AND STRATIFICATION. 



81 



regulated by the casual establishment of animal colo- 

 nies in beds favourable to their existence and repro- 

 duction ; as it is elsewhere shown that the calcareous 

 secondary strata are chiefly of animal origin. But 

 indeed we need not rest the decision of this question 

 on grounds merely possible ; since, in the phenomena 

 of lakes and aestnaries, we have convincing proof of 

 alternations, not only of clay and sand, produced 

 from the materials brought down by rivers,, but of beds 

 of shells and calcareous mud also. 



Thus the origin of strata is derived from deposi- 

 tions of the materials of the dry land under the waters 

 of the sea, and, in some cases, of great inland lakes, 

 intermixed with the spoils of animals that have lived 

 and died through a long succession of ages. If the 

 daily causes of waste pulverize the solid mountains, 

 and the rivers transport their ruins to the sea, so, 

 other causes, acting more extensively and powerfully, 

 must be allowed a share in producing and depositing 

 the materials to which we owe our present stratified 

 rocks. The extent and nature of these operations will 

 be fully examined in its proper place, as they are now 

 in progress, or are past, and as they include that 

 interesting branch of geology which relates to the 

 present surface of the earth. (Chap, xxii.) In the 

 ruins of an antient earth we find the materials which 

 form the present ; as, in the destruction of the land 

 which we now inhabit, nature seems to be preparing 

 habitations for future races of animated beings, 



But though I have here said, that causes operating 

 more extensively and powerfully than the slow actions 

 of waste and transportation, may have aided in pre- 

 paring the materials of the strata, we must beware of 

 allowing more effect to these than they were capable 



VOL, j, G 



