334 POPULAR SCIENCE MONTHLY. 



The presence of these artificial flakes, blades, and other forms 

 of simple implements can only be explained by considering them 

 as a constituent part of the containing bed, having been brought 

 hither by the same agency that brought the sand, pebbles, and clay. 

 AVhen standing before a newly made section of this implement-bear- 

 ing deposit it is easy to picture the slow progress of its accumula- 

 tion. The broad plain has been subjected to overflow, now of water 

 bearing only sand, and then of muddy water; now with current 

 strong enough to roll small pebbles from some distant point, and 

 then periods when the sun shone on the new deposit, dried it, and 

 the loose sand was rippled by the wind. Floods of greater volume 

 occasionally swept across the plain, and ice-incased pebbles were 

 dropped upon its surface, and with this building up of the plateau 

 to a higher level there w r ere also brought to it traces of man's handi- 

 work. Of this, I think, there can be no doubt now. Years ago 

 I endeavored to show from the distribution of rude argillite imple- 

 ments of specialized forms, as arrow points and small blades, trimmed 

 flakes and scrapers, that these objects were older, as a class, than 

 jasper and quartz implements and weapons, and that pottery was 

 made only in the rudest way before " flint " chipping jasper and 

 quartz was established. The more exhaustively this subject was 

 followed up, the proposition became more evidently true, and to-day 

 it is unqualifiedly confirmed by the results obtained from system- 

 atically digging deeply over wide areas of country. The fact that 

 argillite continued in use until the very last does not affect this con- 

 clusion. 



As the high land, now forty or more feet above the river and 

 beyond the reach of its floods of greatest magnitude, was once con- 

 tinually overflowed and gradually built up by the materials the 

 water spread upon it, it is evident that the conditions were mate- 

 rially different when such things happened from what now obtains, 

 and the whole configuration of the country to-day points to but the 

 one conclusion: that these plateau-building floods occurred so long 

 ago as when the river flowed at a higher level and possessed a greater 

 transporting power than at present. This, it is true, was long after 

 the coarse gravel and huge bowlders were transported from the hill- 

 sides of the upper valley, but it was before the river was confined 

 to its present channel, and more significantly before what may be 

 called the soil-making period, itself of long duration and the time of 

 the Indian as such. Not an argillite chip from the sands beneath the 

 soil but speaks of the distant day when this plateau was an almost 

 barren plain, and man saw it, roamed over it, and perhaps dwelt upon 

 it, when but the scantiest vegetation dotted its surface, and only 

 upon the hills beyond its boundary were there trees and herbage. 



