THE ABCHJ3AK 45 



were engaged in the actual study of the geology of the country, almost 

 every portion of our large area (over 15,000 square miles) was more or 

 less carefully examined and the main features of the geology attentively 

 studied ; and if, as is well-nigh inevitable, later study shall convict our 

 work of errors of omission or of incompleteness, it is hoped that the gravity 

 of our sentence may be somewhat mitigated by giving consideration to the 

 rapidity with which the work was necessarily performed. Indeed, it could 

 scarcely be expected that such a corps in four brief months of field work 

 could unravel without error the geology of a country larger than the State 

 of Connecticut. 



SECTION II. 



THE AECH^AI. 



The Archaean system as founded by Professor Dana includes the 

 oldest known rocks — those which lie below all our fossiliferous strata, 

 and which constitute the "only universal formation." It is for the most 

 part composed of crystalline and metamorphic rocks — granite, syenite, 

 gneiss, and micaceous, talcose, hornblendic, and chloritic rocks, with ores 

 of iron, graphite, etc. It has been divided into two ages, an Azoic, or 

 lifeless age, and an Eozoic, or age of the dawn of life. Of the former, 

 the Azoic, we are not as yet accurately informed, either as to its distinc- 

 tive characters or as to its limits. It has, however, been established as 

 distinct from the other members of the Archaean ; first on the philosophi- 

 cal ground tbat there must be a series of rocks in the earth's formation 

 that existed before the beginning of life on its surface; and, second, to 

 separate the Archaean rocks containing evidence of life (the Eozoic) from 

 those in which no evidences of organic existence have been found (the 

 Azoic.) 



The Eozoic has been separated by the Canadian geologists into two 

 periods, the Laurentian and Huronian, which are well distinguished in 

 Canada, where they attain a thickness of nearly 50,000 feet, and have been 

 recognized or separated in various parts of the eastern United States and 

 in Europe Where the rocks of both groups are observed in Canada 



