AGE OP COAL. 



221 



Fisr. 122. 



that age was to a large extent, in point of size, a forest 

 vegetation, and yet but few of the plants which at the 

 present time are of the same family with the largest that 

 existed then are a little taller than a man. The remains 

 found are of various kinds trunks, 

 branches, pieces of bark, cones, 

 leaves, etc. The impressions of 

 leaves upon the laminae of rock are 

 sometimes very beautiful, as seen in 

 Fig. 122. Here we have a carbon- 

 aceous representation of the stem 

 and leaves that is, the carbon of 

 the plant in the decomposition of 

 the vegetable substance is left upon 

 the stone. " The shaly beds," says 

 Dana, "often contain the ancient 

 ferns spread out between the lay- 

 ers with all the perfection they 

 would have in a herbarium, and so abundantly that, 

 however thin the shale be split, it opens to view new im- 

 pressions of plants." The experiments of Professor Gop- 

 pert, of Breslau, go far to explain the various conditions 

 in which we find the remains of plants in the rocks of 

 the coal-measures. He placed fern-leaves in clay, and 

 when they had become dry exposed them to a red heat, 

 and thus obtained striking resemblances to the fossil 

 ferns in the rocks. According to the degree of heat, the 

 leaves were found to be either brown, shining, black, or 

 entirely lost, the impression alone remaining. In this 

 latter case the carbon of the leaves, being diffused in the 

 clay, stained it black, thus showing that the color of the 

 coal-shales is derived from the carbon of the plants in- 

 closed in them. I will now proceed to notice some of 

 the plants of this age. 



320. Calamites. This is a name given to a family of 

 plants that belong to the same tribe with the horse-tails, 

 cat-tails, and rushes of the present day. Two species 



