28 STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 



RusselP" has described conditions on the tundra and in the in- 

 terior of Alaska. He says that " without exaggeration, it may be 

 stated that the whole of Alaska, excepting the steepest rock slopes 

 and the tops of high mountains, is covered with a dense carpet of 

 moss." The reported thickness of peat on the tundra is from 2 to 

 150 even to 300 feet. The peat is growing, though the depth to 

 frozen material is only from 8 to 14 inches. Capps^^ has described 

 an Alaskan peat deposit, exposed in a blufif for more than a mile. 

 The peat, 39 feet thick and resting on unconsolidated glacial till, is 

 fibrous, with abundant stumps and roots, but probably consists mostly 

 of Sphagnum. The mass is divided at 7 feet from the top by 2 feet 

 of white volcanic ash. The surface beyond the edge of the bluff is 

 covered with a thick coat of Sphagnum and supports a dense forest 

 of spruce with little undergrowth. The peat, ash and till are perma- 

 nently frozen at a few inches back from the edge of the bluff', though 

 that is subjected to the long hours of summer sunshine. Even the 

 surface is frozen at a depth of 6 inches in early July. 



The arrangement of roots shown by spruce trees growing at the 

 edge of the bluff as well as by the stumps, which compose a great 

 part of the deposit, is wholly unlike that ordinarily observed. Spruce 

 growing on solid ground, frozen or not, has radial roots, parallel with 

 the surface and penetrating only a few inches ; but, at this White 

 River locality, the roots of trees growing on the edge of the bluff 

 and those of stumps buried at different levels in the peaty mass have 

 a very different arrangement. Instead of a single, flat-based set of 

 radial roots, these trees all show a central stem, often several feet 

 long, from which roots branch off at irregular intervals, with an 

 upper set of roots near the surface, corresponding to those of the 

 normal tree. Investigation proved that roots below the frost-line 

 are still undecayed, though they differ in color from the uppermost 

 set of radial roots and evidently are no longer active. Capps reached 

 the conclusion that, in each case, the seedling spruce, having estab- 

 lished itself on the mossy soil, sent out the normal radial roots ; but 



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

 Soc. Amcr., Vol. I., 1890, pp. 125, 126, 129. 



^1 S. R. Capps, " An Estimate of the Age of the last great Glaciation in 

 Alaska," Journ. Washington Acad., Vol. V., 1915, pp. 108-115. 



