Quite understandably, Sandia has been of keen interest to archaeologists. The geology tells us only that the Folsom and the Sandia occupations of the cave were separated by a cool, moist interval that could reflect a major glacial advance, a minor glacial advance, or merely a postglacial period of lowered temperature and more snow or rain. The last seems the least likely alternative. None of these possibilities gives us a firm date. Accordingly, the development of the radiocarbon “clock” by Willard Libby raised some hope that the age of Sandia points could, at last, be determined. This hope continues, but has yet to be realized. Radiocarbon tests made by H. R. Crane, at the University of Michigan, upon fragments of mammoth tusk indicate an age of at least 20,000 years, with the reasonable possibility that the true age exceeds 30,000 years.[46] The problems remain. The association of Sandia points with mammoth tusk was not as clear as Folsom point with extinct bison. And the problem of the reliability of ivory in radiocarbon tests—as well as the ever-present question of possible contamination—urges caution in accepting this date for Sandia. [Illustration: _A Sandia point, left, compared with two Solutreans. The first of the Solutreans was found with Mousterian artifacts in a cave in Tangier, the second in France. (The Sandia point, after Hibben, 1941; the Solutreans, after Howe and Movius, 1947, and Plant, 1942.)_] A site discovered at Lime Creek, Nebraska, in 1947 may prove to be old. In the sharp bank of the stream C. Bertrand Schultz found crude points, bone awls, scrapers, and tools made out of antlers. Together with fossils of mammals they lay as deep as forty-seven and one-half feet below the surface, in a silt containing the remains of decayed vegetation. Above this soil were seventeen feet of loess, another layer of soil, another layer of loess, and finally a “mature” or well developed, and therefore fairly old top soil. Schultz and W. D. Frankforter write that the seventeen feet of loess covering the earth in which the artifacts were found appears to have been deposited before or at the beginning of the last expansion of the Wisconsin, or final, glaciation.[47] If this is true, it means that the men of Lime Creek lived 25,000 or 35,000 years ago, and that their forebears may have come through the corridor in the ice fields of Canada 5,000 to 18,000 years earlier (see page 27). Antevs and Wormington doubt it.[48] Radiocarbon dates from burned logs found below the Lime Creek artifacts averaged 9,524 ± 450 years.[49] It is possible that these stone tools are contemporaneous with Folsom, or even a bit later. The Milling Stone Appears