230 AN ENQUIRY INTO THE [Ch. XII. 



CHAPTER XII. 



ARE THE PRIMARY SCHISTOSE ROCKS STRATIFIED ? 



Definitions of the term stratum not satisfactory yet the basis of modern 

 classification. If primary slates be stratified, so are also the granitic rocks. 



Primary slates and sedimentary deposits said to be analogous proofs 



thereof advanced by Lyell This opinion of their common origin combated, 



for, according to this evidence, the igneous rocks are analogous to the strati- 

 fied- Involving a contradiction. Granite said to be occasionally stratified. 

 Whence this contrariety of opinion? Attributable to the structure of rocks 



common to the individuals of every geological epoch and every mode of 

 origin. Not dependent on successive depositions but superinduced during 

 consolidation. This no new doctrine as regards igneous rocks ought to be 

 extended to aqueous deposits. The structure of rocks a variety or mode of 



crystallisation This subject demands further investigation/ Conclusion. 



Primary slates not stratified, in the usual acceptation of the word. 



THE question which forms the title of this Chapter may be 

 regarded as very simple, and one that can be immediately 

 answered in the affirmative. It appears, however, to be one 

 of the most complicated in the science of geology : indeed, it 

 may be stated now, as it was by Greenough fifteen years ago, 

 in his excellent Geological Essays, " that the word stratum is 

 so familiar to our ears, that it requires some degree of man- 

 liness to acknowledge ourselves ignorant of its meaning ; and 

 easy as it may seem to determine, whether a given mass be 

 or be not stratified, there is, perhaps, in the whole range of 

 geological investigations, no subject more pregnant with con- 

 troversy/' And, after adducing a mass of contradictory evi- 

 dence on this subject, he concludes by asking many questions, 

 and adds, " Let him who can answer these, rest assured that 

 he has a distinct idea of stratification." 



Now, though so many years have passed away since the 

 President of the Geological Society solicited attention to this 

 important topic, and though during this period the science 



