Complex sentence: A Blue Lias memorial stone, with a Cross of Lorraine, from the abbey was found in 1867 during the fortification of the island and incorporated into an armoury leading to the naming of the "tombstone battery".
Split into simpler sentences: A Blue Lias memorial stone from the abbey, which has a Cross of Lorraine, was found in 1867 during the fortification of the island. It was incorporated into an armoury leading to the naming of the "tombstone battery".