34-4? ON THE APPARENT DISLOCATIONS [Ch. XV. 



selves, by their occasional irregularity of form, will indicate 

 an intimate connection with the basis, as in the rock of Crone- 

 bane, recorded by Weaver, in which they are extended in 

 thin edges between the laminae of the stratum ; a disposition 

 and form certainly not indicative of violent attrition. 



It may, however, be farther urged by the advocates of 

 the Plutonic theory, that the secondary rocks also exhibit 

 examples of nodules and bases possessing a similar com- 

 position, and in which the nodules have the same kind of 

 concretionary structure. Such cases have been recorded : 

 we have noticed one at Crackington Cove *, on the north 

 coast of Cornwall; its nature is not positively determined, 

 but it probably belongs to the same series as the dunstone 

 and dark limestones of Devon, and is therefore a fossiliferous 

 formation of the oldest description. But we cannot admit 

 this as evidence that these rocks are of mechanical origin ; it 

 does not follow, because this conglomerate is situated in a 

 sedimentary deposit, that its lenticular concretions have been 

 produced by transportation and attrition : it only indicates 

 that such nodules may sometimes result from the peculiar 

 aggregation of the particles of rocks during their consolid- 

 ation, whether of aqueous, igneous, or any other origin, just 

 as the same cuboidal, prismatic, lamellar, schistose, or other 

 kinds of structure may have originated in all rocks under 

 similar circumstances: all that is requisite for such an ar- 

 rangement is, that the integrant particles have the necessary 

 degree of motion among themselves during the lapidification ; 

 but the manner in which this is attained does not appear to 

 be material. We are borne out in this conclusion by the 

 fact, that supposed igneous rocks possess the same kind of 

 conglomerated structure as stratified rocks; as shown in 

 Macculloch's sketch of the decomposing granite in the Isle of 

 Manf, and also by the occurrence of the same arrange- 



* Geol. Trans, of Cornwall, vol. iv. p. 178. 

 t Western Isles of Scotland, pi. xxviii. fig. 3. 



