338 Proceedings of the Royal Physical Society. 



Burness and the Brougli of Birsay, and along the western 

 coast line. They are likewise well developed in the island 

 of Eowsay, where they form the characteristic terrace-shaped 

 hills. The lithological characters of the flaggy series in 

 Westray, Eowsay, and the north-west of Pomona, are pre- 

 cisely similar. 



On the coast line also, between Irland Bay and Houton 

 Head, similar strata are met with, rolling about in gentle folds. 



Again the flaggy series of Shapinshay reappears on the 

 headlands of Carness and Work Head, north-east of Kirk- 

 wall, where the general inclination is to the north-west. 



From Inganess Head south-westwards to Scapa Bay, and 

 along the shore to Smoogra Bay, and thence to Orphir Kirk, 

 a strip of red and yellow sandstones with red marls is trace- 

 able. These red and yellow sandstones are the southern 

 prolongations of the Eday sandstones. They are bounded on 

 both sides by faults which bring them against the underlying 

 flagstones. The dislocation which forms the northern boun- 

 dary line has been traced by us for a distance of nearly ten 

 miles from Orphir Kirk north-eastwards by Scapa Bay to the 

 bay east of Inganess Head. The fault is admirably seen at 

 various localities, but perhaps one of the most interesting of 

 these is on the west coast of Scapa Bay, where the main fault 

 as well as a minor dislocation are seen. 



On the high cliff which bounds the west side of Inganess 

 Bay, friable red clays are associated with the red sandstones. 

 They decompose readily, and break up into small cubical 

 fragments. 



Along the shore from Scapa southwards to Howquoy 

 Head, the same red and yellow sandstones are brought into 

 conjunction with the flags by a fault which runs almost 

 parallel with the coast. At Scapa the rocks consist of red 

 mottled sandstones, underlaid by coarse honey-combed 

 yellow and white sandstones, which alternate with cal- 

 careous flags and dark bituminous schists. Owing to numer- 

 ous foldings these beds are often repeated. 



To the east of this arenaceous series, tlie flagstones re- 

 appear in Inganess Bay. They are well developed on the 

 shore near Tankerness, and along the coast line between 



