OF A FORMER WORLD. 51 



those that exist in the overlying group. They may, and do 

 present resemblances, more or less near; but there is a 

 change ; and such a change as indicates that between the 

 close of the one formation, and the opening of the other, a 

 considerable period has elapsed. This remark is applicable 

 to the formations of the palaeozoic and secondary periods - 

 hence each group has its characteristic fossils. It is also 

 true in regard to the rocks of the tertiary period, viewed as 

 groups. But it does not apply to the upper beds of the 

 secondary, and lower beds of the tertiary formations. 

 The time that transpired between the depositing of these, 

 was such as, together with the changes that took place, to 

 break the connexion entirely between the fossils of the one 

 and those of the other. No species found in the chalk, the 

 upper bed of the secondary formation, extends into the Lon- 

 don clay, the lowest in the tertiary groups. There is here 

 a break, of a much greater extent than those that appear to 

 exist between each formation and its successor, of the older 

 periods ; and the length of time which it represents, though 

 uncertain, must be great. 



The only other argument produced*, in favor of the anti- 

 quity of the globe, is derived from the relative position in 

 which the various groups that compose the crust are placed. 

 Groups of rock either lie comformable or uncomformable 

 upon each other. There are few that lie conformable, that 

 is, as you would place one volume fair upon another. But 

 even when this is the case, there are certain indications at 

 the junction that demonstrate, that the surface of the 

 lower group was long consolidated, and exposed to the ele- 

 ments, before it was overlaid by the beds of the upper- 

 Thus, if we find the surface-rock partially decomposed and 

 removed, what remains, hollowed out by water, and these 

 hollows occasionally containing loose pebbles, we may reason- 

 ably conclude that these effects the result of time were 

 produced before the overlying rock had been deposited. 



