National Geographic : 1900 May
ICE CLIFFS ON WHITE RIVER 201 If a concise definition of a glacier be accepted, such isolated masses of buried ice would hardly be included, being in fact a part of and closely related to the frozen subsoil which is found nearly everywhere in the Arctic province. Moreover, the deposits which overlie the ice, as described by Mr Gorman and observed by the writers, are soils and silts, and entirely non-glacial. If these ice masses were buried remnants of former glaciers, then would be asso ciated with them glacial material. Speaking of recent volcanic activity in the valley of White River, Mr Gorman makes the surprising statement that not a trace of the volcanic ash which forms so noticeable a feature at the banks of the Yukon is to be seen along the banks of the White, except near the mouth. If he had possessed even a slight familiarity with the region in question or with the literature* of the subject, he would have known that many hundred square miles in the Upper White River basin are covered with this volcanic ash, with many local drifts from 50 to 100 feet in depth. The ash covers both valley bottoms and mountain tops. The thin stratum shown in the banks of the Yukon is merely the attenuated eastern edge of the deposit which reaches its maximum in the region from which Mr Gorman says it is entirely absent. We entirely agree with his dissent from Heilprin's theory that the ash was deposited in a lake bed covering the upper Yukon basin, but on quite different grounds from those which he adduces. A final case of superficial observation remains to be noted. Mr Gorman states that the water of White River is " surcharged with a mixture of fine blue clay and granitic sand " which gives it the char acteristic white color from which it derives its name. Many of the upper tributaries are glacial streams, and hence carry rock flour and glacial pebbles like other streams of similar origin, but this constitutes only a small proportion of the sediment. Much the larger part consists of the light pumiceous volcanic ash which covers the upper half of the basin, as was proven by a microscopical examination of the sedi ments. Being entirely unconsolidated and only in part covered by vegetation, it is rapidly eroded, and on account of its low specific gravity large quantities of relatively coarse material remain in suspen sion in the water. *An Expedition Through the Yukon District, pp. 146-150; Explorations in Alaska, p. 69 .