532 STEVENSON— FORMATION OF COAL BEDS. [November 3, 



refers to his own observations that, in primitive regions, running 

 streams are generally fringed with trees and that even now in for- 

 ested areas of the United States trees come almost to the water's 

 edge, so that the banks are but slightly abraded by the current. He 

 cites Doni respecting the Sestajone and Lima, two streams rising in 

 the Tuscan Appenines and flowing into the Serchio. In rainy weather 

 the volume of the former is only about half as much as that of the 

 latter and its water limpid ; whereas the water of the latter is turbid, 

 muddy. The drainage areas are almost equal, but the Sestajone 

 winds down between banks clad with firs and beeches, while the 

 Lima flows through a cultivated, treeless valley. 



The writer had opportunity in 1910 to observe the effect of heavy 

 rainfall on the steep wooded slopes in central France, where the 

 rocks are resistant gneisses and granites — a condition much like that 

 of the White mountains. The rainfall during that summer was not 

 merely in excess, it was extraordinary. The showers came suddenly 

 and often resembled the cloudbursts of mountain areas within the 

 United vStates. In many parts of the area, the gorges are deep, with 

 walls often exceeding 35 degrees, at times exceeding 45 degrees. 

 Many gorges have densely wooded walls ; many others have a some- 

 what scanty growth, scattered over the rocky slope with plants grow- 

 ing here and there in decomposed material occupying clefts or accu- 

 mulated behind projecting craggy points. During some showers, the 

 water ran oft' exposed places not in rills but often in broad continuous 

 sheets and the streams were converted into roaring torrents. More 

 than once, after one of these almost cataclysmic rains, the writer 

 passed through some of the gorges and was surprised to find that, 

 apparently.noinjury had been done to vegetation on even the steepest 

 slopes. Tender plants, growing in handfuls of loose material on 

 projections, seemed to be unharmed. The streams were followed 

 for many miles, but they had received only rare stems of trees from 

 undermined banks and the eddies showed no accumulation of plant 

 material. Trees, lining the streams and in many cases growing 

 down to almost the low water line, gave no evidence of having 

 been subjected to the force of a dashing torrent. Tlie conditions 

 differ from those, with which every one is familiar, only in that they 



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