116 



DOMAIN I. SIDEROUS. 



forty upon a slate of only one foot square. But 

 it must be observed that none of the above ani- 

 mals have similar representatives in living zoolo- 

 gy. But what appears most surprising in these 

 impressions, particularly with regard to the large 

 crabs, is, that the body, though there be no sign 

 of its being crushed, may be said to have no 

 thickness whatever. They are rather simple 

 engravings than bodies in relievo, the convexity 

 of these large crabs upon a thin leaf of slate not 

 exceeding the quarter, or even the tenth part, of 

 a line ; nor is it perceivable that the body of the 

 animal at all penetrates the thickness of the leaf 

 where it is adherent. And what still adds to 

 this wonder, is the nearly vertical situation in 

 which these impressions are found in the mine. 

 " A series of leaves of slate may be compared 

 to a set of books placed upon shelves ; and the 

 impressions of crabs and other animals, to en- 

 graved plates in the volumes. They do not, in 

 fact, occupy more thickness; and it is equally 

 difficult to conceive how the body of these ani- 

 mals, though otherwise perfectly defined, should 

 be reduced to a simple surface without thick- 

 ness : and how it should always be found in a 

 vertical situation, which cannot be ascribed to 

 any derangement in the bed itself, since it is 

 still horizontal, and occupies a space of many 



