Reviews and Notices of BooJcs. 453 



rial decay, but which has undergone the bituminous putrefaction, 

 and has thereby been resolved into a nearly homogeneous mass, 

 •which still, however, retains traces of structure and of the forms 

 of the individual flattened plants composing it. As these last are 

 sometimes more distinct than the minute structures, and are ne- 

 cessary for their comprehension, I shall, under the following heads 

 notice botli as I have observed them in the coals in question. 



" 1. The laminae of pitch or cherry coal, when carefully traced 

 over the surfaces of accumulation, are found to present the outline 

 af flattened trunks. This is also true, to a certain extent, of the 

 finer varieties of slate coal ; but the coarse coal appears to con- 

 sist of extensive laminae of disintes^rated veg^etable matter mixed 

 with mud. 



" 2. When the coal (especially the more shaly varieties) is held 

 obliquely under a strong light, in the manner recommended by 

 Goeppert, the surfaces of the laminae present the forms of many 

 well-known coal-plants, as Sigillaria, Stigmaria, Poacites or Cor- 

 daites, Lepidodendron, Ulodendron, and rough bark, perhaps of 

 conifers. 



"3. When the coal is traced upward into the roof-shales, we 

 often find the laminae of compact coal represented by flattened 

 coaly trunks and leaves, now rendered distinct by being separated 

 by clay. 



*' 4. In these flattened trunks it is the outer cortical layer that 

 alone constitutes the coal. This is very manifest when the upper 

 and under bark are separated by a film of clay or of mineral char- 

 coal, occupying the place of the wood. In this condition the bark 

 of a large Sigillaria gives only one or two lines in thickness of 

 coal ; Stigmaria, Lepidodendron, and Ulodendron give still less. 

 In the shales these flattened trunks are often so crushed together 

 that it is difficult to separate them. In the coal they are, so to 

 speak, fused into a homogeneous mass. 



" 5. The phenomena of erect forests explain, to some extent, the 

 manner in which layers of compact coal and mineral charcoal 

 may result from the accumulation of trunks of trees in situ. In 

 the sections at the south Joggins, the usual state of preservation 

 of erect Sigillariae is that of casts in sandstone, enclosed by a thin 

 layer of bark converted into compact, caking, bituminous coal^ 

 while the remains of the woody matter may be found in the bot- 

 tom of the cast in the state of mineral charcoal. In other cases 

 the bark has fallen in, and all that remains to indicate the place 



