rest of the school. It has its own director, currently (2019) Evangelia Kiriatzi, its own research scientists, teaches its own courses, offers its own grants, and issues its own publications. It is, however, governed by the main school's Committee for Archaeology. Fitch Laboratory was founded during a period of growing interest in establishing the provenience of pottery discovered during excavation. The method of archaeology established a sequence of layers at a site, which gave relative dates to the objects found in them; however, the method had limitations. Suppose that pottery in one region was similar to pottery at another, how was this similarity to be interpreted? Did invaders carry the pottery from one site to another? Were the similar pots trade exports? Did the pottery of one region serve as a model for the manufacture of pottery in another? Answers to these questions were provided by the judgements of the lead excavators, but with no method of establishing provenience, these judgements were often highly controversial. For example, there are striking similarities between some Minoan and some Mycenaean pottery. Arthur Evans, Duncan Mackenzie and their supporters were proposing that Mycenaean pottery was a type of Minoan pottery. To the contrary, Carl Blegen and his supporters were affirming a mainland Greek origin for and importation to Crete of Mycenaean pottery. Given some of this pottery at a site, which was it, Minoan or Mycenaean, and how could one establish which? By the 1960s archaeologists were turning to the chemical and physical sciences for answers. The science of geology provided them with petrology, the study of the rock composition of the clay from which the pots were made. Microscopic examination of a thin section of pot material reveals the minerals present in the grains of clay. The mineral composition of pots is then compared to the mineral composition of the rock from which various known clay beds had come. If there were any mineralic distinctions between Mycenaean and Minoan pottery, petrology would discover them. By that time also new methods of chemical analysis of inorganic material were available, which are generally classified as "activation analysis." The general method exploits two natural phenomena: the tendency to form stable atoms with a given energy structure (number and configuration of electrons and neutrons, etc.), and the action of an atom to transduce radiational energy falling on it. The input energy "activates" or superenergizes the atom in