Ivory is an opaque, creamy white, hard, fine-grained, modified dentin that composes the upper incisor teeth of an elephant. Ivory is composed of curved layers of dentine alternating in shade, that intersect one another; the resulting lozenge-shaped structure is elastic and finely grained. The layers of a tusk are deposited from the central pulp, so that the innermost layer is the newest. Most commercial elephant ivory is obtained from the tusks of the African elephant, mainly from eastern and central Africa. (Most of the ivory of the western half of Africa is hard, whereas that from the eastern half is soft. Hard ivory is glassier in texture, harder to cut and more likely to crack than soft ivory.)
Fossil ivory, called odontolite, is a blue variety that is found in small quantities in the frozen soil of northern Siberia. Odontolite was produced by the mammoths of the Pleistocene geological epoch; its blue colour results from saturation by metallic salts. Carved ivory has been used for decorative purposes since the time of the ancient Egyptians. Small pieces of ivory are used for high-quality furniture inlays, chess pieces, and small jewellery. Larger pieces of ivory sometimes have been used in the manufacture of billiard balls, piano keys, and toilet articles.
During the late 1980s, as Africa's elephant herds declined, environmentalists led a world-wide effort to shut down the ivory trade; in 1989 the USA and the European Union banned all ivory imports. Tusks of several other animals such as hippopotamuses, narwhals, sperm whales, and walruses are commonly called ivory and have similar physical properties, and many plastic substitutes for ivory have been developed. Several ivory-like vegetable parts are also used in imitation of ivory; the ivory palm, for example, produces large, white, hard seeds, called ivory nuts, the endosperm of which is commonly known as vegetable ivory. In painting, ivory is a delicate colour deeper in tone than off-white, but not so deep as cream. Research Ivory
The Talgai skull is a fossil humancranium found in 1884 in the Darling Downs squatting district near Talgai, South Queensland, Australia. The fossil attracted no attention until the Sydney meeting of the British Association in 1914. A report presented by Dr S A Smith of Sydney to the Royal Society in 1918 showed the skull to belong to a male of about sixteen years old who was contemporary with Pleistocene marsupials now extinct. The skull's brain capacity was larger than that of modern Australian aborigines, and the enormous palate, while resembling that of the anthropoids more closely than any human jaw yet discovered, most closely resembled the palate of the recently extinct Tasmanians. In 1920 Dubois reported that two skulls found by him in Java in 1890, more primitive than the Australoid, supported the Queensland evidence that early man migrated from Asia into the Australian region in the distant past. Research Talgai Skull
Sir William Boyd Dawkins was a Welsh geologist and archaeologist. He was born in 1838 and died in 1929. Educated at Rossall and Jesus College, Oxford, he studied geology and was connected witli the Geological Survey; became lecturer on geology in the Owens College, Manchester, 1870, and in 1879 became professor of geology and palaeontology there. He travelled extensively and was geological adviser in connection with various engineering and mining enterprises, etc. His chief works were CaveHunting; Early Man in Britain and his Place in the Tertiary Period, a work throwing much light on prehistoric conditions in Britain; British PleistoceneMammalia. Research William Dawkins
The term ice age was first applied in 1837 by the botanist Karl Schimper (following the proposition of theories by, among others, the Swiss civil engineer Ignace Venetz in 1821 and the Swiss naturalist Louis Agassiz in 1837 in contrast to the held belief that the rocks and sediment left behind were caused by the biblical flood) to refer to a period of glaciation occurring in the Earth' s history, but is particularly applied to that in the Pleistoceneepoch, immediately preceding historic times when an ice sheet spread over northern Europe, leaving its remains as far south as Switzerland. There were several glacial advances separated by interglacial stages during which the ice melted and temperatures were higher than today. There were once thought to have been only three or four glacial advances, but recently it has been discovered that about twenty major incidences have occurred during earth's history. Other ice ages have occurred throughout geological time: there were four in the Precambrian era, one in the Ordovician, and one at the end of the Carboniferous and beginning of the Permian. The occurrence of an ice age is governed by a combination of factors known as the Milankovitch hypothesis: firstly, the Earth's change of attitude in relation to the Sun; and secondly the 92,000-year cycle of eccentricity in the earth's orbit around the Sun, changing it from an elliptical to a near circular orbit, the severest period of an ice age coinciding with the approach to circularity. Research Ice Age
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