Dr. Mac Culloch on Quartz Rock. 473 



the correlative of secondary, and involves no hypothesis with regard 

 to the absolute Eeras of rock formations. But I must pass on to 

 further matter of fact, leaving to the labours of future geologists, 

 the actual connections and origin of these breccias, and the distinc- 

 tions to be drawn among this very intricate class of rocks. 



In the district of Appin the quartz rock may be observed in va- 

 rious parts, and although I have not been able in this place any 

 more than in Mar, sufficiently to trace its connexion with the mica 

 slate of the country, I have little doubt that it immediately follows, 

 and possibly alternates with it. It may be seen not far from the 

 castle of Bercaldine, and forms a large detached rock at Alrds. Here 

 it is of a highly indurated character, and bears the marks of a dis- 

 turbed stratification. I do not think it necessary to describe the 

 particular aspect which each rock assumes, as it most frequently 

 happens that various modifications of it are to be met with in the 

 same spot, and I prefer delaying the general description till I have 

 mentioned the several places In which It Is found. 



The same rock occurs in the district of Arlsaig. It occupies there 

 a considerable portion of the shore, and may be traced forming low 

 hills and Interrupted projections, from the point of Arlsalg, nearly to 

 Loch Morrer. It seems here to alternate with mica slate, as I have 

 already mentioned in another place, where I have quoted Professor 

 Playfalr's remarks on it; but possesses much less of the appearance 

 of stratification than in the other Instances which I have enumerated. 



In the island of Sky it occupies a considerable space, and forms 

 that large mountain mass which projects from the general eastern 

 boundary of the island, so as to produce, together with the main 

 land, the narrow passage of the *Kyle rea. Here it assumes a 



* Kyle rea the smooth strait, Kyle ree the King's strait, but both arc corrupt ety- 

 mologies. Kyle rich, the swift strait. 



Vol, II. 3 o 



