418 SIR CHARLES LYELL 



stance of its confirming the assumed want of analogy be- 

 tween geological causes and those now in action. By what 

 train of investigations were geologists induced at length to 

 reject these views, and to assent to the igneous origin of 

 the trappean formations? By an examination of volcanos 

 now active, and by comparing their structure and the com- 

 position of their lavas with the ancient trap rocks. 



The establishment, from time to time, of numerous points 

 of identification, drew at length from geologists a reluctant 

 admission, that there was more correspondence between the 

 condition of the globe at remote eras and now, and more 

 uniformity in the laws which have regulated the changes of 

 its surface, than they at first imagined. If, in this state of 

 the science, they still despaired of reconciling every class of 

 geological phenomena to the operations of ordinary causes, 

 even by straining analogy to the utmost limits of credibility, 

 we might have expected, at least, that the balance of proba- 

 bility would now have been presumed to incline towards the 

 close analogy of the ancient and modern causes. But, after 

 repeated experience of the failure of attempts to speculate 

 on geological monuments, as belonging to a distinct order of 

 things, new sects continued to persevere in the principles 

 adopted by their predecessors. They still began, as each 

 new problem presented itself, whether relating to the animate 

 or inanimate world, to assume an original and dissimilar 

 order of nature; and when at length they approximated, or 

 entirely came round to an opposite opinion, it was always 

 with the feeling, that they were conceding what they had 

 been justified d priori in deeming improbable. In a word, 

 the same men who, as natural philosophers, would have been 

 most incredulous respecting any extraordinary deviations 

 from the known course of nature, if reported to have hap- 

 pened z";i their own time, were equally disposed, as geologists, 

 to expect the proofs of such deviations at every period of 

 the past. * * * * 



