332 Proceedings of the Royal Physical Society. 



eastern promontory of Westray, the flagstones are more highly 

 inclmed to the east. On the islands of Fara Holm and Fara, 

 the same high angle is observable with a similar easterly dip; 

 and there can be little doubt that the grey flags in the latter 

 islets are higher in the series than those at Weatherness. 

 The flagstones exposed on the western shore of Eday between 

 Fara's Ness and Seal Skerry are merely the southern pro- 

 longations of the flaggy beds in Fara and Fara Holm. On 

 the whole, then, the succession of the strata between Westray 

 and Eday is tolerably clear, notwithstanding some short gaps 

 in the sections. 



The structure of the island of Eday is comparatively simple. 

 The strata form a well-marked syncline, the axis of which 

 lies to the west of the Flighty and Fara's Ness Hills, The 

 centre of this trough is occupied by a great series of yellow 

 and red sandstones, which rest conformably on the flagstones 

 already described. The shore sections on the east and west 

 sides of the island are so clear and convincing, that no one 

 can possibly dispute the conformable passage of the flagstones 

 into the overlying arenaceous series. So strongly do the 

 sandstones of Eday resemble the Upper Old Eed Sandstones of 

 Hoy, that Sir Eoderick Murchison placed them on the same 

 horizon. But a minute examination of the coast sections 

 proves that they really belong to the Flagstone series, and are 

 therefore of much older date. 



A traverse along the shore from Fara's Ness to the sandy 

 bay about a mile to the east, shows the gradual alternation of 

 sandstones and flags at the base of the arenaceous series. At 

 the promontory now referred to, the grey flagstones are seen 

 dipping to the east at an angle of 30° ; but not far to the 

 east they are interstratified with bands of flaggy sandstone. 

 These beds are overlaid by false-bedded yellow sandstones 

 which contain numerous brecciated bands made up of angular 

 fragments of crystalline rocks. These false-bedded sandstones 

 likewise contain two thin zones of grey flagstones, which 

 resemble in every respect those at Fara's Ness. It is apparent, 

 therefore, that the change of physical conditions indicated by 

 the respective groups of strata must have been gradual. 



The same conformable passage between the flagstone and 



