Professor E. Forbes on the Oolite in Skye, 89 



described is of no small interest, when considered in its 

 bearing on the physical geography of our area during the 

 oolitic epochs. From the lias up to the cornbrash, or beds 

 probably equivalent to that stage in the series of oolites, we 

 have in the Hebrides, as was indicated by Macculloch, and 

 proved by Murchison, a continuous sequence of marine con- 

 ditions, which, if I might venture to judge from the as yet 

 imperfect evidence of the contained fossils, prevailed in a sea 

 by no means shallow. But at the termination of the deposi- 

 tion of the middle oolitic strata, we have indications of most 

 important changes, and of the conversion of the bed of the 

 Hebridean oolitic sea into an estuarine and terrestrial area, 

 which, after a considerable lapse of time, became submerged 

 under oceanic conditions, and had a new series of marine 

 strata deposited upon it. 



If I read what I have seen aright, the Plutonic phenomena 

 which accompanied these changes were not less interesting. 

 The great and thick sheet of imperfectly columnar basalt 

 which has so wide an extension in the Island of Skye, and 

 plays so important a part in the formation of the magnificent 

 scenery of its coasts, was the product of a submarine erup- 

 tion, which, if we regard this basalt as an overflow, has its 

 geological date marked to a nicety, having occurred at the 

 close of the middle and at the commencement of the upper 

 oolitic period. This vast cap of compact volcanic matter 

 served to assist in the consolidation of the muddy and sandy 

 marine accumulations over which it spread, and the Titanic 

 throes of this region of eruptions elevated the whole probably 

 above the level of the ocean, and converted a part at least of 

 the sea-bed into dry land, the area of which, and of its fresh 

 and brackish waters, became again submerged, to be again 

 overwhelmed by the destructive outpourings of submarine vol- 

 canoes ; their results we now see in the great and thick mass 

 of trap forming the line of hills constituting the chain of the 

 Storr. This trap has features distinct from those presented 

 by the bed between the middle and upper oolites. It is in 

 great part an amygdaloid, and its vesicular character may 

 indicate the formation of it at a different depth of water and 

 under different circumstances — a conclusion consistent with 



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