3 o 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 strati- 

 fication ; for the whole area was full of gravel, and there was no 

 chance of disturbance by natural causes. Now, Dr. Abbott's tes- 

 timony is that up to the year 1888 sixty of the four hundred palaeo- 

 lithic 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 492) found while watching the progress of an ex- 



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.) 



tensive 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). An- 

 other was found in a perpendicular exposure of the bluff imme- 

 diately after the detachment of a large mass of material, and in a 

 surface that had but the day before been exposed, and had not 



