I PROLEGOMENA .3 



to have gone and to go on for ever, is but a 

 fleeting phase of her infinite variety ; merely the 

 last of the series of changes which the earth s sur 

 face has undergone in the course of the millions of 

 years of its existence. Turn back a square foot of 

 the thin turf, and the solid foundation of the land, 

 exposed in cliffs of chalk five hundred feet high on 

 the adjacent shore, yields full assurance of a time 

 when the sea covered the site of the &quot; everlasting 

 hills &quot; ; and when the vegetation of what land lay 

 nearest, was as different from the present Flora of 

 the Sussex downs, as that of Central Africa now is. 1 

 No less certain is it that, between the time during 

 which the chalk was formed and that at which the 

 original turf came into existence, thousands of 

 centuries elapsed, in the course of which, the state 

 of nature of the ages during which the chalk was 

 deposited, passed into that which now is, by 

 changes so slow that, in the coming and going of 

 the generations of men, had such witnessed them, 

 the contemporary conditions would have seemed 

 to be unchanging and unchangeable. 



But it is also certain that, before the deposition 

 of the chalk, a vastly longer period had elapsed, 

 throughout which it is easy to follow the traces 

 of the same process of ceaseless modification and 

 of the internecine struggle for existence of living 

 things ; and that even when we can get no further 



1 See &quot;On apiece of Chalk&quot; in the preceding volume of these 

 Essays (vol. viii. p. 1). 



B 2 



