After travel through Alaska during the Second World War, in 1947 I went to Barrow with a very lively group of biologists. From their productive research developed the Arctic Research Laboratory. While we examined the rather surpris ingly modest metabolic rates of arctic warmblooded animals in cold, PER SCHO LANDER proposed and then carried out measurements of metabolism of some tropi cal animals in Panama. The differences could be formulated to show the basis of adaptation to arctic cold and to tropical warmth. Imagination and logic were required to formulate the comparison so that it could become a part of science, but the essential measurements were derived from animals and plants in their own arctic and tropical environments. Characteristics that adapt the forms of life to climatic conditions of various environments appear clear in the large dimensions of extremely differing climates. At the time of my arrival in Alaska many of the arctic Eskimos were still largely dependent on natural resources of their immediate and local environment, in which great seasonal changes in temperature and solar radiation appeared as dominant factors. The living environment on which they subsisted was also mar kedly affected by the changes of the seasons, in particular by the change in state of water to ice that terminated summer and by the melting that brought the late transition from winter to summer.

The Caledonides are a major orogenic belt that stretches from the Arctic, through Scandinavia, East Greenland, Britain and Ireland into the Atlantic coast of North America. Following the break-up of Rodinia, the Caledonides formed in the Palaeozoic by the drifting of various continents and their eventual aggregation in the Silurian and Devonian. The orogen subsequently fragmented during the opening of the Atlantic Ocean. This volume brings together 25 papers presenting the results of modern research that investigates the orogenic processes and the provenance of specific components of the belt. The contributions reflect different lines of research, linking traditional field studies with modern analytical techniques. In addition three overview papers summarize the main features of the belts in Scandinavia, Svalbard, East Greenland, Britain and Ireland, highlighting the advances made since the last major synthesis of the Scandinavian Caledonides 30 years ago, and discussing important open questions.