"All Plymouth is made up of the results of pilgrimage. How many scores of fathoms deep the real Plymouth shore lies I do not know. It is down there somewhere where it cooled into bathylithic crust back in the gray dawn of time when the earth was made.... All above that is terminal moraine, rock detritus piled upon rock foundation by the glacier. Plymouth Rock itself thus came joy riding from some ledge up Boston way, alighting from this first and greatest New England Transportation System only a few hundred thousand years before Mary Chilton arrived to set foot upon it. Tide and tempest grind pebbles to shifting sand and give and take away beach and bar yearly, but they do not move the boulders very fast. Manomet shore and even Plymouth beach are rock-bound with these, large and small, today as they were when the Pilgrims fought their desperate, sea-beset way by them through the dusk of a winter northeaster and froze in safety under the lee of Clark's Island."