142 THE DAWN OF LIFE. 



able to the generation of crystalline mineral com- 

 pounds. 



'^ In this discovery of organic remains in tlie primary 

 rocks, we hail with joy the dawn of a new epoch in 

 the critical history of these earlier formations. Al- 

 ready in its light, the primeval geological time is 

 seen to be everywhere animated, and peopled with, 

 new animal forms of whose very existence we had 

 previously no suspicion. Life, which had hitherto 

 been supposed to have first appeared in the Primordial 

 division of the Silurian period, is now seen to be 

 immeasurably lengthened beyond its former limit, and 

 to embrace in its domain the most ancient known 

 portions of the earth^s crus-t. It would almost seem 

 as if organic life had been awakened simultaneously 

 with the solidification of the earth's crust. 



*^ The great importance of this discovery cannot be 

 clearly understood, unless we first consider the various 

 and conflicting opinions and theories which had 

 hitherto been maintained concerning the origin of 

 these primary rocks. Thus some, who consider them 

 as the first-formed crust of a previously molten globe, 

 regard their apparent stratification as a kind of con- 

 centric parallel structure, developed in the progressive 

 cooling of the mass from without. Others, while ad- 

 mitting a similar origin of these rocks, suppose their 

 division into parallel layers to be due, like the lamina- 

 tion of clay-slates, to lateral pressure. If we admit 

 such views, the igneous origin of schistose rocks be- 

 comes conceivable, and is in fact maintained by many. 



