The removal of the _pouzzolana_, so called after the volcanic ashes of Pozzuoli in Italy for the works on the Isthmus of Suez, necessitated important excavations, and the cuttings revealed the existence of dwellings which had been bidden away from the light of day for many centuries. The masses of rubbish hiding these prehistoric ruins were some sixty-five feet high, and consisted chiefly of volcanic ashes piled up, for some accidental reason, in comparatively modern times. Beneath the _pouzzolana_ a thin layer of humus contains fragments of pottery of Hellenic origin; which marks the close of the historic period, and covers over the mass of pumiceous tufa vomited out by the volcano. It was in this tufa, which is eight feet thick, that the first signs of buildings were discovered. Further excavation brought to light two houses with doors, windows, and bearing walls. In one of these houses there were five different rooms. Other discoveries rapidly succeeded each other, alike in the island of Therasia and at Acrotiri, the principal island, which has given its name to the group. The plan of these houses is an irregular parallelogram, the angles of which are rounded and the sides more or less curved. This arrangement differs greatly from that adopted in Greece as well as from that in use at Therasia after the time of the volcanic eruptions. The houses too are quite different in their mode of construction. The walls consist of great blocks of lava placed one above the other, without any trace of cement or of lime, and are merely kept in place by a reddish earth mixed with chopped straw or marine algae. Large branches of olive or cypress trees, still with the bark on, are imbedded in the masonry. These pieces of wood, the size of which varies considerably, were probably added to give the necessary solidity to the walls in the numerous earthquakes, the disastrous effects of which were only too well known to the ancient inhabitants of Santorin. It is curious and interesting to note the use of the same expedient among the inhabitants of the islands of the Archipelago who are still exposed to the same danger. The doors and windows are clumsily arched, and the roof seems to have been a low vault. It was made of stones and coated with clay and supported by the trunks of olive trees, the charred remains of which lay upon the floors of the crushed homes. These trunks show no sign of having been touched with metal tools; not a metal nail or clamp has been found, and we cannot but conclude that the remains belong to the age when stone alone was employed. The inside walls were not glazed or decorated in any way, except in one instance, that of a house at Acrotiri, from which the rubbish has been cleared away, revealing on the walls a layer of lime on which was some colored ornamentation which still retained an extraordinary brilliancy when it was discovered.