Elementary theory of x-ray diffraction is explained. Use of x-ray spectrograph to identify elements qualitatively and quantitatively, in whole ceramic pieces at the Museum of Fine Arts, Boston, by x-ray fluorescence is described. The fluorescence spectrum may be either photographed or detected with a Geiger-Muller tube and traced on a chart in an electronic recorder. The composition of ceramic bodies from various known Chinese and Japanese sites were studied and it was found that the ceramic from each site gave a characteristic x-ray diffraction pattern depending upon composition. X-ray diffraction d spacings and intensities are given for pottery from Ruins of Heijo palace, Shosoin, Northern Celadon, Southern Temmoku and others. This means of analysis will become more useful as excavated objects from known localities and clays from known deposits are procured to act as standards. X-ray diffraction will eventually enable one to identify the particular locality in which a ceramic object originated.