SCIENCE 



NEW YORK, APRIL 17, 1891. 



EUROPE DURING AND AFTER THE ICE AGE. 



Ten lectures under this title have been given by Professor 

 James Geikie of the University of Edinburgh, beginning 

 March 13 and ending April 10, as one of the courses of the 

 Lowell Institute, Boston. 



Beginning with descriptions of the physiography of Europe 

 and of the present glaciers of the Alps, Professor Geikie 

 afterward described successively the glacial deposits of the 

 Alps and adjacent lower lands, of the British Isles, and of 

 the Scandinavian Peninsula, northern Germany, Finland, 

 and north-western and northern Russia. The accompanying 

 map of Europe at the climax of the glacial period delineated 

 the maximum area of the European ice-sheet nearly as it is 

 mapped in this authors "Prehistoric Europe," but repre- 

 sented it as extending farther north-east, so as to cover the 

 northern part of the Ural Mountains. A very perfect demon- 

 sti'ation of the origin of the till or bowlder-clay by the agency 

 of land-ice is supplied by this order of presentation, first con- 

 sidering the development of the till, moraines, aryl glacial 

 strise, in the valleys and lowlands bordering the Alps, where 

 glaciers still exist, being evidently the shrunken representa- 

 tives of their formerly much greater extent during the 

 glacial period or ice age. No theorist has ever claimed a 

 marine origin for these glacial deposits. Thence Professor 

 Geikie proceeds to the similar Scottish till, which in all its 

 characteristics and in its distribution, scanty in the valleys 

 of the mountains and highland districts, but spread thickly 

 on the lowlands, is manifestly the exact analogue of the 

 Swiss ground-moraine. Both, therefore, are attributable to 

 land-ice. . And the same argument includes likewise the 

 similar but far more extensive deposits of till and fluvio- 

 glacial detritus which thickly cover the low tracts of Sweden, 

 Denmark, northern Germany, and a large part of Russia. 

 During the final melting of the ice-sheets, much of the finest 

 detritus which had been incorporated with their lower por- 

 tion was borne far away by rivers, and deposited as loess in 

 the valleys and on flat lands, or in some places in broad 

 shallow lakes. 



One interglacial epoch, and perhaps more than one, inter- 

 rupted the severe cold of the ice age in Europe. For a long 

 time, between two epochs of glaciation and accumulation of 

 till, a mild interglacial climate permitted southern animals 

 and plants to extend into Great Britain and northern Ger- 

 many; and during this time the ice-sl^eets were doubtless 

 wholly melted away, or were as much restricted as now, 

 remnants of them lingering only in the Alps and on the 

 mountainous plateau of Scandinavia. 



After this mild and even warm interval, which was of long 

 duration, the glaciers of the Alps again spread out to the 

 lowlands, but not so far as before; and ice-sheets were again 

 accumulated upon the British Isles, Scandinavia, Finland, 

 and northern Germany, but they too were less extensive 

 than in the earlier glacial epoch. The British ice-sheet 

 during that earlier epoch had extended south to the Thames; 



but the ice of the later epoch, according to Professor Geikie, 

 though again wholly enveloping Scotland, reached into 

 England only to Lincolnshire. The earlier British ice-sheet 

 certainly, and the later one probably, were confluent with the 

 ice which deployed from Scandinavia southward in a broad 

 mer de glace over the area of the North Sea, bringing Nor- 

 wegian bowlders to the shores of England. All of Scandi- 

 navia, excepting a small tract of southern Sweden, appears 

 to have been covered by the ice-sheet of the latest glacial 

 epoch, which also, as mapped by Professor Geikie, reached 

 east over Lapland to the White Sea, and over Finland nearly 

 to Lakes Onega and Ladoga, but did not cover the Gulfs of 

 Finland and Riga. Toward the south and west, however, 

 the "great Baltic glacier," a lobe of this latest ice-sheet of 

 north-western Europe, filled the basin of the Baltic Sea and 

 overflowed the low northern margin of Germany to Berlin, 

 and the eastern half of Denmark. The extreme limits of the 

 earliest European ice-sheet are not generally marked by 

 terminal morainic accumulations, but rather by extensive 

 stratified deposits of gravel and sand. On the other hand, 

 the later glaciation is bounded in many places by prominent 

 hilly and knolly terminal moraines, with abundant erratic 

 blocks. 



Since the ice age, there is evidence, in the fossil faunas 

 and floras of marine deposits and peat bogs, that north- 

 western Europe has experienced for some time a climate con- 

 siderably warmer than that of the present day ; and the 

 speaker compared this with the formerly warmer waters of 

 the Atlantic on the shores of New England and the eastern 

 provinces of Canada, which allowed various species of south- 

 ern mollusks in the postglacial or recent epoch to extend 

 northward to the Gulf of St. Lawrence, though now they 

 have become mainly extinct north of Cape Cod, excepting a 

 few colonies that survive in favorable localities. These 

 climatic changes following the glacial period unite the whole 

 quaternary era as characterized from its beginning to the 

 present day by numerous alternations from severity to mild- 

 ness of climate, and the reverse. 



Inquiring what were the causes of the ice age, Professor 

 Geikie pointed out its complex character, with two or more 

 epochs of severe climate and ice accumulation, divided by 

 recession of the ice and long-continued mild conditions; and 

 he especially called attention to the Alpine glaciation and 

 the ice- sheets of north-western Europe as simply the increased 

 and greatly extended development of the glaciers that still 

 are found in Switzerland and Scandinavia. A lowering of 

 the mean temperature of Europeby twelve degrees might grad- 

 ually restore the ice-sheets. The short estimates of the time 

 (7,000 to 10,000 years) that has passed since the latest glacia- 

 tion of the northern United States, given by N. H. Winchell, 

 Andrews, Gilbert, and Wright, from their consideration of the 

 recession of w^aterfalls and erosion of river-gorges, as stated 

 in Wright's "Ice Age in North America," are pronounced 

 by Professor Geikie unreliable; and he maintains the astro- 

 nomic theory of his friend and colleague, the late Dr. James 

 Croll, which accounts for glacial epochs by eccentricity of 

 the earth's orbit, placing the close of the latest glaciation 



