Measurements of the diffusion constants in single crystals of ice in directions parallel and perpendicular to the c-axis are described. The anisotropy of activation energy was obtained. The higher activation energy perpendicular to the c-axis indicates the free interstitial molecular jump mechanism for diffusion in ice. (Author).

The Advanced Study Institute Ice Physics in the Natural and Endangered Environ ment was held at Acquafredda di Maratea, Italy, from September 7 to 19, 1997. The ASI was designed to study the broad range of ice science and technology, and it brought together an appropriately interdisciplinary group of lecturers and students to study the many facets of the subject. The talks and poster presentations explored how basic molecular physics of ice have important environmental consequences, and, con versely, how natural phenomena present new questions for fundamental study. The of lectures discusses these linkages, in order that overall unity of following sunimary the subject and this volume can be perceived. Not all of the lecturers and participants were able to contribute a written piece, but their active involvement was crucial to the success of the Institute and thereby influenced the content of the volume. We began the Institute by retracing the history of the search for a microscopic un derstanding of melting. Our motivation was straightforward. Nearly every phenome non involving ice in the environment is influenced by the change of phase from solid to liquid or vice-versa. Hence, a sufficiently deep physical picture of the melting tran sition enriches our appreciation of a vast array of geophysical and technical problems.