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 . e archaeologist as to the age o^tlie deposit is asked of the geologist, and it is for him tuanswer. In the light of the preceding chapters, a ready an-swer is found to this question. The city of Trenton is builtupon a horseshoe-shaped gravel-deposit which is about threemiles in diameter, extending back about that distance to theeast from the present rive
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 . e archaeologist as to the age o^tlie deposit is asked of the geologist, and it is for him tuanswer. In the light of the preceding chapters, a ready an-swer is found to this question. The city of Trenton is builtupon a horseshoe-shaped gravel-deposit which is about threemiles in diameter, extending back about that distance to theeast from the present river. This deposit is somewhat loweraround its inland boundary than along the river. The prongsof this horseshoe rest, one at Trenton, and the other twomiles below, just north of the house of Dr. Abbott. Thisgravel is thus described by Professor Shaler: The general structure of the mass is neither that of ordi-nary bowlder-clay nor of stratified gravels, such as are formedby the complete rearrangement by water of the elements ofsimple drift-deposits. It is made up of bowlders, pebbles, andsand, varying in size from masses containing one hundredcubic feet or more to the finest sand of the ordinary sea-beach- MAN AND THE GLACIAL PERIOD. 631. Fig. 163.—Typical spction of the Trenton gravel in which the implements described Inthe text are found. Note the distinct stratification and the large angular bowldernear the surface, showing the presence of floating ice, since by no other meanscould such a bowlder get into such a position as here found. The elevation of thesurface is here 50 feet and is about half a mile back from the river edge of the exposure is here between 30 and 40 feet. (Photograph by Abbott.) es. There is little trace of true clay in the deposit ; there israrelv enough to jjive the least trace of cementation to themasses. The various elements are rather confusedly arranged ;the large bowlders not being grouped on any particular level,and their major
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