We visited Newgrange recently, and paid more attention than usual to the walls of white quartz and “river-rounded granite” cobbles — rounded, gray rocks that look something like cannonballs embedded in the walls — because the day was very windy and we appreciated the shelter of the high walls. I idly wondered why they were part of the construction, what purpose they had, but didn’t have any ideas. Today, I came across an intriguing theory regarding carved stone balls found around large stone circles in Scotland.
It seems these stone balls could have served as “ball bearings” when placed in a shallow wooden track, and allowed a relative few people to move heavy stones with economy. The method may have been easier than log-rolling, although the construction of the trackways would have taken time. Perhaps the left-over stone balls could then have been incorporated in the walls of Newgrange? But maybe the river-rounded granites of Newgrange aren’t regular or round enough to facilitate this? It’s hard to tell as they are now part of the walls, and secured in concrete. Some do appear slightly flattened, more like normal river rocks, while others look quite round. They apparently came from a different part of the country to the huge greywacke kerbstones and orthostats used at Newgrange, which raises the question of why these rounded granite stones were used, and not other river-rounded rocks.
Link: Nova special: Secrets of Stonehenge, a documentary which contains info on this theory of transporting huge stone slabs in the stone age.