THE VEGETABLE WORLD. 285 



generally appeared in a striking manner, and appear to 

 have determined the character of the landscape, while 

 the Coniferae and Cycadese, drew back gradually more and 

 more into particular localities, perhaps the former on to 

 the cooler heights, the latter to dry, sunny hills. Among 

 Pandanese and mighty Bull-rushes grazed gigantic Tapirs, 

 and the woods, already formed of deciduous Dicotyledons, 

 were filled with birds and the lesser animals. Whales, 

 walruses and seals traversed the seas. 



While the earth began to cool down gradually from 

 the poles hitherward, to its present temperature, the plants 

 and animals became always more and more localized ; 

 Faunas and Floras of definite zones were formed. Even 

 towards the end of this period, the mammoth required his 

 warm, woolly hair to protect him from the piercing cold 

 in the steppes of Siberia, and used more hardly by Nature 

 than his younger brother the elephant, was forced to live 

 upon the Conifers confined to the north and the higher 

 mountains. The forms of the present world continually 

 made themselves more evident in the Vegetable Creation. 

 Alders and Poplars clothed the new low-grounds ; Chest- 

 nuts and Figs the sunny hills ; and slender Birches con- 

 tested with the Pines the possession of the drier and cooler 

 soils. The giant stream of North America, the Missisippi, 

 annually rolls down to the sea in its flood, immeasurable 

 masses of dead, floating vegetable bodies, vast trunks of 

 trees from the woods in the regions of its sources. In the 

 sea, the currents are too slow to keep these heavy bodies 

 floating, and they sink at the mouth of the river, the inter- 

 spaces between them becoming filled up with mud and 

 drift. From New Orleans, marshy low grounds extend 

 downwards for many miles, which consist entirely of such 

 floated-down masses of plants, cemented together by sand 



