OF THE EARTH. 475 



review, are distinguished from the primary, though 

 they should not every where be inconsecutive. It 

 is sufficient if that occurs in any one instance; be- 

 cause, had they been formed after the primary, 

 in the same period of repose under the same ocean, it 

 could not have happened, even in one. 



I need but repeat now, that the primary strata fur- 

 nished the materials of the secondary ones, being 

 thus, above the ocean ; yet this fact explains another 

 set of geological appearances, of some importance, 

 not yet noticed. This is, the absence of the lower 

 order, as of any other superior ones, among the 

 secondary strata, even when still higher ones are 

 present. The primary ones which had emerged, and 

 could not therefore have been covered by them, be- 

 came depressed by subsequent revolutions, as I shall 

 hereafter show, and thus received the deposits of a 

 later date, which might thus have been stratified in 

 contact with them, even as far up as the uppermost ; 

 while I have formerly shown that this occurrence is 

 frequent, under many modes. And as it will be un- 

 necessary hereafter to point out how this might have 

 occurred in specific cases, in the several portions ot 

 the general series, I shall not repeat the remark. 

 Among the complicated elevations which have taken 

 place, it is easy to find solutions for every such in- 

 stance of intermediate deficiencies : either in this 

 cause, or in the removal of strata which had once been 

 deposited, the foundations of which had been after- 

 wards submerged to receive new ones. 



I must now enquire respecting the period of repose 

 which took place in that world, of which the primary 

 strata "formed the dry land. Of that interval, the 

 highest limit is the period of the elevation of these 

 rocks from the sea, or that of the commencement of 



