The nature of candle ice, stratified ice and ice of radial structure observable on ice island t-3 was investigated. Cores were drilled through the ice island at two sites. Crystallographic examination, and visco-clastic and chlorinity measurements, were made all along the cores. Results indicate that the ice body of t-3 is composed of three strata; the stratum above a heavy dirt layer is composed of iced firn which shows a granular nature with crystalline facets; that below the dirt layer is “basement ice”; and at the bottom is a sea-ice layer 1.8 m. thick. The basement ice is subdivided into four strata. Petrographic studies of dirt samples obtained from the surface and from the ice cores were carried out by an X-ray diffraction method; from the results, the dirt is thought to be dust of Precambrian granite or gneiss, which are the prevailing rocks in Ellesmere Island. The structure of t-3 was inferred from assumptions based on the data obtained from the core drillings at the two sites.