Sayles — Dilemma of Paleoclimatolo gists. 157 



The Lower Ordovician glaciation mentioned above was 

 found by the writer in the presence of T. H. Clark on Sep- 

 tember 21st, 1921, at Levis, Quebec, in shales of Beekman- 

 town age. The evidence of it is a tillite of the submarine 

 or sublacustrine variety, varying in thickness from about 

 four to eight feet. The shale below and above it is very 

 regularly banded suggesting seasonal deposition. 



Note — Since making this discovery Professor Coleman has 

 called the attention of the writer to his Presidential Address 

 before the Royal Society of Canada, in April, 1921, in which he 

 states his belief in the glacial origin of the Levis conglomerates. 



Three papers of great importance to paleoclimatolo- 

 gists have appeared in America in the last three years 

 The first by Knowlton 2 in 1919, the second and the third 

 respectively by Coleman 3 and Schuchert 4 in 1921. Knowl- 

 ton claims on paleobotanical evidence, that before the 

 Pleistocene there was a non-zonal arrangement of earth 

 temperature, and that the surface temperature was warm- 

 humid from poles to equator, for the most part, through- 

 out the entire geological record. He explains this by the 

 hypothesis of Marsden Manson 5 which calls for a cloud 

 sphere that shut out the greater part of sunlight and heat 

 rays, and thus surface temperatures were kept up by the 

 heat of the earth itself through the ocean waters. Knowl- 

 ton claims that glacial periods were often accidents in the 

 history of the earth, and that many of the tillites indicate 

 glaciation of a local nature only. He also claims that 

 Manson 's theory explains the almost tropical distribution 

 of Permo-Carboniferous glaciation better than any other, 

 this notwithstanding the fact that tillites of this age have 

 been found in Alaska. 



Knowlton 's evidence for the general mild climates 

 for the earth during many periods cannot be doubted, 

 but when he totally eliminates seasons during these times 

 of warmth the geologists demand explanations of many 

 things. Coleman and Schu chert have shown many excel- 

 lent reasons for believing that the sun held sway and sea- 

 sons existed in the warm periods as now, although sea- 

 sons were less marked during the warm episodes than our 

 seasons today. 



The writer has asked Dr. Knowlton to explain many 

 things which seemed incompatible with his ideas of a uni* 



Am. Jour. Sci. — Fifth Series, Vol. Ill, No. 18.— June, 1922. 

 32 



