CENOZOIC TIME — QUATERNARY. 941 



included under his second division of the Pliocene, called Newer Pliocene. In 1839, he 

 proposed to substitute Pleistocene for Newer Pliocene, as a fourth division of the Tertiary, 

 characterized by having about 95 per cent of the shells those of living species — a larger 

 proportion, as the name implies, than in the earlier part of the Pliocene. But the new 

 name, as he states, was used by E. Forbes in 1846 and others for the Post-Pliocene instead 

 of the Newer Pliocene, and he withdrew it. The perverted use of the term was partly 

 owing to his retaining Glacial and related topics under the Newer Pliocene — an arrange- 

 ment which was continued into the 5th edition of his Manual of Elementary Geology, 

 published in 1855. This was later changed. But in the 4th edition of the Antiquity of 

 Man (1873) Pleistocene was finally adopted as a substitute for Post-Pliocene. 



The term Quaternary was used by Keboul, of France, in his work La Geologie de la 

 Periode Quaternaire, 8vo., 1833. 



The division of the Post-Tertiary or Quaternary into the three periods mentioned 

 above was presented by the Author in his address on " American Geological History" 

 before the American Association, in August, 1855. (Amer. Jour. Sc, xxii., 305, 1856.) 

 The names for these subdivisions then proposed were the Glacial, an epoch of elevation ; 

 the Laurentian, an epoch of depression ; and the Terrace, an epoch of moderate elevation. 

 In the first edition of this Geology (1863), the terms adopted were Glacial, Champlain, 

 and Terrace. 



The two earlier periods, the Glacial and Champlain, have their more 

 prominent characteristics displayed almost solely over high-latitude regions. 

 They are not represented in tropical latitudes, or in warm temperate 

 latitudes south of the parallel of 35°, except locally about regions of lofty 

 mountains. Moreover, deposits, like those of the Champlain period, were 

 forming through the Glacial period along the southern border of the ice- 

 sheet, owing to the melting that was going on, and the streams that were 

 thereby made, especially in the summers, and still more largely during 

 temporary relaxations of the extreme cold. Further, the Mammals of 

 temperate climates that spread northward over the previously glaciated 

 area when the Champlain period opened, probably were all in existence 

 during the middle and later parts of the Glacial period, after the epoch of 

 extremest cold and maximum extension of the ice had passed, if not earlier. 

 Glacial and Champlain phenomena were thus cotemporaneous. Nevertheless 

 the periods stand well apart in the great epeirogenic movement, or change 

 of level, that separates them, and in the continuation of Champlain con- 

 ditions long after the ice had disappeared. 



Bevieio of modern Glacial phenomena. — The general phenomena and laws of Glacial 

 Geology have been stated on pages 232-250, and illustrated in part by facts from an existing 

 continental glacier — that of Greenland. As there explained, the glacier moves over hills 

 and ridges, up slopes as well as down, the pitch of its upper surface determining its direc- 

 tion and rate of movement. It is greatly aided in excavating work by subglacial streams, 

 that are far more effectual workers than ice ; which streams in Greenland, according 

 to H. Rink, probably branch widely over the country, like a regular river-system, and 

 have at times great volume. It gathers stones, gravel, and sand, for transportation, as 

 well as large rock-masses. It abrades, through the stones at bottom, rocky surfaces 

 passed over, and corrades the transported material, making rock-flour, sand, gravel, and 

 smoothed or scratched stones out of the debris taken aboard ; and it may convert the 

 finer material into clay. It deposits rock-flour and other debris from subglacial streams 



