52 HISTORY of the SOCIETT. 



As I have treated of this theory in a feparate Eflay, particu- 

 larly deflined to the illufti-ation of it, I fhall here content myfelf 

 with a very general outline. 



I. The objedl of Dr Hutton was not, like that of mod 

 other theorifts, to explain the firft origin of things. He was 

 too well flcilled in the rules of found philofophy for fuch an 

 attempt ; and he accordingly confined his fpeculations to thofe 

 changes which terreftrial bodies have undergone fince the efta- 

 blifliment of the prefent order, in as far as diftindl marks of 

 fuch changes are now to be difcovered. 



With this view, the firft general fadl which he has remarked 

 is, that by far the greater part of the bodies which compofe the 

 exterior cruft of our globe, bear the marks of being formed out 

 of the materials of mineral or organized bodies, of more ancient 

 date. The fpoils or the wreck of an older world are every 

 where vifible in the prefent, and, though not found in every 

 piece of rock, they are difFufed fo generally as to leave no doubt 

 that the ftrata which now compofe our continents are all form- 

 ed out of ftrata more ancient than themfelves. 



II. The prefent rocks, with the exceptions of fuch as are not 

 ftratified, having all exifted in the form of loofe materials coUedl- 

 ed at the bottom of the fea, muft have been confolidated and con- 

 verted into ftone by virtue of fome very powerful and general 

 agent. The confolidating caufe which he points out is fubter- 

 raneous heat, and he has removed the objedlions to this hypo- 

 thefis by the introduflion of a principle new and peculiar to 

 himfelf. This principle is the comprefllon which muft have 

 prevailed in that region where the confolidation of mineral fub- 

 ftances was accompliflied. Under the weight of a fuperincum- 

 bent ocean, heat, however intenfe, might be unable to volatilize 

 any part of thofe fubftances which, at the furface, and under 

 the lighter preffure of our atmofphere, it can entirely co fume. 

 The fame prefliire, by forcing thofe fubftances to remain uni- 

 ted, 



