200 ICE CLIFFS ON WHITE RIVER 



below the Donjeck. Tlie Klotassin is not " the cliief eastern tril)utary 

 of the White," but is much smaller than either the Klutlan or Don- 

 jeck. The latter itself receives an eastern tributary, the Kluantu, 

 whicli is larger than the Klotassin. This confusion in identifying the 

 rivers of the region, and the exaggerated estimate of distances, to- 

 gether with the air of confidence which pervades the article in ques- 

 tion, render it very misleading to the geographic student. 



Coming to the main point of the paper, the alleged ice cliffs, it 

 appears tliat Mr Gorman has mistaken the permanently frozen silt in 

 which the river channel is cut for beds of ice, such as were descril)ed 

 by Cantwell on the Kowak. The frozen silts and subsoils are char- 

 acteristic of the Arctic and subarctic regions, and may be observed on 

 almost any stream in tlie Yukon basin. It is difficult to understand 

 why a solidly frozen subsoil should be less favorable for the growth 

 of forests than a layer of clear ice, and indeed Lieutenant Cantwell* 

 describes the ice strata of the Kowak as covered by a few feet of soil 

 bearing " a luxuriant growth of mosses, grass, and the characteristic 

 Arctic shrubbery, . . . and a dense forest of spruce trees from 

 50 to 60 feet high and from 4 to 8 inches in diameter." The " depau- 

 perate condition of the trees " described by Mr Gorman must there- 

 fore be explained b3'some other cause tlian the presence of subjacent 

 ice-strata or a frozen subsoil. 



On tiie Lower White, some eight miles from its mouth, one of the 

 writers had opportunit.y to examine a bluff of frozen silt, of which 

 some 20 feet was exposed by the cutting action of the river. A dense 

 growth of vegetation was found above the frozen silt, including many 

 large spruce trees. Even if masses of clear ice were found in that 

 portion of the White River Valley visited by Mr Gorman they could 

 scarcely be regarded as glacial ice, since tlie region lies mostly out- 

 side the limit of general glaciation and bears few, if any, marks of 

 the former presence of local glaciers. It is conceivable that masses 

 of glacial ice might be preserved for an indefinite period in the sub- 

 arctic climate of Alaska if covered by a thick layer of insulating 

 material, such as moss. It is observed, however, that sand and 

 gravel do not form an efficient non-conductor, and that where the 

 soil is laid bare by burning off or otherwise removing the moss the 

 subsoil thaws out to a considerable depth. Since ice masses at the 

 margin of a ghxcier are at first covered only by sand and gravel, the 

 chances of their preservation until covered by vegetation are small. 



* Nat. Geog. Mag., vol. vii, p. ;Mh. 



