2 A. P. COLEMAN 



similar to those of later, fossiliferous, series. The mystery has 

 largely departed from them. 



So far as the Huronian or Algonkian is concerned everyone 

 admits that the rocks, both sedimentary and eruptive, were formed 

 like those of later times. It is true that the absence of fossils in 

 the east and their great rarity in the West is a puzzle; but all agree 

 that the pre-Cambrian seas were not so different from later waters 

 as to be uninhabitable, and that forces at work in the Huronian 

 did not differ materially from those which formed the Cambrian 

 or later rocks. 



To have this brought concisely before one it is only necessary 

 to read Van Hise and Leith's late edition of the pre-Cambrian 

 geology in North America, a work of admirable completeness and 

 impartiality, summing up a literature of appalling dimensions. 

 The former chaos has then been so far set in order that we find 

 evidence in Huronian or Algonkian times of climates not unlike 

 those of later ages, when wind and weather, flowing rivers and 

 beating waves, and even great ice sheets did their regular work. 

 In northern Ontario glaciers formed bowlder clay in lat. 46 , show- 

 ing no hint of the action of primeval heat, such as the usually 

 accepted version of the Nebular Hypothesis demands. 



But there is much less certainty and much less unanimity 

 regarding pre-Huronian times. The Huronian is cut off from the 

 underlying rocks by one of the greatest known discordances. 

 During the interval left unrecorded in this great unconformity 

 the previous rocks were raised into mountains, metamorphosed by 

 the action of intrusive granite and gneiss, and then profoundly 

 eroded. The proofs of this are to be found in the bowlders of the 

 Huronian tillite, which include all the lower rocks in their present 

 metamorphosed conditions; and in the hummocky plain formed 

 from the previous mountain ranges which in many places underlies 

 the little-disturbed Huronian. 



The world was already very old and had undergone many vicissi- 

 tudes before the Huronian ice sheets began their work. What 

 light can be thrown on the vast and vague pre-Huronian time ? 



Many geologists have been inclined to see in the underlying 

 " basal complex," or Urgebirge, portions of the earth's original 



