138 STEVENSON— FORMATION OF COAL BEDS. [April i8, 



is highest in the upper reaches, where the stream is narrower, but 

 decreases in height where the tiood-plain becomes wide, unless acces- 

 sions have been received from tributaries. Floods of this type do 

 not sweep vegetation from the flood-plain. If one accepting the 

 transport doctrine in full should read of conditions in the Mississippi 

 area with its several floods each year, 40 to 60 feet deep in various 

 parts of the lowland region — sometimes converting areas of 10,000 

 square miles into inland seas — he would expect to learn that that 

 region is in great part a dreary waste, deprived of vegetation and 

 uninhabitable. But not so ; it is the home of millions of people ; it 

 contains many cities with 50,000 to 500,000 inhabitants ; a great part, 

 which has not been cleared for cultivation, is still heavily forested, 

 covered with ancient trees; even the swampy areas, subject to flood 

 from long before settlement by man, abound in the majestic 

 Taxodiiim. These floods lift buildings from their foundations and 

 carry them away; they injure farming land by leaving a deposit of 

 silt or sand ; they disturb property relations by undercutting the 

 banks or by digging a new channel across the necks of horseshoe 

 curves; but they usuall}- are of brief duration and normal condi- 

 tions return. 



Transportation of vegetable materials by streams is no matter 

 of hypothesis. Every stream carries on its surface twigs and leaves 

 torn off by the wind ; rivers carry great quantities of coarse and fine 

 debris, increased in times of high water by trees and shrubs from 

 caving banks ; but the cover of vegetation remains practically un- 

 injured in spite of all attacks. Agassiz, Kuntze, Humboldt, Wallace 

 and other travellers in South America ; Merrill, Frankenfield, 

 Humphreys and Abbot as well as other observers in the Mississippi 

 area ; Livingstone, Cameron, Baker, Stanley and other travellers in 

 Africa ; Medlicott, Blanford and others in India, all tell the same 

 story, as has been shown on earlier pages. The lowland flood rises 

 slowly, it does not scour the surface, it does not destroy the forest 

 growth, large or small, it does not disturb the peat deposits. Even 

 when loaded with cakes of ice, it is powerless against standing trees, 

 as has been observed many times on rivers in the eastern states. 

 The high-level line of floods is ascertained by noting the silt rings on 



