382 ANNUAL. EEPOET SMITHSONIAN INSTITUTION, 1910. 



But opinion had scarcely more than settled down to this interpreta- 

 tion, with a reluctant acceptance of the glacial evidence, when the 

 geologists of Australia, of India, and of South Africa, severally and 

 independently, and later those of South America, brought evidences 

 of still earlier glaciation prevalent over wide areas in those low 

 latitudes. The marks of glaciation were altogether typical and 

 were traced up to and even somewhat bej^ond the tropical circles 

 from both sides and in the same quarter of the globe, from Australia 

 on the south and from India on the north. Moreover, all these cogent 

 evidences were reported for strata referred to the Permian or Permo- 

 Carboniferous times, i. e., from about the middle of our scale of 

 technical time periods. For a score of years the body of geologists 

 who could not personally inspect the evidence doubted its interpreta- 

 tion as surely indicating the presence of ice sheets in those low 

 latitudes and at that early time, but the evidence under constantly 

 renewed and broadened scrutiny by trained glacialists steadily grew 

 till it became irrefutable. There seems now no rational escape from 

 the conclusion that mantles of ice covered large areas in the penin- 

 sula of India, in Australia, in the southern part of Africa, and in 

 South America close upon tlie borders of the Tropics at a time roundly 

 halfwaj^ back to the beginning of the readable record of life. 



On the basis of evidences of like kind and cogency, Strahan and 

 Eeusch, independently, have reported glacial beds in Norway at a 

 much earlier geological horizon, but one not closely determinate. 

 "Willis and Blackwelder have described glacial deposits of early 

 Cambrian age in the valley of the Yangtse in China in latitude as 

 low as 31° N. Howchin and David have described glacial forma- 

 tions of similar age in Australia. In the last two cases the glacial 

 beds lie beneath strata that bear Cambrian trilobites; in other words, 

 they are at the very bottom of the fossil-bearing sediments, 15 

 periods back, or 75,000.000 years ago, on our rough scale. Prof. 

 Coleman has offered what he deems good evidence of glaciation 

 much farther back at the base of the Huronian terrane in Canada, 

 but some skepticism as to the interpretation still lingers. 



Even more pointedly than the epochs of aridity previously cited 

 do these early epochs of glaciation seem irreconcilable with the old 

 view of a hot earth, universally wrapped in a vaporous mantle in 

 early times. They favor, if they do not force, the alternative view 

 that the ancient climates were marked much as the more modern 

 ones have been by periodic and local oscillations and intensifications, 

 and that life was able to survive all of these in some part of the 

 globe, if not in most parts. This warrants the hope, if not the 

 belief, that life may survive similar oscillations and intensifications 

 again and again in the future as in the past. 



