XIV TABLE OF CONTENTS. 



JONES'S SURVEY. 



CoMSTOCK on the Azoic rocks of Northwestern "Wyoming, 515. No reasons other 

 than lithological for calling these rocks Laurentiau, 515, 516. 



POWELL'S SURVEY. 



Report by Newton and Jenney on the Black Hills, 516 ; the Azoic rocks divided 

 into Laurentian and Huronian, but on very slight evidence, 516. 



CALIFORNIA. 



Results of the California Survey, 516, 517. Hunt's views in 1866, and in 1868, 

 before visiting the region, 517. He spends several days there, and discovers 

 that rocks of the Sierra Nevada which contain Jurassic fossils are of Huronian 

 age, 517, 518. Hunt's views of Califoruian geology shown to be fundamentally 

 wrong, 518. 



PAET II. 



E^suMi;, AND General Discussion. 



Introductory remarks, 519. The geology of Canada and New England in an almost 

 hopeless state of confusion, 519, 520. How this condition of things has been 

 brought about, 520. The establishment of the Silurian System by MuRCiilsoN, 

 in 1845, opens the way to the discussion of the question whether the lowest limit 

 of life had been reached, 520. First use of the term Azoic by Murchison, 520, 

 521 ; his definition of that term, 521 ; his hesitating and contradictory statements 

 in reo-ard to it, 521 ; his gradual withdrawal of it in the successive editions of 

 Siluria, 521, 522. Bareande's grouping, in 1846, of the Protozoic and Azoic 

 rocks, 522 ; confusion caused by the use of the term Cambrian already begun, 522. 

 Foster and Whitney, in 1851, describe certain rocks on the south shore of Lake 

 Superior, under the designation of the Azoic System, 522. Similar rocks, in 

 Canada, called by Logan the Jletamorphic Series, but without fully ascertaining 

 their geological position, 523. Logan, in 1854, applies the name Laurentian to 

 these rocks, 523 ; confusion introduced by his inability to distinguish between 

 the Azoic and the Palteozoic, 523. The term Azoic for some time in current use 

 in this country, 523, 524; Dana's use and definition of it in 1862 and 1871, 524; 

 his views in regard to the existence of life during an " azoic " period, 524 ; the 

 position assumed by him in 1874, and the introduction of the term Archaean, 

 •with a definition of it, 524. Confusion of views in regard to the older crystal- 

 line rocks, 525. Some general remarks introductory to the consideration of the 

 subject, 525 ; great interest attaching to the question whether life exists in other 

 worlds than our own, 525 ; importance of fixing the epoch when life began here, 



