290 THEORY of the EARTH. 



ble portion of calcareous earth, in the competition of clay, con- 

 ftitutes a marl, and a fufficient admixture of fand, a loam. 



AN indefinite variety of thofe compofitions of clay form a 

 large portion of the prefent flrata, all indurated and confolidated 

 in various degrees ; but this great quantity of filiceous, argil- 

 laceous, and other compound fubflances, in form of earth or 

 impalpable fediment, correfponds perfectly with that quantity 

 of thofe fame fubftances which muft have been prepared in 

 the formation of fo much gravel and fand, by the attrition of 

 thofe bodies in the moving waters. 



THEREFORE, from the confideration of thofe materials which 

 compofe the prefent land, we have reafon to conclude, that, 

 during the time this land was forming, by the collection of 

 its materials at the bottom of the fea, there had been a former 

 land containing materials fimilar to thofe which we find at pre- 

 fent in examining the earth. We may alfo conclude, that 

 there had been operations fimilar to thofe which we now find 

 natural to the globe, and neceflarily exerted in the actual 

 formation of gravel, fand and clay. But what we have now 

 chiefly in view to illuftrate is this, that there had then been in the 

 ocean afyftem of animated beings, which propagated their fpecies, 

 and which have thus continued their feveral races to this day. 



IN order to be convinced of that truth, we have but to exa- 

 mine the ftrata of our earth, in which we find the remains of 

 animals. In this examination, we not onlydifcover every ge- 

 nus of animal which at prefent exifts in the fea, but probably 

 every fpecies, and perhaps fome fpecies with which at prefent 

 we are not acquainted. There are, indeed, varieties in thofe 

 fpecies, compared with the prefent animals which we examine, 

 but no greater varieties than may perhaps be found among the 

 fame fpecies in the different quarters of the globe. Therefore, 

 the fyftern of animal life, which had been maintained in the 

 ancient fea, had n9t been different from that which now fub- 

 fifts, and of which it belongs to naturalifls to know the hiflory. 



IT 



