Page:Popular Science Monthly Volume 43.djvu/40

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30
THE POPULAR SCIENCE MONTHLY.

a great many acres of the gravel to a depth of twenty or twenty-five feet. Any one can see that in such conditions there has been no chance for "creep" or landslides to have disturbed the stratification; for the whole area was full of gravel, and there was no chance of disturbance by natural causes. Now, Dr. Abbott's testimony is that up to the year 1888 sixty of the four hundred palæolithic implements which he had found at Trenton had been found at recorded depths in the gravel. Coming down to specifications, he describes in his reports the discovery of one (see Primitive Industry, page 493) found while watching the progress of an extensive

PSM V43 D040 Section of the trenton gravel in which the implements were found.jpg

Fig. 1.—Section of the Trenton Gravel., in which the Implements described in the Text are found. The shelf on which the man stands is made in process of excavation. The gravel is the same above and below. (Photograph by Abbott.)

excavation in Centre Street, which was nearly seven feet below the surface, surrounded by a mass of large cobble-stones and bowlders, one of the latter overlying it. Another was found at the bluff at Trenton, in a narrow gorge where the material forming the sides of the chasm had not been displaced, under a large bowlder nine feet below the surface (ibid., page 496). Another was found in a perpendicular exposure of the bluff immediately after the detachment of a large mass of material, and in a surface that had but the day before been exposed, and had not