508 GEOLOGY. 



The most available sites for finding suitable raw material in a con- 

 venient form were the river gravels and the terrace formations. This 

 was especially true in and about the glaciated regions where valley 

 trains of glacial gravels led away from the ice-fields. In these were; 

 usually much quartz, flint, chert, and other available rock, in the con- 

 venient form of pebbles, cobbles, and bowlderets. This material had 

 been selected, as it were, and brought to workable sizes by the ordeal 

 of glacial wear and wash. 



It is a significant fact that the rude artefacs in question have been 

 chiefly found in such gravels. Gravels derived from chert-bearing 

 limestone or quartz-bearing rock arc also fruitful sources. In other 

 words, there is a correspondence between the distribution of the ruder 

 artefacs, and that of the raw material. The distribution of the finished 

 artefacs is much wider and more varied, and hence more consistent 

 with the probable distribution of their use, and their liability to be 

 lost. There is a special infelicity in supposing that great numbers 

 of implements would be lost in glacial rivers during actual glacial 

 stages, for the waters of these rivers must have been cold, silty, and 

 barren of organic matter, as they came from the glacial mill under 

 the ice-fields. They must have been among the most uninviting of 

 all streams for hunting and fishing. But at later stages, when the 

 climate was milder and the streams warmer and clearer, and when 

 the adjacent country was filled with food and game, arid when also 

 the glacial gravels were undergoing readjustment and degradation, 

 and were being exposed in the bluffs and stream beds, these streams 

 must have furnished excellent and convenient grounds for finding 

 raw material for making stone implements. 



The distinct recognition of the two stages in the manufacture of 

 the well known arrow-points, spear-heads, knives, etc., used by the 

 known aborigines of the country, and the strong evidence that mul- 

 titudes of the ruder forms found in the river gravels were products 

 of the first stages of such manufacture, naturally raised the question 

 whether there are any true paleolithic artefacs in North America. 

 The difficulties of discriminating between "paleoliths" and " rejects," 

 if indeed they can be discriminated, is illustrated by Fig. 571, one of 

 the chipped blades of which has been regarded as a typical " paleolith," 

 while the other forms are "rejects." Whether this close resemblance 

 be regarded as merely similitude or as actual identity, it is obvious 



