630 THE ICE AGE IN NORTH AMERICA. 



observers to find implements, has very little weight in 

 discrediting the testimony of others who have been more 

 successful. 



The acrimonious controversy over the genuineness of 

 these implements of supposed glacial age was finally put to 

 rest by a fortunate discovery made by Mr. Ernest Volk, while 

 working under the auspices of the Peabody Museum of Cam- 

 bridge, Mass. The discovery was that of a human femur, in 

 undisturbed gravel twenty feet below the surface, and be- 

 neath a thick deposit of crossbedded coarse gravel which 

 unquestionably belongs to the glacial era. The accompanying 

 illustration of the gravel pit in which this was found lies in 

 the same bank shown in the illustration on p. 521, but after 

 the gravel bank had been excavated 100 feet or more farther 

 back from the river. 



Accepting as now beyond question that these palaeolithic 

 implements at Trenton occur in undisturbed strata of the 

 gravel, of which the evidence just given would seem to be 

 sufficient, the question of the archaeologist as to the age of 

 the deposit is asked of the geologist, and it is for him tu 

 answer. : In the light of the preceding chapters, a ready an- 

 swer is found to this question. The city of Trenton is built 

 upon a horseshoe-shaped gravel-deposit which is about three 

 miles in diameter, extending back about that distance to the 

 east from the present river. This deposit is somewhat lower 

 around its inland boundary than along the river. The prongs 

 of this horseshoe rest, one at Trenton, and the other two 

 miles below, just north of the house of Dr. Abbott. This 

 gravel 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 formed 

 by the complete rearrangement by water of the elements of 

 simple drift-deposits. It is made up of bowlders, pebbles, and 

 sand, varying in size from masses containing one hundred 

 cubic feet or more to the finest sand of the ordinary sea-beach- 



