284 EBLATION OF FORESTS TO THE 



with few exceptiona, already covered with a forest growth when it 

 first became the home of man. This we infer from the extensive 

 vegetable remains — trunks, branches, roots, fruits, seeds, and leaves 

 of trees — so often found in conjunction with works of primitive art, 

 in the boggy soil of districts where no forests appear to have existed 

 within the eras through which written annals reach ; from ancient 

 historical records, which prove that large provinces, where the earth 

 has long been wholly bare of trees, were clothed with vast and almost 

 unbroken woods when first made known to Greek and Roman civiliza- 

 tion ; and from the state of much of North and of South America, as 

 well as of many islands, when they were discovered and colonized by 

 the European race. 



" Whenever a tract of country, once inhabited and cultivated by 

 man, is abandoned by him and by domestic animals, and surrendered 

 to the undisturbed influences of spontaneous nature, its soil sooner or 

 later clothes itself with herbaceous and arborescent plants, and, at 

 no long interval, with a dense forest growth. Indeed^ upon surfaces 

 of a certain stability and not absolutely precipitous inclination, the 

 special conditions required for the spontaneous propagation of trees 

 may all be negatively expressed and reduced to these three : ex- 

 emption from defect or excess of moisture, from perpetual frost, and 

 from the depredations of man and browsing quadrupeds. Where 

 these requisites are secured, the hardest rook is as certain to be over- 

 grown with wood as the most fertile plain, though, for obvious reasons, 

 the process is slower in the former than in the latter case. Lichens 

 and mosses first prepare the way for a more highly organized vegeta- 

 tion. They retain the moisture of rains and dews, and bring it to 

 act, in combination with the gases evolved by their organic processes, 

 in decomposing the surface of the rocks they cover ; they arrest and 

 confine the dust which the wind scatters over them, and their final 

 decay adds new material to the soil already half formed beneath and 

 upon them. A very thin stratum of mould is suflficient for the ger- 

 mination of seeds of the hardy evergreens and birches, the roots of 

 which are often found in immediate contact with the rook, supplying 

 their trees with nourishment from a soil deepened and enriched by 

 the decomposition of their own foliage, or sending out long rootlets 

 into the surrounding earth in search of juices to feed them. 



" The eruptive matter of volcanoes, forbidding as is its aspect, does 

 not refuse nutriment to the woods. The refractory lava of Etna, it is 

 true, remains long barren, and that of the great eruption of 1669 is 

 still almost wholly devoid of vegetation. But the cactus is making 



