308 IMPEKFECTION OF THE Chap. IX. 



a metamorphosed condition. But the descriptions which 

 we now possess of the Silurian deposits over immense 

 territories in Kussia and in North America, do not sup- 

 port the view, that the older a formation is, the more it 

 has suffered the extremity of denudation and metamor- 

 phism. 



The case at present must remain inexplicable ; and 

 may be truly urged as a valid argument against the 

 views here entertained. To show that it may hereafter 

 receive some explanation, I will give the following 

 hypothesis. From the nature of the organic remains, 

 which do not appear to have inhabited profound 

 depths, in the several formations of Europe and of the 

 United States ; and from the amount of sediment, miles 

 in thickness, of which the formations are composed, we 

 may infer that from first to last large islands or tracts 

 of land, whence the sediment was derived, occurred in 

 the neighbourhood of the existing continents of Europe 

 and North America. But we do not know what was 

 the state of things in the intervals between the suc- 

 cessive formations ; whether Europe and the United 

 States during these intervals existed as dry land, or 

 as a submarine surface near land, on which sediment 

 was not deposited, or again as the bed of an open and 

 unfathomable sea. 



Looking to the existing oceans, which are thrice as 

 extensive as the land, we see them studded with many 

 islands; but not one oceanic island is as yet known 

 to afford even a remnant of any palaeozoic or secondary 

 formation. Hence we may perhaps infer, that during 

 the palaeozoic and secondary periods, neither continents 

 nor continental islands existed where our oceans now 

 extend; for had they existed there, palaeozoic and 

 secondary formations would in all probability have been 

 accumulated from sediment derived from their wear and 



