THE PLEISTOCENE CLISERES AND COSERES. 



371 



from a southerly direction, but ranging well toward both the east and the west. 

 They would be strong winds, for under the assumed conditions of our hypoth- 

 esis the barometric gradients would be steep and the storms would be more 

 severe than at present. The constant indraft of air from the deserts would 

 bring with it great amounts of dust, which would be deposited in the regions 

 where the glacial streams were depositing their outwash. The net result 

 would be either the accumulation of pure wind-blown loess in areas not subject 

 to inundation by glacial streams, or the deposition of an intermixture of loess 

 and fluvio-glacial materials in the areas where the streams from the ice were 

 laying down their burdens. The agreement of this condition with that which 

 we know to have been the case during the Glacial epoch scarcely needs to be 

 pointed out" (577). 



Glacial-interglacial cycles. — The existence and number of interglacial stages 

 constitute one of the most debated of geological questions. At present, the 

 weight of opinion is overwhelmingly on the aflSrmative side, and the discussion 

 is almost wholly confined to the niunber of glacial-interglacial cycles. Cham- 

 berlin and Salisbury (1906:3:383) recognize six in North America, and Geikie 

 (1895 : 241) distinguishes the same number for Europe. European opinions, 

 however, are still widely divergent, Keilhack recognizing three, Penck four, 

 and Schulz five (Jerosch, 1903 : 225), the tendency evidently being in the 

 direction of an increased number of divisions. The number of cycles in 

 America seems so well established, and shows such a striking agreement with 

 the number distinguished by Geikie, in spite of the lack of certain correlation 

 between them, that the existence of six glacial and six interglacial phases 

 must be regarded as constituting the most probable view. The American and 

 European stages established upon this basis are shown below. The position 

 in the table is numerical, the earhest stages at the bottom and does not indi- 

 cate correlation, except provisionally. 



Chamberun and Salisburt. 



Geikie. 



Glacial. 

 6. Later Wisconsin. 

 6. Earlier Wisconsin. 

 4. lowan. 

 3. Illinoian. 

 2. Kansan. 

 1. Jerseyan. 



Glacial. 



Interglacial. 

 6. Glado-lacustrine. XII. 



XI. 6. Upper Turbarian. 

 5. (Unnamed.) X. 



IX. 6. Lower Turbarian. 

 4. Peorian. VIII. 



VII. 4. Mecklenburgian. 

 3. Sangamon. VI. 



v. 3. Folandian. 

 2. Yarmouth. IV. 



III. 2. Saxonian. 

 1. Aftonian. II. 



I. 1. Scanian. 



InterglacicU. 

 (Postglacial.) 



5. Upper Forestian. 



4. Lower Forestian. 



3. Neudeckian. 



2. Helvetian. 



1. Norfolkian. 



The Pleistocene flora. — This appears to be wholly identical as to genera, and 

 essentially identical as to species with that of to-day (Penhallow, 1900 : 334; 

 Reid, 1899 : 171). While the advances of the ice were enormously destructive 

 of vegetation, they seem to have had no such effect upon the flora and its 

 life-forms. A small number of genera occur in the Miocene which are not 

 found in existence to-day, but, as they are lacking in both the PHocene and 

 Pleistocene, it is not certain that their extinction was due to the ice. Out of 

 267 species listed by Reid for Europe from the Preglacial to the Roman epoch, 

 all occur to-day, while 213 persisted through one or more glacial epochs. 

 However, these are practically all species of boreal and cold-temperate regions 



