NORTH UIST. GEOLOGY. 145 



character, being interspersed with grains of felspar 

 and quartz, or passing into a rock intermediate between 

 granite and schist, or ultimately acquiring the external 

 appearance of a gneiss of which the laminar tendency 

 is produced by foliated portions of the schist. Some- 

 thing similar occurs in the schist in this place. Where 

 it approaches the granite veins it is much disturbed in 

 its position, and the laminae become twisted and bent, 

 or disappear altogether. Often, it is found to contain 

 grains of granitic matter distinctly interspersed ; which 

 accumulating in some places, there is at length seen a 

 perfect transition from schist to granite. In examin- 

 ing the contact of these distinct bodies, many varieties 

 produced by this transition can be seen disposed 

 in every mode of confusion. The surfaces which have 

 been exposed to the action of the sea often show the 

 marks of this mixture of character where it is not so 

 easily detected by a fracture. They are every where 

 thickly strewed with prominent points, the crystals 

 of a harder matter which has resisted corrosion. This 

 rough schist is mixed with the smooth, but in no 

 evenness of order or regularity of alternation, the two 

 kinds, as well as the accompanying granite veins, being 

 every where confounded together in an irregular manner. 

 There can be no hesitation in considering the rough 

 schist as a portion of the smooth, altered by the con- 

 tiguity or influence of the granite veins. The phe- 

 nomena here are perfectly similar to those which occur 

 both in the schist and limestone found in the vicinity 

 of the granite in Glen Tilt; of which I have given 

 an account in the Transactions of the Geological Society. 

 The same varieties of schist may also be observed 

 at the foot of Heval, and on the shores of Rona. They 

 constitute a rock distinct from gneiss, and will probably 

 be considered as of more recent formation. It has indeed 

 been said that clay slate, to which the schist in question 

 belongs, is removed from gneiss as well as from granite 



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