468 THE CARBONIFEROUS SYSTEM. 



I would here emphatically state that all my observations at the 

 Joggins confirm the conclusion, which I arrived at many years ago 

 from the study of the coals of Pictou and Sydney, that the layers of 

 clear shining coal (pitch or cherry coal) are composed of flattened 

 trunks of trees, and that of these usually the bark alone remains ; 

 further, that the lamination of the coal is due to the superposition of 

 layers of such flattened trunks alternating with the accumulations of 

 vegetable matter of successive years, and occasionally with fine vege- 

 table muck or mud spread over the surface by rains or by inundations. 

 In connexion with this, it is to be observed that the density and im- 

 permeability of cortical tissues not only enable them to endure after 

 wood has perished or been resolved into bits of charcoal, but render 

 them less liable than the wood to mineral infiltration. 



Rate of Growth of Carhonifert/us Plants. — Very vague statements 

 are often made as to the supposed rapid rate of growth of plants in 

 the Carboniferous period. Perhaps the most trustworthy facts in 

 relation to this subject are those which may be obtained from the 

 coniferous trees. In some of these (for instance, Dadoxylon materi- 

 arium, D. anmdatum, and D. antiquius) the rings of growth, which 

 were no doubt annual, are distinctly marked. On measuring these 

 in a number of specimens, and comparing them with modem species, 

 I find that they are about equal in dimensions to those of the Balsam 

 Fir or the Yellow Pine of America. Assuming, therefore, similarity 

 in habit of growth and extent of foliage to these species, we may infer 

 that, in regard to coniferous trees, the ordinary conditions of growth 

 were not dissimilar from those of Eastern America in its temperate 

 regions at present. When, however, we compare the ferns and 

 Lycopodiaceoi of the Coal formation with those now growing in 

 Eastern America, we see, in the much greater dimensions and 

 luxuriance of the former, evidence of a much more moist and 

 equable climate than that which now subsists ; so that we may 

 suppose the growth of such plants to have been more rapid than 

 it is at present. These plants would thus lead us to infer a warm 

 and insular climate, perhaps influenced by that supposed excess of 

 carbonic acid in the atmosphere which, as Tyndall and Hunt inform 

 us, would promote warmth and moisture by impeding terrestrial 

 radiation. AVith this would also agree the fact that the conifers 

 have woody tissues resembling those of the pine trees of the milder 

 climates of the southern hemisphere at present. 



If we fipply these considerations to Sigillaria, we may infer that 

 the conditions of moisture and uniformity of temperature favourable 

 to ferns and Lycopodiacece were also favourable to these curious 



