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bf the ftrata for more than fome few hundreds of yards. 

 There is, however, one curious inftance of an ifland, 

 near the coaft of Pembrokefhire, called Caldy Ifland, 

 where the earth fufFered the action of fo unufual a 

 difruption, that the ftrata, of which the whole ifland is 

 compofed, are placed in a vertical pofition, fo that 

 their edges are all expofed to view, and they may be 

 obferved in fucceflion from one end of the ifland to 

 the other. Here then we have the fingular opportu- 

 nity of obferving in what order they were originally 

 placed, to the depth of two miles. At one end of the 

 ifland they are not more than a foot thick, but increafe, 

 as we proceed, till they terminate in a ftratum of red 

 ftone, more than a mile in thick nefs, which, with good 

 reafon, is fuppofed to have been the loweft of them all 

 before they were elevated and thrown upon their edges. 

 The thinner ftrata, which were originally uppermoft, 

 have fofiil fliells and corallines in them ; but I have 

 not heard that any thing like the traces of lava are to 

 be found to countenance the fuppofition, that this fin- 

 gular accident was occafioned by the explofive force of 

 a volcano. 



The order of the ftrata in Derbyfhire is as follows : 

 i. Millftone-grit, a coarfe fand-ftone compofed of 

 granulated quartz and quartz pebbles, a. Shale or 

 fhiver, or black laminated clay, much indurated. 

 3. Li me -ftone, in various laminae. 4. Toad-ftone, a 

 black porous fubftance, hard, refembling fcoriae, and 

 apparently a volcanic production. 5. Lime-ftone. 

 . Toad-ftone. 7. Lime- ftone. 8. Toad-ftone. 

 9. Lime-ftone again. Such (the toad-ftone excepted) 

 appears to be the general order in which the ftrata 

 appear through the different regions of the earth, or 

 at leaft wherever the lime-ftone predominates, which 

 is in a confiderable proportion, though it muft be 

 * remarked 



