The ice age in North America and its bearing upon the antiquity of man5th edwith many new maps and illus., enland rewritten to incorporate the facts that bring it up to date, with chapters on Lake Agassiz and the Probable cause of glaciation . Fui. 189—Front view of skull aud femur boues of Lansing Skeleton. (Courtesy of Recordsof the Past.) the valley from A to C, and the water which in dry weathercomes into its head continually disappears in the gravelunderneath, whose surface at the entrance of the turmel is. Fig. 190—Side view of skull and femur bones of Lansing Skeleton. (Courtesy of Reco
The ice age in North America and its bearing upon the antiquity of man5th edwith many new maps and illus., enland rewritten to incorporate the facts that bring it up to date, with chapters on Lake Agassiz and the Probable cause of glaciation . Fui. 189—Front view of skull aud femur boues of Lansing Skeleton. (Courtesy of Recordsof the Past.) the valley from A to C, and the water which in dry weathercomes into its head continually disappears in the gravelunderneath, whose surface at the entrance of the turmel is. Fig. 190—Side view of skull and femur bones of Lansing Skeleton. (Courtesy of Recordsof the Past.) twenty feet below the rock exposure, while a well a little farthereast was sunk to a depth of t wentj^-four feet without strikingrock, and the railroad immediately east of the mouth of the 682 THE ICE AGE IN NORTH AMERICA. buried gorge is supported by piles driven thirty feet intothe alluvium. Above A this ravine lies wholly in the en-veloping loess. From this it is evident that the rock erosion in the lowerpart of the tril)utary entering at A is neither post-glacial norinterglacial, but is a remnant of preglacial erosion when thewhole region was so much elevated that the river had loweredits bed a considerable depthbelow that now occupied by it. AtOmaha the rock bottom of the river is known to be eightyfeet below its present bottom. Since the advent of the con-tinental ice-sheet the preglacial gorge has been aggraded toa considerable extent, and meanwhile, during the lowan stageof the
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