'911] STEVENSON— FORMATION OF COAL BEDS. 573 



reports that the peat of the Everglades in southern Florida rests on 

 sand, rock or marl. Grisebach, cited by Friih, endeavored to ex- 

 plain this apparently anomalous condition for north Germany by 

 the suggestion, that, in very wet years, peat may have been formed 

 in that region even on sands and, being itself practically impermea- 

 ble, it may have prepared the way for a Hochmoor. Be that as it 

 may, the fact remains that a swamp may begin on an apparently 

 permeable surface; the Everglades are at little above sea level, but 

 Okefinokee is 50 miles from the ocean and 115 feet above mean 

 tide — and its mucky peat contains 85 per cent, of combustible mate- 

 rial. In this latter case, one must believe that the underlying sand 

 is not far from an impermeable stratum and that it is saturated with 

 moisture or that by absorption of humic acid the sand itself has 

 been rendered impermeable. 



Peat and Peaty Materials. — Russell'* describes the Alaskan tun- 

 dra as a swampy, moderately level country having a cover of mosses 

 and lichens with some ferns and many small flowering plants. Below 

 this dense carpet of vegetation is dark humus. Ponds and lakelets 

 abound, surrounded by banks of moss, and occasionally one finds 

 groves of alders and dwarf willows on their borders. The under- 

 lying black humus shows few indications of its vegetable origin. It 

 is 2 feet thick at St. Michaels but is 12 feet at a mile farther east. 

 He saw 15 feet on the Yukon and a depth of 150 to 300 feet is 

 assigned to it at the head of Kotzebue sound. The flora of the 

 tundra is essentially cryptogamic, but two species of Equisctum 

 flourish with rank luxuriance in great spaces along the Yukon. So 

 vast is this accumulation, in both area and thickness, that Russell 

 ventures to suggest that some coal seams may have had similar 

 origin. If the tundra coast of Alaska should subside, its peat would 

 be covered with sediments and be ready for transformation into lig- 

 nite or coal. Its associated plants and animals would indicate the 

 climatic conditions, but the overlying sanastone and shale might con- 

 tain leaves and tree trunks, floated in bv rivers from warmer regions. 



But where the swamp is forested, especially if the wood resist 



'* I. C. Russell, "Notes on the Surface Geology of Alaska," Bull. Geol. 

 Soc. Amer., Vol. I., 1890, pp. 125-128. 



171 



