Ch. XVI.] TO THE PREVAILING THEORY. 371 



bring the matter into as small a compass as possible, so as to 

 render the nature of the dissent more evident. 



In the first place, it is contended that the primary slates 

 are not stratified, if it be thereby understood that they con- 

 sist of sedimentary beds arranged by the agency of water 

 after the manner of the fossiliferous deposits. The analogy 

 between the arrangement of the beds, and of the laminae, in 

 the rocks of both formations, is not disputed; but it has been 

 argued that it furnishes no evidence that the primary slates 

 are of a mechanical or aqueous origin, since not only granite, 

 but also trap, and even lava, present the same appearances: 

 in short, we maintain that arrangements which only mark the 

 varieties of concretionary structure produced during the con- 

 solidation of the once mobile particles of rock, and which do 

 not characterise any particular formation, cannot be admitted 

 to prove that the primary slates were originally sedimentary 

 deposits. 



Since, therefore, the supposed indications of stratification 

 are as applicable to granite as to the crystalline slates with 

 which it is associated, it might be inferred that this unstratified 

 rock is also stratified, and that the generally esteemed igneous 

 rock is of aqueous origin. How can this dilemma be 

 avoided ? Are there any other characters, common to the so 

 called primary strata and the fossiliferous groups, by which 

 they may be distinguished in all cases from the granitic rocks ? 

 The form and structure of beds, and the alternations of rocks 

 varying in mineral composition, as already stated, do not 

 afford any criterion ; nor can we adopt the transitions between 

 these two classes of strata as evidence of the primary slates 

 being stratified, and of aqueous origin, for these again are 

 connected with granite by a more complete bond of union, by 

 that kind of transition which we have called the mineral, in 

 order to keep it distinct from the mechanical, which obtains 

 in the former case. 



A lengthened consideration of these difficulties has led us to 

 infer that the prevailing classification, which divides rocks 



B B 2 



