HUTTONIAN THEORY. 



11 





2 



where the one ended and the other began, what- 

 ever difficulties we might perceive in the Nep- 

 tunian theory, we fhould find it hard to fubfti- 



:e a better 

 be. that. 



its room. But the truth feems 

 the cafes we are now treating of, 



no fuch gradat 



fts 



d that, thougl 



wh 



th 



kinds of roek come into contact 



a change is often obferved, by the ftrata having 

 acquired an additional degree of induration, yet 

 the line of feparation 



is well defined, and 



be precifely afcertained 



Th 



at 



ft 



IS cer 



tain, that 



umerable fpecimens, exhibiting 



fuch lines of feparation, are to be met with 



herev 



has been taken 



; and 



obtain a frefli 



fradure of the ftone, and to remove the effedls 

 of accidental caufes, even where the two rocks are 

 moft firmly united, and moft clofely affimilated, 

 I am perfuaded that no uncertainty has ever re- 

 mained as to the line of their feparation.' 



iration.' For 

 thefe reafons, it feems probable that the gradual 

 tranfition of bafaltes into 



the adjoining ft 



in all cafes imaginary, and is, in truth, a mere il- 

 lufion, proceeding from hafty and inaccurate 

 obfervation. 



73. Another remarkable fad in the natural 

 hiftory of the whinftone rocks, remains yet to be 

 mentioned, and with it I ftiall conclude the ar- 

 gument, as far as thefe rocks are concerned. 



Some 



\ 



t 



