3 2 4 ARCHEOZOIC ERA 



origin they best adjust themselves. The constitution of the system 

 makes it clear that it does not represent the original crust of the earth 

 or its downward extension. It cannot be affirmed, however, that 

 no part of what is now classed as Archean is referable to an original 

 crust; that is, it cannot be affirmed that no part of the Archean is 

 referable to an azoic or pre-zoic period, strong as the evidence 

 against such reference may seem. On the other hand, all the facts 

 now known concerning the Archean adjust themselves to the 

 planetesimal hypothesis, or to the modified form of the gaseo- molten 

 hypothesis. They cannot, however, be said to establish either, or 

 to preclude other hypotheses of the origin of the earth. 



Life. The presence in the Archean system of carbonaceous 

 material and of limestones, seems to imply the presence of life 

 during the era of its formation. Since no fossils have been found, 

 nothing is known of the character of the life, and little, except by 

 inference, of its abundance. 



Duration of the era. Of the duration of the Archeozoic era 

 nothing can be said beyond the general statement that it was very 

 great, a conclusion which is independent of any theory of the 

 earth's origin. If the planetesimal hypothesis is correct, there is 

 no readily assignable lower limit to the Archean system, and the 

 duration of the Archeozoic era may exceed that of all subsequent 

 time. 



Climate. Nothing is known of the climate of the era except 

 that it seems to have been such as to permit the existence of life, 

 and the ordinary phases of sedimentation. 



