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rock at Saffron Walden by my friend Thomas Walfbrd^ 

 Esq. We have the spines from various places. Its great 

 curiosity is, that the shell part is extremely perfect as a 

 Carbonate of Lime, although filled up with Flint; which has 

 scarcely disturbed it, notwithstanding its having overflowed 

 as it were at both ends. This is also said to be a variety of 

 the Echinus Cidarls; to which we do not readily assent. 

 P. Rashleigh, Esq. has figured another species, Echinus 

 circinatus, under similar circumstances; which not being 

 uncommon, serves well to show that nature performs the 

 same offices by similar means in various places; and, as 

 Mr. Rashleigh observes, its particular structure will point 

 out to the theorist that it is not the immediate effect ofjire, 

 in the common acceptation of that term, but, with the aid 

 of other principles, modifying the operation so as to give 

 another idea. 



