NATURAL THEOLOGY. 



361 



snail, with its pillar and convolution, is a very ar- 

 tificial fabric ; whilst a snail, as it should seem, is 

 the most numb and unprovided of all artificers. 

 In the midst of variety, there is likewise a regular- 

 ity which could hardly be expected. In the same 

 species of snail the number of turns is usually, if 

 not always, the same. The sealing up of the 

 mouth of the shell by the snail is also well calcu- 

 lated for its warmth and security ; but the cerate 

 is not of the same substance with the shell. 



II. Much of what has been observed of snails 

 belongs to shell-fish and their shells, particularly 

 to those of the univalve kind ; with the addition 



Spondylus — prickly oyster. 



of two remarks — one of which is upon the great 

 strength and hardness of most of these shells. I 

 do not know whether, the weight being given, art 

 can produce so strong a case as are some of these 

 shells ; which defensive strength suits well with 



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