WILLIAM SMITH. 249 



which attend the sparry substance occupying the 

 place of the shell, which has been removed, in the 

 lias, and the empty cavity, where the shell was, 

 surrounding a loose stony cast of the interior, in 

 the freestone (oolite). 



That his mind was now actively employed in 

 tracing out the bearings of the extensive subject 

 before him, will be evident from the following 

 extract, dated August, 1797 : — 



^^ Locality of plants^ iiisects, birds , etc.^ arises from 

 the nature of the strata. 



" Where art has not diverted the order of things 

 and nature is left to herself, a considerable locality 

 may be observed in many animals and vegetables 

 as well as mineral productions, by which they 

 evidently attached to particular soils to such a 

 degree that, if this subject were studied with 

 attention, it would form one of the principal 

 external characteristics of the strata underneath. 

 Though it may seem mysterious to some, that birds, 

 beasts, insects, etc., which have the liberty of roving 

 at pleasure, should feel any particular attachment 

 for this or that soil, yet the wonder ceases when we 

 consider how the chain of natural things is linked 

 together, and how these creatures are taught to 

 cull their food from insects that are lodged in, or 

 seeds that are produced from, particular plants 

 that grow upon particular soils." 



Smith had seen layers of limestone crowded with 

 shells succeeded by others containing corals. He 

 found ammonites and oysters in some, and insect 



