﻿1861.] 



MURCHISON AND GELKIE HIGHLANDS. 



203 



5s 



Of 



be 



mm 



a prevalent dip in this region may be, 

 \ even though it should seem to be 

 perfectly regular. The strata, con- 

 v ' sisting of gneiss, mica-schist, and mi- 

 \- N ' caceous quartz-rock, are exposed for 

 \ \ about 100 yards, and, as shown in the 

 ! j accompanying diagram (fig. 17), are 

 /' / folded upon each other in such a way 

 \ \ that the same stratum is repeated 

 \ ; seven times in that space. The actual 

 / i thickness of the beds in this section 

 / is perhaps not more than 10 or 15 

 yards — that is, from a seventh to a 

 tenth of their apparent thickness. In 

 \ walking over the edges of these highly 

 inclined strata, with possibly here and 

 "\ there the indication of a south-easterly 

 ! ; dip, we might very naturally set down 

 <' the beds as one continuous series; and, 

 without a clear transverse section, it 

 would be diflicult to prove that they 

 j were not. 

 / The other section is represented in 



fig. 18. It shows another way in 

 which the vertical thickness of these 

 upper gneissose rocks may be reduced 

 \ from its enormous apparent magni- 

 tude. Instead of vertical folds, we 

 J are often presented, as in the rocks 

 depicted in this figure, with contorted 

 bedding, which even more than the 

 former tends to modify our estimate 

 \ of thickness. 



•' .There can be no doubt that these 



I sections are truly typical of the struc- 

 ; ture of the metamorphic regions of 

 Scotland. Theyshow us how the rocks 

 \ are folded on the small scale, while the 

 ) synclinal axis of Loch Quoich proves 

 / how these are repeated by great 

 troughs and arches. The large amount 

 of repetition thus induced makes it 

 no longer difficult to conceive that the 

 gneissose and micaceous flaggy rocks 

 of the' Highlands do not attain so gigantic a thickness as they for- 

 merly seemed to do, and that in truth they need not be regarded as 

 more than equal to the lower half of the Silurian system in other 

 regions. 



Arisaig to Banavie. — A transverse section which we examined 

 with great care, and which perhaps offers the best natural expo- 



