One hundred and twenty years ago, the first obsidian implements were reported from Hopewellian mounds by Squier and Davis (1848). Since that time, a number of regions have been suggested as the source area: Alaska, the Pacific Coast, Yellowstone National Park, New Mexico, and central Mexico. Neutron activation analysis of the elemental composition of Hopewellian obsidian indicates two separate element groups. One of these, the 150 Group, has its source at Obsidian Cliff in Yellowstone. The second, the 90 Group, is also located in Yellowstone, but the exact flow has not yet been discovered.

In the presence of a large excess of gaseous methane, 54.4±0.5% of p28 formed by (n, 'Y) activation was found to become stabilized in organic combination. The effects of inert-gas additives in moderating the reaction of Il28 with CH. were determined in an effort to ascertain the mechanism. The data, extrapolated to zero mole-fraction methane, indicate that xenon is capable of reducing the organic 1 128 to 11% whereas neon, argon, and krypton each reduce it to only about 36%. These data suggest that of the 54.4% organic P.28, about 18.4% forms as a result of hot 11.28 reactions, 11% as a result of excited iodine atoms or 1+ ions in the ap 2 , aPI, and/or apo states, and 25% as a result of reactions of 1+ (lD2) ions.

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