36 Unconformity. 



the sea, the strata No. 2 have been won from that old 

 land and deposited on the upturned and denuded edges 

 of the strata No. 1. This constitutes a case of uncon- 

 formable stratification, and this alone marks the lapse 



FIG. 8. 



1. Old disturbed strata, 



2. Later beds lying unconformably upon them. 



of immense periods of geological time, first by the 

 deposition, consolidation, and upheaval of the strata 

 No. 1, and secondly in the deposition of the strata 

 No. 2, which were made from the waste of No. 1. 



There are many cases of this kind of unconformity 

 extending through all geological time from the 

 Laurentian epochs onwards. If, in addition to this, we 

 consider the meaning of the progressive changes of 

 genera and species of animals and plants, as we proceed 

 from the older to the newer formations (as expressed 

 in Chapter II.), it soon becomes obvious, that as yet 

 we have no means of even attempting to form any 

 clear idea of the time that has elapsed since life first 

 appeared on the surface of the world, whether we adopt 

 the original view of a distinct creative act for each 

 individual species, or prefer the later one of evolution 

 and progressive development. 



To explain in some detail the anatomical structure 

 or existing Physical Geography of our island, as de- 

 pendent on the nature of its strata and the alterations 

 and denudations they have undergone is the main 

 object of this book. In making this attempt I shall 



