10 PRINCIPLES OF GEOLOGY. 



FREED 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 admitted, that, to as 

 great a depth as we can ascertain, our planet is composed of various but 

 definite rocks, possessing constant characters, whereby they may be dis- 

 tinguished, and that they are arranged 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 re- 

 gularity of structure to prevail ; extending our views, we perceive that 

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

 widely-spread formations ; and finally combining together observations 

 made in distant regions, we ascend to a grand principle of universal 

 analogy in the construction of our planet. If, then, such analogy 

 pervades the structure of different regions, it will be necessary, in stating 

 general laws, to call in the aid of extensive research ; but particular 

 laws for each country can only be derived from local investigation. 



Possibly those who are accustomed to trace across our island the 

 wonderful regularity of strata, or who know the strong resemblance 

 which they exhibit in countries far removed from each other, may 

 have expected more sweeping assertions than I have thought it cor- 

 rect to maintain. They might, perhaps, have been little surprised at 

 a bold declaration, that all our secondary rocks may be discovered 

 with their proper characters over all the continent, when the labours 

 of foreign geologists have been as successful as our own. But this 

 would be an unjust view of the matter ; in several instances it is 

 absolutely disproved. The utmost that can be expected, is to trace a 

 general conformity and universal analogy of deposits. To what ex- 

 tent this conformity reaches, much as geologists have done, they have 

 not yet demonstrated. It is ascertained that there are certain formations 

 which possess a mineralogical character, and a geological position so 



