LOCH KEN DISTRICT. 151 



greywacke when next the granite they are interesting and 

 completely different from those exhibited at the Needle's 

 Eye, inasmuch as the slate invariably passes into a perfect 

 slaty aggregate of brown micaceous scales. In regard to 

 the positions of the two rocks to each other, they are rather 

 remarkable : there is the most perfect intermixture, the 

 one with the other ; layers of granite, in many instances, not 

 more than two or three lines in breadth occurring completely 

 isolated in the strata, and without any visible connexion 

 with the main mass of the rock. The very reverse of this 

 is also, in many places to be observed, masses of the slate 

 altered into brown mica, occurring imbedded in the granite. 

 In their position these granitic masses enveloped in the slate 

 agree with the greywacke, conforming in every instance 

 with the contortions visible in it ; a circumstance which very 

 frequently attends junctions of granite with stratified rocks. 

 At the planes of junction here there is never to be observed 

 a well marked boundary line ; on the contrary, there is a 

 transition of both rocks into each other, of such a nature 

 that, if a theory concerning the origin of granite were to be 

 formed only from the phenomena of this point, it would in- 

 cline any one to consider both mineral masses as merely mo- 

 difications of each other, and the effect of one and the same 

 cause or system of causes. 



II. Loch Ken District.* 

 Another group of granitic rocks is met with in the neigh- 

 bourhood of Loch Ken in Kirkcudbright : as several junc- 

 tions, however, of these rocks with the greywacke have 

 been described in the Transactions of the Royal Society of 

 Edinburgh, we shall here only notice a few localities shortly. 



* The geognosy of this district is described by Dr Grierson in a me- 

 moir and map laid before the Wernerian Society, and published in the 

 3d volume of the Annals of Philosophy, and also in a memoir in the 2d 

 volume of the Wernerian Memoirs, entitled " Mineralogical Observations 

 on Galloway." 



