530 



SCIENCE. 



[N. S. Vol. II. No. 43. 



and denudation ; that renewed accumula- 

 tion and growth of the ice sheets, but mostly 

 without extending to their earlier limits, 

 were followed by a general depression of 

 these burdened lands, after which the ice 

 again retreated, apparently at a much faster 

 rate than before, with great supplies of loess 

 from the waters of its melting ; that moder- 

 ate reelevation ensued, and that during the 

 farther retreat of the ice sheets prominent 

 moraines were amassed in many irregular 

 but roughly parallel belts, where the front 

 at successive times paused or re-advanced 

 under secular variations in the prevailingly 

 temperate and even warm climate by which, 

 between the times of formation of the mo- 

 raines, the ice was rapidly melted away. 



Such likeness in the sequence of glacial 

 conditions doubtless implies contempo- 

 raneous stages in the glaciation of these two 

 continents; and the present writer believes 

 that it is rather to be interpreted as a series 

 of phases in the work of a single ice sheet 

 on each area than as records of several 

 separated and independent epochs of glaci- 

 ation, differing widely from one another in 

 their methods of depositing drift. 



Under the latter view, however, Geikie 

 distinguishes no less than eleven stages or 

 epochs, glacial and interglacial, which he 

 has very recently named (Journal of Geol- 

 ogy, Vol. III., pp. 241-269, April-May, 

 1895), since the publication last year of the 

 new edition of his ' Great Ice Age,' in 

 which, however, they were fully described. 

 These divisions of the Glacial period are 

 as follows: 1. The Scanian or first glacial 

 epoch; '2. The Norfolkian or first inter- 

 glacial epoch ; 3. The Saxonian or second 

 glacial epoch; 4. The Helvetian or second 

 interglacial epoch; 5. The Bolandian or 

 third glacial epoch ; 6. The Neudeckian or 

 third interglacial epoch; 7. The Mecklen- 

 burgian or fourth glacial epoch; 8. The 

 Lower Forestian or fourth interglacial 

 epoch ; 9. The Lower Tui-bariau or fifth 



glacial epoch ; 10. The Upper Forestian or 

 fifth interglacial epoch ; and 11. The Upper 

 Turbarian or sixth glacial epoch. 



The earliest application of such geo- 

 graphic names to the successive stages and 

 formations of the Ice age appears to be 

 that of Chamberlin in his two chapters con- 

 tributed to the new third edition of Geikie's 

 admirable work before mentioned, in which 

 he names the Kansan, East lowan, and 

 East Wisconsin formations. For the second 

 and third he has since adopted the shorter 

 names, lowan and Wisconsin. This classi- 

 fication he has more recently extended 

 (in the Journal of Geology, Vol. III., pp. 

 270-277, April-May, 1895), the interglacial 

 stage and deposits between the Kansan and 

 lowan till formations being named Aftonian, 

 and the Toronto interglacial formation, 

 previously named, being referred, with 

 some doubt, to an interval between the 

 lowan and Wisconsin stages. Chamberlin 

 correlates, with a good degree of confidence, 

 his Kansan stage of maximum North 

 American glaciation with the maximum in 

 Europe, which is Geikie's Saxonian epoch ; 

 the Aftonian stage as Geikie's Helvetian ; 

 the lowan as the European Polandian ; and 

 the Wisconsin or moraine-forming stage of 

 the United States as the Mecklenburgian, 

 which was the stage of the ' great Baltic 

 glacier' and its similarly well developed 

 moraines. According to the law of priority, 

 the names of the Kansan, lowan and Wis- 

 consin formations and stages should also 

 be applied to these European divisions of 

 the Glacial series, for the studies of Geikie 

 and Chamberlin show them to be in all 

 probability correlative and contempo- 

 raneous. 



Diifering much from the opinions of Gei- 

 kie, and less widely from those of Cham- 

 berlin, concerning the importance, magni- 

 tude and duration of the interglacial stages, 

 but agreeing with Dana, Hitchcock, Wright, 

 Kendall, Falsan, Hoist, Nikitin and others 



