1 (return) Neogene: Pleistocene Pliocene Miocene. Palaeogene: Oligocene Eocene. This differs chiefly from Lyell's classification in the introduction of the term Oligocene for the upper part of the original Eocene, which was somewhat unwieldy. In the earlier editions of the "Antiquity of Man" and of the "Principles of Geology," the strata here classed as Pleistocene were designated as Post-pliocene. The term "diluvium," now obsolete in Britain but still lingering on the Continent, is equivalent to Pleistocene. This subdivision is still sometimes separated from the Tertiary, as the Quaternary epoch. This, however, is unnecessary and indeed objectionable, as attributing too great importance to relatively insignificant deposits. There is no definite break, either stratigraphical or palaeontological, at the top of the Pliocene, and it is most natural to regard the Tertiary epoch as still in progress. Equally unnecessary is the separation of the post-glacial deposits as "Recent," a distinction which still prevails in many quarters, apparently with the sole object of adding another name to an already over-burdened list.] 2 (return) 3 (return) 4 (return) 5 (return) 6 (return) 7 (return) 8 (return) 9 (return) 10 (return) 11 (return) 12 (return) The stages of Palaeolithic culture now recognised are as follows:— Below the Mesvinian comes the nebulous region of "eoliths," which are not yet definitely proved to be of human workmanship. The Neanderthal skull belongs to the Mousterian stage, but the oldest known definitely human remain, the jaw from the Mauer sands near Heidelberg, may be older than any of these, indeed by some it is assigned to the first interglacial period of Penck and Bruckner (see Note 32). For figures of the types of implement characterising each period, see "Guide to the Antiquities of the Stone Age in the Department of British and Medieval Antiquities," British Museum, 2nd edition, London, 1911, pages 1 to 74. This publication gives an admirable summary of recent knowledge on this subject. For an excellent and critical summary of the latest researches on Palaeolithic man up till the end of the Aurignacian period, see Duckworth, "Prehistoric Man," Cambridge, 1912. See also note 44.] 13 (return) 14 (return) 15 (return) 16 (return) 17 (return) Mention may conveniently be made here of the supposed discovery of the remains of pre-glacial man at Ipswich, which appears to be founded on errors of observation. The boulder-clay above the interment is, according to the best authorities, merely a landslip or flow.] 18 (return) 19 (return) 20 (return) Pleistocene: Peat and Alluvium Gravel Terraces of the present river systems Gravels of the old river-systems Plateau gravels Chalky boulder-clay Interglacial sands and gravels and Contorted Drift Cromer Till Arctic Plant Bed. Pliocene: Cromer Forest Series Weybourn Crag Chillesford Crag Norwich Crag Red Crag Coralline Crag. 21 (return) 22 (return) From a study of these erratics it has been found possible to draw important conclusions as to the direction and sequence of the ice streams which flowed over these regions during the different stages of the glacial period.] 23 (return) A great amount of valuable information concerning the glacial conditions of Greenland is to be found in the "Meddelelser om Gronland," a Danish publication, but containing many summaries in French or English. For a good account of the phenomena seen in the coastal region of the west coast, see Drygalski, "Gronland-Expedition," a large monograph published by the Gesellschaft fur physischen Erdkunde, Berlin, 1897.] 24 (return) 25 (return) 26 (return) 27 (return) The shell-bearing deposits of Moel Tryfan were examined by a committee of the British Association. (See "Report of the British Association" Dover, 1899, pages 414 to 423.) At the end of this report is an extensive bibliography.] 28 (return) 29 (return) 30 (return) 31 (return) 32 (return) 33 (return) 34 (return) 35 (return) The greatest development of the Loess is in Central Asia and in China. (See Richthofen, "China," Berlin, 1877.) In China the Loess reaches a thickness of several thousand feet, and whole mountain-ranges are sometimes almost completely buried in it. In the deserts of Central Asia the formation of the Loess is still in progress. A very similar deposit, called adobe, is also found in certain parts of the Mississippi valley. The Loess is a fine calcareous silt or clay of a yellowish colour, quite soft and crumbling between the fingers. However, it resists denudation in a remarkable manner, and in China it often stands up in vertical walls hundreds of feet in height. This property is probably assisted by the presence of numerous fine tubes arranged vertically and lined with calcium carbonate; these are supposed to have been formed in the first place by fibrous rootlets.] 36 (return) 37 (return) As examples of astronomical explanation, we may take the well-known theory of Adhemar and Crohl, which is founded on changes in the ellipticity of the earth's orbit. This is expounded and amplified by Sir Robert Ball in his "Cause of an Ice Age." The weak point of this theory, which is mathematically unassailable, is that it proves too much, and postulates a constant succession of glacial periods throughout earth-history, and for this there is no evidence. The geographical explanations are chiefly founded on supposed changes in the distribution of sea and land, with consequent diversion of cold and warm currents. Another suggestion is that the glaciated areas had undergone elevation into mountain regions, but this is in conflict with evidence for submergence beneath the sea in certain cases. Meteorological hypotheses, such as that of Harmer, founded on a different arrangement of air pressures and wind-directions, seem to offer the most promising field for exploration and future work, but it is clear that much still remains to be explained.] 38 (return) 39 (return) 40 (return) 41 (return) 42 (return) 43 (return) 44 (return) |