1. The Last Great Arctic climate. 30,000-18,000 B. C. Glaciation. 2. The Retreat of the Severe continental 18,000-6000 B. C. Glaciers. climate. 3. The Continental Phase. Continental climate. 6000-4000 B. C. 4. The Maritime Phase. Warm and moist. 4000-3000 B. C. 5. The Later Forest Phase. Warm and dry. 3000-1800 B. C. 6. The Peat-Bog Phase. Cooler and moister. 1800 B. C.-300 A. D. 7. The Recent Phase. Becoming drier. 300 A. D.- Brooks bases his chronology largely on De Geer's measurements of the annual layers of clay in lake bottoms but makes much use of other evidence. According to Brooks the last glacial epoch lasted roughly from 30,000 to 18,000 B. C., but this includes a slight amelioration of climate followed by a readvance of the ice, known as the Buhl stage. During the time of maximum glaciation the British Isles stood twenty or thirty feet higher than now and Scandinavia was "considerably" more elevated. The author believes that this caused a fall of 1 deg.C. in the temperature of the British Isles and of 2 deg.C. in Scandinavia. By an ingenious though not wholly convincing method of calculation he concludes that this lowering of temperature, aided by an increase in the area of the lands, sufficed to start an ice sheet in Scandinavia. The relatively small area of ice cooled the air and gave rise to an area of high barometric pressure. This in turn is supposed to have caused further expansion of the ice and to have led to full-fledged glaciation. About 18,000 B. C. the retreat of the ice began in good earnest. Even though no evidence has yet been found, Brooks believes there must have been a change in the distribution of land and sea to account for the diminution of the ice. The ensuing millenniums formed the Magdalenian period in human history, the last stage of the Paleolithic, when man lived in caves and reindeer were abundant in central Europe.[96] At first the ice retreated very slowly and there were periods when for scores of years the ice edge remained stationary or even readvanced. About 10,000 B. C. the edge of the ice lay along the southern coast of Sweden. During the next 2000 years it withdrew more rapidly to about 59 deg.N. Then came the Fennoscandian pause, or Gschnitz stage, when for about 200 years the ice edge remained in one position, forming a great moraine. Brooks suggests that this pause about 8000 B. C. was due to the closing of the connection between the Atlantic Ocean and the Baltic Sea and the synchronous opening of a connection between the Baltic and the White Seas, whereby cold Arctic waters replaced the warmer Atlantic waters. He notes, however, that about 7500 B. C. the obliquity of the ecliptic was probably nearly 1 deg. greater than at present. This he calculates to have caused the climate of Germany and Sweden to be 1 deg.F. colder than at present in winter and 1 deg.F. warmer in summer.