200 the WONDERS OF GEOLOGY. Lect. III. 



interspersions of fluviatile and alluvial debris, and intru- 

 sions of volcanic matter. 



It is necessary to premise, that there are three ele- 

 ments of classification applicable to stratified rocks ; 

 namely, 1st, their mineral structure; 2dly, their order of 

 superposition ; and 3dly, the nature of the organic remains 

 which they contain : the following arrangement is in ac- 

 cordance with these principles. The terms by which the 

 formations and their subdivisions are designated, express 

 the predominant characters by which they are distin- 

 guished. 



A CHRONOLOGICAL SYNOPSIS OF THE PRINCIPAL 

 ROCKS AND STRATA. 



{Commencing ivitJi the uppermost or newest deposits.) 



ifcssiTtferous Strata. 



I. The Human or Modern Epoch. — Alluvium or 

 Drift ; comprising the superficial deposits described in the 

 previous Lecture, and which are characterized by the 

 remains oiMan, and of animals and plants, contemporaneous 

 with the human race. 



Observations. — To this epoch belong those superficial accumulations 

 of alluvial debris, and of drifted gravel, sand, boulders, &c, of rocks 

 of all ages, in which, with shells, and bones of existing species of 

 animals, are associated those of the Mammoth, Irish Elk, and other 

 extirpated genera; together with the remains of the more ancient 

 extinct mammalia, that occur in caverns and fissures of various rocks. 

 The line of demarcation between the most ancient beds of this epoch, 

 and the most modern of the following, cannot be strictly defined ; 

 and the separation can only be regarded as conventional. In Europe, 

 the elevation of the Alps appears to have been the grand physical 

 event which marked the close of the tertiary period ; for in all deposits 

 of later age, existing species have been met with. 



II. The Tertiary Epoch. — An extensive series com- 

 prising many isolated groups of marine, fluvio-marine, and 



