310 THE woui.r. 



CHAPTER XIV. 



The, second Epoch. 



" And later yet the sea o'erspread 

 The spot where now we walk ; 

 And this was once aa ocean's bed, 

 The ocean of the chalk." Anon. 



THE epoch now to be considered, is in many respects the most 

 interesting, as it is certainly the most abundant in its fossil re- 

 mains. In our present volume we can only glance at the char- 

 teristic features, leaving wholly untouched those minor details, 

 which often make the most interesting part of a history. We 

 can therefore only hope that the reader will make a beginning 

 here, but search elsewhere for more extended and minute infor- 

 mation. Immediately above thecoal measures, lies a coarse sandy 

 deposit, which appears to be the ruins of some more ancient rock, 

 consolidated by pressure and the infiltration of water impregnated 

 with iron. The shores of the previously existing lands, seem to 

 have gradually been depressed, forming vast beds of coal; upon 

 these, the beds of sand and marl were loosely and rapidly de- 

 posited, and are not exceedingly rich in their fossil remains. 

 There is however, one interesting and remarkable fact connected 

 with these deposits, and that is, distinct tracks of reptiles and 

 birds; to these we shall allude again presently. The lowest 

 member of the new red sandstone group is the magnesian lime- 

 stone, so called from having a considerable portion of carbonate 

 of magnesia mixed with its carbonate of lime; it is a stone ex- 

 ceedingly valuable for building purposes. This limestone con- 

 tains a few fossils, corals and shells, and occasionally a few frag- 

 ments or whole skeletons of fishes. The fishes are all remarka- 

 ble for a peculiar structure of tail characteristic also of the fishes 

 of the older strata, this structure is called by M. Agassiz the hcte- 



