Manganoxyd-Phasen als Pigmente antiker Vasenmalerei
function (dots) and the fitted survivor function (continuous line) for ear thquakes with M ~ 2.0 in Eastern Canada for the period t925-1965 (Ranalli, in preparation). Seismic zoning in terms of frequency isolines of damaging earthquakes is therefore a useful first step in ear thquake risk analysis. In order to refine the ear thquake risk index ~ however, it is necessary to weigh it for magnitude, focal depth, and ground response. Ultimately, an empirically based relation between ground acceleration, distance, and magni tude is required, so tha t ear thquake risk can be translated into terms of more immediate relevance to h u m a n and social problems.
Keramiken und Wandmalereien der Ausgrabungen von Thera
The artists on Thera followed the tradition of Minoan Crete in the techniques of vase and wall painting, e.g. they adopted talc as a white pigment in vase painting, but they also employed their own methods. Significant improvements in quality occurred in both islands during tile change from the Kamares to the late Minoan ceramics. Cypriot influences are revealed in the use of manganese black as a ceramic pigment and of jarosite in wall paintings. Calcium hydroxide has been found in a vase buried by ash from the Thera volcano and conserved without carbonization for 3.500 years.
Fifth Century Intentional Red Glaze
During 1938 and 1939 one of us (M.F.) spent two seasons as Chemist for the Agora Excavations in Athens. At that time certain chemical and physical properties of the black and intentional red glazes were investigated. These showed that the chemical composition of the two glazes is very similar, the essential difference being that the iron is reduced in the black and oxidized in the red glaze. The Second World War and other duties caused that