488 ON THE SUCCESSIVE FORMS 



globe : and they may perhaps assist in proving what 

 has already appeared probable from other arguments,, 

 that every period of revolution has occupied an inde- 

 finite time, and has consisted in a long succession 

 of unequal, though similar actions. 



To proceed with this investigation, I must now re- 

 mark that the ocean of this last earth was the resi- 

 dence of all the beings now preserved in our secondary 

 strata. If they were a separate creation, they form 

 the last., previous to that which now inhabits the 

 earth ; as every posterior revolution appears to have 

 been of too partial a nature to produce any change 

 adequate to the entire destruction of life. But as the 

 repose of this ocean, or the time which intervened be- 

 tween that depression of the strata which has thus 

 been examined, and the subsequent elevation, next to 

 come under review, is measured by the thickness of 

 the last marine deposit, we may try to conjecture, 

 within general and comparative limits, what its du- 

 ration was. The red marl and its preceding limestone, 

 with the lias, and the oolithe, form the most general 

 and most widely extended portions of this de- 

 posit, and are of great depth ; and if, to these, we add 

 the remaining strata up to the Chalk inclusive, we 

 shall have the extreme measure of repose which is at- 

 tainable. Comparatively therefore, we are enabled to 

 determine, that the period of repose during which the 

 coal strata remained beneath the ocean, was greater 

 than that during which they were forming on the sur- 

 face of the dry land, and greater also than that during 

 which the inferior secondary strata were generated. 



Although, for the purpose of examining the revo- 

 lutions of the coal strata, and the state of that ocean 

 which followed their depression, it has been necessary 

 to speak of the superior secondary strata as they are 



