28 THE CBUST WE DWELL UPON. 



ceptions of that Creative Wisdom which has exerted itself 

 in this world of ours ages before the human race became 

 witnesses of its beauties or participators in its bounties. 

 And the clearer we can render this history, the more 

 minute our analysis of the earth's crust ; and the closer the 

 connection we can establish between the successive stages 

 of its formation, the more attractive and instructive will the 

 geological record become. * 



In arranging the rock-formations of the earth, we may 

 either divide them, as the older geologists did, into Pri- 

 mary, Secondary, and Tertiary ; or looking, as modern 

 geologists do, more especially at their fossils, we may adopt 

 the subdivisions, Eozoic, Palceozic, Mesozoic, and Caino- 

 zoic. In either case these main divisions contain several 

 formations of marine, estuary, or lacustral origin, and these 

 it is customary to name either after their prevalent rocks, 

 their most characteristic fossils, or some geographical area 

 in which they are typically displayed. Thus the Cretaceous 

 or Chalk system is so named from chalk -rock forming 

 its most distinctive feature in the south of England, and 

 the Old Red Sandstone from its consisting largely of red- 

 dish-coloured, sandstones; while the Silurian is named after 

 the district between England and Wales, where it is typi- 

 cally developed, and which was anciently inhabited by the 

 Silures, and the Laurentian because typically displayed in 

 the region of the St Lawrence. Adopting this plan (and 

 it matters little what the nomenclature, provided we be 

 certain of the chronological order), the stratified rocks of 

 the crust may be arranged in the following manner not 

 going into minutiae, but simply presenting such leading 

 features as may convey to the miscellaneous reader some idea 

 of the sequence that prevails among the stratified systems, 

 and the ascent of life, vegetable and animal, as it makes its 

 appearance from the lowest to the highest formations : 



