DUBLIN, IRELAND—The Journal reports that a geographic information system survey of the section of the River Boyne that runs through the Brú na Bóinne World Heritage Site has revealed anomalies that may be log boats or large boulders associated with the construction of passage tombs some 5,000 years ago. Boulders used in the construction of Newgrange and Knowth were probably moved up and down the river on rafts, rather than log boats, according to Stephen Davis of University College Dublin. Fishing weirs were also detected in the survey, he added. Davis said the non-invasive survey, when combined with airborne laser scanning surveys of the monuments, will help researchers understand the Neolithic landscape. “For an observer from the river, the ridge on which Newgrange, Knowth, and Dowth are located would have formed a northern barrier beyond which there was no visibility,” he said. “To the south the steep slopes again block the observer’s views.” To read about a Brú na Bóinne monument uncovered by a summer heat wave in 2018, go to "The Marks of Time: Late Neolithic Monument."