456 Sayles — Dilemma of Paleoclimatolo gists. 



Art. XLI. — The Dilemma of the Paleoclimatolo gists; by 

 Robert W. Sayles, Harvard University. 



The so-called Glacial Theory was promulgated about 

 1835 by Agassiz and Carpentier. Since that time geolo- 

 gists have sought 'diligently to discover the cause or 

 causes of periods of giaciation, and one theory after 

 another has been propounded to account for them, but up 

 to the present time no one of the many explanations has 

 proved wholly adequate. 



In 1855 A. C. Ramsey advocated the glacial origin of 

 certain breccias of Permian age in the Midland district of 

 England, but there were very few who accepted his view. 

 In 1856 the Blandford Brothers discovered the Talchir 

 glacial conglomerate or tillite in the Cuttack district of 

 India. Discoveries of tillites of the same age as those of 

 India were soon made in South Australia and South 

 Africa, then in South America, North America at Boston, 

 then in Alaska. There are a number of conglomerates in 

 other parts of the world of late Carboniferous or early 

 Permian age which may be glacial in origin. 



Tillites that occur at other points in the time scale have 

 now been made known. Thus, in 1908, Coleman found 

 glacial striae on pebbles and bowlders in the Cobalt con- 

 glomerate of Huronian age at Cobalt, Ontario. Although 

 geologists had accepted the Permo-Carboniferous giacia- 

 tion and the late Proterozoic or early Cambrian evidence 

 of giaciation, it was more or less of a strain on their faith 

 to believe that the earth was cool enough to permit of a 

 period of giaciation in the Huronian. But the gradually 

 increasing confidence in the planetesimal hypothesis of 

 Chamberlin and Moulton would do away with presump- 

 tion of a hot globe growing progressively cooler and 

 cooler, which was the prevailing belief of the geologists 

 of the 19th century — this, of course, based on the nebular 

 hypothesis of La Place. 



More evidence of giaciation from all parts of the geolog- 

 ical column has come in. In addition to the Huronian and 

 Permo-Carboniferous glaciations, evidence of giaciation 

 in the Late Proterozoic, Lower Cambrian, Lower Ordo- 

 vician, Silurian, Late Silurian or Early Devonian, Trias- 

 sic, Cretaceous, Eocene, and Miocene, has been found. 1 



1 For references, arranged alphabetically, see the close of this paper. 



