IN GLEN TILT. $*7S 



described. An account of this dyke was laid before the Geological 

 Society of London, in a paper by Mr Bennett, read in March 1812. 

 A notice of it appears in Nicholson's Journal, for April 1812, which is 

 the source of my information. 



Note C, Parag. 133. 



When Dr Hutton communicated his views respecting Glen Tilt to 

 the Society, he signified his intention of giving at some future time a 

 full description of the phenomena he had observed ; and, in the first 

 volume of his Theory of the Earth, he promised to introduce it in the 

 course of the work. At his death he left a third volume of this publi- 

 cation nearly ready for the press. Mr Playfair has favoured me 

 with a sight of the manuscript, which contains a more particular ac- 

 count of the author's observations upon the junctions of granite and 

 primary strata, in Glen Tilt, in Arran, and in Galloway. His descrip- 

 tions are not minute, but were to have been illustrated by en- 

 gravings, from drawings made on the spot; partly by the late Mr 

 Clerk of Eldin, who accompanied him in two or three of his minera- 

 logical excursions. When describing the appearances in the bed of 

 the Tilt, he says, " The granite is here found breaking, and displa- 

 " cing the strata, in every conceivable manner, including the frag- 

 " ments of the broken strata, and interjected in every possible direc- 

 ** tion among the strata, which appear. This is to be seen, not in one 

 " place only of the valley, but in many places, where the rocks ap- 

 " pear, or where the river has laid bare the strata." If Dr Hutton 

 has called the sienite granite, this can hardly be considered as a mis- 

 take in nomenclature at the time when he wrote ; and, though the 

 W T ernerian School have insisted much upon the distinction of those 

 substances, it appears of little consequence in forming a theory for the 

 origin of that great tribe of crystallised aggregates, to which they 



Vol. VII. P. IL' 3B 



