Tracking the Trails of Ancient Glaciers

On an outcrop of volcanic bedrock near the paath sit half a dozen erratic boulders, some weighining as much as twenty tons, of a coarse-grainned pink granite. Once, I chipped off a sample of)f the rock and followed the bedrock scratches northth, looking for the source. Like an Indian trail of bent twigs. le scratches led me several miles out of Easton into the town of Stoughton, where I found what I was looking for, a south-facing ledge of bedrock that under the hand magnifier was identical t...