86 STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 



two white ones escaped the fire and were left as seed trees. Poplars have 

 since grown up and now have a height of fifty or sixty feet or more. Back 

 from the shore, where the seed has been blown, in the shade of the poplars, 

 there is now a pretty growth of young pine trees, four or five feet in height." 



In a letter, W. G. Miller states that the condition is familiar in many 

 portions of Ontario. 



Rock streams may still be seen at many places in the Allegheny 

 mountains and in their path the forest has been removed. But even 

 these coarse breccias become covered. Agnew^^^ says that, when he 

 returned by canal from Harrisburg to western Pennsylvania, he ob- 

 served long stretches of stone-covered mountain side, bare of all 

 vegetation from base to summit, the slope varying from 25 to 40 

 degrees. In later years, coming to Harrisburg to sit on the Supreme 

 bench, he could find none of the naked spaces. The rocky surface 

 had become covered with trees, the few remaining bare spaces being 

 merely dots in the forest. The writer may add his testimony to the 

 same efifect. Rock streams are not wanting now in the Allegheny 

 Mountains but they are not those, which were striking features in the 

 scenery forty years ago; they are of later origin. 



Forest growth may appear quickly after an area has emerged 

 from marine conditions. One finds dense forests and great peat 

 deposits directly on Post-Pliocene marine beds at many places along 

 the Atlantic coastal plain of the United States. Darwin^^^ saw on 

 the island of Chiloe a bed of marine shells, the species being Venus 

 costellata and Ostrca edulis, both now living in the adjacent bays. 

 These were closely packed, eiribedded in and covered by a very 

 black, damp, peaty mould, 2 to 3 feet thick, out of which a great 

 forest of trees was growing. 



It has been showai that forests on plains or even on rolling sur- 

 faces may bring about formation of peat deposits, but this does not 

 occur always. Trees growing on peat have been entombed, others 

 not associated with peat have met similar fate. River deposits have 

 overspread extensive areas of forest, so that one finds in the rock 



118 D. Agnew, "Nature's Reforesting," Proc. Amcr. Phil. Soc, Vol. 

 XVIII., 1878, pp. 26, 27. 



ii'-* C. Darwin, " Geological Observations in South America," London, 

 1846, p. 28. 



