OVERLYING ROCKS. 513 



There are many different aspects in this rock, 

 arising from the colours of the felspar, which, 

 besides those just named, may be of a dull white, 

 or ash-coloured, or of an ochry hue, or of reddish 

 tints. The two last, it must however be remarked, 

 are rare among these syenites. It varies also ex- 

 tremely, in the proportions of the ingredients ; 

 and those varieties are the most remarkable, which 

 contain a small proportion of hornblende. 



B. Felspar, hornblende, and mica. 



This variety does not appear to be common. 

 It has been called micaceous greenstone. 



C. Felspar, hornblende, and chlorite. 



D. Felspar, hornblende, mid steatite. 



These also are rare, but they are found in 

 Sky. 



E. Felspar, quartz, hornblende, and mica. 



This variety occurs in Sky, and apparently 

 elsewhere, in connection with some of the pre- 

 ceding, and incumbent on conchiferous limestone. 

 Its geological situation therefore admits of no 

 doubt, notwithstanding its resemblance to granite. 

 Its existence in this situation, and the presence of 



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