Principles of Geology. 9 



clay, chalk, and other strata of inferior hardness, and not crystallized, 

 but amply stored, nay filled to admiration, with plants, corals, shells, 

 and other remains of organized beings. Besides these, there is a 

 third division of rocks ; viz. slenite, porphyry, basalt, &;c. which are 

 of local occurrence, appear in peculiar forms, and present particular 

 phenomena. They repose indiscriminately upon the rocks of the 

 mountains or those of the plains, and occasionally divide them by 

 dykes, yet have only an accidental connexion with either. Such is 

 the general character of the geology of Britain. And I may appeal 

 to the progress of the science for proof, that such is the general char- 

 acter of the whole face of the earth. 



In every country the great mountain ranges are composed of the 

 lowest rocks with which we are acquainted. There may be other 

 rocks below the granitic series, but we have not yet found means to 

 observe them. Therefore, as being the lowest, and consequently the 

 most ancient rocks, included in the compass of our observation, we 

 call them Primary. Those more horizontally deposited rocks which 

 fill wide plains, and rest upon the subterranean slopes of the former 

 series, composed of various alternations of calcareous, siliceous, and 

 argillaceous substances, with local deposits of coal, and generally 

 abounding in shells and other organic remains, are universally termed 

 Secondary. Those rocks which rest indiscriminately on the primary 

 or the secondary series, lie in irregular patches, and send off veins 

 or branches into both primary and secondary, being in fact super- 

 added to both, yet conjoined to neither, receive the name of Inde- 

 pendent or Overlying. 



FiiEED from theoretical views, or rather under the influence of very 

 opposite and contradictory theories, all parties confirm this relation 

 of facts, and agree in the conclusion, that the earth exhibits every 

 where the same principles of structure. It is now universally ad- 

 mitted, that, to as great a depth as we can ascertain, our planet is 

 composed of various but definite rocks, possessing constant charac- 

 acters, whereby they may be distinguished, and that they are ar- 

 ranged upon one another in a constant relative order. 



The mode of investigation by which this result has been obtained, 

 appears to me satisfactory. Beginning at home, we find certain reg- 

 ularity of structure to prevail ; extending our views, we perceive 

 that the rocks of our district are not insulated deposits, but portions 



Vol. XXL— No. 1. 2 



