

 he feels that the evidence is not sufficient to justify the assertion that 

 they did not originate in vegetable structure. 



In 1892 and 1893 there appeared papers by Bertrand and Renault 

 describing Bogheads and related types. Afterwards those observers 

 published their results independently. The later studies of Renault 

 concern the matter in hand only indirectly and they will receive 

 consideration in another portion of this work. It is necessary, how- 

 ever, to make detailed reference to Bertrand's contributions, for, 

 though they consider similar topics, the conclusions have a notable 

 bearing on the formation of coal beds ; and in this connection, the 

 stratigraphical relations of the several types must be given. With- 

 out that one cannot appreciate the full bearing of the studies. The 

 joint study by Bertrand and Renault''*^ was of boghead obtained 

 from Permian beds at Autun, France. This deposit occupies an 

 area of 7 kilometers by 150 to 450 meters. The chief constituent 

 is a thallophyte, Pila bibractciisis, which makes up about three fourths 

 of the mass ; the remaining fourth being the " fundamental mate- 

 rial " with some clay. A'egetable debris is wanting, but pollen of 

 Cordaitcs and remains of fishes are present. 



These observers recognized the bodies of yellow, red and other 

 tints, which had been mentioned by earlier students, but their study 

 proved that " certain resin-like bodies represent the organic gelose 

 and even entire organisms. A great proportion of the yellow and 

 red bodies enclosed in coals are in this category and M. P. F. 

 Reinsch has the great merit of making this known." The inferior 

 gelatinous plants have been preserved in this way when buried in 



^"C. Eg. Bertrand ct B. Renault, " Pila bihractcnsis et le boghead d'Autun," 

 Bull. Soc. d'Hist. Nat. d'Autun, V., 1892, Separate, pp. 95, pi. 2. 



88 



