From this list of missing blue stones we may safely deduct two; two
pieces of rock are known to be beneath the turf, and there may be others.
The most satisfactory derivation of Sarsens or Sassens is from the
Anglo-Saxon word for a rock or stone—_ses_, plural _sesen_ or _sesons_.
The Inner Circle of blue stones and Inner Horse-shoe are composed of the
“Blue Stones,” igneous rocks.