226 PEOCEEDINGS 01" THE GEOLOGICAL SOCIETY. [Jail. 10, 



inconceivable that throughout the enormous masses of Eozoic serpen- 

 tine, the siliceous segments, if merely concretionary, should never ex- 

 ceed a minuteness that is rarely encountered among ordinary minerals. 

 Every one who has been accustomed to attend to the subject of 

 evidence is well aware that the concurrence of a number of separate 

 and independent facts, not one of them possessing much probative 

 value in itself, may lead to a moral certainty scarcely inferior to 

 that obtained from demonstration. This is the case when the ag- 

 gregate of these facts is capable of being reconciled with a single 

 hypothesis, and with that one only, and when the facts can only be 

 otherwise accounted for by a number of separate hypotheses having 

 no mutual connexion. — The consistency of all the characters I have 

 enumerated with the theory of the organic origin of the Eozoic 

 limestone is no less remarkable than the difficulty of accounting for 

 their concurrence by any hypothetical combination of chemical and 

 physical agencies. It will be sufficient here to advert to a few 

 points of the case under this double aspect. If the relation of the 

 calcareous and siliceous components be such as is here maintained — 

 the siliceous residue left by decalcification being the internal cast of 

 the cavities, canals, and tubuli of the calcareous skeleton, and there- 

 fore being the model of the original body of the animal — every fea- 

 ture which it presents is found to be closely paralleled by the inter- 

 nal cast of a recent Nummuline shell. But if the collocation of 

 these two minerals has been the result of inorganic agencies, the 

 following points have to be separately accounted for: — 1. The 

 succession of regularly alternating lamellae; 2. the segmental ag- 

 gregation uniformly presented by the siliceous lamellae ; 3. the 

 occasional separation of the segments by calcareous septa; 4. the 

 structural union of both minerals in the proper wall of the chambers; 

 5. the peculiar dendritic formations carrying the siliceous component 

 into the very midst of the calcareous. Was the calcai'eous portion 

 first formed and the siliceous afterwards deposited by infiltration, or 

 was the siliceous portion first formed and subsequently penetrated 

 by calcareous deposit ? if so, by what conceivable process of Assur- 

 ing could a system of cavities of such regularity and constancy of 

 arrangement have been produced? or if it be supposed that the 

 laminae were successively superposed, what agency can be imagined 

 to have brought about the regular alternation of the materials ? and 

 how can the segmental arrangement of hoth sides of the siliceous 

 laminae be accounted for ? If each siliceous lamina were deposited 

 upon a preexisting calcareous lamina, its under side would take the 

 form of the subjacent surface : and how can the calcareous surface 



altered by subsequent metamorphism, — a circumstance frequently met with in 

 rocks of undoubtedly organic origin. But in the numerous examples I have met 

 with of the arrangement referred to by Messrs. King and Eowney, it is so des- 

 titute of the characters of the true chambered structure and asbestiform layer, 

 that I should have no hesitation in regarding it as either originally a product 

 of inorganic agencies, or as the result of metamorphic changes in a structure 

 originally organic, which have caused the formation of the thick serpentinous- 

 layers in which these appearances present themselves. 



