6o BISTORT of the SOCIETY. 



It is unneceiTary to carry our conjectures concerning the 

 train of Dr Hutton's difcoveries to a greater length ; the de- 

 velopment of the principles now enumerated, and the compari- 

 fon of the refults with the facts obferved in the natural hiftory 

 of minerals, led to thofe difcoveries, by a road that will be eafily 

 traced by thofe who fludy his theory with attention. 



It might have been expected, when a work of fo much 

 originality as this Theory of the Earth, was given to the world, 

 a theory which profeffed to be the refult of fuch an ample and 



accurate 



the earth. It refts, therefore, as to its evidence, partly on its conformity to ana- 

 logy, and partly on the explanation which it affords of the phenomena alluded to. 

 In fuppofing that it derives probability from the laft -mentioned fource, we are 

 far from affuming any thing unprecedented in found philofophy. A. principle is 

 often admitted in phyfics, merely becaufe it explains a great number of appear- 

 ances ; and the theory of Gravitation itfelf refts on no other foundation. 



The degree of this evidence will perhaps be differently appreciated, according 

 to a man's habits of thinking, or the clafs of ftudies in which he has been chiefly 

 engaged. To Dr Hutton himfelf it appeared very ftrong ; for he confidered the 

 fact of the liquefaction of mineral fubftances by heat as fo completely eftablifhed, 

 that it affords a full proof of the fufibility of thofe fubftances having been increafed 

 by the compreflion which they endured in the bowels of the earth. In his view 

 of the matter, no other proof feemed neceffary, and he did not appear to think 

 that the direct teftimony of experiment, could it have been obtained, would have 

 added much to the credibility of this part of his fyftem. 



For my part, I will acknowledge that the matter appears to me in a light 

 fomewhat different, and that though the arguments juft mentioned are fufficient to 

 produce a very ftrong conviction, it is a conviction that would be ftrengthened by 

 an agreement with the refults even of fuch experiments as it is within our reach 

 to make. It feems to me, that it is with this principle in geology, much as it is 

 with the parallax of the earth's orbit in aftronomy ; the difcovery of which, 

 though not neceffary to prove the truth of the Copernican System, would be a 

 moft pleafing and beautiful addition to the evidence by which it is fupported. So, 

 in the Huttonian geology, though the effects afcribed to compreflion, are fairly 

 deducible from the phenomena of the mineral kingdom itfelf, compared with cer- 

 tain analogies which fcience has eftablifhed, yet the teftimony of direct experi- 

 ment would make the evidence complete, and would leave nothing that incredulity 

 itfelf could poflibly defiderate. 



