fROGEEDlNGS OF GEOLOGICAL SOCIETIES. 



307 



been filled with ore prior to the great spread of deposits of red and brown iron* 

 ore which took place in S. W. England and South Wales soon after the deposition of 

 the coal-measures. 



The interest attached to these pseudomorphous changes, and to the scale on 

 which they have taken place, is heightened by comparison with the ores of Siegen, 

 of Sommorostro near Bilboa, and those brought by Dr. Livingstone from Central 

 Africa. 



4. " On Native Copper in the Llandudno Mines, near Great Orme's Head, North 

 Wales." By Capt. W. Vivian, of the Llandudno Mine. Communicated by J. 

 Taylor, Esq., F.G.S. 



The author described some microscopic arborescent crystallizations of native 

 copper occurring with ruby copper in small cavities in a brown limestone, which 

 contains yellow bisulphuret of copper. Harder sulphurous ore occvirs in the bed 

 below, and carbonates and oxides of copper in the bed above. The arborescent 

 copper is probably the result of the decomposition of copper ores, and has been 

 formed subsequently to the crystals of lime in the limestone, which are often 

 tipped with an octahedron of ruby-oxide, or overlaid with spikes of the native 

 copper. 



5. *' On the Slate-rocks and Trap-veins of Easdale and Oban." By Professor 

 James Nicol, F.Gr S. 



The author first described the mineral characters of the clay-slate of the Islands 

 of Easdale and Sell, and noticed the iron-pyrites and the veins of calc-spar and of 

 quartz occurring in the slate as well as gritty and calcareous strata that are detected 

 as interstratified with the more highly cleaved beds of the slate ; also some soft car- 

 boniferous beds and some hard calcareous nodules, imbedded in the slate. In one 

 of these nodular masses, at a depth of 140 feet from the surface, a small quantity 

 of bitumous coal was stated to have been lately found. Fucoidal or annelidal 

 markings occasionally appear in the slates. Professor Nicol then described the 

 original but obscure stratification of the Easdale slate, which, with care, is seen 

 to present beds disposed in undulations, and, where most clearly seen, dip at a 

 high angle to the west or north-west. Near Oban, and along the Sound of Kerrera, 

 the stratification is more distinct, and the strata are very much contorted. The 

 slaty cleavage of the district Avas then treated of in detail. Its average strike 

 varies 20° from that of the beds ; and the direction of strata and cleavage-planes 

 have evidently a connection with the more ancient and deep-seated causes which 

 have produced the most striking features in the configuration of the country ; they 

 are nearly parallel to the shores of Loch Linnhe, to the Island of Lismore, and to 

 the great depressions occupied by Loch Etive, Loch Awe, and Loch Fyne. The 

 trap-veins of Easdale and Oban were next described, especially a pitch-stone at 

 Seil ; and were shown to be of three periods. At least two sets of the veins 

 appear to be of a date subsequent to the Jurassic period ; and the author remarked, 

 as an instance of the very recent date of many of the great convulsions by which 

 the present physical outline of Scotland has been produced, that the mountain- 

 clifi", 1,200 to 1,500 feet high, forming the coast of Morne, between Ardtornish 

 and Loch Linnhe, consists in half of the old gneiss, in half of lias- strata and 

 recent trap, brought side by side with each other along an enormous fault, and 

 now smoothed down into one uniform mass. In conclusion. Professor Nicol 

 stated that he considered the Easdale slate to be of Lower Silurian age, but 

 younger than the slates of Birnam and Dunkeld. 



Specimens illustrative of the several papers were exhibited ; also a series of 

 North American fossils collected, described, and presented by Professor Jules 

 Marcou of Zurich. 



SwiNEY Lectures on Geology, m connection with the British Mxtseitm.— 

 This annual course of twelve lectures was commenced by Dr. A. G. Melville, Professor 

 of Natural History in the Queen's University, Ireland, at the Museum of Practical 

 Geology, Jermyn-street, on the 14th of June, and delivered as follows : — June 14th, 

 Subject-matter of Geology; Classes of Kocks. 15th, Composition of Rocks; 



