460 ON THE SUCCESSIVE FORMS 



of the finer strata which commonly follow them, 

 equally prove the length of such intervals of repose, 

 before they were again lifted above the waters by 

 subsequent revolutions ; but they do not prove in the 

 same decisive manner, that the rocks from which we 

 still suppose them to have been produced, were ac- 

 tually indurated. Neither is the motion or the trans- 

 portation of the materials so well indicated in the 

 finer strata; while the fragments found in the con- 

 glomerates, often tend to illustrate other circumstan- 

 ces of importance, which could not be proved by the 

 examination of those. 



The presence and position of organic fossils, are 

 circumstances of a limited, though certain value, in 

 proving revolutions on the surface of the globe; 

 though this species of evidence is sometimes rendered 

 nugatory, by the multitude of concomitant circum- 

 stances which affect these bodies, and by the doubt 

 in which we must consequently remain respecting 

 their successions or interruptions. It is true, that 

 some are found in the primary rocks, elevated high 

 above the level of the present ocean. It is equally 

 true that they are found similarly imbedded in the 

 secondary strata, as well as in some deposits, subse- 

 quent to these, or independent of them. It has also 

 been shown that certain strata do not contain them, that 

 the antient are less numerous than the modern, that 

 they differ in some degree as to the species, and that 

 many appear to be extinct. But none of these facts 

 are sufficient to prove, absolutely, that there has been 

 an interruption in the races of these beings; or that 

 an antient set of inhabitants was extinguished before 

 a subsequent one was formed. Unless that could be 

 proved, they offer no further testimony, in most 

 (ayes, on the subject of revolutions, than the con- 



