MONIAN SYSTEM OP ROCKS. 527 



brownish granite. Standing isolated in the Ordovician, and 

 between the boss and the road, there is another, in which quartzose, 

 micaceons, and calcareous materials are inextricably mixed. All 

 the exposures inland are of this general character, one kind or 

 other of the materials prevailing ; but near the boundary along the 

 northern fault the rock next the granite is clearlj^ foliated, and 

 under the microscope is seen to differ from ordinary grey gneiss 

 only in having certain patches decomposed, and containing much 

 more felspar than quartz. 



We are now in a position to examine the coast. Here nothing is 

 covered ; every inch of the rocks for more than a mile is visible and 

 accessible ; if there is any confusion, it must arise from the nature 

 of the rocks. It is well nigh impossible adequately to describe the 

 extraordinary phenomena here revealed. The description by 

 Sir A. Ramsay is very faithful ; but Dr. Callaway seems to have 

 been altogether led astray. If, however, we really saw on this 

 coast the proof that metamorphism could produce these rocks out of 

 the neighbouring black shales or their associates, it would be a 

 still more wonderful place than it is. The main feature is the 

 extraordinary way in which the harder and more crystalline 

 portions go in and out and lose themselves in the softer and more 

 stratified. At one place we find the whole clifi'-side for many yards 

 composed of crystalline rocks ; from this they pass over into isolated 

 knobs on the surface, and so to lumps or strings amongst the softer 

 material, and the lumps may degenerate in size until they are no 

 larger than pebbles. It is thus that such confusion is produced : 

 but it is seen to be a confusion due to their origin, and not to dis- 

 turbance. They have undoubtedly been squeezed, the spectral 

 polarization of their constituents proves that ; but if this has brought 

 about their foliation, it has also contorted the lines of foliation, 

 which are related to the occurrence of the more crystalline masses, 

 and do not amount to folds. This is particularly the case with the 

 portion south of Forth Lygan, where the harder parts are fewer. 



The microscopic structure of these rocks will not allow us to look 

 to progressive or sporadic metamorphism to account for the 

 differences within the mass, still less, therefore, for the mass itself. 

 The rocks, which look in one place like pelites, in another like 

 mica-schists, are, in fact, not like any of the rocks so named before ; 

 they consist of the same minerals as the crj^stalline rocks them- 

 selves. Quartz is one of these, and is perfectly clear in both, only 

 larger in the crystalline portions. Eelspar, spotted with spangles of 

 calcite or sericite till there is scarcely any original felspar left, is 

 the next abundant mineral in the crystalline portions ; but there is 

 often no felspar left or produced in the ground-mass of the others. 

 The main difference is the indefinite amount of mica produced in 

 the schistose and the corresponding amount of unaltered dust 

 in the non-schistose rocks; another important difference is the 

 development of garnets in those that cannot be called granitic. 

 From this we learn that there are actually more varieties of 

 minerals in the non-granitic than in the granitic masses, and these 



Q.J.G.S. No. 175. 2 k 



