136 ANCIENT AND MODERN CHANGES. 
softer rock has in the lapse of ages been abstracted, 
and disclosed the denser substance to view. 
Not to dispute the efficacy of existing physical 
operations on the superficial portions of the globe, 
one axiom with me is—in direct difference from 
the new theory of the identity ofancient and modern 
causes of change—to draw the line of demarcation 
between the two, feeling satisfied of their perfect 
incongruity, and of the absence of those superior 
agencies which apparently operated in the former. 
Doubtlessly, the commoner properties attached to 
matter and motion have ever been the same from 
the first ages, but, to account for the introduction 
of new principles, new combinations, and new and 
stupendous influences, we need allow the introduc- 
tion also of a power which in latter eras has not 
interfered. Can the chemical affinity and cohesion 
of particles as they exist in our ancient strata,—can 
the combinations of heterogeneous rocks, as evinced 
among a great number of formations,—can the ap- 
pearance of new materials on the earth, carbonate 
of lime forinstance,—can the uplifting of our ancient 
rocks,—can these, and other original changes of the 
earth be really ranged as collateral actions with 
those now witnessed? If however we disregard 
the modern changes of our globe we assuredly shut 
our eyes on phenomena intrinsically important, and 
may probably confound with primeval conditions, 
modern circumstances and substances incongruous 
therewith, so far at least as system and theory are 
concerned. It has accordingly been my endeavour 
to give due weight to those recent changes discover- 
able with us, during the preceding pages devoted to 
the second part of the geological department of this 
work. To theorize consistently with respect to our 
grauwackeé rocks, I found it requisite to withdraw 
all confidence in the system which forces present 
agencies to play a part in causing their production 
