6.H Geological Society : — 



3. 'Notes on the Dyke at Crookdene (Northumberland), and its 

 delations to the Collywell, Morpeth, and Tynemouth Dykes.' By 

 Miss M. K. Heslop, M.Sc, and Dr. J. A. Smythe. 



The dyke at Crookdene is exposed in the bed and banks of the 

 Wansbeck about 15 miles above Morpeth. It is intruded along a 

 fault-fissure in beds of Bernician age, and apparently comes to a 

 natural head. The basalt is characterized, microscopically, by 

 narrow lath-shaped felspars and curved augites. Macroscopically, 

 its most interesting feature is the occurrence of large inclusions of 

 a felspar, which is shown by chemical analysis to be closely allied 

 to anorthite. The exterior of the inclusions in contact with the 

 ground-mass is strongly zoned, the latter showing a slightly chilled 

 edge ; the individual crystals are intergrown and are cracked, 

 faulted, and in places completely shattered. In no case is the 

 dislocation great, and, in fact, the crystals seem to have burst 

 in situ. These phenomena point to a plutonic origin of the 

 felspathic inclusions and connect them with the porphyrinic 

 felspars of the Tynemouth Dyke, for which a similar origin has 

 already been suggested by Dr. Teall 



The dyke which comes to a head in the coast-section at 

 Collywell, about 24 miles distant, shows almost precisely the 

 same peculiarities. Chemical and microscopical examination of 

 the two basalts and their felspathic inclusions show them to be 

 practically identical. Considering these facts and the general 

 field-relationships of the dykes, it appears probable that they belong 

 to the same intrusion. 



The work of Dr. Teall upon the dykes at Tynemouth and 

 Morpeth has been amplified by further observations. The re- 

 semblances among the four dykes are so strong as to render it 

 probable that they are derived from a common source. The 

 observed differences are such as could be readily accounted for by 

 differences of physical condition operating during the period of 

 consolidation of the dvkcs. 



December 1st, 1909.— Prof. AY. J. Sollas, LL.D., Sc.D., F.R.S., 

 President, in the Chair. 



The following communications were read : — 



1. ' The Tremadoc Slates and Associated Rocks of South-East 

 Carnarvonshire.' By William George Fearnsides, M.A., F.G.S., 

 Fellow of, and Lecturer in Natural Sciences at, Sidney Sussex 

 College, Cambridge. 



2. ' On some Small Trilobites from the Cambrian Pocks of Comley 

 (Shropshire).' By Edgar Sterling Cobbold, F.G.S. 



3. * The Pocks of Pulau I T bin and Pnlau Nanas (Singapore)/ 

 By John Brooke Scrivenor, M.A., F.G.S. 



Pulau Ubin and Pulau Nanas are islands set in the eastern 

 entrance to the Straits of Johore, and consist of igneous rocks 



