8 Principles of Geology. 



oolite, calcareous grit, Oxford clay, Kelloways rock, cornbrash, the 

 Bath oolite rocks, lias, red marl and sandstone, raagnesian limestone, 

 coal series, mountain limestone, and slate rocks. The series in the 

 south of England is precisely accordant, except that the magnesian 

 limestone is there deficient, and that the Kimmeridge clay is covered 

 by .some strata which do not reach into Yorkshire. Besides, we find 

 the Yorkshire strata actually united with those of the same name in 

 other parts of England, so that there can be no doubt of the gen- 

 eral continuity of the strata, and of constancy in their order of suc- 

 cession. The same conclusion is upheld by independent research in 

 foreign countries. There, as in England, it is demonstrated, that, to 

 as great a depth as can be accurately examined, various rocks are 

 laid on one another, in a certain consecutive series, by which it is not 

 difficult to assign to each its unvarying place in the scale ; and that 

 these rocks are not formed in insulated patches, but in widely-ex- 

 tended strata, which hold their courses across provinces and kingdoms. 



This encourages us to inquire whether there be not some general 

 analogy of the rocks, not only across islands and kingdoms, but even 

 across whole continents ; for if this should prove to be the case, we 

 shall be enabled to propose general lav^s of structure, applying equally 

 to every part of the globe. For the purpose of this comparison, we 

 must not think to employ the characters of individual rocks, however 

 remarkable they may appear, but we must group together analogous 

 formations, and look only on the greater features of nature. We 

 must consider the physiognomy of the-carth, and, amidst many local 

 variations, trace hues of general agreement. 



Reviewing the series of British rocks, we shall observe three great 

 divisions, of which two are extremely obvious ; the rocks of the 

 mountains and the strata of the plains: the third division possesses, 

 perhaps, quite as definite characters, but they are not manifested 

 without more research. The mountainous regions of Britain are 

 composed of hard, often crystallized rocks, variously associated and 

 related to one another, commonly stratified at high angles of declina- 

 tion, and for the most part destitute of organic remains. Such are 

 granite, gneiss, mica slate, quartz rock, primitive limestone, serpen- 

 tine, and slate. From the Shetland Isles to Cornwall, a general con- 

 formity in character unites the mountain groups. From these eleva- 

 tions, the rocks above-named dip or decline on all sides into the earth, 

 sink deep under the more level regions, and are there covered up 

 and buried beneath various deposits of limestone, sandstone, coal, 



