monuments. To the north and east of the county, much finer sands and gravels are found, including ball clay, which was widely mined on the heaths around Wareham. The fine particles that make up the clay are believed to have originated in the west, where rocks were being broken down by the alternating dry, humid conditions and torrential rain, which in turn formed rivers and carried the material to its current position. Overlying the clay is the Agglestone grit, an iron-cemented sandstone, which forms the Agglestone near Studland, and has been used in the buildings in and around the heathland where it is found. Fossilised palms taken from the cliffs at Bournemouth confirm that Dorset had a tropical climate at the time. Creech Barrow Hill is crowned with a unique early Eocene limestone that has yielded some important fossils. Outcrops of rock from the Barton Group occur along the coast between Bournemouth and Hengistbury Head. Late Paleogene to Neogene During this period, Dorset drifted a further 9° north, the climate cooled rapidly, and by the late Eocene was temperate. Mainly terrestrial with fresh and brackish water environments, the county, despite its low-lying nature, remained largely without marine influences except for some minor incursions at the end of the ice ages. The late Palaeogene deposits that filled the Hampshire Basin as the sea levels fell are not found in Dorset, nor are the Neogene, which are absent from virtually all of the British Isles. The collision of the African and Eurasian plates that occurred around this time caused a violent uplift in the south of the county, the results of which can be seen clearly at Stair Hole, where the strata run almost vertically. Further, but less dramatic folding and uplift, along the county's subsurface faults, coupled with continuing erosion of Jurassic and Cretaceous sediments, created Dorset's modern landscape and drainage patterns. Quaternary During the last 2,600,000 years, Britain was subjected to a number of extreme fluctuations in temperature, which included three ice ages. Dorset was not affected by glaciation, but did experience very low temperatures with permafrost on the high ground. Sudden changes in sea level, and successive warming and cooling, significantly modified the landscape. The two raised beaches at Portland created 210,000 and 125,000 years ago are a dramatic testament to the fluctuations in sea levels. The causes of these two fluctuations were twofold - the growth of the