EARTH 's DEEPEST GEAVES. 197 



XXXIV. EARTH'S DEEPEST GRAVES. 



THE EOZOIC ANIMAL. 



WE are down now, on the bottom rocks of the earth's crust. 

 This is the home of the vitrified and crystalline bowlders 

 which overstrew the surface. There are fifty thousand feet 

 of later strata resting above these rocks in regions where the 

 series is complete. But here, and over extensive regions, the 

 deep Eozoic beds have been arched up to the surface, and no 

 newer rocks have ever formed over them ; or if they were, 

 have subsequently been worn away. Luckily for the geologist, 

 the modern sun-light has been let into them, and we have 

 gained some general knowledge of them, though [it must be 

 confessed, a very great amount of ignorance remains. Let us 

 see what has been found out. 



In the first place, deep as we have ever penetrated into 

 these Eozoic rocks, they all retain some traces of stratification. 

 In most cases, the stratification is very obscure; in many 

 cases, it is quite obliterated, but rocks of this sort furnish some 

 evidence of their original bedding. Often they differ from 

 stratified rocks in no other particular. Sometimes we can trace 

 them into continuity with stratified rocks. In all cases the 

 crystals which they contain, and the crystalline condition of 

 the rocks indicate solidification from a state of solution or soft- 

 ening which requires the presence of water. Grant us water 

 and heat, and the present condition would be produced from 

 ordinary ocean sediments. We must look upon all these rocks 

 as ocean-born. Hard and crystalline as they now are, we must 

 think of them as at one time in the condition of ocean-slime. 

 These rocky beds have been successively ocean bottom. These 

 rocks too, have successively rested as sediments upon an ocean- 

 bottom preexisting. There must have been an ocean-bottom 

 for the very first sediments to rest on. Let us remember this. 



In the next place, the very oldest rocks known are granites, 

 syenites, gneisses, and hornblendic schists. Not having seen 

 the bottom of this series, we can not state its thickness. At 

 a higher level, have been found, in the north-west, conglom- 



