282 THE HISTORY OF 



(perhaps plants of the Cactus tribe), with Calamites, 

 Stigmarias, and Conifers. Still we find no trace to show 

 that animals inhabited these islands, but in the sea Sharks 

 were already chasing the smaller fish, the shore was 

 fringed with numerous forms of Coral ; the Trilobites, 

 strange Crab-like animals, wonderful creatures allied to the 

 Nautilus, and the elegant, lily-like Encrinites and Penta- 

 crinites, gave rich variety to the aquatic Fauna. Over the 

 whole globe is that Flora the same, from the now frozen 

 caves of Iceland, to the glowing coast of Malabar. Long 

 must this vegetation have endured, often must the soil, 

 covered with a thick layer of humus from the remains of 

 dead plants, have sunk beneath the surface of the ocean, 

 been covered with a new layer of deposits and again been 

 upheaved, affording new soils to successive productions of 

 the same luxuriant vegetation ; since it is this vegetation 

 which has left behind the incalculably vast, half-destroyed 

 vegetable masses which, as Coal, now constitute almost one 

 of the most essential portions of the natural riches of a 

 country. We often find from twenty to thirty layers of 

 Coal, one above another, always separated by layers of 

 calcareous deposits enclosing marine animals. We often 

 find the upright stems of whole woods in such carboniferous 

 deposits, proving that the whole land sank down slowly and 

 without any considerable revolutions, beneath the surface 

 of the sea, as even now occurs on the south-west coast of 

 North America ; nay, we find such stems, with their roots 

 sunk below in the Coal, that is in the soil so rich in humus 

 which nourished them, while their upper portions are 

 enclosed in calcareous layers subsequently deposited upon 

 the soil. When it is considered, that almost a century is 

 required to form a layer of humus nine inches thick, by 

 the most luxuriant vegetation of the tropics, that this 

 layer, to convert it into Coal, must be compressed into a 



