332 POPULAR SCIENCE MONTHLY. 



sidered carefully before a final conclusion can be reached. The 

 broad, elevated plateau extending eastward from the present bank 

 of the river offers facilities for studying the evidences of man's occu- 

 pancy in this region such as are to be found in few localities. The 

 principal reason for this is that almost no local disturbance has oc- 

 curred since the original deposition of the sand that overlies the 

 gravel and underlies the soil. The natural history of these under- 

 lying sands has recently received a good deal of attention, because, 

 unlike the deeper gravels, there is perfect accord as to the occur- 

 rences therein of artificially chipped objects; and the suggestion that 

 they are of intrusive origin being set aside as untenable, the geolo- 

 gists are now divided on the question whether the sand is wind-blown, 

 a modified dune, and so not necessarily old even in years, or the 

 result of intermitting overflow of water, usually carrying a consider- 

 able amount of sand and often heavy with washings from some dis- 

 tant clay bank. The objections to the " eolian " theory are that 

 pebbles and bowlders, even of considerable weight, are scattered at 

 all elevations through the sand, and these pebbles, as a rule, do not 

 present any evidence of exposure to eroding sands, but are smooth 

 and glassy, or the typical water-worn pebbles of a brook or the river 

 bed, and more significant is the fact that the sands themselves are of 

 different degrees of fineness, layer upon layer, and are nowhere clean 

 or free from clay; and finally the thin layers of clay are clearly con- 

 tinuous over such extensive areas that in no sense can they be called 

 segregations of that material. On the other hand, a carefully in- 

 stituted comparison of the sand from the surface of the field to its 

 junction with the gravel proper shows its identity with a deposit 

 made by water in comparatively recent times. ISTo difference what- 

 ever could be detected. The sand dune, modified by rains and 

 finally leveled to a plain, presents, in section, no such appearance 

 as the sands that overlie the gravels of glacial origin. Without 

 a scintilla of reason, however, many geologists declare that no de- 

 posit of sand can be of any geological significance if it contains traces 

 of man not clearly intrusive. The latter fact necessitates the former 

 claim, all of which, I submit, is nonsense. 



Fig. 3 illustrates how artificially chipped pebbles occur in this 

 underlying sand. The upper portion shows the superficial soil re- 

 moved to its point of contact with the sand. This is determined by 

 the change of color from dark brown to light yellowish brown, and 

 it is generally so very abrupt a change that no doubt arises as to 

 where the soil ends and the sand begins. The sand proper is shown 

 by the position of the object the measuring rule and trowel. It 

 will be noticed that the implement is lying flat, as such an object 

 would almost necessarily be if transported by water, and not per- 



