THE PROBLEM OF THE LIZARD ROCKS. 355 



If we looli at the most characteristic rocks of the district, 

 the serpentine, we are confronted at once by a multiplicity of 

 divergent opinions. 



Are the rocks eruptive or are they sedimentary rocks 

 metamorphosed in situ ? And whether eruptive or sedimentary, 

 through how many stages of metamorphosis have they passed 

 before reaching their present state ? Has the metamorphosis 

 been sudden through contact with volcanic heat, or has it been 

 brought about through dynamic causes, enormous pressure and 

 friction, producing heat and consequent displacement and re- 

 arrangement of particles ? Or has the metamorphism been 

 produced by what may be called the " wet process," the slow 

 filtering in and permeating of water holding mineral solutions, 

 and transforming and recasting the whole mass into new 

 compounds ? And if any of these causes have thus acted upon 

 the serpentine, how are we to proceed to the analysis and true 

 classifications of the surrounding medium, those puzzling beds 

 of hornblendic schists, themselves a secondary metamorphic 

 product ? And if we should find a solution to this question we 

 still remain confronted by the infinite variety and intermixture of 

 hornblendic, chloritic, and granitic rocks, and above all by the 

 innumerable dikes and extensive tabular masses of Gahhro, of 

 which remarkable rock specimens were exhibited to you at last 

 year's meeting by Mr. Howard Fox, F.G.S. 



Sedgwick called this rock porphyritic felstone, which at all 

 events implies some meaning, but modern geologists have adopted 

 the name of " gabbro," which only indicates that the Cornish 

 rock resembles another rock in Italy locally called "gabbro," 

 and thus we have substituted one name for another without 

 thereby explaining the nature of the thing itself. 



To crown this babel of names, we are asked by some 

 geologists to admit that a number of granitic dikes intersect the 

 district and come out in the coast line. And thus is raised the 

 question of the fundamental granite and of those beds of 

 crystalline gneissose rocks, through which the serpentine and its 

 agglomerates are supposed to have been ejected, or if not ejected, 

 upon which they are supposed to lie as in a basin. 



