reached the wider international scientific community. The Swedish Time Scale In 1897 De Geer was appointed professor of geology at Stockholm University, and went on to become the university's president from 1902 to 1910. With the help of numerous students from both Stockholm and Uppsala, De Geer began to piece together short, but overlapping, varve sequences in south east Sweden to create a longer year-by-year chronology of glacial retreat for the Lateglacial period. The urban expansion of Stockholm provided perfect conditions for De Geer and his colleagues, who made good use of numerous exposures of laminated sediment in the many pits and cuttings that exposed the glacial lake sediments of the Baltic basin. Estuarine sediments exposed along the valley of the Angermanalven River, allowed De Geer to further extend the chronology into the early Holocene. The resulting varve chronology was called the Swedish Time Scale, and geologists outside Sweden soon followed suit using varved sediments to build high-resolution chronologies of glacial retreat, most notably Matti Sauramo in Finland. Global expeditions, teleconnections, and controversy De Geer firmly believed the main control on varve sedimentation was solar radiation acting on glacier meltwater production, and that consequently, varved sediments represented a "..gigantic, natural self-registering thermograph" (De Geer 1926) and varve curves (varve thickness plotted against varve number or year), which he often referred to as "solar curves", a reliable proxy for past changes in solar radiation. Ultimately, De Geer hoped his studies of varves would explain the fundamental cause of Ice Ages - "If the last glaciation everywhere should show to be synchronous and the origin of the last Ice Age thus to be of a general nature, the assumption of a cosmic cause would scarcely be avoidable." In 1915 De Geer matched, or 'teleconnected", varve curves from Sweden to varve curves from Finland and Norway. This first attempt at long-distance correlation marked the start of two decades travelling around the world by De Geer and his colleagues, searching out varve sequences for potential teleconnections. In 1920 De Geer travelled to North America with his wife and two assistants, Ernst Antevs and Ragnar Liden. Antevs remained in North America at the end of the trip, where he worked on the North American varve chronology. Further trips included Erik Norin's visit to the Himalayas (1924–1925), Erik Nilsson's visit to East Africa (1927–28), and Carl Caldenius' visit to South America (1925–1929), and later to New