iron shaft : primus - the first letter and introduction iron shaft : secundus - how he joined the tenth legion , and got his nickname iron shaft : tertius - how he helped the druids , and saved caesar iron shaft : quaternus - poison , pearls , druids and skulls iron shaft : quintus - how caesar got his ships other works by john hulme are : in the mendel series - a fictionalized account of the life and times of gregor mendel - the discoverer of genetics .