234 Reports &, Proceedings — Liverpool Geological Society. 



the east side of the archipelago the principal submarine feature is 

 a steep bank rising from depths of 35-40 fathoms to about 20 fathoms. 

 It has a general N.N.E. direction and a very straight trend, and 

 undoubtedly is a continuation of the east coast of Caithness, which is 

 to be correlated with the great fault that winds down past Brora and 

 Helmsdale, bringing in the Secondary rocks on its eastern side. 

 This is distinctly a land feature now submerged. Dr. Flett showed 

 that the land had sunk in stages ; periods of rapid depression 

 alternated with pauses when subsidence was slow. In this way he 

 explained the origin of certain very level areas on the sea bottom, 

 covering wide stretches around the islands. One of these submarine 

 flats lay at a depth of 18 fathoms and the other at 8 fathoms. 

 At different periods Scapa Flow and Kirkwall Bay were large fresh- 

 water lakes surrounded by swampy land. These changes had taken 

 place since Neolithic man first inhabited the islands. In Sutherland- 

 shire the land had risen to some extent, as was shown by raised-beach 

 platforms at 100, 50, and 25 feet above the present sea-level. 

 It seemed in every way probable that while Scotland as a whole was 

 rising, Orkney and also Shetland were being submerged, and the 

 submarine flats of Orkney corresponded in origin and date to the 

 raised beaches of the rest of Scotland. 



V. — Liverpool Geological Society - . 



March 13, 1917.— J. H. Milton, Esq., F.G.S., F.L.S., President, 



in the Chair. 



The following papers were read : — 



1. "On an interesting Occurrence of Secondary Rutile in the 

 Millstone Grit." By H. W. Greenwood. 



The grit in which the rutile occurs forms the base of a long ridge 

 of hill which commences about a mile north-east of Macclesfield, runs 

 for about two miles in a northerly direction, and terminates just above 

 the village of Bollington. The particular exposure described occurs 

 in a quarry on the hillside overlooking Bollington. The rock contains 

 a quantity of light yellowish interstitial decomposition product, and 

 it is in this and also in small cavities lined with iron-stained debris 

 that the secondary rutile occurs in little glistening grains of a brilliant 

 pink colour, sometimes deepening to a port wine tint. In some parts 

 of the rock the crystals occur in such quantity as to become the 

 dominant heavy mineral. The evidence points to the rutile having 

 been formed from the alteration of a titaniferous biotite. In addition 

 to the secondary rutile there are also deep yellowish red usually 

 rounded grains which form part of the original constituents of the 

 rock. Anatase is also abundant, generally growing on leucoxene, 

 and staurolite was also noted. 



2. "A Comparison between the Structure of the Assynt District 

 of North- West Scotland and that of the Swiss Fore Alps." By J. S. 

 Daly, B.A. 



A detailed analysis of the structure of both regions was first given, 

 and the similarity between them then made clear in an interesting 

 manner. 



