524 THE AZOIC SYSTEM AND ITS SUBDIVISIONS. 



required by the results of recent geological research," adopts the term 

 "Azoic," but not in the exact sense in which it was used by Foster 

 and Whitney. He includes under that designation all the rocks which 

 were in existence at the time animal life began, stating his views in the 

 following words : " The Azoic rocks constitute the only universal forma- 

 tion. They cover the whole globe, and were the floor of the oceans and 



the rocks of all emerged land when animal life was first created 



Whatever events occurred upon the globe from the era of the elevated 

 temperature necessary to fusion, down to the time when the climate 

 and waters had become fitted for animal life, are events in the Azoic 

 age." 



But farther on {I. c, p. 145), Dana advocates the idea that there 

 may have been life on the globe during the Azoic period, for he says, 

 "The term 'Azoic,' as here used, implies absence of life, but not neces- 

 sarily of the lowest grades." He then gives the following "reasons in 

 favor of the existence of life of some kind [in the Azoic]." 1st. The 

 formation of limestone strata. 2d. The occurrence of graphite in the 

 limestone and other strata. 3d. The occurrence of anthracite in small 

 pieces in the iron-bearing rocks of Arendal, Norway, which rocks are 

 probably Azoic in age. He then proceeds to give reasons why, suppos- 

 ing the existence of life of some kind, it is more likely to have been 

 vegetable than animal. But he distinctly admits {l. c, p. 147) that 

 " whenever the earliest plant, however minute, was created, then the 

 grand idea of life first had expression, and a new line of progress in the 

 earth's history was announced." And, still farther on (/. c, p. 178), he 

 admits that " the life of the Potsdam period is the beginning of the systevi 

 of life deciphered in American geological history.''^ 



In the second edition of his Manual, the Preface of which bears date 

 March 1, 1874, Dana takes a position in reference to the Azoic sys- 

 tem materially different from that previously occupied by him. He 

 now introduces the term "Archsean," and defines "Archaean Time" as 

 " the beginning, including a ver}' long era without life, and finally that 

 in which appeared the earliest and simplest forms of plants and ani- 

 mals." Farther on, however, {I. c, p. 146,) he says, that "Archa\an 

 time includes strictly, as its commencement, an Azoic age, or the era in 

 which the physical conditions were incompatible with the existence of 

 life. But this era, so far as now known, is toithout recognizable records ; 

 for no' rocks have yet been shown to be earlier in date than those which 

 are now supposed to have been formed since the first life began to 

 exist." 



