OPPONENTS AND OBJECTIONS. 171 



Laurentian life less anomalous than may at first sight 

 be supposed. One of these is the fact that the dis- 

 covery of Eozoon brings the rocks of the Laurentian 

 system into more full harmony with the other geolo- 

 gical formations. It explains the origin of the Lau- 

 rentian limestones in consistency with that of similar 

 rocks in the later periods, and in like manner it helps 

 us to account for the graphite and sulphides and iron 

 ores of these old rocks. It shows us that no time was 

 lost in the introduction of life on the earth. Otherwise 

 there would have been a vast lapse of time in which, 

 while the conditions suitable to life were probably pre- 

 sent, no living thing existed to take advantage of 

 these conditions. Further, it gives a more simple 

 beginning of life than that afforded by the more com- 

 plex fauna of the Primordial age ; and this is more in 

 accordance with what we know of the slow and gradual 

 introduction of new forms of living things during the 

 vast periods of Palaeozoic time. In connection with 

 this it opens a new and promising field of observation 

 in the older rocks, and if this should prove fertile, its 

 exploration may afford a vast harvest of new forms to 

 the geologists of the present and coming time. 

 This result will be in entire accordance with what 

 has taken place before in the history of geological dis- 

 covery. It is not very long since the old and semi- 

 metamorphic sediments constituting the great Silurian 

 and Cambrian systems were massed together in geo- 

 logical classifications as primitive or primary rocks, 

 destitute or nearly destitute of organic remains. The 



