THE proble:m: of the lizard rocks. 491 



converted into that peculiar variety of hornblendic schist which 

 characterises the locality, others have been converted into true 

 serpentine, and others, again, into a rock of an intermediate 

 character." 



Finally, Mr. Teall, author of British Petrography, bringing 

 the result of his extensive microscopical investigations to bear 

 uj)on the subject, contends that the foliated structure of the allied 

 gabbro rocks is a secondary structure due to earth movements 

 acting upon the solid rock, and is the result of pressure or 

 regional metamorphism. 



In thus going over and attempting to classify these various 

 opinions, I could not but arrive at the conclusion that there is an 

 evolution in geological as in all other opinions. 



Geology is only just now emerging from its infancy. When, 

 following the venerable example of Cuvier and Humboldt, every 

 writer on geology felt bound to give his own account of the 

 creation, starting with the assumption of vast subterranean 

 masses of molten matter, and having thus secured his ' ' Deus ex 

 machina," he could draw upon it unreservedly for the explana. 

 tion of all volcanic phenomena, and of many others not even 

 remotely volcanic. 



And thus the suspicion steals upon us that those geological, 

 equally with theological opinions, appear to be hereditary. For, 

 in spite of the philosophical researches of Mallet on earthquakes, 

 and the still more modern and far-reaching researches of con- 

 tinental and English geologists on earth movements in mountain 

 formation, we have a distinct survival of these supernatural 

 igneous theories amongst living geologists of the older school, 

 who are unwiUing to ascribe to simply dynamic causes the 

 infinite compression, displacements, and metamorphism of rock 

 masses ; we cannot, consequently, expect at their hands a theory 

 which will explain all the facts open to observation. 



In my first paper I referred to the impending International 

 Congress at London, and I now propose, in conclusion, to give 

 a condensed summary of the information there gathered, which, 

 I hope, may throw a fresh light upon the question of the Lizard 

 rocks. 



