ALGONKIAN 36 1 



(3) That these rocks are intrusive igneous masses, newer than 

 certain strata which rest upon them. 



(4) That they were formed by the metamorphism of sedi- 

 mentary rocks, the massive kinds representing, in large part, the 

 extreme stage of metamorphism by which the sediments were 

 actually melted. Others of the massive kind are igneous intru- 

 sions of all subsequent dates. 



While we have, as yet, no means of definitely deciding among 

 these conflicting opinions, yet the present trend of investigation 

 seems to be distinctly in favour of the first view, or some modifi- 

 cation of it. Certain it is that, if the original crust of the earth be 

 anywhere preserved, it is in the Archaean rocks. As these have 

 been subjected to all the folding and crushing which the earth's 

 crust has undergone, it is not surprising that they should have 

 acquired such a complex and intricate structure and have been so 

 radically metamorphosed. It is hardly necessary to say that the 

 Archaean, as here limited, has yielded no evidence of life, all of 

 those evidences which are generally spoken of as found in the 

 Archaean being of later date, but this negative testimony is of no 

 great value. If these rocks be actually transformed sediments, 

 the profound metamorphism which they have undergone would 

 have thoroughly destroyed any traces of fossils that they might 

 have originally contained. We cannot tell when life was first 

 introduced upon the earth, but we may be very confident that no 

 living thing could have existed when the surface of the crust was 

 glowing hot, or in the oceans boiling even under the enormous 

 atmospheric pressures which accompanied their first condensation. 



II. ALGONKIAN 



This is the name recently proposed by the United States Geo- 

 logical Survey for the great series of sedimentary and metamorphic 

 rocks which lie between the basal Archaean complex and the oldest 

 Palaeozoic strata. While it is possible, though not very likely, that 

 more advanced knowledge may lead us to distribute these rocks 

 partly into the Archaean and partly into the Palaeozoic, yet for 



