“He said that flakes prepared for points and other implements seemed to be an object of trade or commerce among the Indian tribes that he came in contact with; that there were but few places where chert or quartzite was found of sufficient hardness, and close and even grain, to flake well, and at those places there were men very expert at flaking.”[37] Mr. Sellers had known Catlin, the artist and traveller, in his youth, while he was still an expert worker in wood and ivory in the service of the elder Catlin, a musical instrument maker in Philadelphia; and from him he learned much relative to the modes of operation and the sources of material of the Indian workers in stone. “He considered making flakes much more of an art than the shaping them into arrow or spear points, for a thorough knowledge of the nature of the stone to be flaked was essential, as a slight difference in its quality necessitated a totally different mode of treatment. The principal source of supply for what he termed home-made flakes was the coarse gravel bars of the rivers, where large pebbles are found. Those most easily worked into flakes for small arrow points were chalcedony, jasper, and agate. Most of the tribes had men who were expert at flaking, and who could decide at sight the best mode of working. Some of these pebbles would split into tolerably good flakes by quick and sharp blows, striking on the same point. Others would break by a cross fracture into two or more pieces. These were preferred, as good flakes could be split from their clean fractured surface, by what Mr. Catlin called ‘impulsive pressure,’ the tool used being a shaft or stick of between two and three inches in diameter, varying in length from thirty inches to four feet, according to the manner of using them. These were pointed with bone or buckhorn.” It is thus apparent that among rude tribes of modern centuries, as in the prehistoric dawn, exceptional aptitude and skill found recognition as readily as in any civilised community. There were the quarriers and the skilled workmen, on whose joint labours the whole community largely depended for the indispensable supply of all needful tools.