CHAPTER XLIV. 



CRUST OF THE EARTH GEOLOGICAL SYSTEMS EOZOIC, PRIMARY, 

 SECONDARY, TERTIARY, PREHISTORIC FORMATIONS. 



THE crust of Great Britain has been carefully examined, and from the 

 results of investigations at various periods, the earth 

 has been divided into a series of strata which follow 

 the same order of succession. Sometimes certain 

 strata may not be present, and they may be replaced 



TERTIARY 

 STRATA. 



1 1 UPPER AND by others, but the same order of succession will be 

 [ SECONDARY found. The order is as follows, commencing at the 

 lowest. The illustration is taken in the opposite 

 direction : 



LOWER 

 I SECONDARY 

 STRATA. 



"Eozoic." 



Palaezoic, 



or 

 Primary. 



Mesozoic, 



or 

 Secondary. 



Kainzoic, 



or 

 Tertiary. 



Quaternary. 



f Laurentian 

 ~j Cambrian 



/ Silurian 



) Old Red Sandstone 



j Carboniferous 



\ Permian 



/ Triassic (Upper Red 



j Sandstone) 



1 Oolitic 



\ Cretaceous 



{Eocene 

 Miocene 

 Pliocene 

 Post-tertiary 



Recent Prehistoric 



~\ Until recently believed to 

 > be without traces of living 

 ) creatures; hence " Eozoic." 



/ Shell -fish, seaweed, 

 f ferns, fish, low reptiles. 



Birds, marsupials, reptiles. 



(Superior life. Mammals, 

 with great vegetable life, on 

 (to plants and animals now 

 existing. Man. 



THE PAL^EZOIC SYSTEMS. 



LAURENTIAN SYSTEM. It will be perceived 

 from the above list that the Laurentian Rocks are 

 the oldest. The name is derived from the St. 

 Lawrence formations, and was given to the strata by 

 Sir William Logan. They arc metamorphosed rocks 

 older than the Cambrian. These rocks are sedimen- 

 tary, of very old deposition, and of a crystalline 

 Fig. 6 4 6. -Systems. nature, consisting of quartz, gneiss, etc. The granite 



was probably formed by the fusion of its component constituents, quartz, 



PRIMARY 

 STRATA. 



