XXI. NEW ZEALAND. Wellington. *New Zealand Institute. Dunedin. Otago Institute. * XXII. BRAZIL. Rio de Janeiro. Commissao Geologica do Imperio do Brazil. *National Muscum of Rio de Janeiro. Society's Library and Museum-5 St Andrew Square. Officer of Society-THOMAS DAWSON, 5 St Andrew Square. The Members of the Society are requested to intimate to the Honorary TRANSACTIONS OF THE EDINBURGH GEOLOGICAL SOCIETY. SESSION 1879-80. I.-On Crag Structure as illustrated on the Southern Slopes of the Queen's Park. By ANDREW TAYLOR, F.C.S., Associate. (Read 18th December 1879, since re-written.) It will be convenient in the subsequent remarks to accept Boue's designation of the sweep of Salisbury Crags as extending from their commencement opposite Holyrood to where the Queen's Drive curves round towards Dunsappie, just above the gatekeeper's lodge at Duddingston Loch. Of course many crags are included in this area. But it is only within the scope of this paper to show that on the south flanks of Salisbury Crags, in the open rock models on the large scale, in the quarries from the "Hause" to the "Cat's-Nick," may be demonstrated a mode of structure of the greenstone distinct from that of a coulée flow from a crater. And, though analogy is not identity, this will raise as yet a moot point that Samson's Ribs are in anyway part of the exposed neck of the old volcano, or that its connected crags on either side are flows from it. Indeed, this study may induce us to advert to Lord Greenock's opinion, that the igneous rocks of Edinburgh were not projected as modern lavas from a vertical crater, but injected laterally across the bedding of the aqueous strata. We do not maintain this theory, but it is valuable as a record of rock phenomena which the fashionable one does not account for. Boue long ago characterised the notion of Arthur Seat being a cone of volcanic aggregation, the hill itself being the analogue of Vesuvius, and Salisbury Crags of the more ancient Somma, as a notion only feasible at first sight. The enormous mass of aqueous strata interbedded with the dykes of the hill, as seen above the VOL. III. PART III. X Hunter's Bog, and the high inclinations of the strata go decidedly against the uniformitarian notions of the methods of volcano forming. An inspection of the model of the Queen's Park made to scale by the sappers and miners of the Ordnance Survey, now in the Edinburgh Museum of Science and Art, will clear the mind from many preconceived ideas, whilst a subsequent visit to the summit will suggest new lines of inquiry, which will be further strengthened by a survey of the hill from the deck of a steamer near Inchkeith. All writers maintain that the rocks of the Queen's Park have been subjected to enormous denudation, but few, if any, have shown how far its physiography has been thus affected. Vulcanicity is always assumed to be the main agent in rock sculpture. After a somewhat singular fashion this reasoning has been confined to Arthur Seat itself. We are told that in the great denudation which left bare its many surrounding hills, the trappean beds, intercalated with the surroundings of the aqueous strata, only played the subordinate part of the protectors. How far can the hill itself be thus explained? On either side of it are clear examples of violent torrent action. In making the old Dalkeith railway tunnel in 1827, when aqueous strata were seen to run below Samson's Ribs, large boulders of the rocks of the hill, were found in the superficial clay; and, in forming the main line of the North British Railway, as Mr Milne-Home has described, similar beds of rock spoil were disclosed. The structural anatomy of Arthur Seat exhibits a succession of hard and soft beds, and its projecting prominences follow the endings of the softer strata. Except the apex on the summit no evidences of projection from a cone strike the eye. The student, with Maclaren in hand, of course attempts to work out the continuity of the crags on the Holyrood and Duddingston sides of the hill, but Professor Judd has already protested against this, and Mr Mallet has conclusively shown how it is impossible to trace such continuity to a centre amongst the more modern dykes of Etna and Vesuvius. Atmospheric and other agents of denudation have broken up these dykes into forms rivalling the power of vulcanicity in their fantastic shapes. Indeed, the disruptive breaks of the dykes on the south flanks of the Queen's Drive are clearly figured in these recent illustrations of Mr Mallet's. Whilst the great blocks seen on the roadside above Samson's Ribs, and nowhere else in the trap tuff, may find a parallel in the way he tells certain slags round a Westmoreland iron-furnace were cemented together by a hard paste, whose constituents were mainly derived from water covering them. This will be all the more likely if, as we shall presently suggest, there may be another mode of origin of the blocks than direct projection from a volcanic cone. Meanwhile, from the point of |