Santorini, a medieval Italian corruption of Sant’Irene, the patron saint of Thera, is the name given to a small group of volcanic islands, almost the southernmost of the Grecian archipelago. The geographical position of Giorgios Kameni, at about the center of the group, is latitude 36° 24' north and longitude 25° 24' east. The islands lie on the curving belt or zone of active or recently extinct volcanoes3 that extends from Kolantziki4 (on the coast of Megara, east of the Isthmus of Corinth), through Ægina,4 Methana,4 Poros,4 Milos (with Kimolos, Antimilos, and Polyvos),5 Santorini,6 Nisyros,7 and Kos,8 to Kalymnos, and probably northwardly through Mount Pagos at Smyrna,9 to Phocea and Pergamon.9 The lavas along this volcanic line are much alike and are almost all dacitic and andesitic, with a few basalts. The zone constitutes a well-defined, although small, comagmatic region, which forms an arc or festoon bordering the sunken . . .