Rl^SUMI^, AND GENERAL DISCUSSION. 547 



had as to the nature and age of the rocks to be designated by that term, 

 with especial reference to the name " Archaean," introduced by Dana, 

 as ah-eady mentioned, and which has of late years to a considerable 

 extent replaced both the Azoic of the Lake Superior Survey and the 

 Laurentian and Huronian of the Canada geologists. 



Dana, in that edition of his Manual in which he first introduces the 

 term Archtean, expressly says that " this formation [the Archtuan] was 

 first distinctly recognized in its true importance in the Ifeport of Fos- 

 ter and Whitney on the Lake Superior region, where it was named ' the 

 Azoic si/stem,^ " so that the natural inference would be that he intended 

 his " Archaean " to be the exact equivalent of the " Azoic" of the Lake 

 Superior geologists. As defined by him, however, this new designation 

 has by no means the same signification as has the term which it was 

 apparently intended to replace. 



In endeavoring to ascertain, by examination and comparison of the 

 statements made in reference to the Archajan in the latest edition of 

 Dana's Manual, what rocks this author really did mean to include in 

 that formation, we find considerable difficulty, so vague and contradictory 

 are the expressions of his views on this point. 



We are distinctly told, however, that " Archaau Time" includes "the 

 era in which appeared the earliest and simplest forms of ayiimals'" ; it also 

 embraces, as we are informed, " an era in which the 2^hysical conditions 

 were incomjiatible loith the existence of UfeP Thus it appears evident that 

 the author of the term Archaean clearly intended to include under that 

 designation a series of stratified fossiliferous rocks, and also other rocks, 

 which preceded these in age, and were formed before life existed on the 

 globe. 



But we are informed by the same author, that the first appearance of 

 life, of whatever rank that life might be, was an event of the highest 

 interest in the geological history of the earth. We would go even far- 

 ther than that, and say that it was an event far transcending in impor- 

 tance any other one which has ever taken place on this planet. And, 

 bearing this in mind, we would insist that so great a transformation in 

 the earth's condition should be recognized in our geological nomencla- 

 ture. At all events, it would, as it seems to us, be in the highest degree 

 unphilosophical to call by the same name rocks which not only difl'ered 

 in their geological age, but also in regard to the all-important point <if 

 having been formed before and after the introduction of life upon the 

 glolie. 



The facts are, however, that the fossiliferous portion of Dana's 



