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 . ace 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
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 . ace 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 axes not always distinctly coinciding with thehorizon. All the pebbles and bowlders, so far as observed, aresmooth and water-worn, a careful search having failed to showevidence of distinct glacial scratching or polishing on theirsurfaces. The type of pebble is the subovate or discoidal,and though many depart from this form, yet nearly all ob-served by me had been worn so as to show that their shapehad been determined by running water. The materials com-prising the deposit are very varied, but all I observed couldapparently with reason be supposed to have come from the. —(ini vol deposit at Trenton, N. J., whc-re Mr. \olk found a human femur In Dec-ember, The arrow points to the spot where the femur was discovered.(Courtesy of Recordis of t he Past.) MAN AND THE GLACIAL PERIOD. 633 extensive valley ot the river near wliich they lie, except per-haps the fragments of some rather rare hypogene rocks.* It is now settled that the rocks from which these bedswere derived are all in place in the upper Delaware The distinction between the river-s^ravel and that whichoverlies the larger part of southern New Jersey is marked inseveral ways. The Trenton gravel is much coarser than thegeneral deposit, it is also largely composed of fresher lookingand softei pebbles, showing that it has been subject
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Keywords: ., bookauthoruphamwarren18501934, bookcentury1900, bookdecade1910
