THE ISLE OF EfGG, 1 4f> 



tance from the coast, however, especially on the east side 

 of the island, this fact is most distinctly evident, and the 

 inclination appears not to exceed an angle of seven or 

 eight degrees. 



As the geognostical account of this island, which we 

 now lay before the Society, was the result of a somewhat 

 detailed examination, we shall endeavour to notice the se- 

 veral rocks of the district both individually and collective- 

 ly, — individually as their mineral and organic characters 

 are concerned ; collectively, as relating to the modes by 

 which they are connected with each other. 



The secondary strata, which we shall first describe, are 

 only visible in the cliffs' which skirt the island from the 

 neighbourhood of Kildonan* on the east, to the Bay of 

 Laig on the west. Generally, they are much obscured by 

 their own debris and that of the associated trap-rocks ; 

 sometimes, however, good sections may be obtained, and 

 the several strata examined with accuracy over a consi- 

 derable space. The sandstone of this island is white, being 

 composed of grains of quartz held together by a basis of 

 calcareous matter through which iron-pyrites is abundant- 

 ly disseminated. It is distinctly granular, and forms beds, 

 in many instances, of very considerable thickness, t Asso- 



* Kil Donan, — i. e. the Tomb of Donan, the tutelar saint of Eigg. 



t In mineral characters the oolitic sandstone differs nothing from 

 the sandstones of the independent coal-formation. Composed, therefore, 

 as it is, almost entirely of quartz particles, and remembering the in- 

 variable sameness in the characters of both of these sandstones though 

 differing in geological age, over Britain, Continental Europe, and from 

 areas of immense extent, it becomes a subject of interest to ask, whence 

 has this enormous mass of quartz been derived ! To this question no 

 satisfactory answer can be given. Knowing the white sandstones as of 

 a derivative origin, and not as of an original formation, it would be de- 

 sirable to fix upon some primordial or older derivative quartz-deposits 

 from the breaking up and erosion of whicli they may have been formed. 



