. 466 



Dr. Hutton having eftabliflied, as he fuppofes, that his ftrata could 

 not have been confolidated by aqueous folution, proceeds to prove a 

 priori, that it mud have been by igneous fufion. 



I truft the reader will forgive me, for not following him through 

 what Dr. Hutton himfelf calls (page 250) a long chemico-mmereal dif- 

 quifition), and efpecialiy when I inform him, that it contains near thirty 

 quarto pages ; nor is it neceffary, as the Doctor proceeds to prove the 

 fame propofition a pojieriori, and here I apprehend all parties will be 

 better able to underftand each other. He now ftates the appearances 

 the ftrata of the world ought to exhibit upon each fuppofition, be- 

 ginning with aqueous folution ; in this cafe, he fays, (page 258; " thefe 

 " maffes fhould be found precifely in the fame ftace, as when they 

 -' were originally depofited from the water." 



" But if by igneous fufion, (page ZjgJ then in cooling they mud 

 " have formed rents or feparations of their fubdance, by the unequal 

 " degrees of contraftion which contiguous ftrata may have fufFered.— 

 " There is not in nature any appearance more diftiuft than this of 

 " the perpendicular fiffures and feparations in ftrata. -There is no con- 

 " folidated ftratum that wants them, here is, therefore, a clear deci- 

 " fion of the qucftion." And again, fame page, (259) " in propor- 

 " tion as ftrata are deep, in their perpendicular feftion, the veins are 

 " wide, and placed at greater diftances ; in like manner, when ftrata 

 " are thin, the veins are many, but proportionably narrow." 



It is very extraordinary that Dr. Hutton, after pofuively and re- 

 peatedly refting his proof of igneous fufion upon thefe perpendicular 

 fiffures, occafioned by cotftraftion in cooling, fliould not give us a 

 fingle inftance of the faft, nor refer us to any particular place where 

 fuch fiffures are to be found ; we know that the contraftion, after fuch 

 a violent heat, muft be very great ; he himfelf admits, that, in deep 

 ftrata, the veins are wide, and in thinner ftrata frequent, yet, in all 

 the ftrata I have examined, on our northern coaft. for thirty miles, and' 

 many of them from 50 to 60 feet thick, at Portrufh too, where thin 



ftrata 



