140 Reports and Proceedings — Geological Society of London. 



maximum thickness is exposed. The rocks are traceable on the 

 mainland from near St. Ishmaels on Milford Haven to Wooltack 

 Head, and on the west occupy the islands of Midland, Skomer, and 

 the Smalls. The thickness exposed is some 3,000 feet, and the 

 lateral extension some 25 miles. The district described is that portion 

 of the mainland known as the Wooltack Peninsula, and the islands 

 on the west. The chief evidence bearing on the age of the series 

 is obtainable from the mainland sections, and indicates that the 

 rocks are of pre-IJpper Llandovery age ; but, from a consideration 

 of the geology of the neighbouring country, it is probable that their 

 true age is Arenig. The rocks are chiefly subaerial lava-flows of 

 extreme thinness and great lateral extent ; they are frequently inter- 

 stratified with red clays, and are separated into two main groups 

 by a thick mass of sedimentary rocks barren of fossils. There is an 

 almost complete absence of pj'roclastic rocks, a fact which points 

 to the eruptions being of the fissure type. 



The lavas form well-defined groups in the field, and range from 

 extremely acid varieties with a silica percentage of about 80 to others 

 with a percentage of less than 50. The rocks of the series fall into 

 eight chief types, two of which are of necessity new ; in order of 

 increasing basicity they are as follows : soda-rhyolites, soda-trachytes 

 (including olivine- and hypersthene-bearing varieties), keratophyres, 

 skomerites, marloesites, mugearites, olivine-basalts, and olivine- 

 dolerites. The .last-named are pi'obably intrusive. All these types 

 are described in the paper, and several analyses are tabulated. The 

 first five types maybe included in the alkaline class; they are rich 

 in soda, and most of the felspars belong to albite-oligoclase varieties. 

 The last three types are normal sub-alkaline rocks, in which the 

 felspars range from oligoclase to labradorite. 



The author does not consider that the Skomer rocks have been 

 albitized to a sufficient degree to mask their original characters, and 

 regards them as a mixture of alkaline rocks of Pantellerian affinities, 

 with a subordinate series of more basic sub-alkaline rocks, the most 

 basic of which are probably intrusive. 



At 7 p.m., before the Ordinary Meeting, a Special General Meeting, 

 at which 92 Fellows were present, was held in order to consider 

 the resolutions submitted to them by the Council (see Geol. Mag., 

 February, p. 94). 



Resolutions a, b, and d were carried unanimously, and Resolution c 

 was carried by 57 Ayes to 10 Noes. 



2. February 8, 191 1.— Professor W. W. Watts, Sc.D., M.Sc, F.P.S., 

 President, in the Chair. 

 Professor T, W. Edgeworth David, C.M.G., D.Sc, F.R.S., F.G.S., 

 gave an account of the researches pursued by him in conjunction 

 with Mr. P. E. Priestley, Geologist to the British Antarctic Expe- 

 dition of 1907-9, in the course of that expedition, more especially 

 the investigations connected with glacial geology. The lecture, 

 which was illustrated by a series of beautiful lantern-slides and by 

 numerous rock-specimens collected from the Antarctic continent, was 



