254 Outlines of Geology. 



mica slate. The peculiar and differing dip of the respective 

 strata, and the singular manner in which they are pierced and 

 traTersed by veins of felspar, chlorite, and quartz, and lastly 

 their association with micaceous iron, are circumstances which 

 will not escape the eye of the observer in his journey through this 

 district, the beauty and magnificence of which, in regard to gene- 

 ral scenery, is not less than its diversified geological peculiarities. 



Mica-slate abounding in garnets, and often speckled with red 

 patches, originating in their decomposition, and becoming syeni- 

 tic from the interspersion of hornblende, is prevalent upon the 

 banks of the Tay, at and about Dunkeld ; but it is in Glentilt 

 that the geologist, both practical and theoretical, will find the 

 most ample materials for the study of the associations and junctions 

 of the primitive series of rocks. For a detailed account of Glen- 

 tilt, I must refer those who are desirous of visiting it with the ad- 

 vantage of previous information to the account drawn up by the 

 late Lord Webb Seymour, and to a very able paper upon the 

 same district, in the Geological Transactions, by Dr. Mac Culloch. 

 He that is tinctured with the Huttonian doctrines, will here find the 

 Plutonists upon their strong ground, and will not feel disinclined 

 to join in that complete contempt for the Neptunian theorists, 

 which the language of Mr. Playfair is so well calculated to in- 

 spire. But he that is above the trammels of authority, and who 

 dares to doubt its edicts, and to refer to his own unprejudiced and 

 unbiassed opinion, will even here, in the Plutonic fastnesses, find 

 matter to awaken his doubts, and to teach him the imperfection 

 and faultiness of all geological theory. 



In the immediate neighbourhood of Blair, the Tilt exhibits 

 upon its banks a deep section of the rocks that form its bed, and, 

 what is remarkable, the micaceous strata here, and also at the 

 falls of the Bruar, incline nearly at the same angle to several 

 points of the compass, giving a curious interweavement and con- 

 fusion to their assemblage. Ascending a few miles up the glen, 

 we observe granular limestone, either embedded in, or interstrati- 

 fied with, the micaceous and gneiss rock, particularly well seen a 

 little below Gilbert's bridge, and occasionally accompanied and 



