1871.] JAMIESOI^^— BANFFSHIRE METAMORPHIC ROCKS. 105 



venie Castle, close by the edge of the stream. Here the slate 

 troughs the quartz iu a synclinal fold, which is much more abrupt at 

 one side than it is at the other ; for as we walk along the river from 

 north-west to south-east, we find the slate disappearing under the 

 quartz at an angle of from 20° to 25°, and emerging again to the 

 south-eastward almost vertically. The quartz-rock is here much 

 crushed and disintegrated, as if by the nip it had got in the sharp 

 curve of the synclinal fold. 



The Granite — its Oeigim". 



The granite of this region, I am inclined to think, has resulted 

 from the fusion and recrystallization of the arenaceous beds. It is 

 evident that the granite has originated after the deposition of these 

 old sedimentary strata, because they are everywhere penetrated by 

 its veins and injected masses, as may be well seen in the district 

 around Lower Craigellachie. The granite, however, does not de- 

 range the strike of the beds to the degree that such a mass of 

 foreign material should have done had it been erupted in an igne- 

 ous condition, or forced up in any other conceivable way. I would 

 rather suppose that the heat from the interior of the earth gra- 

 dually approached the base of these sedimentary beds and, by heat- 

 ing, caused them to expand and thereby become wrinkled into 

 huge folds, as a necessary consequence of a great mass of swollen 

 matter having to find room in the space occupied by the same 

 matter when in a cold and contracted state. The portions most 

 liable to be fused would be softened and dissolved in situ, and be 

 injected with enormous force, in consequence of the pressure, into 

 all the openings and crevices around them. Crystallization would 

 then take place as the whole very slowly cooled. In some such 

 way, I imagine, the granite of this region has been formed out of 

 the lower arenaceous and silty beds, and the greenstone of the 

 Portsoy district out of the more argillaceous strata. The heat, as 

 well as the watery vapour under such immense pressure, would pro- 

 bably penetrate further into the arenaceous beds than into the 

 closer-grained clays. These views are confirmed by finding the 

 granite occupying the room of what should have been gneiss or 

 quartz-rock and the greenstone replacing the argillaceous beds. 

 The serpentine of this region, as I have before mentioned, seems 

 to have resulted from the metamorphism of beds containing much 

 magnesia. In some places around Lower Craigellachie and the 

 southern base of Ben Aigan, the gneiss is plentifully streaked with 

 granite, as if partial fusion had just begun. These portions are 

 found along the circumference of the great mass of granite, and 

 seem to me to represent the gradual passage of arenaceous or silty 

 strata by way of gneiss into granite. And here I may mention that 

 the gneiss and quartz-rock of this region, even where most si- 

 liceous, always contains a proportion of felspar. The softening and 

 fusion, as it progressed, would advance more rapidly along certain 

 lines where the mineral matter was of such a nature as to yield most 

 readily to the influence of the forces acting upon it. 



