268 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1916. 



Koolgardie a somewhat tilted conglomerate j like that of the American 

 Huronian, overlies the steeply dipping gneissoid rocks. 



PRE-HURONIAN LAND CONDITIONS. 



No unchanged land surface has yet been found below the peneplain 

 just described, but important land areas can be inferred with cer- 

 tainty, though now obliterated by squeezing and folding and the 

 metamorphism due to eruptive granites. The great development of 

 clastic sedimentary rocks included under the names of Seine Series, 

 Sudbury Series, Temiscaming Series, etc., widely distributed over the 

 Canadian Shield, imply broad lands and even mountain ranges far 

 older than those destroyed before the Huronian. 



They generally begin with a great basal conglomerate, so coarse 

 and bowldery sometimes as to suggest ice action, but squeezed and 

 rolled out and folded in wdth other rocks in ways that make the find- 

 ing of striated stones or a striated surface beneath quite hopeless. It 

 is, however, highly probable that the climate was in general cool and 

 moist, for the rocks are gray and often include arkoses, with little 

 weathered feldspars, though Lawson speaks of the Seine conglomer- 

 ate in one place as " fanglomerate " of desert formation. The rocks 

 as a whole suggest a continental origin, and their materials must 

 have come from the weathering of land surfaces. Some of the gray- 

 wackes and slates are very evenly bedded and show regular altera- 

 tions of coarser and finer materials, caused by varying seasons, either 

 warm and cold or wet and dry. They resemble the stratified silt and 

 clay laid down in glacial lakes at the end of the Pleistocene. Seder- 

 hohn's Bothnian slates, with seasonal banding, probably of somewhat 

 the same age, show similar conditions in Finland. 



Land can be discovered still farther down in the misty depths of 

 time, for the pebbles of the Seine and Dore conglomerates include far 

 older sedimentary rocks derived from the Keewatin or Couchiching 

 or Grenville series, showing vast destruction of land surfaces in pre- 

 Laurentian ages at the very beginning of the geological record. 



These glimpses of American land surfaces in a past twice removed 

 from the ancient pre-Huronian continent give one a strange vista 

 into a dim antiquity almost infinitely remote from a dweller in the 

 post-Pleistocene. There is no visible beginning to dry land on the 

 continent of America. 



WHY SHOULD THERE BE DRY LAND? 



Though it is commonly accepted that there were lands in the 

 earliest known times, there are geologists who hold a theory of the 

 origin of the world which logically excludes the possibility of land 

 showing itself above the sea. The original nebular hypothesis, if 



